TECHNICAL COMMITTEE ON EXPLOSION PROTECTION …...NFPA 69 First Draft and NFPA 68 Second Draft Meeting Agenda . January 24-26, 2017 8:00 AM - 5:00 PM EST ... Jason Krbec CV Technology,

TECHNICAL COMMITTEE ON EXPLOSION PROTECTION SYSTEMS NFPA 69 First Draft and NFPA 68 Second Draft Meeting Agenda

January 24-26, 2017 8:00 AM - 5:00 PM EST Courtyard Charleston Historic District

Charleston, SC

Note: Continental Breakfast will be provided each day starting at 7:00 AM. Lunch will be provided on the first day.

1. Welcome. Larry Floyd, Chair

2. Introductions.

3. Approval of Meeting Minutes from February 1-2, 2016. (Attachment A)

4. Staff updates. Laura Montville, NFPA Staff

a) Committee membership and roster update. (Attachment B)

b) Fall 2017 and Fall 2018 revision cycle schedules. (Attachment C)

c) Overview of NFPA Process.

5. Review of Public Comments and Committee Inputs: NFPA 68. (Attachment D)

6. Task Group Reports

a) Task Group on Avep Calculation: Erdem Ural (chair), Samuel Rodgers, Nathan Egbert, Jerome Taveau

b) Task Group on Flow Resistance Coefficients: Samuel Rodgers, Nathan Egbert, Erdem Ural, Robert Zalosh

c) Task Group on Plastic Buckets: Martin Clouthier

d) Task Group on Gas Deflagration Fireball Equation: Martin Clouthier, Robert Zalosh, Geof Brazier, Scott

Ostrowski, Grant Roach

e) Task Group on Full Filter Housing Volume: Mitchel Rooker (chair), Samuel Rodgers, Bill Stevenson, Robert

Zalosh, Dan Guaricci

f) Task Group on Reorganization of Chapter 7: Samuel Rodgers, Robert Zalosh, Mitchel Rooker

g) Task Group on Inertia Effect and Tether Requirements: Erdem Ural, Mitch Rooker, and Steven McCoy

h) Task Group on Large Scale Gas Explosions: Larry Floyd (Chair), Martin Clouthier, Robert Zalosh, Erdem Ural,

Henry Febo, Alfonso Ibarreta, and Kelly Thomas

7. Review of Public Inputs: NFPA 69: (Attachment E)

8. New Business.

NFPA 69 First Draft and NFPA 68 Second Draft Meeting Agenda January 24 - 26, 2017 - Charleston, SC

Page 1 of 187

9. Next Meeting.

10. Adjourn.


Page 2 of 187

Attachment A: Previous Meeting Minutes

NFPA 69 First Draft and NFPA 68 Second Draft Meeting Agenda

January 24 - 26, 2017 - Charleston, SC Page 3 of 187

TECHNICAL COMMITTEE ON EXPLOSION PROTECTION SYSTEMS First Draft Meeting Minutes

February 1-2, 2016 8:00 AM - 5:00 PM EST Hilton St. Petersburg Carillon Park

St. Petersburg, FL

Attendees:

Committee Members:

Larry Floyd, Chair BASF, AL

Venkateswara Bhamidipati Powder Process Solutions, MN

Martin Clouthier Clouthier Risk Engineering, Canada

William Cosey* Savannah River Nuclear Solutions, LLC, SC

Michael Davies* PROTEGO, Germany

Randal Davis IEP Technologies, MA

Nathan Egbert Schenck Process LLC, MO

Henry Febo FM Global, MA

Robert Feldkamp Nordson Corporation, OH

Dan Guaricci ATEX Explosion Protection, L.P., FL

Manuel Herce E.I. DuPont de Nemours & Company, DE

Alfonso Ibarreta* Exponent, Inc., MA

David Kirby Baker Engineering & Risk Consultants, Inc., WV

Steven McCoy Ingredion, IN

Scott Ostrowski ExxonMobil Research and Engineering, rep. American Petroleum

Institute, TX

Samuel Rodgers Honeywell, Inc., VA

Mitchel Rooker BS&B Safety Systems, LLC, OK

Bill Stevenson CV Technology, Inc., FL

David Trull XL Global Asset Protection Services, WA

Erdem Ural* Loss Prevention Science & Technologies, Inc., MA

Robert Zalosh Firexplo, MA

Thomas Heidermann* Braunschweiger Flammenfilter G, Germany

Jason Krbec CV Technology, Inc., FL NFPA 69 First Draft and NFPA 68 Second Draft Meeting Agenda


David Nieman Bechtel Corporation, VA

Alvin Grant Roach* Professional Loss Control Inc., Canada

Thomas Scherpa* DuPont, NH

Laura Montville, Staff Liaison National Fire Protection Association, MA

Guests:

Chelsea Tuttle National Fire Protection Association, MA

Timothy Heneks CV Technology, Inc., FL

*Participated by teleconference

1. Call to Order and Welcome. Chair Larry Floyd called the meeting to order at 8:00 AM, February

1, 2016 and welcomed all committee members and guests.

2. Introductions and Update of Committee Roster. Committee members introduced themselves

and Laura Montville provided an update on new committee members appointed by the Standards

Council in December.

3. Approval of Minutes. The minutes from the NFPA 68 and 69 meeting held on September 9-10,

2015 were approved.

4. Staff updates. Laura Montville gave a presentation covering the Fall 2017 revision cycle

schedule and an overview of the NFPA Process. She also showed how Technical Committee

members and the public can access Report on Proposals (ROP), Report on Comments (ROC), and

meeting minutes from previous revision cycles.

5. Review of Public Inputs NFPA 68. The committee reviewed 14 Public Inputs and created First

Revisions accordingly. The committee actions will be available in the First Draft Report. Several task

groups were established to discuss various issues and present recommendations to the committee at

the Second Draft meeting.

Task Group on Avep Calculation. Public Input 8 provided an example calculation using

Equation 8.4.1 where an initially elevated pressure resulted in a reduction of required vent

area, and where all units did not cancel out. A task group was established to verify

Equation 8.4.1. The task group members are Erdem Ural (chair), Samuel Rodgers, and

Nathan Egbert.


Page 5 of 187

Task Group on Flow Resistance Coefficients. In response to Public Inputs 9 and 11, a

task group has been formed to ensure that the K-factors in the tables in A.8.5 are

consistent with those used in the example problem. The example will be modified to reflect

long radius elbows and to show the inlet and outlet K factors. The task group members are

Samuel Rodgers, Nathan Egbert, Erdem Ural, and Robert Zalosh.

Task Group on Plastic Buckets. A task group was established to review section 8.8.3.4

(created by First Revision 8) on the use of plastic buckets in bucket elevators, including any

testing to support the provision on plastic buckets in VDI 2263. Martin Clouthier is chair of

the task group and other interested parties should contact him.

The staff liaison was asked to review First Revision 10 as it relates to NFPA 69.

Task Group on Gas Deflagration Fireball Equation. A task group was established to

review 7.7.1 and A.7.7, to compare gas flame jets to fireballs, and consider a revised

definition for hazard zone or use an alternate term (fireball or flame length). The task group

was asked to review the committee response to Committee Input 12 and reference

Bartnecht, pg. 573-574. The task group members are Martin Clouthier, Robert Zalosh, Geof

Brazier, and Scott Ostrowski.

Task Group on Full Filter Housing Volume. A task group was formed to review A.8.7.3

modified by First Revision 14, which revised the images to indicate more realistic

applications and clearly show when to use full filter housing volume in venting equations.

The task group will confirm that venting correlations are sufficiently conservative so that

filter elements can be placed in front of the vent. The task group members are Mitchel

Rooker (chair), Samuel Rodgers, Bill Stevenson, and Robert Zalosh. Dan Guaricci

volunteered to check this data.

Task Group on Reorganization of Chapter 7. A task group was formed to reorganize the

hierarchy of Chapter 7 to clarify constants and common equations used in the low pressure

and high pressure vent area equations. The task group will also develop an example using

the gas equations, to be located in the Annex. The task group members are Samuel

Rodgers, Robert Zalosh, and Mitchel Rooker.

6. Task Group Reports

a) Task Group on Fireball Equations. Bill Stevenson (Chair), Erdem Ural, Alfonso Ibarreta,

Jerome Taveau, Robert Zalosh, Mitchel Rooker, and Dave Kirby. The task group reported that

they compared available data with the fireball dimensions predicted by Equation 8.9.2, and the

equation adequately covers the data. They recommended that language be added to the


Page 6 of 187

annex so that users consider other factors, such as wind speed and direction, particle size,

and vent configuration when evaluating fireball hazards. The committee created a First

Revision accordingly.

b) Task Group on Metal Dusts (6.1.2-6.1.2.2). Jerome Taveau (Chair), Tim Meyers, Robert

Zalosh, Martin Clouthier, Sam Rodgers, and Erdem Ural. Based on recent testing that has

shown that certain metal dusts exhibit significantly higher Kst values in 1 m3 tests than in 20 L

tests, the task group recommended a revision to require testing in a 1 m3 vessel or application

of a safety factor to 20L Kst results for aluminum, hafnium, magnesium, tantalum, and titanium

dusts. A First Revision was created to reflect this recommendation.

c) Task Group on Inertia Effect and Tether Requirements (8.2.6.2). Erdem Ural, Mitch

Rooker, Steve Stuart, Joe Gillis, and Steven McCoy. Although it was brought to the attention of

the committee that this equation does not sufficiently bound the weight of some vent panels,

the task group reported that they could not find any improvements to the equation to put forth

at this time. A Committee Input was created and the task group will re-visit the inertia effect

and tether requirements before the Second Draft meeting.

d) Task Group on Large Scale Gas Explosions (7.2.6.3, 7.2.6.4, and gas venting example for

the annex). Larry Floyd (Chair), Martin Clouthier, Robert Zalosh, Erdem Ural, Henry Febo,

Alfonso Ibarreta, and Kelly Thomas. The task group presented their review of large scale test

data on vent area adjustments for obstructed enclosures (presentation attached). They

recommended a revision to the threshold criteria for accounting for obstructions and a revision

to the equation that represents the effect of those obstructions to be more consistent with test

data. A First Revision was created accordingly. The task group will draft an example of

applying these equations to an obstructed arrangement before the Second Draft meeting.

7. Additional Issues for Consideration.

a) Proposed TIA 1210 and related changes to 8.2.2.1, Figure 8.1.1.4, and 8.4.1. The

committee agreed that the revisions proposed in TIA 1210 should be incorporated into the next

edition of the document and created a First Revision accordingly.

b) Use of equation 7.2.6.1(e) when Pred<0.9 bar. Equation 7.2.6.1(e) was revised to account for

the possibility of higher initial temperatures and pressures, so that the equation does not result

in velocity greater than the speed of sound.

c) Organization of Chapter 7. This was addressed by Committee Input 21 and formation of a

task group.


Page 7 of 187

d) Vent deflection devices. The committee discussed inclusion of vent deflection devices in

NFPA 68 and determined that a revision is unnecessary at this time.

e) Deflagration pipeline propagation. The committee briefly discussed deflagration pipeline

propagation as it applies to NFPA 654 and determined that no revisions to NFPA 68 are

needed.

f) Values for the K-flow resistance coefficient and inclusion of appropriate references in

Figure A.8.5(a). This was addressed by the formation of a task group.

g) Committee member recognition. A handful of current and former members of the committee

have been nominated to receive Committee Service awards. To nominate others, please

contact NFPA.

8. New Business. Samuel Rodgers presented a proposed change to Equation 7.2.6.1(c) to account

for low burning velocity materials (presentation attached). A First Revision was created to adjust the

equation, consistent with the original range of test data, to produce a more appropriately bounded

vent area as Su approaches zero.

9. Next Meeting. The committee scheduled two web/teleconference meetings to discuss Task

Group progress before the Public Comment closing date of November 17, 2016. These meetings will

be held on Tuesday, August 9 and Tuesday October 4 at 10:00 AM EDT.

The NFPA 68 Second Draft meeting was scheduled to be held in conjunction with the NFPA 69 First

Draft meeting on January 24-26, 2017 in Orlando, FL or Charleston, SC. Details will be provided as

they become available.

10. Adjourn. The meeting adjourned at 5:00 PM on February 2, 2016.


Page 8 of 187

Attachment B: Committee Roster



Address List No PhoneExplosion Protection Systems EXL-AAA

Laura E. Moreno01/10/2017

EXL-AAA

Larry D. Floyd

ChairBASF1379 Ciba RoadMcIntosh, AL 36553-5436

U 7/29/2005EXL-AAA

Luke S. Morrison

SecretaryProfessional Loss Control Inc.PO Box 162Fredericton, NB E3B 4Y9 CanadaAlternate: Alvin Grant Roach

SE 1/1/1987

EXL-AAA

Venkateswara Sarma Bhamidipati

PrincipalPowder Process Solutions1620 Lake Drive WestChanhassen, MN 55317

IM 03/07/2013EXL-AAA

Martin P. Clouthier

PrincipalJensen Hughes6178 Cedar StreetHalifax, NS B3H 2J7 Canada

SE 11/30/2016

EXL-AAA

William V. F. Cosey

PrincipalSavannah River Nuclear Solutions, LLC118 Beauregard LaneAiken, SC 29803

U 12/08/2015EXL-AAA

Michael Davies

PrincipalPROTEGOIndustriestrasse llBraunschweig, D-38110 GermanyAlternate: Thomas Heidermann

M 1/14/2005

EXL-AAA

Randal R. Davis

PrincipalIEP Technologies/HOERBIGER417-1 South StreetMarlborough, MA 01752-3149

M 7/14/2004EXL-AAA

Nathan R. Egbert

PrincipalSchenck Process LLC7901 NW 107th TerraceKansas City, MO 64153

SE 08/17/2015

EXL-AAA

Robert J. Feldkamp

PrincipalNordson Corporation300 Nordson DriveAmherst, OH 44001Alternate: Edward L. Jones

M 7/29/2005EXL-AAA

Richard G. Fredenburg

PrincipalState of North CarolinaDepartment of Agriculture & Consumer Services2 West Edenton Street (27601)1050 Mail Service CenterRaleigh, NC 27699-1050International Fire Marshals Association

E 04/05/2016

EXL-AAA

Dan A. Guaricci

PrincipalATEX Explosion Protection, L.P.2629 Waverly Barn Road, Suite 121Davenport, FL 33897

M 7/1/1991EXL-AAA

Michael D. Hard

PrincipalHard Fire Suppression Systems, Inc.400 East Wilson Bridge Road, Suite AWorthington, OH 43085Fire Suppression Systems AssociationAlternate: Kirk W. Humbrecht

M 10/1/1994

EXL-AAA

Manuel Herce

PrincipalE. I. DuPont de Nemours & Company974 Centre RoadCRP 723-2111Wilmington, DE 19805-1269Alternate: Thomas C. Scherpa

U 12/08/2015EXL-AAA

Alfonso F. Ibarreta

PrincipalExponent, Inc.9 Strathmore RoadNatick, MA 01760-2418Alternate: Timothy J. Myers

SE 3/4/2009

1NFPA 69 First Draft and NFPA 68 Second Draft Meeting Agenda January 24 - 26, 2017 - Charleston, SC

Page 10 of 187



EXL-AAA

Steven A. McCoy

PrincipalIngredionPO Box 1084Indianapolis, IN 46206NFPA Industrial Fire Protection Section

U 10/10/1997EXL-AAA

Scott W. Ostrowski

PrincipalExxonMobil Research and Engineering4500 Bayway DriveBaytown, TX 77520-2127American Petroleum Institute

U 08/17/2015

EXL-AAA

James O. Paavola

PrincipalDTE Electric Company2000 Second Ave., Room 421 GODetroit, MI 48226

U 1/10/2002EXL-AAA

Stefan Penno

PrincipalRembe GmbH Safety & ControlGallbergweg 21Brilon NRW, D-59929 GermanyAlternate: Gerd Ph. Mayer

M 11/2/2006

EXL-AAA

Samuel A. Rodgers

PrincipalHoneywell, Inc.15801 Woods Edge RoadColonial Heights, VA 23834-6059

U 4/1/1996EXL-AAA

Mitchel L. Rooker

PrincipalBS&B Safety Systems, LLCPO Box 470590Tulsa, OK 74147-0590Alternate: Geof Brazier

M 10/10/1997

EXL-AAA

Cleveland B. Skinker

PrincipalBechtel Infrastructure and Power Corporation12011 Sunset Hills RoadReston, VA 20190Alternate: David M. Nieman

SE 3/4/2009EXL-AAA

Bill Stevenson

PrincipalCV Technology, Inc.15852 Mercantile CourtJupiter, FL 33478Alternate: Jason Krbec

M 7/22/1999

EXL-AAA

David R. Stottmann

PrincipalST StoragePO Box 996Parsons, KS 67357Alternate: Keith McGuire

M 11/2/2006EXL-AAA

Jérôme R. Taveau

PrincipalFike Corporation704 SW 10th StreetBlue Springs, MO 64015-4263Alternate: Jef Snoeys

M 03/07/2013

EXL-AAA

James Kelly Thomas

PrincipalBaker Engineering & Risk Consultants, Inc.3330 Oakwell Court, Suite 100San Antonio, TX 78218Alternate: David C. Kirby

SE 8/9/2011EXL-AAA

David E. Trull

PrincipalGlobal Asset Protection Services, LLC17804 NE 100th CourtRedmond, WA 98052-3273Alternate: Todd A. Dillon

I 03/03/2014

EXL-AAA

Erdem A. Ural

PrincipalLoss Prevention Science & Technologies, Inc.2 Canton Street, Suite A2Stoughton, MA 02072

SE 1/16/1998EXL-AAA

Robert G. Zalosh

PrincipalFirexplo20 Rockland StreetWellesley, MA 02481

SE 1/1/1991


Page 11 of 187



EXL-AAA

John A. LeBlanc

Voting AlternateFM Global1151 Boston-Providence TurnpikePO Box 9102Norwood, MA 02062-9102

I 8/5/2009EXL-AAA

Geof Brazier

AlternateBS&B Safety Systems, LLC7455 East 46th StreetTulsa, OK 74145Principal: Mitchel L. Rooker

M 3/21/2006

EXL-AAA

Todd A. Dillon

AlternateGlobal Asset Protection Services, LLC1620 Winton AvenueLakewood, OH 44107Principal: David E. Trull

I 7/16/2003EXL-AAA

Thomas Heidermann

AlternateBraunschweiger Flammenfilter GIndustriestrasse 11Braunschweig, 38110 GermanyPrincipal: Michael Davies

M 10/23/2013

EXL-AAA

Kirk W. Humbrecht

AlternatePhoenix Fire Systems, Inc.744 West Nebraska StreetFrankfort, IL 60423-1701Fire Suppression Systems AssociationPrincipal: Michael D. Hard

M 7/19/2002EXL-AAA

Edward L. Jones

AlternateNordson Corporation300 Nordson Drive, M/S 42Amherst, OH 44001Principal: Robert J. Feldkamp

M 7/29/2005

EXL-AAA

David C. Kirby

AlternateBaker Engineering & Risk Consultants, Inc.1560 Clearview HeightsCharleston, WV 25312-5948Principal: James Kelly Thomas

SE 1/1/1983EXL-AAA

Jason Krbec

AlternateCV Technology, Inc.15852 Mercantile CourtJupiter, FL 33478Principal: Bill Stevenson

M 10/18/2011

EXL-AAA

Gerd Ph. Mayer

AlternateRembe, Inc.3809 Beam Road, Suite KCharlotte, NC 28217Principal: Stefan Penno

M 03/05/2012EXL-AAA

Keith McGuire

AlternateCST StoragePO Box 996Parsons, KS 67357Principal: David R. Stottmann

M 11/2/2006

EXL-AAA

Timothy J. Myers

AlternateExponent, Inc.9 Strathmore RoadNatick, MA 01760-2418Principal: Alfonso F. Ibarreta

SE 10/20/2010EXL-AAA

David M. Nieman

AlternateBechtel Corporation11720 Plaza America DriveReston, VA 20190-4757Principal: Cleveland B. Skinker

SE 08/17/2015

EXL-AAA

Alvin Grant Roach

AlternateProfessional Loss Control Inc.346 Queen Street, Suite 105Fredericton, NB E3B 1B2 CanadaPrincipal: Luke S. Morrison

SE 08/17/2015EXL-AAA

Thomas C. Scherpa

AlternateDuPont71 Valley RoadSullivan, NH 03445Principal: Manuel Herce

U 8/9/2011


Page 12 of 187



EXL-AAA

Jef Snoeys

AlternateFike CorporationToekomstlaan 52Herentals, B-2200 BelgiumPrincipal: Jérôme R. Taveau

M 3/21/2006EXL-AAA

Laurence G. Britton

Nonvoting MemberProcess Safety Consultant848 Sherwood RoadCharleston, WV 25314

SE 1/1/1983

EXL-AAA

Vladimir Molkov

Nonvoting MemberUniversity of UlsterFireSERT Institute(Block 27)Newtonwnabbey, BT37 0QB Northern Ireland, UK

SE 10/6/2000EXL-AAA

Laura E. Moreno

Staff LiaisonNational Fire Protection Association1 Batterymarch ParkQuincy, MA 02169-7471

01/06/2015


Page 13 of 187

Attachment C: Fall 2017 & Fall 2018 Revision

Schedule



Process

StageProcess Step Dates for TC

Dates for TC

with CC

Public Input Closing Date 1/7/2016 1/7/2016

Final date for TC First Draft Meeting 6/16/2016 3/17/2016Posting of First Draft and TC Ballot 8/4/2016 4/28/2016Final date for Receipt of TC First Draft ballot 8/25/2016 5/19/2016Final date for Receipt of TC First Draft ballot ‐ recirc 9/1/2016 5/26/2016Posting of First Draft for CC Meeting 6/2/2016Final date for CC First Draft Meeting 7/14/2016Posting of First Draft and CC Ballot 8/4/2016Final date for Receipt of CC First Draft ballot 8/25/2016Final date for Receipt of CC First Draft ballot ‐ recirc 9/1/2016Post First Draft Report for Public Comment 9/8/2016 9/8/2016

Public Comment closing date 11/17/2016 11/17/2016Notice published on Consent Standards (Standards that receive No Comments).

Note: Date varies and determined via TC ballot._ _

Appeal Closing Date for Consent Standards (15 Days) (Standards That Received

No Comments)_ _

Final date for TC Second Draft Meeting 5/18/2017 2/9/2017Posting of Second Draft and TC Ballot 6/29/2017 3/23/2017Final date for Receipt of TC Second Draft Ballot 7/20/2017 4/13/2017Final date for receipt of TC Second Draft ballot ‐ recirc 7/27/2017 4/20/2017Posting of Second Draft for CC Mtg 4/27/2017Final date for CC Second Draft Meeting 6/8/2017Posting of Second Draft for CC Ballot 6/29/2017Final date for Receipt of CC Second Draft ballot 7/20/2017Final date for Receipt of CC Second Draft ballot ‐ recirc 7/27/2017Post Second Draft Report for NITMAM Review 8/3/2017 8/3/2017

Notice of Intent to Make a Motion (NITMAM) Closing Date 8/31/2017 8/31/2017Posting of Certified Amending Motions (CAMs) and Consent Standards 10/12/2017 10/12/2017Appeal Closing Date for Consent Standards (15 Days after posting) 10/27/2017 10/27/2017SC Issuance Date for Consent Standards (10 Days)

Tech Session Association Meeting for Standards with CAMs 6/4‐7/2018 6/4‐7/2018

Appeal Closing Date for Standards with CAMs (20 Days after ATM) 6/27/2018 6/27/2018Council Issuance Date for Standards with CAMs* 8/14/2018 8/14/2018

Comment

Stage (Second

Draft)

Tech Session

Preparation

(& Issuance)

Appeals and

Issuance

2017 FALL REVISION CYCLE

Public Input

Stage

(First Draft)

* Public Input Closing Dates may vary according to standards and schedules for Revision Cycles may change. Please check the

NFPA Website for the most up‐to‐date information on Public Input Closing Dates and schedules at www.nfpa.org/document # (i.e.

www.nfpa.org/101) and click on Next Edition tab.


Page 15 of 187

Fall 2018 Revision Cycle

Process Stage Process Step Dates for TCDates for TC

with CC

Public InputStage (First Draft)

Public Input Closing Date* 1/05/2017 1/05/2017

Final Date for TC First Draft Meeting 6/15/2017 3/16/2017

Posting of First Draft and TC Ballot 8/03/2017 4/27/2017

Final date for Receipt of TC First Draft ballot 8/24/2017 5/18/2017

Final date for Receipt of TC First Draft ballot - recirc 8/31/2017 5/25/2017

Posting of First Draft for CC Meeting 6/01/2017

Final date for CC First Draft Meeting 7/13/2017

Posting of First Draft and CC Ballot 8/03/2017

Final date for Receipt of CC First Draft ballot 8/24/2017

Final date for Receipt of CC First Draft ballot - recirc 8/31/2017

Post First Draft Report for Public Comment 9/07/2017 9/07/2017

Comment Stage(Second Draft)

Public Comment Closing Date* 11/16/2017 11/16/2017

Notice Published on Consent Standards (Standards that received no Comments)Note: Date varies and determined via TC ballot.

Appeal Closing Date for Consent Standards (Standards that received no Comments)

Final date for TC Second Draft Meeting 5/17/2018 2/08/2018

Posting of Second Draft and TC Ballot 6/28/2018 3/22/2018

Final date for Receipt of TC Second Draft ballot 7/19/2018 4/12/2018

Final date for receipt of TC Second Draft ballot - recirc 7/26/2018 4/19/2018

Posting of Second Draft for CC Meeting 4/26/2018

Final date for CC Second Draft Meeting 6/07/2018

Posting of Second Draft for CC Ballot 6/28/2018

Final date for Receipt of CC Second Draft ballot 7/19/2018

Final date for Receipt of CC Second Draft ballot - recirc 7/26/2018

Post Second Draft Report for NITMAM Review 8/02/2018 8/02/2018

Tech SessionPreparation (&

Issuance)

Notice of Intent to Make a Motion (NITMAM) Closing Date 8/30/2018 8/30/2018

Posting of Certified Amending Motions (CAMs) and Consent Standards 10/11/2018 10/11/2018

Appeal Closing Date for Consent Standards 10/26/2018 10/26/2018

SC Issuance Date for Consent Standards 11/05/2018 11/05/2018

Tech Session Association Meeting for Standards with CAMs

Appeals andIssuance

Appeal Closing Date for Standards with CAMs

SC Issuance Date for Standards with CAMs

TC = Technical Committee or PanelCC = Correlating Committee

As of 8/30/2016


Page 16 of 187

Attachment D: NFPA 68 Public Comment &

Committee Input Reports



Public Comment No. 4-NFPA 68-2016 [ Chapter 7 ]

Chapter

7 Venting7 Venting Deflagrations of Gas Mixtures and Mists

7.

1 Introduction1 Introduction .

7.1.1 *

This chapter shall apply to the design of deflagration vents for enclosures that contain a flammable gas orcombustible mist and that have an L/D of ≤5.

7.1.1.

1 1

This chapter shall be used in conjunction with the information contained in the rest of this standard.

7.1.1.

2 2

Chapter 6

Chapter 6 and 3.3.31.1 shall be reviewed before

determining the value of P red to be used in

using this chapter.

7.1.2 *

The design of a deflagration vent for an enclosure containing a combustible mist shall be based on a valueof S u equal to 0.46 m/s unless a value of S u applicable to the mist of a particular substance is

determined by test.

National Fire Protection Association Report http://submittals.nfpa.org/TerraViewWeb/ContentFetcher?commentPara...


Page 18 of 187

7.2 VentingGlobal FR-30

7.2 Venting by Means of Low Inertia Vent Closures.

7.2.

1 1 Low Inertia Vent Closure Equations for Low P red

When P red ≤ 0.5 bar-g, the minimum required vent area, A v 0 , shall be determined by Equation

7.2.1a and Equation 7.2.1b:

http://submittals.nfpa.org:80/TerraView/Content/68-2013.ditamap/2/E68-206.jpg [7.2.1a]

http://submittals.nfpa.org:80/TerraView/Content/68-2013.ditamap/2/E68-207.jpg [7.2.1b]

where:

A v 0 = the vent area calculated from Equation 7.2.1a (m 2 )

A s = the enclosure internal surface area determined according to 7.2.5 (m 2 )

P red = the maximum pressure developed in a vented enclosure during a vented deflagration (bar-g)

S u = fundamental burning velocity of gas-air mixture (m/s)

ρ u = mass density of unburned gas-air mixture (kg/m 3 )

= 1.2 for flammable gases with stoichiometric concentrations less than 5 vol%, and an initial temperature of20°C

λ =ratio of gas-air mixture burning velocity accounting for turbulence and flame instabilities invented deflagration to the fundamental (laminar) burning velocity , determined according to 7.2.6

G u = unburned gas-air mixture sonic flow mass flux

= 230.1

( kg/m 2 -s

for an enclosure initial temperature of 20°C

)

C d = vent flow discharge coefficient , determined according to 7.2.4

P max =the maximum pressure developed in a contained deflagration by ignition of the same gas-airmixture (bar-g)

P 0 = the enclosure pressure prior to ignition (bar-g)

γ b = ratio of specific heats for burned gas-air mixture



Page 19 of 187

= 1.1 to 1.2, depending on the gas mixture

7.2.1.

1 1

The C value for flammable gases and vapors with a P max value less than 9 bar-g and a stoichiometric

(near worst case) fuel concentration no greater than about 10 percent shall be permitted to be calculatedusing Equation 7.2.1.1 for use in Equation 7.2.1a :

http://submittals.nfpa.org:80/TerraView/Content/68-2013.ditamap/2/E68-210.jpg [7.2.1.1]

7.2.1.

2

The

2

When applying Equation 7.2.1a, the value of P stat shall be less than P red as specified for the

following conditions:

For

(1) For P red ≤ 0.1 bar-g (1.5 psig), P stat ≤ P red - 0.024 bar-g (50 psf).

For

(2) For P red > 0.1 bar-g (1.5 psig), P stat < 0.75 P red .

7.2.

2 2 Low Inertia Vent Closure Equations for High P red

When P red > 0.5 bar-g, the minimum required vent area, A v 0 , shall be determined from Equation

7.2.2a and Equation 7.2.2b:

http://submittals.nfpa.org:80/TerraView/Content/68-2013.ditamap/2/E68-208.jpg [7.2.2a]

http://submittals.nfpa.org:80/TerraView/Content/68-2013.ditamap/2/E68-209.jpg [7.2.2b]

where:

A v 0 = the vent area calculated from Equation 7.2.2a (m 2 )

A s = the enclosure internal surface area determined according to 7.2.5, (m 2 )



Page 20 of 187




λ =ratio of gas-air mixture burning velocity accounting for turbulence and flame instabilities invented deflagration to the fundamental (laminar) burning velocity, determined according to7.2.6

G u = unburned gas-air mixture sonic flow mass flux (kg/m 2 -s)

C d = vent flow discharge coefficient, determined according to 7.2.4

P max=

the maximum pressure developed in a contained deflagration by ignition of the same gas-airmixture (bar-g)



P stat = nominal vent deployment or burst pressure (bar-g)

7.2. 3* Gas-Air Mixture Parameters

7. 2. 3. 1

The internal surface area, A s , in Equation 7.2.2a shall be determined according to 7.2.5 .

*

The design of a deflagration vent for an enclosure containing a combustible mist shall be based on a valueof S u equal to 0.46 m/s unless a value of S u applicable to the mist of a particular substance is

determined by test.

7.2.

23 .2 *

The burning velocity, S u , shall be the maximum value for any gas concentration unless a documented

hazard analysis shows that there is not a sufficient amount of gas to develop such a concentration.

7.2. 3.3

It shall be permitted to assume a mass density of unburned gas-air mixture, r u , equal to 1. 2 kg/m 3 for

flammable gases with stoichiometric concentrations less than 5 vol% and initially at ambient temperature

7 . 2. 3

.4

It shall be permitted to assume an unburned gas-air mixture sonic flow mass flux, G u , equal to 230.1

kg/m 2 -s for an enclosure initially at ambient temperatures

7.2.3.5

It shall be permitted to assume the ratio of specific heats for burned gas-air mixture, g b , equal to 1.15 for

flammable gases with stoichiometric concentrations less than 5 vol% and initially at ambient temperatures

7.2.3.6

It shall be permitted to assume the unburned gas-air mixture dynamic velocity, m u , equal to 1.8 × 10 -5

kg/m-s for flammable gases with stoichiometric concentrations less than 5 vol% and initially at ambient



Page 21 of 187

temperatures

7.2.3.7

It shall be permitted to assume the unburned gas-air mixture sound speed, a u , equal to 343 m/s for

flammable gases with stoichiometric concentrations less than 5 vol% and initially at ambient temperatures

7.2.4 Enclosure Parameters

7.2.4.1

The value of C d shall be 0.70 unless the vent occupies an entire wall of the enclosure, in which case a

value of 0.80 shall be permitted to be used.

7.2.

3 4.2*

The value of

λ for the gas and particular enclosure shall be determined according to 7.2.6 .

P 0 shall be greater than or equal to the normal operating pressure and chosen to represent the likely

maximum pressure at which a flammable gas mixture can exist at the time of ignition.

7.2.4

The L / D of

.3*

For initially elevated pressures, the enclosure shall be

determined according to Section 6.4 .

located to accommodate the blast wave.

7.2.5 *

Calculation Calculation of Internal Surface Area.

7.2.5.1 *

The internal surface area, A s , shall include the total area that constitutes the perimeter surfaces of the

enclosure that is being protected.

7.2.5.1.

1 1

Nonstructural internal partitions that cannot withstand the expected pressure shall not be considered to bepart of the enclosure surface area.

7.2.5.1.

2 2

The enclosure internal surface area, A S , in Equation 7.2.2 includes the roof or ceiling, walls, floor, and

vent area and shall be based on simple geometric figures.

7.2.5.1.

3 3

Surface corrugations and minor deviations from the simplest shapes shall not be taken into account.

7.2.5.1.

4 4

Regular geometric deviations, such as saw-toothed roofs, shall be permitted to be “averaged” by addingthe contributed volume to that of the major structure and calculating A S for the basic geometry of the



Page 22 of 187

major structure.

7.2.5.1.5 *

The internal surface of any adjoining rooms shall be included.

7.2.5.

2 2

The surface area of equipment and contained structures shall be neglected.

7.2.6 *

Determination Determination of Turbulent Flame Enhancement Factor, λ.

7.2.6.

1 1

The baseline value, λ 0 , of λ shall be calculated from Equations 7.2.6.1a through 7.2.6.1f:

http://submittals.nfpa.org:80/TerraView/Content/68-2013.ditamap/2/E68-211.jpg [7.2.6.1a]

http://submittals.nfpa.org:80/TerraView/Content/68-2013.ditamap/2/E68-212.jpg [7.2.6.1b]

http://submittals.nfpa.org:80/TerraView/Content/68-2013.ditamap/2/E68-213r3.jpg [7.2.6.1c]

http://submittals.nfpa.org:80/TerraView/Content/68-2013.ditamap/2/E68-214.jpg [7.2.6.1d]

http://submittals.nfpa.org:80/TerraView/Content/68-2013.ditamap/2/E68-253r2.jpg [7.2.6.1e]

http://submittals.nfpa.org:80/TerraView/Content/68-2013.ditamap/2/E68-216.jpg [7.2.6.1f]

where:


= 1.2 for flammable gases with stoichiometric concentrations less than 5 vol%, and an initial temperature of20°C



Page 23 of 187


D he = the enclosure hydraulic equivalent diameter as determined in Chapter 6 (m)

µ u = the unburned gas-air mixture dynamic velocity

= 1.8 × 10 -5

( kg/m-s

for gas concentrations less than 5 vol% at ambient temperatures

)

β 1 = 1.23

β 2 = 2.37 × 10 −3 m/s

D v = the vent diameter as determined through iterative calculation (m)

u v = maximum velocity through vent (m/s)


a u = the unburned gas-air mixture sound speed

= 343 m

(m /s

for gas concentrations less than 5 vol% at ambient temperatures

)

θ = 0.39

7.2.6.

2 2

The total external surface area, A obs , of the following equipment and internal structures that can be in

the enclosure shall be estimated:

Piping

(1) Piping , tubing, and conduit with diameters greater than

1 ⁄ 2

1⁄2 in.

Structural

(2) Structural columns, beams, and joists

Stairways

(3) Stairways and railings

Equipment

(4) Equipment with a characteristic dimension in the range of 2 in. to 20 in. (5.1 cm to 51 cm)

7.2.6.



Page 24 of 187

3 3

When A obs < 0.2 A S , λ 1 shall be equal to λ 0 as determined in 7.2.6.1 .

7.2.6.

4 4

When A obs > 0.2 A S , λ 1 shall be determined as follows:

[7.2.6.4]

7.2.6.5

The L / D of the enclosure shall be determined according to Section 6.4.

7.2.6.6

For L / D values less than 2.5, λ shall be set equal to λ 1 .

Global FR-30

7.2.6.

6 7

For L / D values from 2.5 to 5 and for P red no higher than 2 bar-g, λ shall be calculated as follows:

http://submittals.nfpa.org:80/TerraView/Content/68-2013.ditamap/2/E68-248.jpg [7.2.6.

6

7 ]

7.2.6.

7 8

Equations for determining λ shall be subject to the following limitations:

(1) S u < 3 m/s (300 cm/s).

(2) P max < 10 bar-g.

The

(3) The maximum air velocity in the enclosure prior to ignition is no greater than 5 m/s.

The

(4) The enclosure is isolated from possible flame jet ignition and pressures caused by a deflagration inan interconnected enclosure.

7.2.6.

8



Page 25 of 187

9

For long pipes or process ducts where L / D is greater than 5, the requirements of

Chapter 9

Chapter 9 shall be used.

7.2.6.

9 Methods10 Methods to Reduce Flame Enhancement.

7.2.6.

910 .

1 1

The value of λ shall be permitted to be reduced for gas deflagrations in relatively unobstructed enclosuresby the installation of noncombustible, acoustically absorbing wall linings, provided that large-scale testdata confirm the reduction.

7.2.6.

910 .

2 2

The tests shall be conducted with the highest anticipated turbulence levels and with the proposed walllining material and thickness.

7.

2.7 Partial3 Partial Volume Effects.

7.

2.7.1 3.1

When a documented hazard analysis demonstrates that there is insufficient gas in the enclosure to form astoichiometric gas-air mixture occupying the entire enclosure volume, the vent area, A v 0 , calculated

from Equation 7.2. 1a or Equation 7.2. 2a , as appropriate, shall be permitted to be reduced as describedin 7.

2

3 .

7.

3 .

7.

2.7.2 3.2

A partial volume fill fraction, X r , shall be calculated as follows:

http://submittals.nfpa.org:80/TerraView/Content/68-2013.ditamap/2/E68-218.jpg [7.

2

3 .

7.



Page 26 of 187

2]

where:

V gas = maximum volume of gas that can be mixed with air in the enclosure

V enc = enclosure volume

x st = stoichiometric volume concentration of gas

7.

2.7.3 3.3

If X r < 1, the minimum required vent area, A v 1 shall be calculated from the following equation:


2

3 .

7.

3]

where:

A v 1 = vent area for partial volume deflagration

A v 0 = vent area for full volume deflagration as determined from Equation 7.2.1a or 7.2.2a

X r = fill fraction > Π

Π = P red / P max

7.3

Effects.4

If X r > 1, A v1 = A v0

7.4 Effects of Panel Inertia.

7.

34 .1 *

When the mass of the vent panel ≤ 40 kg/m 2 , Equation 7.

3

4 .2 shall be used to determine if an incremental increase in vent area is needed, and Equation 7.

3

4 .3 shall be used to determine the value of that increase.

7.

34 .

2 2

The vent area determined in 7.2.7 shall be adjusted for vent mass when the vent mass exceeds M T as



Page 27 of 187

calculated in Equation 7.3.2:


3

4 .2]

where:

M T = threshold mass (kg/m 2 )


n = number of panels

V = enclosure volume (>1 m 3 )

7.

34 .

3 3

For M > M T , the required vent area, A v 2 , shall be calculated as follows:


3

4 .3]

where:

A v2 = vent area for panel inertia (m 2 )

M = mass of vent panel (kg/m 2 )

A v 1 = vent area determined in 7.2.7 (m 2 )

F SH = 1 for translating panels or 1.1 for hinged panels

7.4

* Effects.4

If M < M T, A v2 = A v1

7.5 * Effects of Vent Ducts.

7.

45 .1 *

Where

Equations 7.2.6, 7.2.6.4, 7.3.2, and 7.3.3 are used with vent ducting

vent ducting is used , a lower value , P’ red , shall be used in place of the actual P red in all equations in



Page 28 of 187

this chapter .

7.

45 .

2 2

Duct lengths shorter than 3 m (10 ft) and shorter than four duct hydraulic diameters in length shall betreated using Curve A in Figure 7.

4

5 .2 . For ducts exceeding either of these limitations, Curve B shall be used.

Figure 7.

4

5 .2 Maximum Pressure Developed During Venting of Gas, With and Without Vent Ducts.

http://submittals.nfpa.org:80/TerraView/Content/68-2013.ditamap/2/G68-22.jpg

7.

45 .2.

1 1

For vent ducts with lengths of less than 3 m (10 ft) and shorter than four duct hydraulic diameters, thefollowing equation shall be permitted to be used to determine P′ red :


4

5 .2.1]

7.

45 .2.

2



Page 29 of 187

2

For vent ducts with lengths of 3 m to 6 m (10 ft to 20 ft) or shorter vent ducts longer than four ducthydraulic diameters, the following equation shall be permitted to be used to determine P′ red :


4 (See Section

5 .2.2]

7.

45 .3 *

Duct lengths shorter than 3 m (10 ft) shall be treated as 3 m (10 ft) in length for calculation purposes.

7.

45 .3.

1 1

If longer ducts are needed, P′ red shall be determined by appropriate tests.

7.

45 .3.

2 2

Vent ducts and nozzles with total lengths of less than one hydraulic diameter shall not require a correction.

7.

4.4

The vented material discharged from an enclosure during a deflagration shall be directed to a safe outsidelocation to avoid injury to personnel and to minimize property damage.

6

.8.)

7.4.5 *

If it is necessary to locate enclosures that need deflagration venting inside buildings, vents shall notdischarge within the building

* Fireball Dimensions .

7.

4.5.1 *

Vent ducts shall be used to direct vented material from the enclosure to the outdoors.

7.7.1

The hazard

7.4.6

*

A vent duct shall have a cross section at least as great as that of the vent itself.

7.4.7 *

Vent ducts shall be as straight as possible.



Page 30 of 187

7.4.7.1

If bends are unavoidable, they shall be as shallow-angled as practical (that is, they shall have as long aradius as practical).

7.4.8

Where vent ducts vent through the roof of an enclosure, consideration shall be given to climatic conditions.(See Section 6.5 .)

7.5 Effects of Initial Elevated Pressure.

7.5.1

For calculations that involve elevated pressure, the procedure in 7.5.1.1 and 7.5.1.2 shall be used.

7.5.1.1 *

The value that is used for P 0 shall be chosen to represent the likely maximum pressure at which a

flammable gas mixture can exist at the time of ignition. It shall be permitted to be as low as the normaloperating pressure.

7.5.1.2 *

The enclosure shall be located to accommodate the blast wave.

7.6 Vent Design.

See also Sections 6.5 through 6.7 .

7.6.1

If an enclosure is subdivided into compartments by walls, partitions, floors, or ceilings, each compartmentthat contains an explosion hazard shall be provided with its own vent.

7.6.2 *

Each closure shall be designed and installed to move freely without interference by obstructions such asductwork or piping.

7.6.3 *

Guarding shall be provided to prevent personnel from falling against vent closures.

7.6.4 *

The vent area for a building shall be distributed as evenly as possible over the building’s skin.

7.6.5

Vent closures shall open dependably.

7.6.5.1

The proper operation of vent closures shall not be hindered by deposits of snow, ice, paint, stickymaterials, or polymers.

7.6.5.2

Operation of vent closures shall not be prevented by corrosion or by objects that obstruct the opening ofthe vent closure, such as piping, air-conditioning ducts, or structural steel.

7.6.5.3

Vent closures shall withstand exposure to the materials and process conditions within the enclosure that isbeing protected.

7.6.5.4

Vent closures shall reliably withstand fluctuating pressure differentials that are below the design releasepressure and shall also withstand any vibration or other mechanical forces to which they can be subjected.

7.6.6

When multiple vents are provided, the vent area shall be distributed symmetrically and evenly on theenclosure external surfaces.

7.7 * Fireball Dimensions.



Page 31 of 187

.1

The hazard zone from a vented gas deflagration shall be calculated by the following equation:

http://submittals.nfpa.org:80/TerraView/Content/68-2013.ditamap/2/E68-29.jpg [7.7.1]

where:

D = axial distance (front-centerline) from vent (m)

V = volume of vented enclosure (m 3 )

n = number of evenly distributed vents

7.

76 .

2 2

The hazard zone measured radially (to the sides, measured from the centerline of the vent) shall becalculated as 0.5 D .

7.

8 7 Deflagration Venting of Enclosures Interconnected with Pipelines.

For interconnected enclosures, explosion isolation or suppression shall be provided in accordance withNFPA 69, unless a documented risk assessment acceptable to the authority having jurisdictiondemonstrates that increased vent area prevents enclosure failure. (See A.8.12.2 .)

Additional Proposed Changes

File Name Description Approved

68-Chapter_7-First_Draft_-_Additional_Changes20161004.docm

68-Chapter_7-First_Draft_-_Additional_Changes20161004.pdf

Statement of Problem and Substantiation for Public Comment

The current chapter 7 organization results in confusion as to the applicability of certain adjustments and corrections, either to the low pressure gas equation, the high pressure gas equation or both. It is also not clear that it is permitted to use physical properties for the specific gas mixture, as opposed to typical properties for many combustible mixtures. Lastly, the constraints on vent duct configuration and design, other than the effect of duct length, are redundant to material in Chapter 6.

This proposed revision clarifies by order and numbering scheme the applicability of the various adjustments and corrections to required vent area, explicitly requires physical properties for the combustible gas mixture while permitting use of the typical properties, and removes redundant vent duct configuration and design requirements.

Related Public Comments for This Document

Related Comment Relationship

Public Comment No. 5-NFPA 68-2016 [Sections A.7.1.1, A.7.1.2, A.7.2.2.2, A.7.2.5,A.7.2.5.1, A...]

Related Item

Committee Input No. 21-NFPA 68-2016 [Chapter 7]

Submitter Information Verification



Page 32 of 187

Submitter Full Name: Samuel Rodgers

Organization: Honeywell, Inc.

Street Address:

City:

State:

Zip:

Submittal Date: Wed Nov 16 13:27:11 EST 2016



Page 33 of 187

Chapter 7 Venting Deflagrations of Gas Mixtures and Mists

7.1 Introduction.

7.1.1*

This chapter shall apply to the design of deflagration vents for enclosures that contain a flammable gas or combustible mist and that have an L/D of ≤5.

7.1.1.1

This chapter shall be used in conjunction with the information contained in the rest of this standard.

7.1.1.2

Chapter 6 and 3.3.31.1 shall be reviewed before determining the value of Pred to be used using in tthis chapter.

7.1.2* The design of a deflagration vent for an enclosure containing a combustible mist shall be based on a value of Su equal to 0.46 m/s unless a value of Su applicable to the mist of a particular substance is determined by test.

Global FR-30 7.2 Venting by Means of Low Inertia Vent Closures. 7.2.1 Low Inertia Vent Closure Equations for Low Pred When Pred ≤ 0.5 bar-g, the minimum required vent area, Av0, shall be determined by Equation 7.2.1a and Equation 7.2.1b:

[7.2.1a]

[7.2.1b] where:

Av0 = the vent area calculated from Equation 7.2.1a (m2)

As = the enclosure internal surface area (m2)determined according to 7.2.5 (m2)

Pred = the maximum pressure developed in a vented enclosure during a vented deflagration (bar-g)

Su = fundamental burning velocity of gas-air mixture (m/s)

ρu = mass density of unburned gas-air mixture (kg/m3) = 1.2 for flammable gases with stoichiometric concentrations less than 5 vol%, and an initial temperature of 20°C

λ = ratio of gas-air mixture burning velocity accounting for turbulence and flame instabilities in vented deflagration to the fundamental (laminar) burning velocity, determined according to 7.2.6

Formatted: Font: Bold

Formatted: Font: Bold, Subscript


Page 34 of 187

Gu = unburned gas-air mixture sonic flow mass flux = 230.1 (kg/m2-s) for an enclosure initial temperature of 20°C

Cd = vent flow discharge coefficient, determined according to 7.2.4

Pmax = the maximum pressure developed in a contained deflagration by ignition of the same gas-air mixture (bar-g)


γ b = ratio of specific heats for burned gas-air mixture = 1.1 to 1.2, depending on the gas mixture

7.2.1.1 The C value for flammable gases and vapors with a Pmax value less than 9 bar-g and a stoichiometric (near worst case) fuel concentration no greater than about 10 percent shall be permitted to be calculated using Equation 7.2.1.1 for use in Equation 7.2.1a:

[7.2.1.1] 7.2.1.2 When applying Equation 7.2.1a, tThe value of Pstat shall be less than Pred as specified for the following conditions: (1) For Pred ≤ 0.1 bar-g (1.5 psig), Pstat ≤ Pred - 0.024 bar-g (50 psf). (2) For Pred > 0.1 bar-g (1.5 psig), Pstat < 0.75 Pred. 7.2.2 Low Inertia Vent Closure Equations for High Pred When Pred > 0.5 bar-g, the minimum required vent area, Av0, shall be determined from Equation 7.2.2a and Equation 7.2.2b:

[7.2.2a]

[7.2.2b] where:

Av0 = the vent area calculated from Equation 7.2.2a (m2)

As = the enclosure internal surface area determined according to 7.2.5, (m2)


Formatted: Subscript


Page 35 of 187


ρu = mass density of unburned gas-air mixture (kg/m3)

λ = ratio of gas-air mixture burning velocity accounting for turbulence and flame instabilities in vented deflagration to the fundamental (laminar) burning velocity, determined according to 7.2.6

Gu = unburned gas-air mixture sonic flow mass flux (kg/m2-s)

Cd = vent flow discharge coefficient, determined according to 7.2.4

Pmax = the maximum pressure developed in a contained deflagration by ignition of the same gas-air mixture (bar-g)



Pstat = nominal vent deployment or burst pressure (bar-g)

7.2.2.1 The internal surface area, As, in Equation 7.2.2a shall be determined according to 7.2.5. 7.2.2.27.2.3** Gas-Air Mixture Parameters 7.2.3.1* 7.1.2* The design of a deflagration vent for an enclosure containing a combustible mist shall be based on a value of Su equal to 0.46 m/s unless a value of Su applicable to the mist of a particular substance is determined by test. 7.2.3.2* The burning velocity, Su, shall be the maximum value for any gas concentration unless a documented hazard analysis shows that there is not a sufficient amount of gas to develop such a concentration. 7.2.3.3 It shall be permitted to assume a mass density of unburned gas-air mixture, u, equal to 1.2 kg/m3 for flammable gases with stoichiometric concentrations less than 5 vol% and initially at ambient temperature

7.2.3.4

It shall be permitted to assume an unburned gas-air mixture sonic flow mass flux, Gu, equal to 230.1 kg/m2-s for an enclosure initially at ambient temperatures

7.2.3.5 It shall be permitted to assume the ratio of specific heats for burned gas-air mixture, b , equal to 1.15 for flammable gases with stoichiometric concentrations less than 5 vol% and initially at ambient temperatures 7.2.3.6 It shall be permitted to assume the unburned gas-air mixture dynamic velocity, u, equal to 1.8 × 10-5 kg/m-s for flammable gases with stoichiometric concentrations less than 5 vol% and initially at ambient temperatures 7.2.3.7

Formatted: Indent: Left: 0"

Formatted: Font: Symbol, 11 pt








Page 36 of 187

It shall be permitted to assume the unburned gas-air mixture sound speed, au, equal to 343 m/s for flammable gases with stoichiometric concentrations less than 5 vol% and initially at ambient temperatures

7.2.2.3 7.2.4 Enclosure Parameters 7.2.4.1 The value of Cd shall be 0.70 unless the vent occupies an entire wall of the enclosure, in which case a value of 0.80 shall be permitted to be used. 7.2.4.2* Others The value of P0 shall be greater than or equal to the normal operating pressure and chosen to represent the likely maximum pressure at which a flammable gas mixture can exist at the time of ignition. 7.2.4.3* For initially elevated pressures, tThe enclosure shall be located to accommodate the blast wave. ? 7.2.3 The value of λ for the gas and particular enclosure shall be determined according to 7.2.6. 7.2.4 The L/D of the enclosure shall be determined according to Section 6.4. 7.2.5* Calculation of Internal Surface Area. 7.2.5.1* The internal surface area, As, shall include the total area that constitutes the perimeter surfaces of the enclosure that is being protected. 7.2.5.1.1 Nonstructural internal partitions that cannot withstand the expected pressure shall not be considered to be part of the enclosure surface area. 7.2.5.1.2 The enclosure internal surface area, AS, in Equation 7.2.2 includes the roof or ceiling, walls, floor, and vent area and shall be based on simple geometric figures. 7.2.5.1.3 Surface corrugations and minor deviations from the simplest shapes shall not be taken into account. 7.2.5.1.4 Regular geometric deviations, such as saw-toothed roofs, shall be permitted to be “averaged” by adding

the contributed volume to that of the major structure and calculating AS for the basic geometry of the major structure. 7.2.5.1.5* The internal surface of any adjoining rooms shall be included. 7.2.5.2 The surface area of equipment and contained structures shall be neglected. 7.2.6* Determination of Turbulent Flame Enhancement Factor, λ. 7.2.6.1 The baseline value, λ0, of λ shall be calculated from Equations 7.2.6.1a through 7.2.6.1f:



Page 37 of 187

[7.2.6.1a]

[7.2.6.1b]

[7.2.6.1c]

[7.2.6.1d]

[7.2.6.1e]

[7.2.6.1f] where:

ρu = mass density of unburned gas-air mixture (kg/m3) = 1.2 for flammable gases with stoichiometric concentrations less than 5 vol%, and an initial temperature of 20°C


Dhe = the enclosure hydraulic equivalent diameter as determined in Chapter 6 (m)

µu = the unburned gas-air mixture dynamic velocity = 1.8 × 10-5 (kg/m-s) for gas concentrations less than 5 vol% at ambient temperatures

β 1 = 1.23

β 2 = 2.37 × 10−3 m/s

Dv = the vent diameter as determined through iterative calculation (m)

uv = maximum velocity through vent (m/s)


au = the unburned gas-air mixture sound speed = 343 (m/s) for gas concentrations less than 5 vol% at ambient temperatures

θ = 0.39

7.2.6.2


Page 38 of 187

The total external surface area, Aobs, of the following equipment and internal structures that can be in the enclosure shall be estimated: (1) Piping, tubing, and conduit with diameters greater than 1⁄2 in. (2) Structural columns, beams, and joists (3) Stairways and railings (4) Equipment with a characteristic dimension in the range of 2 in. to 20 in. (5.1 cm to 51 cm) 7.2.6.3 When Aobs < 0.2AS, λ1 shall be equal to λ0 as determined in 7.2.6.1. 7.2.6.4 When Aobs > 0.2AS, λ1 shall be determined as follows:

𝜆1 = 𝑒𝑥𝑝 (√𝐴𝑜𝑏𝑠

𝐴𝑠− 0.2)

[7.2.6.4] 7.2.6.5

7.2.4 The L/D of the enclosure shall be determined according to Section 6.4.

7.2.6.5 6 For L/D values less than 2.5, λ shall be set equal to λ1.

Global FR-30 7.2.6.6 7 For L/D values from 2.5 to 5 and for Pred no higher than 2 bar-g, λ shall be calculated as follows:

[7.2.6.67] 7.2.6.7 8 Equations for determining λ shall be subject to the following limitations: (1) Su < 3 m/s (300 cm/s). (2) Pmax < 10 bar-g. (3) The maximum air velocity in the enclosure prior to ignition is no greater than 5 m/s. (4) The enclosure is isolated from possible flame jet ignition and pressures caused by a deflagration in an interconnected enclosure. 7.2.6.8 9 For long pipes or process ducts where L/D is greater than 5, the requirements of Chapter 9 shall be used. 7.2.6.9 10 Methods to Reduce Flame Enhancement. 7.2.6.910.1

Formatted: Underline

Formatted: Font: 14 pt









Page 39 of 187

The value of λ shall be permitted to be reduced for gas deflagrations in relatively unobstructed enclosures by the installation of noncombustible, acoustically absorbing wall linings, provided that large-scale test data confirm the reduction. 7.2.6.910.2 The tests shall be conducted with the highest anticipated turbulence levels and with the proposed wall lining material and thickness. 7.2.73 Partial Volume Effects. 7.2.73.1 When a documented hazard analysis demonstrates that there is insufficient gas in the enclosure to form a stoichiometric gas-air mixture occupying the entire enclosure volume, the vent area, Av0, calculated from Equation 7.2.1a or Equation 7.2.2a, as appropriate, shall be permitted to be reduced as described in 7.2.73.3. 7.2.73.2 A partial volume fill fraction, Xr, shall be calculated as follows:

[7.2.73.2] where:

Vgas = maximum volume of gas that can be mixed with air in the enclosure

Venc = enclosure volume

xst = stoichiometric volume concentration of gas

7.2.7.33.3 If Xr < 1, the minimum required vent area, Av1 shall be calculated from the following equation:

[7.2.73.3] where:

Av1 = vent area for partial volume deflagration

Av0 = vent area for full volume deflagration as determined from Equation 7.2.1a or 7.2.2a

Xr = fill fraction > Π

Π = Pred/Pmax

7.3.4

If Xr > 1, Av1 = Av0

7.3 4 Effects of Panel Inertia. 7.34.1* When the mass of the vent panel ≤ 40 kg/m2, Equation 7.34.2 shall be used to determine if an incremental increase in vent area is needed, and Equation 7.34.3 shall be used to determine the value of that increase.


Page 40 of 187

7.34.2 The vent area determined in 7.2.7 shall be adjusted for vent mass when the vent mass exceeds MT as calculated in Equation 7.3.2:

[7.34.2] where:

MT = threshold mass (kg/m2)


n = number of panels

V = enclosure volume (>1 m3)

7.34.3 For M > MT, the required vent area, Av2, shall be calculated as follows:

[7.34.3] where:

Av2 = vent area for panel inertia (m2)

M = mass of vent panel (kg/m2)

Av1 = vent area determined in 7.2.7 (m2)

FSH = 1 for translating panels or 1.1 for hinged panels

7.4.4

If M < MT, Av2 = Av1

7.45* Effects of Vent Ducts. 7.45.1* Where Equations 7.2.6, 7.2.6.4, 7.3.2, and 7.3.3 are used with vent ducting is used, a lower value, P’red, shall be used in place of the actual Pred in all equations in this chapter.. 7.45.2 Duct lengths shorter than 3 m (10 ft) and shorter than four duct hydraulic diameters in length shall be treated using Curve A in Figure 7.45.2. For ducts exceeding either of these limitations, Curve B shall be used. Figure 7.45.2 Maximum Pressure Developed During Venting of Gas, With and Without Vent Ducts.


Formatted: Superscript




Page 41 of 187

7.45.2.1 For vent ducts with lengths of less than 3 m (10 ft) and shorter than four duct hydraulic diameters, the following equation shall be permitted to be used to determine P′red:

[7.45.2.1] 7.45.2.2 For vent ducts with lengths of 3 m to 6 m (10 ft to 20 ft) or shorter vent ducts longer than four duct hydraulic diameters, the following equation shall be permitted to be used to determine P′red:

[7.45.2.2] 7.45.3* Duct lengths shorter than 3 m (10 ft) shall be treated as 3 m (10 ft) in length for calculation purposes. 7.45.3.1 If longer ducts are needed, P′red shall be determined by appropriate tests. 7.45.3.2


Page 42 of 187

Vent ducts and nozzles with total lengths of less than one hydraulic diameter shall not require a correction. 7.45.4 The vented material discharged from an enclosure during a deflagration shall be directed to a safe outside location to avoid injury to personnel and to minimize property damage. (See Section 6.8.) 7.45.5* If it is necessary to locate enclosures that need deflagration venting inside buildings, vents shall not discharge within the building. 7.45.5.1* Vent ducts shall be used to direct vented material from the enclosure to the outdoors. 7.45.6* A vent duct shall have a cross section at least as great as that of the vent itself. 7.45.7* Vent ducts shall be as straight as possible. 7.45.7.1 If bends are unavoidable, they shall be as shallow-angled as practical (that is, they shall have as long a radius as practical). 7.45.8 Where vent ducts vent through the roof of an enclosure, consideration shall be given to climatic conditions. (See Section 6.5.) 7.5 6 Effects of Initial Elevated Pressure. 7.56.1* For calculations that involve elevated pressure, Tthe value that is used for P0 shall be chosen to represent the likely maximum pressure at which a flammable gas mixture can exist at the time of ignition. the procedure in 7.5.1.1 and 7.5.1.2 shall be used. 7.56.1.1* The value that is used for P0 shall be chosen to represent the likely maximum pressure at which a flammable gas mixture can exist at the time of ignition. P0 It shall be permitted to be as low as the normal operating pressure. 7.56.1.2* The enclosure shall be located to accommodate the blast wave. 7.6 7 Vent Design. See also Sections 6.5 through 6.7. 7.67.1 If an enclosure is subdivided into compartments by walls, partitions, floors, or ceilings, each compartment that contains an explosion hazard shall be provided with its own vent. 7.67.2* Each closure shall be designed and installed to move freely without interference by obstructions such as ductwork or piping. 7.67.3* Guarding shall be provided to prevent personnel from falling against vent closures. 7.67.4*


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The vent area for a building shall be distributed as evenly as possible over the building’s skin. 7.67.5 Vent closures shall open dependably. 7.67.5.1 The proper operation of vent closures shall not be hindered by deposits of snow, ice, paint, sticky materials, or polymers. 7.67.5.2 Operation of vent closures shall not be prevented by corrosion or by objects that obstruct the opening of the vent closure, such as piping, air-conditioning ducts, or structural steel. 7.67.5.3 Vent closures shall withstand exposure to the materials and process conditions within the enclosure that is being protected. 7.67.5.4 Vent closures shall reliably withstand fluctuating pressure differentials that are below the design release pressure and shall also withstand any vibration or other mechanical forces to which they can be subjected. 7.67.6 When multiple vents are provided, the vent area shall be distributed symmetrically and evenly on the enclosure external surfaces. 7.786* Fireball Dimensions. 7.786.1 The hazard zone from a vented gas deflagration shall be calculated by the following equation:

[7.7.1] where:

D = axial distance (front-centerline) from vent (m)

V = volume of vented enclosure (m3)

n = number of evenly distributed vents

7.786.2 The hazard zone measured radially (to the sides, measured from the centerline of the vent) shall be calculated as 0.5D. 7.8 97 Deflagration Venting of Enclosures Interconnected with Pipelines. For interconnected enclosures, explosion isolation or suppression shall be provided in accordance with NFPA 69, unless a documented risk assessment acceptable to the authority having jurisdiction demonstrates that increased vent area prevents enclosure failure. (See A.8.12.2.)


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Public Comment No. 2-NFPA 68-2016 [ Section No. 8.1.1.4 ]

8.1.1.4

The general flowchart given in Figure 8.1.1.4 shall be used to select applicable vent sizing methods.

Figure 8.1.1.4 Dust Explosion Vent Sizing Calculation Flowchart. The flowchart is verymisleading. It appears that you are done with the vent sizing calculations if Pinitial is higher than0.2 barg and any panel mass used is fine.


The flowchart seems incomplete and misleading. See text above. The order of the flowchart should be the same as the order of the equations in the body of the document.

Related Item

First Revision No. 31-NFPA 68-2016 [Sections 8.1, 8.2, 8.3, 8.4]



Page 45 of 187


Submitter Full Name: James Koch

Organization: The Dow Chemical Company

Affilliation: The American Chemistry Council

Street Address:

City:

State:

Zip:

Submittal Date: Thu Nov 03 13:31:09 EDT 2016



Page 46 of 187


8.2.3.2*

When enclosure pressure is initially > 0.2 bar-g (20 kPa) or < −0.2 bar-g (−20 kPa) , Avep/Av 0 shall be

determined from the following equation:

[8.2.3.2]

INSERT A COEFFICIENT 1.2 AFTER THE EQUAL SIGN AND BEFORE Av1.

where:

Avep = vent area (m2)

A v1 = vent area as calculated by 8.2.2.2 or Equation 8.2.2.3

Pstat = static burst pressure of the vent (bar-g)

Pinitial = enclosure pressure at moment of ignition (bar-g)

Peffective = 1/3 Pinitial (bar-g)

Πeffective = (Pred − Peffective )/(PE max − Peffective )

Pred = reduced pressure

PE max = [(Pmax + 1) · (Pinitial + 1)/(1 bar-abs) − 1] maximum pressure of the unvented deflagration

at pressure (bar-g)

Pmax = maximum pressure of an unvented deflagration initially at atmospheric pressure (bar-g)

NOTE: Consider adding a multiplier in front of Equation 8.2.3.2. The present form generally underpredictsthe limited data available. Furthermore, the Committee was unable to find data to validate the equation forignition at subatmospheric pressure. We are awaiting additional data from Dr. Alfert, and will revisit theequation when data become available.



Hi-P_Worked_out_example.pdf


This equation has been developed using very few data points. Yet, the present form of the equation generally underpredicts the limited data available. Committee is unaware of data for subatmospheric ignition.

Related Item

Public Input No. 8-NFPA 68-2015 [Section No. 8.4.1]


Submitter Full Name: Erdem Ural

Organization: Loss Prevention Science and Technologies, Inc.



Page 47 of 187

Street Address:

City:

State:

Zip:




Page 48 of 187

REPLACE A8.4.1 WITH THE FOLLOWING: A8.4.1 Worked out example: Consider a 10 m3 spherical enclosure, which can take a Pred of up to 5 bars. It will be operated at the initial pressure of 2 bars. Dust testing produced Pmax of 8.5 bars, and Kst of 290 bar-m/s at initially atmospheric conditions. Enclosure will be protected by a deflagration vent with a Pstat of 2.6 bar. Calculate the necessary vent area. Using eq. 8.2.2, Avo = 10^(-4) (1+1.54*2.6^(4/3)) * 290 * 10^(3/4) * (8.5/5-1)^0.5 = 0.888 m2 Since the enclosure is spherical L/D = 1, and: Av1 = Avo = 0.888 m2 Peffective = 1/3 * 2 bar = 0.667 bar PmaxE = ((8.5 + 1) * (2 + 1)/1 – 1) = 27.5 bar Pi-effective = (5 – 0.667) / (27.5 – 0.667) = 0.161 Required minimum vent area (per eq. 8.4.1): Avep = 0.888 * (1 + 1.54 * ((2.6-2)/(1+0.667))^1.333)*(1/0.161-1)^0.5/(1+1.54*2^1.333)/(8.5/2.6-1)^0.5 = 0.518 m2 ADDITIONAL RECOMMENDATIONS:

1) ELIMINATE ALLOWANCE FOR L/D > 2. REASON: the form exponential in eq. 8.2.2, exp(-0.95*Pred^2) diminishes or eliminates the L/D effect for initially elevated pressure. The Committee has no data to substantiate any correction for L/D effect for initially elevated or reduced pressure. Alternatively, replace exp(-0.95*Pred^2) with exp(-0.95*(Pred/(1+Pinit))^2)

2) ELIMINATE THE USE OF 8.2.2 AND 8.2.3. Recast 8.4.1 as a standalone vent sizing equation for non-atmospheric initial pressure. 8.4.1 unnecessarily forces users to evaluate Av1 and

only to cancel each other out later. Furthermore, the square root in

produces imaginary numbers when Pred > Pmax, which can happen at elevated initial pressure.

3) Consider adding a multiplier in front of 8.4.1. The present form generally underpredicts the limited data available. We are awaiting additional data from Dr. Alfert.

4) The committee needs to revisit the degree of conservatism/non-conservatism expected from vent equations. In older editions, correlations were selected to envelope the data. The committee preparing the 2002 edition went through extensive philosophical debates and decided to provide a good representation of data, instead. The reason for this approach was that the committee felt test data (Kst for example) were obtained using worst case conditions, and that actual accidental explosions turn out to be much more timid. Over the last 15 years,


Page 49 of 187

committee composition changed significantly. It will be helpful for the current committee to revisit this fundamental question.


Page 50 of 187

Public Comment No. 10-NFPA 68-2016 [ Sections 8.2.3.3, 8.2.3.4 ]

Sections 8.2.3.3, 8.2.3.4

8.2.3.3 *

When enclosure pressure is initially < −0.2 bar-g, the vent area correction in Equation 8.2.3.2 shall beevaluated over the range between operating pressure and atmospheric pressure and the largest vent areacorrection applied.

8.2.3.4

When enclosure pressure is initially < −0.2 bar-g, it shall be permitted to use a value of 1.1 as the vent areacorrection for this section.


The use of the equation for subatmospheric ignition can not be substantiated because the Committee was unable to find data to validate the equation for ignition at subatmospheric pressure. We are awaiting additional data from Dr. Alfert, and will revisit the equation when data become available.

Related Item





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Page 51 of 187


8.2.3.5

When enclosure pressure is initially > 0.2 bar-g, deflagration vents shall be permitted only when thefollowing conditions are met:

(1) Enclosure L/D ≤ 2

(2) Vent duct length L/D ≤ 1

(3) Panel density M ≤ MT and ≤ 40 kg/m2

(4) vaxial and vtan < 20 m/s

(5) No allowance for partial volume

(6) Equation 8.2.3.2 used to calculate the necessary vent area adjustment

Note: 1) ELIMINATE ALLOWANCE FOR L/D > 2. REASON: the form exponential in eq. 8.2.2,exp(-0.95*Pred^2) diminishes or eliminates the L/D effect for initially elevated pressure. The Committee hasno data to substantiate any correction for L/D effect for initially elevated or reduced pressure. Alternatively,replace exp(-0.95*Pred^2) with exp(-0.95*(Pred/(1 Pinit))^2)


Note: 1) ELIMINATE ALLOWANCE FOR L/D > 2. REASON: the form exponential in eq. 8.2.2, exp(-0.95*Pred^2) diminishes or eliminates the L/D effect for initially elevated pressure. The Committee has no data to substantiate any correction for L/D effect for initially elevated or reduced pressure. Alternatively, replace exp(-0.95*Pred^2) with exp(-0.95*(Pred/(1 Pinit))^2)

Related Item





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City:

State:

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Public Comment No. 11-NFPA 68-2016 [ Section No. 8.7.1 ]

8.7.1*

It shall be permitted to remove the volume occupied by the filter elements, provided the filter elementswould If the vent closure is separated from the filters such that the filters do not obstruct the free vent flowof hot gases, unburned material, and flame during a deflagration. Methods for achieving this objective shallinclude but not be limited to the following:

Shortening or removing a row of filters nearest the vent closure such that the area normal to andbetween the filters and the vent closure equals or exceeds the vent closure area. In this case, a restrainingbar shall be installed to hold back the filters to prevent them from being deflected toward and obstructingthe free flow of hot gases, unburned material, or flame through the vent during a deflagration path, thevolume used in Equation 8.2.1.1 shall be the collector volume on the dirty side of the filters. This isapplicable for vertical filters when the vent closure is entirely below the bottom of the filters. It is applicablefor horizontal filter cartridges when the vent closure is located beyond the free end of the filter cartridges .


The existing language is too complicated and the suggested ways of removing and restraining filters near the vent are now known not to produce the desired effect of allowing unobstructed venting and a corresponding lower value of Pred.

Related Item

Public Input No. 15-NFPA 68-2015 [Section No. 8.7]



Submitter Full Name: Robert Zalosh

Organization: Firexplo

Street Address:

City:

State:

Zip:


* Separating the vent closure from the filters, usually by locating the vent closure below the filters forstandard vertical filters, but other configurations include, for example, horizontal cartridges and pleated flatpanel filters, which could have side or top venting. If this methodology is used, the principle of separationof vent closure from filters shall be maintained regardless of filter design and orientation.

*



Page 53 of 187


8.7.3*

Where the requirements of 8.7. 1 are not met, the total dirty volume of the enclosure on the dirty side ofthe tube sheet, including the volume occupied by the filters, shall be calculated. 3.1 When the vent closureobstructs the vent flow from the filtered section of the collector by being entirely above the bottom ofvertical filters, or entirely within the projected length of horizontal filters, the entire volume of the collector,including the clean side, shall be used in Equation 8.2.1.1.

8.7.3.2 When the vent closure partially obstructs the vent flow from the filtered section of the collector, thevolume used in Equation 8.2 shall be dirty side volume plus the clean side volume multiplied by the fractionof the vent closure area located in the filtered section of the collector, i.e. in the vent flow path from thefiltered area.


The existing section is inconsistent with test data. The revised section allows for a common situation in which there is partial blockage of the vent flow. It is an interpolation of test data for vent locations that are entirely unobstructed, and are entirely obstructed.

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Page 54 of 187


8.7.3 * Where the requirements of 8.7.1 are not met,

the total dirty volume of the enclosure on the dirty side of the tube sheet, including the volume occupied bythe filters, shall be calculated

full scale tes ng is required to verify the design .


There is no test data or theoretical analysis to support the calculation procedure in the current text. Those who have data for a particular case can supply that to the committee for evaluation and possible addition to 68.



Public Comment No. 16-NFPA 68-2016 [Section No. A.8.7.3]

Related Item

Public Input No. 1-NFPA 68-2015 [Chapter 2]


Submitter Full Name: Mitchel Rooker

Organization: Bsb Safety Systems Llc

Street Address:

City:

State:

Zip:

Submittal Date: Thu Nov 17 09:43:28 EST 2016



Page 55 of 187


8.9.5

Equation 8.9.2, Equation 8.9.3, and Equation 8.9.4 shall be valid for the following conditions:

(1) Enclosure volume: 0.3 m3 ≤ V ≤ 10,000 m3

(2) Reduced pressure: Pred ≤ 1 bar-g

(3) Static activation pressure: Pstat ≤ 0.1 bar-g

(4) Deflagration index: KSt ≤ 200 bar-m/s

(5) Pmax ≤ 9 bar-g


The committee needs to address the constraints given for the fireball length equation. We are required to limit access to the hazard area, but the equation is extremely limited in applicability. There are many industrial examples (Kst >200) that cannot use the equation given. How do we determine the hazard area when we are outside these constraints?

Related Item

First Revision No. 30-NFPA 68-2016 [Global Input]





Street Address:

City:

State:

Zip:

Submittal Date: Thu Nov 03 14:29:12 EDT 2016



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Public Comment No. 5-NFPA 68-2016 [ Sections A.7.1.1, A.7.1.2, A.7.2.2.2, A.7.2.5,

A.7.2.5.1, A... ]



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SectionsA.7.1.

1, A.7.1.2, A.7.2.2.2, A.7.2.5, A.7.2.5.1, A.7.2.5.1.5, A.7.2.6, A.7.3.1, A.7.4, A.7.4.1, A.7.4.3, A.7.4.5, A.7.4.5.1

A.7.1.1

1

Examples of enclosures include a room, building, vessel, silo, bin, pipe, or duct [A3.3.7]. The highpressure equation is not likely to be applicable to buildings since P red is greater than 0.5 bar (7.2 psi).

The user is cautioned that fast-burning gas deflagrations can readily undergo transition to detonation.NFPA 69 provides alternative measures that should be used.

A.7.

1.2

2.3

Gas-air mixture parameters depend on the properties of the fuel component(s) as well as the temperatureand pressure of the enclosure prior to ignition. Thermodynamics programs can be used to determine thenecessary mixture parameters. These include Gaseq (http://www.gaseq.co.uk/), Chemical Equilibriumwith Applications (http://www.grc.nasa.gov/WWW/CEAWeb/ceaHome.htm) , and STANJAN(http://navier.engr.colostate.edu/~dandy/code/code-4/)

A.7.2.3.1

The following information is offered to aid the user in determining an appropriate burning velocity to usewhen dealing with aerosols (mists).

The burning velocity of aerosols varies according to the fuel-to-air ratio, droplet diameter, and vaporfuel–to–total fuel ratio (Ω), as illustrated in Figure A.7. 2.3. 1

.2

(a) . The burning velocity ratio is the ratio of the mist fundamental burning velocity to that of the pure vapor.The effect of increased burning velocity in the range of 5 μm to 35 μm is believed to be evident primarily influids of relatively low volatility, such as heat transfer fluids, that can be released above their atmosphericboiling point. In those circumstances, they can form an aerosol consisting of very small droplets that canfall into the 5 to 35 μm range.

The general effect of burning velocity on liquid mists released below their flash points in the order of 50 μmas compared with dusts of similar particle size and vapors is shown in Figure A.7. 2.3. 1

.2

(b) .

Figure A.7. 2.3. 1

.2

(a) Burning Velocity Predictions Versus Aerosol Droplet Size at Different Values of Ω.



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Figure A.7. 2.3. 1

.2

(b) Burning Velocity of Mixtures of Air with Flammable Vapors, Aerosols, or Dusts. (Reprinted fromLees, Lees Loss Prevention in the Process Industries .)


The dimensionless Spalding mass transfer number ( B ) is defined as follows:



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http://submittals.nfpa.org:80/TerraView/Content/68-2013.ditamap/2/E68-246.jpg [A.7. 2.3. 1

.2

]

where:

q st = mass ratio of fuel to air at stoichiometric concentration

H = heat of combustion

C pa = specific heat of air

T = temperature of the gas ( g ), boiling point of the fuel ( b ), surface temperature of the fuel ( s )

L = latent heat of vaporization

C p = specific heat of the fuel

At the time of this writing, the committee is unaware of any aerosol testing that has definitively correlateddeflagrations of small droplet diameter (0 to 30 μm) aerosols to vent area. This information is provided asa word of warning [117].

A.7.2.

2.2

3.2

Annex D lists values of S u for many gases and vapors.

A.7. 4. 2

.5

If pressure excursions are likely during operation, the value of P 0 can be the maximum pressure

excursion during operation or the pressure at the relief valve when in the fully open position.

A.7.4.3

Venting from enclosures at initially elevated pressures results in severe discharge conditions.

A.7.2.5

Following is a sample calculation of internal surface area:

Step 1. Consider the building illustrated in Figure A.7.2.5(a) , for which deflagration venting is needed.

Figure A.7.2.5(a) Building Used in Sample Calculation, Version I (Not to Scale).



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Step 2. Divide the building into sensible geometric parts (Parts 1 and 2) as shown in Figure A.7.2.5(b) .

Figure A.7.2.5(b) Building Used in Sample Calculation, Version II (Not to Scale).


Step 3. Calculate the total internal surface area in each part of the building.

Part 1 Surface Area ( A

S 1

S1 )

Floor =

51.8 m × 9.15 m = 474 m 2

.

(170 ft × 30 ft = 5100 ft 2 )

Roof =

51.8 m × 9.65 m = 499 m 2

.

(170 ft × 31.6 ft = 5372 ft 2 )

Rear wall =

51.8 m × 6.1 m = 316 m 2

.

(170 ft × 20 ft = 3400 ft 2 )

Front wall = (36.6 m × 9.15 m)

+

(15.25 m × 3.05 m) = 381 m 2

.

[(120 ft × 30 ft)

+



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(50 ft × 10 ft)] = 4100 ft 2

Side walls (rectangular part) =

2 × 9.15 m × 6.1 m = 111 m 2

.

(2 × 30 ft × 20 ft = 1200 ft 2 )

Side walls (triangular part) =

9.15 m × 3.05 m = 28 m 2

.

(30 ft × 10 ft = 300 ft 2 )

Total Part 1: A S 1 = 1809 m 2 (19,472 ft 2 )

Part 2 Surface Area (A S 2 )

Floor =

15.25 m × 9.15 m = 139 m 2

.

(50 ft × 30 ft = 1500 ft 2 )

Roof =

15.25 m × 9.15 m = 139 m 2

.

(50 ft × 30 ft = 1500 ft 2 )

Front wall =

15.25 m × 6.1 m = 93 m 2

.

(50 ft × 20 ft = 1000 ft 2 )

Side walls =

2 × 9.15 m × 6.1 m = 111 m 2

.

(2 × 30 ft × 20 ft = 1200 ft 2 )

Total Part 2: A S 2 = 483 m 2 (5200 ft 2 )

Step 4. Thus, the total internal surface area for the whole building, A S , is expressed as follows:

A S = 1809 m 2 (19,472 ft 2 )

+

483 m 2 (5200 ft 2 ) = 2292 m 2 (24,672 ft 2 )

A.7.2.5.

1

1

The calculated vent area can be reduced by the installation of a pressure-resistant wall to confine thedeflagration hazard area to a geometric configuration with a smaller internal surface area, A S .

A.7.2.5.1.



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5

5

Such rooms include adjoining rooms separated by a partition incapable of withstanding the expectedpressure.

A.7.2.

6

6

In many industrial enclosures, the gas phase is present in a turbulent condition. An example is thecontinuous feed of a flammable gas-oxidant mixture to a catalytic partial oxidation reactor. Normally thismixture enters the reactor head as a high-velocity turbulent flow through a pipe. As the gas enters thereactor head, still more turbulence develops due to the sudden enlargement of the flow cross section.Appurtenances within an enclosure enhance turbulence.

The susceptibility of a turbulent system to detonation increases with increasing values of the fundamentalburning velocity. In particular, compounds that have values close to that of hydrogen are highly susceptibleto detonation when ignited under turbulent conditions. It should be noted that venting tends to inhibit thetransition from deflagration to detonation, but it is not an effective method of protecting against the effectsof a detonation once the transition has occurred. Where the likelihood for detonation exists, alternativesolutions, such as those in NFPA 69 should be considered.

A.7.

3.1

4.1

Where M is greater than 40 kg/m 2 , it is necessary to perform testing or apply alternative explosionprotection methods per NFPA 69.

A.7.

4

5

The deflagration vent area requirement is increased where a vent discharge duct is used. Where adeflagration is vented through a vent duct, secondary deflagrations can occur in the duct, reducing thedifferential pressure available across the vent.

A.7.

4.1

The use of a vent duct with a cross section greater than that of the vent can result in a smaller increase inthe pressure that develops during venting, P red , than when a vent duct of an equivalent cross section is

used [93], but this effect is difficult to quantify because of limited test data.

Vent ducts should be as short and as straight as possible. Any bends can cause dramatic andunpredictable increases in the pressure that develops during venting.

5.1

It should be noted that P red is still the maximum pressure developed in a vented deflagration. P′ red is

not an actual pressure.

A.7.

4.3

5.3

Testing has been done with 3 m (10 ft) and 6 m (20 ft) duct lengths. The effect of ducts longer than 6 m(20 ft) has not been investigated.

A.7.

4.5

Flames and pressure waves that discharge from the enclosure during venting represent a threat topersonnel and could damage other equipment.



Page 63 of 187

A.7.4.5.1

If a vented enclosure is located within a building, it should be placed close to an exterior wall so that thevent ducts are as short as possible.

A.7.4.6

The use of a vent duct with a larger cross section than that of the vent can result in a smaller increase inthe pressure that develops during venting ( P red ) than when a vent duct of an equivalent cross section is

used [93], but this effect is difficult to quantify because of limited test data. A special requirement for ventduct cross sections in situations where the vent closure device is a hinged panel is discussed in A.6.7.4 .

A.7.4.7

In general, bends can cause increases in the pressure that develops during venting.

A.7.5.1.1

If pressure excursions are likely during operation, the value of P 0 can be the maximum pressure

excursion during operation or the pressure at the relief valve when in the fully open position.

A.7.5.1.2


A.7.6.2

Such a design ensures that the flow of combustion gases is not impeded by an obstructed closure.

A.7.6.3

A vent closure can open if personnel fall or lean on it.

A.7.6.4

Situations can arise in which the roof area or one or more of the wall areas cannot be used for vents, eitherbecause of the location of equipment or because of exposure to other buildings or to areas normallyoccupied by personnel.

A.7.7

The

6

The fireball from a vented gas or dust deflagration presents a hazard to personnel in the vicinity. Peoplecaught in the flame itself will be at obvious risk from burns, but those who are outside the flame area canbe at risk from thermal radiation effects. The heat flux produced by the fireball, the exposure time, and thedistance from the fireball are important variables to determine the hazard.

The number of vents, n , should be those vents whose discharge directions are separate and evenlydistributed around the circumference of a vessel or along the central axis. If multiple vent panels cover asingle vent opening, they should not be treated as separate for this purpose.



68-Chapter_7-Annex_A-First_Draft_-_Additional_Changes.docm

68-Chapter_7-Annex_A-First_Draft_-_Additional_Changes.pdf


The current arrangement of Chapter 7 produced some confusion as to applicability of certain adjustments and corrections. A proposal for reorganizing Chapter 7 was submitted. This submittal aligns the annex items.



Public Comment No. 4-NFPA 68-2016 [Chapter 7]

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Page 64 of 187

Committee Input No. 21-NFPA 68-2016 [Chapter 7]




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Page 65 of 187

Important Notice: The document has been provided in Microsoft Word format for the purpose of

NFPA 68 Task Group work. This document is the copyright property of the National Fire

Protection Association (NFPA), Copyright © 2016 NFPA, and may not be used for any other

purpose or distributed to any other persons or parties outside of the NFPA Task Group.

Annex A Explanatory Material

Annex A is not a part of the requirements of this NFPA document but is included for informational

purposes only. This annex contains explanatory material, numbered to correspond with the

applicable text paragraphs.

A.7.1.1

Examples of enclosures include a room, building, vessel, silo, bin, pipe, or duct [A3.3.7]. The high pressure equation is not likely to be applicable to buildings since Pred is greater than 0.5 bar (7.2 psi). The user is cautioned that fast-burning gas deflagrations can readily undergo transition to detonation. NFPA 69 provides alternative measures that should be used.

A.7.2.3

Gas-air mixture parameters depend on the properties of the fuel component(s) as well as the temperature and pressure of the enclosure prior to ignition. Thermodynamics programs can be used to determine the necessary mixture parameters. These include Gaseq (http://www.gaseq.co.uk/), Chemical Equilibrium with Applications (http://www.grc.nasa.gov/WWW/CEAWeb/ceaHome.htm) , and STANJAN (http://navier.engr.colostate.edu/~dandy/code/code-4/)

A.7.2.3.1

The following information is offered to aid the user in determining an appropriate burning velocity to use when dealing with aerosols (mists).

The burning velocity of aerosols varies according to the fuel-to-air ratio, droplet diameter, and vapor fuel–to–total fuel ratio (Ω), as illustrated in Figure A.7.2.3.1(a). The burning velocity ratio is the ratio of the mist fundamental burning velocity to that of the pure vapor. The effect of increased burning velocity in the range of 5 μm to 35 μm is believed to be evident primarily in fluids of relatively low

volatility, such as heat transfer fluids, that can be released above their atmospheric boiling point. In those circumstances, they can form an aerosol consisting of very small droplets that can fall into the 5 to 35 μm range.

The general effect of burning velocity on liquid mists released below their flash points in the order of 50 μm as compared with dusts of similar particle size and vapors is shown in Figure A.7.2.3.1(b).

Figure A.7.2.3.1(a) Burning Velocity Predictions Versus Aerosol Droplet Size at Different

Values of Ω.


Formatted: Font: Not Bold

Formatted: Font: Not Bold

Deleted: 1.2

Deleted: 1.2

Deleted: 1.2

Deleted: 1.2


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Figure A.7.2.3.1(b) Burning Velocity of Mixtures of Air with Flammable Vapors, Aerosols, or

Dusts. (Reprinted from Lees, Lees Loss Prevention in the Process Industries.)

Deleted: 1.2


Page 67 of 187





The dimensionless Spalding mass transfer number (B) is defined as follows:

[A.7.2.3.1]

where:

qst = mass ratio of fuel to air at stoichiometric concentration

H = heat of combustion

Cpa = specific heat of air

T = temperature of the gas (g), boiling point of the fuel (b), surface temperature of the fuel (s)

L = latent heat of vaporization

Cp = specific heat of the fuel

At the time of this writing, the committee is unaware of any aerosol testing that has definitively correlated deflagrations of small droplet diameter (0 to 30 μm) aerosols to vent area. This information is provided as a word of warning [117].

Deleted: 1.2


Page 68 of 187





A.7.2.3.2

Annex D lists values of Su for many gases and vapors.

A.7.4.2

If pressure excursions are likely during operation, the value of P0 can be the maximum pressure excursion during operation or the pressure at the relief valve when in the fully open position. A.7.4.3


A.7.2.5

Following is a sample calculation of internal surface area:

Step 1. Consider the building illustrated in Figure A.7.2.5(a), for which deflagration venting is needed.

Figure A.7.2.5(a) Building Used in Sample Calculation, Version I (Not to Scale).

Step 2. Divide the building into sensible geometric parts (Parts 1 and 2) as shown in Figure A.7.2.5(b).

Figure A.7.2.5(b) Building Used in Sample Calculation, Version II (Not to Scale).

Deleted: 2.2.2


Page 69 of 187





Step 3. Calculate the total internal surface area in each part of the building.

Part 1 Surface Area (AS1)

Floor = 51.8 m × 9.15 m = 474 m2 .

(170 ft × 30 ft = 5100 ft2)

Roof = 51.8 m × 9.65 m = 499 m2 .

(170 ft × 31.6 ft = 5372 ft2)

Rear wall = 51.8 m × 6.1 m = 316 m2 .

(170 ft × 20 ft = 3400 ft2)

Front wall = (36.6 m × 9.15 m) + (15.25 m × 3.05 m) = 381 m2 .

[(120 ft × 30 ft) + (50 ft × 10 ft)] = 4100 ft2

Side walls (rectangular part) = 2 × 9.15 m × 6.1 m = 111 m2 .

(2 × 30 ft × 20 ft = 1200 ft2)

Side walls (triangular part) = 9.15 m × 3.05 m = 28 m2 .

(30 ft × 10 ft = 300 ft2)

Total Part 1: AS1 = 1809 m2 (19,472 ft2)

Part 2 Surface Area(AS2)


Page 70 of 187





Floor = 15.25 m × 9.15 m = 139 m2 .

(50 ft × 30 ft = 1500 ft2)

Roof = 15.25 m × 9.15 m = 139 m2 .

(50 ft × 30 ft = 1500 ft2)

Front wall = 15.25 m × 6.1 m = 93 m2 .

(50 ft × 20 ft = 1000 ft2)

Side walls = 2 × 9.15 m × 6.1 m = 111 m2 .

(2 × 30 ft × 20 ft = 1200 ft2)

Total Part 2: AS2 = 483 m2 (5200 ft2)

Step 4. Thus, the total internal surface area for the whole building, AS, is expressed as follows:

AS = 1809 m2 (19,472 ft2) + 483 m2 (5200 ft2) = 2292 m2 (24,672 ft2)

A.7.2.5.1

The calculated vent area can be reduced by the installation of a pressure-resistant wall to confine the deflagration hazard area to a geometric configuration with a smaller internal surface area, AS.

A.7.2.5.1.5

Such rooms include adjoining rooms separated by a partition incapable of withstanding the expected pressure.

A.7.2.6

In many industrial enclosures, the gas phase is present in a turbulent condition. An example is the continuous feed of a flammable gas-oxidant mixture to a catalytic partial oxidation reactor. Normally this mixture enters the reactor head as a high-velocity turbulent flow through a pipe. As the gas enters the reactor head, still more turbulence develops due to the sudden enlargement of the flow cross section. Appurtenances within an enclosure enhance turbulence.

The susceptibility of a turbulent system to detonation increases with increasing values of the fundamental burning velocity. In particular, compounds that have values close to that of hydrogen are highly susceptible to detonation when ignited under turbulent conditions. It should be noted that venting tends to inhibit the transition from deflagration to detonation, but it is not an effective method of protecting against the effects of a detonation once the transition has occurred. Where the likelihood for detonation exists, alternative solutions, such as those in NFPA 69 should be considered.

A.7.4.1

Where M is greater than 40 kg/m2, it is necessary to perform testing or apply alternative explosion protection methods per NFPA 69.

A.7.5

Deleted: 3

Deleted: 4


Page 71 of 187





The deflagration vent area requirement is increased where a vent discharge duct is used. Where a deflagration is vented through a vent duct, secondary deflagrations can occur in the duct, reducing the differential pressure available across the vent.

A.7.5.1

It should be noted that Pred is still the maximum pressure developed in a vented deflagration. P′red is not an actual pressure.

A.7.5.3

Testing has been done with 3 m (10 ft) and 6 m (20 ft) duct lengths. The effect of ducts longer than 6 m (20 ft) has not been investigated.

A.7.6

The fireball from a vented gas or dust deflagration presents a hazard to personnel in the vicinity. People caught in the flame itself will be at obvious risk from burns, but those who are outside the flame area can be at risk from thermal radiation effects. The heat flux produced by the fireball, the exposure time, and the distance from the fireball are important variables to determine the hazard.

The number of vents, n, should be those vents whose discharge directions are separate and evenly distributed around the circumference of a vessel or along the central axis. If multiple vent panels cover a single vent opening, they should not be treated as separate for this purpose.

Deleted: 4

Deleted: The use of a vent duct with a cross section greater than that of the vent can result in a smaller increase in the pressure that develops during venting, Pred, than when a vent duct of an equivalent cross section is used [93], but this effect is difficult to quantify because of limited test data.¶Vent ducts should be as short and as straight as possible. Any bends can cause dramatic and unpredictable increases in the pressure that develops during venting.¶

Deleted: 4

Deleted: A.7.45.5 ¶Flames and pressure waves that discharge from the enclosure during venting represent a threat to personnel and could damage other equipment.¶A.7.45.5.1 ¶If a vented enclosure is located within a building, it should be placed close to an exterior wall so that the vent ducts are as short as possible.¶A.7.45.6 ¶The use of a vent duct with a larger cross section than that of the vent can result in a smaller increase in the pressure that develops during venting (Pred) than when a vent duct of an equivalent cross section is used [93], but this effect is difficult to quantify because of limited test data. A special requirement for vent duct cross sections in situations where the vent closure device is a hinged panel is discussed in A.6.7.4.¶A.7.45.7 ¶In general, bends can cause increases in the pressure that develops during venting.¶A.7.56.1.1 ¶If pressure excursions are likely during operation, the value of P0 can be the maximum pressure excursion during operation or the pressure at the relief valve when in the fully open position.¶A.7.56.1.2 ¶Venting from enclosures at initially elevated pressures results in severe discharge conditions.¶A.7.6.2 ¶Such a design ensures that the flow of combustion gases is not impeded by an obstructed closure.¶A.7.6.3 ¶A vent closure can open if personnel fall or lean on it.¶A.7.6.4 ¶Situations can arise in which the roof area or one or more of the wall areas cannot be used for vents, either because of the location of equipment or because of exposure to other buildings or to areas normally occupied by personnel.¶

Deleted: 7


Page 72 of 187

Public Comment No. 6-NFPA 68-2016 [ Section No. A.8.2.3.2 ]

A.8.2.3.2

There are no additional conditions on the use of Equation 8.2.3.2 when enclosure pressure is initially lessthan −0.2 bar-g.

REPLACE A8.2.3.2 WITH THE FOLLOWING:

A8.2.3.2 Worked out example:

Consider a 10 m3 spherical enclosure, which can take a Pred of up to 5 bars. It will be operated at the initialpressure of 2 bars. Dust testing produced Pmax of 8.5 bars, and Kst of 290 bar-m/s at initially atmosphericconditions. Enclosure will be protected by a deflagration vent with a Pstat of 2.6 bar. Calculate the necessaryvent area.

Using eq. 8.2.2,

Avo = 10^(-4) (1 1.54*2.6^(4/3)) * 290 * 10^(3/4) * (8.5/5-1)^0.5 = 0.888 m2

Since the enclosure is spherical L/D = 1, and:

Av1 = Avo = 0.888 m2

Peffective = 1/3 * 2 bar = 0.667 bar

PmaxE = ((8.5 1) * (2 1)/1 – 1) = 27.5 bar

Pi-effective = (5 – 0.667) / (27.5 – 0.667) = 0.161

Required minimum vent area (per eq. 8.4.1):

Avep = 0.888 * (1 1.54 * ((2.6-2)/(1 0.667))^1.333)*(1/0.161-1)^0.5/(1 1.54*2^1.333)/(8.5/2.6-1)^0.5 = 0.518m2


Providing a worked out example will be helpful to users.

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Public Comment No. 18-NFPA 68-2016 [ Section No. A.8.5 ]



Page 74 of 187

A.8.5



Page 75 of 187

The flow resistance coefficient K for the vent duct correlation is defined on the static pressure drop, ∆P,from the enclosure to the duct exit at a given average duct flow velocity, U:

[A.8.5a]

Another convention used by some reference books is to define K on the total pressure drop or on anothervelocity scale. The user should ensure that the loss coefficients used in the calculations are consistent withthe definition of K adopted for the vent duct calculations. See Ural [114] for additional information.

The user should note that inlet loss can vary depending on the shape of the vent closure inlet attachmentto the vessel ; however, most typically a flanged flush inlet would be appropriate. Figure A.8.5(a)

showsshow the loss coefficient for two different inlet designs as well as a plain duct outlet .

Figure A

Rain hats or other outlet covers provide additional resistance as in Figure A.8.5(d).

FIGURE A .8.5(a)

Loss

Loss Coefficients for Inlets

.

and Plain Duct Outlet

Figure A.8.5(b) shows a round elbow and loss coefficents for various radii of curvature. Figure A.8.5(c)shows a rectangular elbow and loss coefficients for various duct aspect ratios and radii of curvature. Losscoefficients for 45 degree bends and 30 degree bends are proportionally less than the tabulated 90 degreebends. Figure A.8.5(d) provides loss coefficients for a typical rain hat design.

Figure A.8.5(b) Loss Coefficients for Round Elbows.



Page 76 of 187

Figure A.8.5(c) Loss Coefficients for Square and Rectangular Elbows.

Figure A.8.5(d) Loss Coefficients for Rain Hats.

The equations are nonlinear and, under certain combinations of input values, result in two possiblesolutions for vent area for a given Pred . The lower value of vent area is the meaningful solution, and the

upper value is an artifact of the form of the equation set. There are certain combinations of Pred and vent

duct length where no vent area is large enough and no solution is obtainable. When that occurs, it could bepossible to vary Pred or vent duct length to converge to a solution. If that solution is not satisfactory, NFPA

69 can provide alternatives.

There is a minimum value for Pred as vent area increases, beyond which solutions are not meaningful.

That value occurs approximately when the volume of the duct exceeds a fraction of the volume of thevessel. When solving the equations, constraining Avf as follows will typically isolate the smaller root:

[A.8.5b]

For the following input values, Figure A.8.5(e) illustrates the potential solutions:

V = 500 m3

Pmax = 8.5 bar-g

KSt = 150 bar-m/s

Pstat = 0.05 bar-g

Pred = 0.5 bar-g

Vessel L/D = 4

ℇ ? = 0.26 mm

Straight duct, no elbows, fittings, or rain hats.

Figure A.8.5(e) Av vs. Duct Length.



Page 77 of 187

Example problem. Given Figure A.8.5(f) and the following conditions, calculate Pred :

Figure A.8.5(f) Example Vent Duct Installation.

Enclosure volume, V = 25 (m3)

Enclosure L/D = 4

Vent diameter, Dv = 1.5 (m)

Duct diameter, Dh = 1.5 (m)

Av = 1.77 (m2)

Pstat = 0.25 (bar-g)

KSt = 200 (bar-m/s)

Pmax = 8 (bar-g)

Duct length = 12 (m)

Duct effective roughness, ℇ ? = 0.26 (mm)

Elbows = 2 × 90 degrees , long radius (R/D=1.5)



Page 78 of 187

Elbow flow resistance = 2 ×

10 .

239 =

2.40.78 (see Figure A.8.5(b))

Rain hat flow resistance = 0.

7573 (H=0.5D, see Figure A.8.5(d))

While Section 8.5 provides the equations in a form to calculate the vent area based on an allowable Pred ,

this example shows how to determine the resulting Pred for a given vent area. In general, such calculations

will be iterative. These input parameters are provided for demonstration purposes. Ural [114] can bereferenced for additional discussion on how they were selected.

Solution:

(1) Compute the friction factor for the problem. For practically all vent ducts, the Reynolds number is solarge that a fully turbulent flow regime will be applicable. In this regime, the friction factor is only afunction of the ratio of the internal duct surface effective roughness (ℇ ? ) to duct diameter. The ductfriction factor can thus be calculated using a simplified form of the Colebrook equation:

[A.8.5c]

The effective roughness for smooth pipes and clean steel pipes is typically 0.0015 mm and 0.046 mm,respectively. Recognizing that the pipes used repeatedly in combustion events could be corroded, avalue of ℇ ? = 0.26 mm is assumed.

From Equation A.8.5c, fD = 0.013:

[A.8.5d]

K= 1.5 0.107 0.78 0.73

where: K

=

4

3 .



Page 79 of 187

757

117

K inlet

=

1.5 (static pressure loss for flush duct entry, see Figure A.8.5(a))

K elbows

=

2

0 .

4

78

K exit

=

0.

75

73

(2) Assume a Pred value of 1 bar-g. The solution is iterative, where the assumed value of Pred is

replaced with the calculated value of Pred until the two values substantially match. A 1 percent

difference between iterations is typically considered acceptable convergence.

(3) From Equation 8.2.1.1:

[A.8.5e]

(4) From Equation 8.2.2.3:

[A.8.5f]

(5) From Equation 8.5.1d, and using the intended vent area of 1.77 m2:

[A.8.5g]

(6) From Equation 8.5.1e, and using the installed vent area of 1.77 m2:

[A.8.5h]

(7) From Equation 8.5.1c, with A v4 equal to A v1, assuming no increase for turbulence, inertia, or partial

volume:



Page 80 of 187

(A.8.5g)

[A.8.5i]

(8) Because the calculated value of A vf is not equal to the installed vent area, go back to Step 2, and

change P red until the A vf calculated in Step 7 is equal to the specified vent area of 1.77 m2. A trial-

and-error process (or the goal seek button in Excel) satisfies the requirement in Step 8 when Pred =

3.52 bar 2.72 bar -g.

(9) From 8.5.9, Equation A.8.5j and Equation A.8.5k show that there is no deflagration-to-detonation-transition (DDT) propensity for this particular application:

[A.8.5j]

[

( A.8.

5k]5i)

Because Lduct = 12 m, Leff = min [12, 63 75 ] = 12 m ≤ 55 m. Therefore, DDT is not expected.



Updated_Section_8.5_Annex.docx

Figure_A_8_5_a_Rev1.ppt


The current Figure A.8.5(a) shows the velocity head loss for duct entrances, not the static pressure loss, and the lack of a plain end discharge in the figure makes it confusing to users as to which convention is being applied. Other corrections are to show long radius elbows in the example problem, consistent with Chapter 6 requirements. The change to long radius elbows results in a reduction in the iterated Pred, as would be expected.

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Public Input No. 11-NFPA 68-2015 [Section No. A.8.5]






Page 81 of 187

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Page 82 of 187

Updated Section A.8.5 [note to editor – update text introducing Figure A.8.5(a) as well as the figure to show 2 and 1.5 for duct inlet K-factors as opposed to 0.93 and 0.49, respectively. This is to modify the values to reflect K based on static pressure drop.] [Existing introducing text and Figure A.8.5(a) to be replaced]

The user should note that inlet loss can vary depending on the shape of the vent closure inlet attachment to the vessel; however, most typically a flanged flush inlet would be appropriate. Figure A.8.5(a) show the loss coefficient for two different inlet designs as well as a plain duct outlet. Rain hats or other outlet covers provide additional resistance as in Figure A.8.5(d).


Page 83 of 187

FIGURE A.8.5(a) Loss Coefficients for Inlets and Plain Duct Outlet [Note to editor – update Figure A.8.5(f) to show longer radius elbows, not short radius] Example problem. Given Figure A.8.5(f) and the following conditions, calculate Pred: Enclosure volume, V = 25 (m3) Enclosure L/D = 4 Vent diameter, Dv = 1.5 (m) Duct diameter, Dh = 1.5 (m) Av = 1.77 (m2) Pstat = 0.25 (bar-g) KSt = 200 (bar-m/s) Pmax = 8 (bar) Duct length = 12 (m) Duct effective roughness, = 0.26 (mm) Elbows = 2 × 90 degrees, long radius (R/D=1.5) Elbow flow resistance = 2 × 0.39 = 0.78 (see Figure A.8.5(b)) Rain hat flow resistance = 0.73 (H=0.5D, see Figure A.8.5(d)) While Section 8.5 provides the equations in a form to calculate the vent area based on an allowable Pred , this example shows how to determine the resulting Pred for a given vent area. In general, such calculations will be iterative. These input parameters are provided for demonstration purposes. Ural [114] can be referenced for additional discussion on how they were selected. Solution: (1) Compute the friction factor for the problem. For practically all vent ducts, the Reynolds number is so large that a fully turbulent flow regime will be applicable. In this regime, the friction factor is only a function of the ratio of the internal duct surface effective roughness () to duct diameter. The duct friction factor can thus be calculated using a simplified form of the Colebrook equation:

The effective roughness for smooth pipes and clean steel pipes is typically 0.0015 mm and 0.046 mm, respectively. Recognizing that the pipes used repeatedly in combustion


Page 84 of 187

events could be corroded, a value of = 0.26 mm is assumed. From Equation A.8.5a, fD = 0.013:

K= 1.5 + 0.107 + 0.78 + 0.73 where: K = 3.117 Kinlet = 1.5 (static pressure loss for flush duct entry, see Figure A.8.5(a)) Kelbows = 0.78 Kexit = 0.73 (2) Assume a Pred value of 1 bar-g. The solution is iterative, where the assumed value of Pred is replaced with the calculated value of Pred until the two values substantially match. A 1 percent difference between iterations is typically considered acceptable convergence. (3) From Equation 8.2.2:

(4) From Equation 8.2.3:

(5) From Equation 8.5.1(b), and using the intended vent area of 1.77 m2:

(6) From Equation 8.5.1(c), and using the installed vent area of 1.77 m2:


Page 85 of 187

(7) From Equation 8.5.1(a), with Av4 equal to Av1, assuming no increase for turbulence, inertia, or partial volume:

A 1.02 ∙ 1 1.18∙ 0.85 . ∙ 6.37 . ∙ .

. (A.8.5g)

A 4.67m (8) Because the calculated value of Avf is not equal to the installed vent area, go back to Step 2, and change Pred

until the Avf calculated in Step 7 is equal to the specified vent area of 1.77 m2. A trial-and-error process (or the goal seek button in Excel) satisfies the requirement in Step 8 when Pred = 2.72 bar-g. (9) From 8.5.9, Equation A.8.5h and Equation A.8.5i show that there is no deflagration-to-detonation-transition (DDT) propensity for this particular application:

L 8-2.723 ∙

. (A.8.5i)

74.5m Because Lduct = 12 m, Leff = min [12, 75] = 12 m <55 m. Therefore, DDT is not expected.


Page 86 of 187

Figure A.8.5(a)


Page 87 of 187

Inserted Duct InletK = 2

Flush Duct InletK = 1.5

Inside of Enclosure

Inside of Enclosure

Plain Duct OutletK = 0

Proposed Figure A.8.5(a)

Enclosure Wall

Vent

Enclosure Wall

Vent


Page 88 of 187

Public Comment No. 16-NFPA 68-2016 [ Section No. A.8.7.3 ]

A.8.7.3

Figure A.8.7.3, in comparison to Figure A.8.7.1(1)(a) and Figure A.8.7.1(2)(a) , shows situations for verticaland horizontal elements in which neither separation nor a clear path is provided.

Figure A.8.7.3 Insufficient Separation for Vertical and Horizontal Filter Elements.

At this time, there is insufficient data to provide guidance for accounting for the venting flow blockagefactor, for any of the common industrial designs. The blockage factor is depends on the following itemsamong others:

(1) Element Flow Restriction: Venting flow encounters flow resistance (K factor loss) through the matrixof element (bags/cages, cartridges, panels). There is also a restriction due to the blockage of thevent area, reducing the vent efficiency. This blockage may change during the explosion event.Elements may initially cause X degree of restriction, but then bend, collapse, burn, or fragment; andthen cause Y degree of restriction.

(2) Thermal & Turbulence Absorption: The matrix of elements absorbs explosion heat which reducesPred. The turbulence might also be reduced, which would be beneficial.

(3) Separation Distances: The separation between the elements and between the outer elements andthe enclosure wall will affect both the items above.

(4) Clean-Side Design: The parameters of the clean side of the collector will determine how muchexplosion pressure is dissipated in downstream equipment volume.

(5) Explosion Parameters: The influence of the above items depend upon volume, vent parameters, Kst,Pmax, etc.


I believe the proposed addition is helpful information.



Public Comment No. 15-NFPA 68-2016 [Section No. 8.7.3]

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Page 90 of 187

Public Comment No. 17-NFPA 68-2016 [ Section No. A.10.4 ]



Page 91 of 187

A.10.4



Page 92 of 187

Where the vent closure panel is a double-wall type (such as an insulated sandwich panel), single-wall metalvent panel restraint systems should not be used. The restraint system shown in Figure A.10.4(a) should be

used for double-wall panels. The panel area should be limited to 3.1 m2 (33 ft2), and its mass should be

limited to 12.2 kg/m2 (2.5 lb/ft2). Forged eyebolts should be used. Alternatively, a “U” bolt can besubstituted for the forged eyebolt. A shock absorber device with a fail-safe tether should be provided.

The bar washer on the exterior of the panel should be oriented horizontally, should span the panel width(less 2 in. and any panel overlap), and should be attached to the panel with as many bolts as practical (i.e.,at every panel flat for a corrugated panel). High-quality wire rope clips should be used to ensure therestraint system functions properly. It is noted that this panel restraint system was developed based on testsin which the peak enclosure pressure achieved was approximately 1 psig or less; hence, its performance athigher explosion pressures might not be reliable.

Figure A.10.4(a) An Example of a Restraint System for Double-Wall Insulated Metal Vent Panels.

Where large, lightweight panels are used as vent closures, it is usually necessary to restrain the ventclosures so that they do not become projectile hazards. The restraining method shown in Figure A.10.4(b)illustrates one method that is particularly suited for conventional single-wall metal panels. The key featureof the system includes a 50 mm (2 in.) wide, 10 gauge bar washer. The length of the bar is equal to thepanel width, less 50 mm (2 in.) and less any overlap between panels. The bar washer–vent panel assemblyis secured to the building structural frame using at least three 10 mm ( 3⁄8 in.) diameter through-bolts.

Figure A.10.4(b) An Example of a Restraint System for Single-Wall Metal Vent Panels.

The restraining techniques shown are specific to their application and are intended only as examples. Eachsituation necessitates individual design. Any vent restraint design should be documented by the designer.No restraint for any vent closure should result in restricting the vent area. It is possible for a closure tetherto become twisted and to then bind the vent to less than the full opening area of the vent.



Page 93 of 187

The stiffness of the double-wall panel is much greater than that of a single-wall panel. The formation of theplastic hinge occurs more slowly, and the rotation of the panel can be incomplete. Both factors tend to delayor impede venting during a deflagration.

The component sizes indicated in Figure A.10.4(a) have been successfully tested for areas up to 3.1 m2

(33 ft2) and for mass of up to 12.2 kg/m2 (2.5 lb/ft2). Tests employing fewer than three rope clips have, insome instances, resulted in slippage of the tether through the rope clips, thus allowing the panel to becomea free projectile.

The shock absorber is a thick, L-shaped piece of steel plate to which the tether is attached. During venting,the shock absorber forms a plastic hinge at the juncture in the “L,” as the outstanding leg of the “L” rotatesin an effort to follow the movement of the panel away from the structure. The rotation of the leg providesadditional distance and time, over which the panel is decelerated while simultaneously dissipating some ofthe panel’s kinetic energy.

The L-shaped shock absorber must be ductile, annealed steel, and properly tuned to eachventing design. Stronger is not always better. The shock absorber is a one-time use items. Replace it whenthe panel is replaced. The wire rope and other attachment items may also need replacement after use.

Replace the panel soon after an opening event. Wind will eventually fatigue the tether systemand the dangling panel will fall to the ground.


Add two sentences to end of current text. It should be pointed out that the L-shape shock absorber must have specific metal properties, be tuned for each different application, and be replaced after each panel opening. Also the tether will fatigue and the panel will fall if left to dangle in the wind for days.

Related Item





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Page 94 of 187

Committee Input No. 21-NFPA 68-2016 [ Chapter 7 ]

Chapter 7

7.1

7.1.1*

7.1.1.1

7.1.1.2

7.1.2*

7.2

7.2.1

(7.2.1a)

(7.2.1b)



Page 95 of 187

7.2.1.1

(7.2.1.1)

7.2.1.2

7.2.2

(7.2.2a)

(7.2.2b)

7.2.2.1

7.2.2.2*

7.2.2.3

7.2.3

7.2.4

7.2.5*

7.2.5.1*



Page 96 of 187

7.2.5.1.1

7.2.5.1.2

7.2.5.1.3

7.2.5.1.4

7.2.5.1.5*

7.2.5.2

7.2.6*



Page 97 of 187

7.2.6.1

(7.2.6.1a)

(7.2.6.1b)

(7.2.6.1c)

(7.2.6.1d)

(7.2.6.1e)

(7.2.6.1f)

7.2.6.2

7.2.6.3



Page 98 of 187

7.2.6.4

(7.2.6.4)

7.2.6.5

7.2.6.6

(7.2.6.6)

7.2.6.7

7.2.6.8

7.2.6.9

7.2.6.9.1

7.2.6.9.2

7.2.7

7.2.7.1

7.2.7.2

(7.2.7.2)



Page 99 of 187

7.2.7.3

(7.2.7.3)

7.3

7.3.1*

7.3.2

(7.3.2)

7.3.3

(7.3.3)

7.4*

7.4.1*

7.4.2



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Figure 7.4.2 Maximum Pressure Developed During Venting of Gas, With and Without Vent Ducts.

7.4.2.1

(7.4.2.1)

7.4.2.2

(7.4.2.2)

7.4.3*

7.4.3.1

7.4.3.2

7.4.4

7.4.5*

7.4.5.1*

7.4.6*

7.4.7*



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7.4.7.1

7.4.8

7.5

7.5.1

7.5.1.1*

7.5.1.2*

7.6

7.6.1

7.6.2*

7.6.3*

7.6.4*

7.6.5

7.6.5.1

7.6.5.2

7.6.5.3

7.6.5.4

7.6.6



Page 102 of 187

7.7*

7.7.1

(7.7.1)

7.7.2

7.8

Supplemental Information

File Name Description


Submitter Full Name:

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CommitteeStatement:

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NFPA 68 VENT CALCULATIONS FOR GAS MIXTURES AND MISTS

I believe that KG is no longer relevant to this standard. Resolution: Yes, all references to KG are irrelevant.

Is chapter 7 intended to apply to process equipment as well as rooms and building compartments? Much of the wording seems to be directed towards rooms and building compartments. Resolution: Yes, within the bounds of applicability for the equations, chapter 7 applies to both equipment and buildings. For example, the high pressure equation is not likely to be applicable to buildings since Pred is greater than 0.5 bar (7.2 psi).

§7.2.1 provides the basic equations for calculating the vent area when Pred ≤ 0.5 bar. Provided for info… see below.

§7.2.2 provides the basic equations for calculating the vent area when Pred > 0.5 bar. Provided for info… see below.

§7.2.1.2 provides constraints on Pstat. Based upon the numbering scheme (§7.2.1.2 under §7.2.1), it should be clear that these constraints apply when Pred ≤ 0.5 bar.


Page 104 of 187

Resolution: Yes, 7.2.1.2 is only applicable to the low pressure equation, 7.2.1. But, there are no constraints on Pstat following §7.2.2. Are there really no constraints intended for Pstat as it is used in §7.2.2 for Pred > 0.5 bar? Resolution: No, Chapter 7 does not apply any constraints to Pstat for the high pressure case. However, §6.5.7 and 6.5.8 do establish generally applicable constraints on Pstat. Or is §7.2.1.2 intended to apply to both the low pressure and the high pressure equations, regardless of what the numbering would imply? Resolution: No, 7.2.1.2 is only applicable to the low pressure case. §7.2.2.1 refers to §7.2.5 for instructions for calculating As for use in equation 7.2.2a. But, As is also used in equation 7.2.1a. And, no instructions are provided in the 7.2.1.x sequence to similarly refer to §7.2.5 to calculate As for use in equation 7.2.1a. Is it intended that §7.2.5 be used to calculate As for use in both equations 7.2.1a and 7.2.2a? Resolution: §7.2.5 is intended to provide instructions for


Page 105 of 187

calculating As for use in both equations 7.2.1a and 7.2.2a. Suggestion: Consider deleting §7.2.2.1. If you do this, it will be clearer that §7.2.5 is intended to apply to both equations 7.2.1a and 7.2.2a. Leaving §7.2.2.1 in will prompt the question of why there is no corresponding requirement for equation 7.2.1a. §7.2.2.1 is superfluous. Similarly, §7.2.2.2 provides guidance on determining Su. Is this guidance intended to apply to both equations 7.2.1a and 7.2.2a? Common sense would indicate that it is, but the numbering scheme would imply that it is only pertinent to equation 7.2.2a. Resolution: §7.2.2.2 is intended to provide instructions for determining Su for use in both equations 7.2.1b and 7.2.2a. Suggestion: Renumber §7.2.2.2 so that it does not appear to be a subsidiary requirement to §7.2.2.

Also, §7.2.2.3 provides guidance on determining Cd. Is this guidance intended to apply to both equations 7.2.1a and 7.2.2a? Common sense would indicate that it is, but the numbering scheme would imply that it is only pertinent to equation 7.2.2a.


Page 106 of 187

Resolution: §7.2.2.3 is intended to provide instructions for determining Cd for use in both equations 7.2.1a and 7.2.2a. Suggestion: Renumber §7.2.2.3 so that it does not appear to be a subsidiary requirement to §7.2.2. §7.2.7.1 only mentions using the partial volume correction with equation 7.2.2a. Is it truly the intent that the partial volume correction will not be used with equation 7.2.1a? Resolution: §7.2.7.1 is intended to provide instructions for applying the partial volume correction to both equations 7.2.1a and 7.2.2a. Suggestion: Renumber §7.2.7.1 to clarify that the partial volume correction is applicable to both equations 7.2.1a and 7.2.2a.

§7.3 addresses vent panel inertia. But, equation 7.3.3 shows the inertia adjustment applied to Av1, which is the vent area after application of the partial volume correction. Depending upon your answer to the question immediately above, is it truly the intent that the vent panel inertia correction will not be used with equation 7.2.1a? Resolution: §7.3 is intended to provide instructions for applying the vent panel inertia


Page 107 of 187

correction to both equations 7.2.1a and 7.2.2a. Suggestion: Clarification of the applicability of §7.2.7.1 (above) may remove any ambiguity as to the applicability of §7.3. The definition of terms after equation 7.3.3 states that FSH is defined in Chapter 8. The information on FSH in Chapter 8 seems inconsistent with the information in Annex G for another term defined as “shape factor”… denoted cs.

Are these the same concepts? Resolution: FSH and cs are not intended to refer to the same parameter. Suggestion: Clarify this inconsistency in nomenclature.

§7.4.1 states that a lower value for Pred is to be substituted into equations 7.2.6, 7.2.6.4, 7.3.2 and 7.3.3. By equation 7.2.6, I am assuming that you mean 7.2.6.1e. Is that the intent? Resolution: Yes. Note that Pred does not appear in equation 7.2.6.4. Resolution: This is an error in the equation references. Also, Pred appears in equations 7.2.1a and 7.2.2a. Is the substitution intended to be made in these equations also?


Page 108 of 187

Resolution: This is an error in the equation references. Is it the intent that the vent duct correction can be applied to the low pressure (equation 7.2.1a) case? Resolution: Yes. The substitution of the adjusted value of P’ red is intended to be applied to any equation in which Pred appears. This applies to both the low pressure and the high pressure cases. Suggestion: Correct the equation references in §7.4.1. As to the substituted value for Pred, is it the intent that the value for P’ red determined in 7.4.2 be substituted for Pred in each relevant equation? Resolution: Yes. Substituting P’ red (which is lower than Pred) in the equations ensures that the pressure actually experienced when venting through ducts does not exceed the allowable Pred. Suggestion: An example calculation in the annex would be helpful to demonstrate the intent here. It appears that the equations in §7.4.2.1 and §7.4.2.2 are the equations for the curves Figure 7.4.2. Is that correct? Resolution: Yes.


Page 109 of 187

With regard to reflecting the effects of higher pressure, what are the “procedures” mentioned in §7.5.1? I don’ t see anything that looks like a procedure in §7.5.1.1 or §7.5.1.2. Is the intent that you just substitute the appropriate value of Po in the various equations, without constraints (apart from the limit on Pred of 0.5 bar in equation 7.2.1a)? Resolution: Yes. There is no limit on the value of Po that can be used in equation 7.2.2a. As noted above, the values of Po that can be used in 7.2.1a are limited to the extent that Pred must not exceed 0.5 bar. Suggestion: reword §7.5.1 to eliminate the word “procedure” and simply state the intent, as outlined above.


Page 110 of 187

Committee Input No. 23-NFPA 68-2016 [ Section No. 7.2.1 [Excluding any Sub-Sections]

]

(7.2.1a)

(7.2.1b)



Organization:

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CommitteeStatement:



Page 111 of 187

-

ResponseMessage:



Page 112 of 187

Committee Input No. 24-NFPA 68-2016 [ Section No. 7.2.6.1 ]

7.2.6.1

(7.2.6.1a)

(7.2.6.1b)

(7.2.6.1c)

(7.2.6.1d)

(7.2.6.1e)

(7.2.6.1f)



Organization:

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Page 113 of 187

City:

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CommitteeStatement:

- -

ResponseMessage:



Page 114 of 187


7.2.6.6

(7.2.6.6)



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CommitteeStatement:

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Page 115 of 187

Committee Input No. 12-NFPA 68-2016 [ Section No. 7.7.1 ]

7.7.1

(7.7.1)



Organization:

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Submittal Date:

Committee Statement

CommitteeStatement:



Page 116 of 187

ResponseMessage:



Page 117 of 187


8.2.6.2

(8.2.6.2)



Organization:

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Page 118 of 187

Committee Input No. 33-NFPA 68-2016 [ Chapter D ]

Annex D



Page 119 of 187

D.1



Page 120 of 187

Gas

Fundamental

BurningVelocity

(cm/s) Gas

Fundamental

BurningVelocity

(cm/s)



Page 121 of 187

Gas

Fundamental

BurningVelocity

(cm/s) Gas

Fundamental

BurningVelocity

(cm/s)

Gas Table D.1(a)

Andrews and

Bradley [84] France and Pritchard [85]

(in air)In air In oxygen



Page 122 of 187

D.2 Pmax

Flammable Material

Pmax

(bar-g)





Page 123 of 187

Organization:

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Page 124 of 187

Attachment E: NFPA 69 Public Input Report


Page 125 of 187

Public Input No. 24-NFPA 69-2017 [ Section No. 1.3.1.2.1 ]

1.3.1.2.1

These methods shall be permitted to be used independently to reduce the frequency of deflagrationsproviding another explosion protection method is also used in accord with Chapter 10, 13, or 14 of thisstandard or deflagration venting in accord with NFPA 68 .

Statement of Problem and Substantiation for Public Input

The existing wording allows these ignition source detection and control systems to be used only to reduce the frequency of deflagrations. Without additional installed explosion protection, allowing an unmitigated, albeit infrequent, deflagration does not provide the same level of explosion prevention as other methods in this standard.




Street Address:

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Submittal Date: Thu Jan 05 10:10:12 EST 2017



Page 126 of 187

Public Input No. 3-NFPA 69-2015 [ Chapter 2 ]

Chapter 2 Referenced Publications

2.1 General.

The documents or portions thereof listed in this chapter are referenced within this standard and shall beconsidered part of the requirements of this document.

2.2 NFPA Publications.

National Fire Protection Association, 1 Batterymarch Park, Quincy, MA 02169-7471.

NFPA 61, Standard for the Prevention of Fires and Dust Explosions in Agricultural and Food ProcessingFacilities, 2013 edition.

NFPA 68, Standard on Explosion Protection by Deflagration Venting, 2013 edition.

NFPA 70®National Electrical Code® , 2014 edition.

NFPA 72® , National Fire Alarm Code, 2013 edition.

NFPA 86, Standard for Ovens and Furnaces, 2011 edition.

NFPA 271, Standard Method of Test for Heat and Visible Smoke Release Rates for Materials andProducts Using an Oxygen Consumption Calorimeter, 2009 edition.

NFPA 326, Standard for the Safeguarding of Tanks and Containers for Entry, Cleaning, or Repair, 2010edition.

NFPA 484, Standard for Combustible Metals, 2012 edition.

NFPA 654, Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing,and Handling of Combustible Particulate Solids, 2013 edition.

2.3 Other Publications.

2.3.1 API Publications.

American Petroleum Institute, 1220 L Street, NW, Washington, DC 20005-4070.

ANSI/ API 510, Pressure Vessel Inspection Code: In-Service Inspection, Rating, Repair, and Alteration,Ninth Tenth Edition, 2006 2014 .

2.3.2 ASME Publications.

American Society of Mechanical Engineers, Three ASME International , Two Park Avenue, New York,NY 10016-5990.

ASME Boiler and Pressure Vessel Code, Section VIII, 2010 2017 .

ASME B31.3, Process Piping, 2012 2016 .

2.3.3 ASTM Publications.

ASTM International, 100 Barr Harbor Drive, P.O. Box C700, West Conshohocken, PA 19428-2959.

ASTM D 257 D257 , Standard Test Methods for DC Resistance or Conductance of Insulating Materials,2007 2014 .

ASTM D 3574 D3574 , Standard Test Methods for Flexible Cellular Materials — Slab, Bonded and MoldedUrethane Foams, 2011.

ASTM E 2079 E2079 , Standard Test Method for Limiting Oxygen (Oxidant) Concentration for Gases andVapors, 2007, reapproved 2013 .



Page 127 of 187

2.3.4 ISO Publications.

International Organization for Standardization, 1, ch. de la Voie-Creuse, Case postale 56, CH-1211Geneva 20, ISO Central Secretariat, BIBC II, Chemin de Blandonnet 8, CP 401, 1214 Vernier, GenevaSwitzerland .

ISO 16852, Flame Arresters — Performance Requirements, Test Methods and Limits for Use , 2008,Corrigendum, 2009 .

2.3.5 Military Specifications.

Department of Defense Single Stock Point, Document Automation and Production Service DLA DocumentServices , Building 4/D, 700 Robbins Avenue, Philadelphia, PA 19111-5094.

MIL-DTL-83054C, Baffle and Inerting Material, Aircraft Fuel Tank, 2003. (Transformed on 03-NOV-2009into QPL in the QPD)

MIL-PRF-87260B, Foam Material, Explosion Suppression, Inherently Electrically Conductive, for AircraftFuel Tanks, 2006. (Transformed on 27-APR-2007 into QPL in the QPD)

2.3.6 U.S. Government Publications.

U.S. Government Printing Publishing Office, 732 North Capitol Street, NW, Washington, DC20402 20401-0001 .

Title 29, Code of Federal Regulations, Part 1910.146, “Permit-Required Confined Spaces Standard.”

Title 29, Code of Federal Regulations, Part 1910.147, “The Control of Hazardous Energy (Lock-Out/Tag-Out).”

Title 30, Code of Federal Regulations, Part 75.

Title 33, Code of Federal Regulations, Part 154, “Waterfront Facilities.”


Title 46, Code of Federal Regulations, Part 32, “Shipping.”



Title 49, Code of Federal Regulations, Part 173.24, U.S. Department of Transportation, “GeneralRequirements for Packaging and Packages.”

2.3.7 Other Publications.

Bartknecht, W., Explosions: Course, Prevention, Protection, Springer-Verlag, Heidelberg, Germany, 1989.

Merriam-Webster's Collegiate Dictionary, 11th edition, Merriam-Webster, Inc., Springfield, MA, 2003.

2.4 References for Extracts in Mandatory Sections.


NFPA 72 ® , National Fire Alarm Code®, 2013 edition.

NFPA 302, Fire Protection Standard for Pleasure and Commercial Motor Craft, 2010 edition.

NFPA 497, Recommended Practice for the Classification of Flammable Liquids, Gases, or Vapors and ofHazardous (Classified) Locations for Electrical Installations in Chemical Process Areas, 2012 edition.



Referenced SDO names, addresses, standard names, numbers, and editions.

Related Public Inputs for This Document

Related Input Relationship

Public Input No. 4-NFPA 69-2015 [Chapter H]



Page 128 of 187


Submitter Full Name: Aaron Adamczyk

Organization: [ Not Specified ]

Street Address:

City:

State:

Zip:

Submittal Date: Sat Dec 05 21:50:48 EST 2015



Page 129 of 187

Public Input No. 6-NFPA 69-2016 [ Section No. 2.2 ]

2.2 NFPA Publications.


NFPA 4, Standard for Integrated Fire Protection and Life Safety System Testing, 2015 edition

NFPA 61, Standard for the Prevention of Fires and Dust Explosions in Agricultural and Food ProcessingFacilities, 2013 edition.


NFPA 70®National Electrical Code® , 2014 edition.

NFPA 72® , National Fire Alarm Code, 2013 edition.

NFPA 86, Standard for Ovens and Furnaces, 2011 edition.

NFPA 271, Standard Method of Test for Heat and Visible Smoke Release Rates for Materials andProducts Using an Oxygen Consumption Calorimeter, 2009 edition.


NFPA 484, Standard for Combustible Metals, 2012 edition.



In coordination with Public Input #5 (if approved), adding referenced NFPA standard.


Submitter Full Name: Kimberly Gruner

Organization: Fike Corporation

Street Address:

City:

State:

Zip:

Submittal Date: Wed Jan 06 17:19:48 EST 2016



Page 130 of 187

Public Input No. 21-NFPA 69-2016 [ Section No. 2.3.3 ]

2.3.3 ASTM Publications.


ASTM D 257 D257 , Standard Test Methods for DC Resistance or Conductance of Insulating Materials,2007 2014 .

ASTM D 3574 D3574 , Standard Test Methods for Flexible Cellular Materials — Slab, Bonded and MoldedUrethane Foams, 2011.

ASTM E 2079 E2079 , Standard Test Method for Limiting Oxygen (Oxidant) Concentration for Gases andVapors, 2007 (2013) .


updates


Submitter Full Name: Marcelo Hirschler

Organization: GBH International

Street Address:

City:

State:

Zip:

Submittal Date: Thu Dec 22 17:16:38 EST 2016



Page 131 of 187

Public Input No. 5-NFPA 69-2016 [ New Section after 4.2.1.3 ]

4.2.1.4

Systems integrated with the Explosion Prevention System which provide fire protection and life safety shallbe planned, tested, documented, and maintained in accordance with NFPA 4 Standard for Integrated FireProtection and Life Safety System Testing.


Many installations utilize various individual systems (Explosion Prevention, Fire Alarm or signaling system, emergency communication system, process control, etc.) for fire protection and life safety where each may utilize their own code, standard, or acceptance criteria. NFPA 4 is a new standard that provides requirements for testing integrated systems together so that the entire fire protection and life safety system objective is accomplished.


Submitter Full Name: Kimberly Gruner

Organization: Fike Corporation

Street Address:

City:

State:

Zip:

Submittal Date: Wed Jan 06 16:54:27 EST 2016



Page 132 of 187

Public Input No. 8-NFPA 69-2016 [ New Section after 7.2.3.1.2 ]

7.2.3.1.3

In no case shall the adjusted LOC value for carbon dioxide inerting result in a value lower than that requiredfor nitrogen inerting.



Issued_TIA_69-14-1_002_.pdf TIA 69-14-1


NOTE: This public input originated as TIA 69-14-1 issued on April 6, 2016 by the NFPA Standards Council. Per the NFPA Regs, this TIA must be reconsidered by the Technical Committee for the next edition of the document.


Submitter Full Name: TC EXL-AAA

Organization: NFPA

Street Address:

City:

State:

Zip:

Submittal Date: Wed May 04 14:51:12 EDT 2016



Page 133 of 187

Tentative Interim Amendment

NFPA® 69

Standard on Explosion Prevention Systems

2014 Edition

Reference: 7.2.3.1.2, 7.2.3.1.1(new), A.3.3.25, and Table C.1(a) TIA 14-1 (SC 16-4-9 / TIA Log #1211) Pursuant to Section 5 of the NFPA Regulations Governing the Development of NFPA Standards, the National Fire Protection Association has issued the following Tentative Interim Amendment to NFPA 69, Standard on Explosion Prevention Systems, 2014 edition. The TIA was processed by the Technical Committee on Explosion Protection, and was issued by the Standards Council on April 6, 2016, with an effective date of April 26, 2016. A Tentative Interim Amendment is tentative because it has not been processed through the entire standards-making procedures. It is interim because it is effective only between editions of the standard. A TIA automatically becomes a public input of the proponent for the next edition of the standard; as such, it then is subject to all of the procedures of the standards-making process. 1. Revise Subparagraph 7.2.3.1.2 to read as follows:

7.2.3.1.2 For gases and vapors, if the LOC values according to ASTM E 2079 are not available, then the LOC values obtained in flammability tubes shall be used after adjustment by subtracting 1.5 2 percent by volume oxidant for LOC values of 10 percent or greater and by multiplying by a factor of 0.85 for LOC values less than 10 percent, as indicated in the adjusted columns in Table C.1(a).

2. Add new Subparagraph 7.2.3.1.3 to read as follows: 7.2.3.1.3 In no case shall the adjusted LOC value for carbon dioxide inerting result in a value lower than that required for nitrogen inerting.

3. Revise Annex A.3.3.25 to read as follows:

A.3.3.25 Limiting Oxidant Concentration (LOC). Materials other than oxygen can act as oxidants. The LOC depends upon the temperature, pressure, and fuel concentration as well as the type of diluent. Preliminary results of the ASTM E 2079, Standard Test Methods for Limiting Oxygen (Oxidant) Concentration in Gases and Vapors, round robin tests for gases and vapors revealed that the LOC data that were obtained using different test methods and that are listed in a majority of reference publications are nonconservative. The old Bureau of Mines data were obtained mostly in a 50 mm diameter flammability tube. This diameter might be too small to mitigate the flame-quenching influence, thereby impeding accurate determination of the LOC of most fuels. The 4 L minimum volume specified in ASTM E 2079 would correspond to a diameter of at least 200 mm (7.9 in.). As a result, some LOC values determined using


Page 134 of 187

this standard are approximately 1 percent by volume oxygen lower than the previous values measured in the flammability tube, and a few are even up to 1.5 2 percent by volume lower. The lower LOC values obtained in larger chambers are more appropriate for use in fire and explosion hazard assessment studies. A data comparison can be found in Table A.3.3.25.

4. Replace Table C.1(a) and associated notes with the following:


Page 135 of 187


Page 136 of 187

Issue Date: April 6, 2016 Effective Date: April 26, 2016

(Note: For further information on NFPA Codes and Standards, please see www.nfpa.org/codelist) Copyright © 2016 All Rights Reserve

NATIONAL FIRE PROTECTION ASSOCIATION


Page 137 of 187


7.2.3.1.2

For gases and vapors, if the LOC values according to ASTM E 2079 are not available, then the LOC valuesobtained in flammability tubes shall be used after adjustment by subtracting 2 1.5 percent by volumeoxidant for LOC values of 10 percent or greater and by multiplying by a factor of 0.85 for LOC values lessthan 10 percent, as indicated in the adjusted columns in Table C.1(a) .








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Page 138 of 187


NFPA® 69


2014 Edition

Reference: 7.2.3.1.2, 7.2.3.1.1(new), A.3.3.25, and Table C.1(a)

TIA 14-1

(SC 16-4-9 / TIA Log #1211)

Pursuant to Section 5 of the NFPA Regulations Governing the Development of NFPA Standards, the National Fire Protection

Association has issued the following Tentative Interim Amendment to NFPA 69, Standard on Explosion Prevention Systems,

2014 edition. The TIA was processed by the Technical Committee on Explosion Protection, and was issued by the Standards

Council on April 6, 2016, with an effective date of April 26, 2016.

A Tentative Interim Amendment is tentative because it has not been processed through the entire standards-making procedures. It is

interim because it is effective only between editions of the standard. A TIA automatically becomes a public input of the proponent for

the next edition of the standard; as such, it then is subject to all of the procedures of the standards-making process.

1. Revise Subparagraph 7.2.3.1.2 to read as follows:

7.2.3.1.2 For gases and vapors, if the LOC values according to ASTM E 2079 are not available, then the

LOC values obtained in flammability tubes shall be used after adjustment by subtracting 1.5 2 percent by

volume oxidant for LOC values of 10 percent or greater and by multiplying by a factor of 0.85 for LOC

values less than 10 percent, as indicated in the adjusted columns in Table C.1(a).

2. Add new Subparagraph 7.2.3.1.3 to read as follows:

7.2.3.1.3 In no case shall the adjusted LOC value for carbon dioxide inerting result in a value lower than

that required for nitrogen inerting.


A.3.3.25 Limiting Oxidant Concentration (LOC). Materials other than oxygen can act as oxidants. The

LOC depends upon the temperature, pressure, and fuel concentration as well as the type of diluent.

Preliminary results of the ASTM E 2079, Standard Test Methods for Limiting Oxygen (Oxidant)

Concentration in Gases and Vapors, round robin tests for gases and vapors revealed that the LOC data that

were obtained using different test methods and that are listed in a majority of reference publications are

nonconservative. The old Bureau of Mines data were obtained mostly in a 50 mm diameter flammability

tube. This diameter might be too small to mitigate the flame-quenching influence, thereby impeding

accurate determination of the LOC of most fuels. The 4 L minimum volume specified in ASTM E 2079

would correspond to a diameter of at least 200 mm (7.9 in.). As a result, some LOC values determined using


Page 139 of 187

this standard are approximately 1 percent by volume oxygen lower than the previous values measured in the

flammability tube, and a few are even up to 1.5 2 percent by volume lower. The lower LOC values obtained

in larger chambers are more appropriate for use in fire and explosion hazard assessment studies. A data

comparison can be found in Table A.3.3.25.



Page 140 of 187


Page 141 of 187

Issue Date: April 6, 2016

Effective Date: April 26, 2016

(Note: For further information on NFPA Codes and Standards, please see www.nfpa.org/codelist)

Copyright © 2016 All Rights Reserve



Page 142 of 187

http://www.nfpa.org/codelist

Public Input No. 35-NFPA 69-2017 [ New Section after 7.7.2.5 ]

7.7.2.6 Risk Assessment

A documented risk assessment acceptable to the AHJ shall be permitted to be conducted to determine thesafety margin to be maintained between the worst credible case LOC and safety interlocks addressed in7.7.2.5.


While 7.7.2.4 addresses the factors to consider when establishing a safety margin, the minimum 2% value in 7.7.2.5 does not permit the user to reduce the safety margin where process uniformity and measurement accuracy are improved.




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Page 143 of 187

Public Input No. 13-NFPA 69-2016 [ Section No. 8.1 ]

8.1 * Application.

The technique for combustible concentration reduction shall be permitted to be considered where a mixtureof a combustible material and an oxidant is confined to an enclosure and where the concentration of thecombustible can be maintained below the lower flammable limit (LFL) or minimum explosible concentration(MEC) .


The technique of using combustible concentration reduction should apply to both vapors and combustible dusts. The wording in this entire chapter makes it appear to only apply to vapors. LFL is used throughout the entire section and the appropriate terminology for combustible dusts is MEC. The entire chapter should be updated as needed to clarify.





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Page 144 of 187


8.2.1

All of the following factors shall be considered in the design of a system intended to reduce the combustibleconcentration below the LFL:

(1) Required reduction in combustible concentration

(2) Variations in the process, process temperature and pressure, and materials being processed

(3) Operating controls

(4) Maintenance, inspection, and testing

(5) Concentration variation with time and space


In some applications the combustible concentration will vary with time (i.e., transient behaviors) or location. To prevent ignition it is not sufficient that the bulk enclosure volume stays below the LFL, but that the local concentration must also stay below the LFL. There have been instances where this has been neglected. Local concentration becomes important for rapid releases of combustible vapors (transient scenarios) and fugitive emissions in low-ventilation enclosures (localized high-concentration scenarios).


Submitter Full Name: D Allan Coutts

Organization: AECOM

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Submittal Date: Tue Jan 03 10:46:26 EST 2017



Page 145 of 187


8.3.1* Combustible Concentration Limit.

The combustible concentration shall be maintained at or below 25 percent of the LFL for all foreseeableoperating conditions , unless the following conditions apply:

(1) Where continuously monitored and controlled with safety interlocks, the combustible concentrationshall be permitted to be maintained at or below 60 percent of the LFL.

(2) Aluminum powder production systems designed and operated in accordance with NFPA 484,Standard for Combustible Metals, shall be permitted to be maintained at or below 50 percent of theLFL.


Many processes and other operations involving combustible vapors and particulates have significant fluctuations in combustible material loadings or ventilation rates that will produce corresponding variations in concentrations of combustible materials. Use of the combustible concentration reduction method of explosion prevention should account for all foreseeable variations in operating conditions and material loadings.




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Page 146 of 187


9.3. 1 General .

Optical sensing systems and gas sensing systems

6

Systems shall be listed or approved as a complete system that includes a means to actuate automaticshutdown or other actions described in 9.1.4 and 9.1.5.


The existing requirements in 9.3.1 are just for optical and gas sensising systems. They should be applicable to any system covered by this chapter.




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Page 147 of 187


12.2.4.5.1

Close-clearance rotary valves shall be designed with a clearance between vane and valve body of < or =0.2 mm (0.0079 in.).


The clearance requirement should be less than or equal to 0.2 mm.




Affilliation: The American Chemsitry Council

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Submittal Date: Tue Dec 06 10:51:19 EST 2016



Page 148 of 187

Public Input No. 30-NFPA 69-2017 [ Section No. 13.3.4.1 ]

13.3.4.1 *

The dimensionless ratio, R, is the ratio of the maximum deflagration pressure, in absolute pressure units, tothe maximum initial pressure at which the deflagration pressure was tested , in consistent absolutepressure units.


The "maximum initial pressure" referenced in this section can easily be confused or mistaken as the same as the "maximum initial pressure, Pi, referenced in the section above. Use of Pi from section 13.3.4 will product erroneous results as this is typically an elevated value where the initial pressure at which most Pmax testing is completed is atmospheric. 'R' must be based on the initial pressure at which the Pmax testing was performed.


Submitter Full Name: Nathan Egbert

Organization: Schenck Process LLC

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Page 149 of 187

Public Input No. 33-NFPA 69-2017 [ Sections 13.3.6, 13.3.7 ]

Sections 13.3.6, 13.3.7

13.3.6*

The maximum initial pressure for positive pressure systems shall be as follows:

(1) For positive pressure systems that handle gases and liquids, the maximum initial pressure, Pi, shall be

the maximum initial pressure at which a combustible atmosphere is able to exist, but a pressure nothigher than the setting of the pressure relief device plus its accumulation.

(2) For positive pressure systems that handle dusts, the maximum initial pressure shall be the greater ofthe following two pressure values:

(3) Maximum possible discharge pressure of the compressor or blower that is suspending ortransporting the material

(4) Setting of the pressure relief device on the vessel being protected plus its accumulation

(5) For gravity discharge of dusts, the maximum initial pressure shall be the atmospheric gauge pressure(0.0 013 bar or 0.0 psi).

13.3.7

For systems operating under vacuum, the maximum initial pressure shall not be less than atmosphericgauge pressure (0.0 013 bar or 0.0 psi).


The sections incorrectly equate 0 bar-gauge with 0 psig. The intention is normal atmospheric pressure, 0 psig, or 0.013 bar-gauge.




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Page 150 of 187


13.4.1

If not required by local jurisdiction, inspection Inspection and maintenance shall be in accordance with API510, Pressure Vessel Inspection Code: Maintenance Inspection, Rating, Repair, and Alteration.


Inspections and maintenance should be in compliance with API 510, whether or not a local regulation requires some other inspection. Eliminating the initial "if" phrase will make it clearer that API 510 is the relevant inspection standard.




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Page 151 of 187

Public Input No. 22-NFPA 69-2017 [ New Section after A.1.2.3 ]

A-1.1 Scope

Establishing the applicability of NFPA 69 requires an understanding of the process, the associated hazards,protective features established other codes and standards, and the system resiliency. The presence of lowconcentrations of combustible gases or dusts does not mandate the application of NFPA 69; however,achieving low concentrations through active or passive approaches may warrant the application of thisstandard to achieve sufficient reliability. For example, if enclosure ventilation is required to maintain thecombustible concentration below 25 percent of the LFL, application of this standard should be considered,especially if the reliability of the ventilation flow is not addressed by a code or standard addressing theexplosion hazard. Also, merely demonstrating that a single container release into an enclosure stays below100 percent of the LFL is not an appropriate approach to determine nonapplicability of this standard. In sucha scenario the combustible concentration will vary from 100%25 to the uniformly dispersed concentration,so an ignitable concentration will exist during the release transient.


There have been instances where no explosion protection controls have been provided based on the logic that since ventilation is provided, ignitable concentrations can't occur. In such instances there are usually two significant assumptions: (1) the ventilation would never be impeded and (2) assuring that the bulk combustible concentration stayed below 100 percent of the LFL provided sufficient explosion prevention margin. In one example small passive ventilation filters, in relation to the enclosure volume, were argued to avoid the need for compliance with NFPA 69. Subsequent analysis identified the need for hardware modifications and extensive controls (operating, inspection, testing, and maintenance procedure) to avoid the potential for explosions. Application of NFPA 69 during the design phase would have avoided the rework and complicated protection concepts.


Submitter Full Name: D Allan Coutts

Organization: AECOM

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Submittal Date: Tue Jan 03 09:53:09 EST 2017



Page 152 of 187

Public Input No. 20-NFPA 69-2016 [ Section No. A.3.3.25 ]



Page 153 of 187

A.3.3.25 Limiting Oxidant Concentration (LOC).

Materials other than oxygen can act as oxidants. The LOC depends upon the temperature, pressure, andfuel concentration as well as the type of diluent. Preliminary results of the ASTM E 2079, Standard TestMethods for Limiting Oxygen (Oxidant) Concentration in Gases and Vapors, round robin tests for gases andvapors revealed that the LOC data that were obtained using different test methods and that are listed in amajority of reference publications are nonconservative. The old Bureau of Mines data were obtained mostlyin a 50 mm diameter flammability tube. This diameter might be too small to mitigate the flame-quenchinginfluence, thereby impeding accurate determination of the LOC of most fuels. The 4 L minimum volumespecified in ASTM E 2079 would correspond to a diameter of at least 200 mm (7.9 in.). As a result, someLOC values determined using this standard are approximately 1 percent by volume oxygen lower than theprevious values measured in the flammability tube, and a few are even up to 1.5 percent by volume lower.The lower LOC values obtained in larger chambers are more appropriate for use in fire and explosionhazard assessment studies. A data comparison can be found in Table A.3.3.25.

Table A.3.3.25 Effect of Test Enclosure on LOC Values When Using Nitrogen as Diluent

LOC Values

Gas or Vapor

Flammability Tube

5 cm Diameter*

(

%

%25 by Volume)

120 L Sphere

60 cm Diameter†

(

%

%25 by Volume)

Hydrogen (H 2 ) 5.0 4.6

Carbon monoxide (CO)

(at high humidity) 5.5 4.8

Methane (CH 4 ) 12.0 11.2

Ethylene (C 2 H 4 ) 10.0 8.5

Propane (C 3 H 8 ) 11.5 10.6

*Data from J. M. Kuchta, U.S. Bureau of Mines, Bulletin 680, 1985.

†Data from Isaac Zlochower, PRL (NIOSH – Pittsburgh Research Laboratory) 2005, unpublished and notpeer-reviewed.

Note: The data were obtained in accordance with ASTM test method E 2079, at 1 atm and at 20°C–23°C(68°F–73°F) on N2-Air-Fuel mixtures. Electric spark was created by the discharge of a 54°C (130°F)

capacitor, initially charged to 300 V, through a 15 kV transformer. The standard criterion [i.e., minimum 6.9kPa (1 psi) or 7 percent absolute pressure rise] was used to detect ignition.

Generally, LOC decreases as the pressure or temperature prior to ignition increases. Best practice is to testthe LOC at the appropriate temperature and pressure. Deviations from the test fuel composition andtemperature might possibly be accounted for by using appropriate techniques. For dusts, an appropriatetest apparatus should be used in conjunction with a strong ignition source, such as described in the draft ofstandard ASTM WK 1680 E2931, Standard Test Method for Limiting Oxygen (Oxidant) Concentration ofCombustible Dust Clouds , being developed by the ASTM E 27.05 Explosibility and Ignitability of DustClouds Committee, or in CEN EN 14034-4, Determination of Explosion Characteristics of Dust Clouds, Part4.


ASTM E27.05 developed standard E2931 in 2013.



Page 154 of 187



Public Input No. 19-NFPA 69-2016 [Section No. H.1.2.5]




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Page 155 of 187


A.3.3.25 Limiting Oxidant Concentration (LOC).

Materials other than oxygen can act as oxidants. The LOC depends upon the temperature, pressure, andfuel concentration as well as the type of diluent. Preliminary results of the ASTM E 2079, Standard TestMethods for Limiting Oxygen (Oxidant) Concentration in Gases and Vapors, round robin tests for gases andvapors revealed that the LOC data that were obtained using different test methods and that are listed in amajority of reference publications are nonconservative. The old Bureau of Mines data were obtained mostlyin a 50 mm diameter flammability tube. This diameter might be too small to mitigate the flame-quenchinginfluence, thereby impeding accurate determination of the LOC of most fuels. The 4 L minimum volumespecified in ASTM E 2079 would correspond to a diameter of at least 200 mm (7.9 in.). As a result, someLOC values determined using this standard are approximately 1 percent by volume oxygen lower than theprevious values measured in the flammability tube, and a few are even up to 2 1.5 percent by volumelower. The lower LOC values obtained in larger chambers are more appropriate for use in fire and explosionhazard assessment studies. A data comparison can be found in Table A.3.3.25.

Table A.3.3.25 Effect of Test Enclosure on LOC Values When Using Nitrogen as Diluent

LOC Values

Gas or Vapor

Flammability Tube

5 cm Diameter*

(% by Volume)

120 L Sphere

60 cm Diameter†

(% by Volume)

Hydrogen (H2) 5.0 4.6

Carbon monoxide (CO)

(at high humidity) 5.5 4.8

Methane (CH4) 12.0 11.2

Ethylene (C2H4) 10.0 8.5

Propane (C3H8) 11.5 10.6

*Data from J. M. Kuchta, U.S. Bureau of Mines, Bulletin 680, 1985.

†Data from Isaac Zlochower, PRL (NIOSH – Pittsburgh Research Laboratory) 2005, unpublished and notpeer-reviewed.

Note: The data were obtained in accordance with ASTM test method E 2079, at 1 atm and at 20°C–23°C(68°F–73°F) on N2-Air-Fuel mixtures. Electric spark was created by the discharge of a 54°C (130°F)

capacitor, initially charged to 300 V, through a 15 kV transformer. The standard criterion [i.e., minimum 6.9kPa (1 psi) or 7 percent absolute pressure rise] was used to detect ignition.

Generally, LOC decreases as the pressure or temperature prior to ignition increases. Best practice is to testthe LOC at the appropriate temperature and pressure. Deviations from the test fuel composition andtemperature might possibly be accounted for by using appropriate techniques. For dusts, an appropriatetest apparatus should be used in conjunction with a strong ignition source, such as described in the draft ofstandard ASTM WK 1680 Test Method for Limiting Oxygen (Oxidant) Concentration of Combustible DustClouds, being developed by the ASTM E 27.05 Explosibility and Ignitability of Dust Clouds Committee, or inCEN EN 14034-4, Determination of Explosion Characteristics of Dust Clouds, Part 4.







Page 156 of 187




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24 of 46 1/10/2017 4:17 PM


Page 157 of 187


NFPA® 69


2014 Edition


TIA 14-1

(SC 16-4-9 / TIA Log #1211)



























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Page 159 of 187


Page 160 of 187







Page 161 of 187



A.5.1

The SFPE Engineering Guide to Performance-Based Fire Protection outlines a process for using aperforance-based approach in the design and assessement of building fire safety.


The SFPE Guide outlines a process that can be used by designers who are using the performance-based approached outlined in Section 5.1.


Submitter Full Name: Chris Jelenewicz

Organization: SFPE

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Page 162 of 187


A.4.2.3.1

For infomation on the hazards associated with flammable gas and vapor explosions, see the SFPEHandbook of Fire Protection Engineering , 5th edition, Chapter 69, Flamable Gas and Vapor Explosions.

For information on the hazards associated with dusts explosions, see the SFPE Handbook of FireProtection Engineering , 5th edition, Chapter 70, Dust Explosions.


The SFPE Handbook of Fire Protection Engineering provides detailed information on gas and vapor explosion hazards in Chapter 69 and dust explosions in Chapter 70 that can be helpful for a designed who is tasked with performing a hazard analysis.



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Page 163 of 187


A.4.2.3.2

For information on a methodology for performing and documenting a risk assessement, see the SFPEEngineering Guide to Fire Risk Assessemen t, 2006.


The SFPE Guide to Fire Risk Assessment provides a methodology on how to perform and document a risk assessment.



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Page 164 of 187

Public Input No. 16-NFPA 69-2016 [ Section No. A.10.1 ]

A.10.1

Explosion suppression systems mitigate the hazardous effects of a deflagration within a protectedenclosure by detecting the deflagration in the early stages of formation (incipient) and extinguishing thefireball before the pressure exceeds the pressure resistance of the enclosure. An explosion suppressionsystem typically consists of explosion detectors, high rate discharge (HRD) suppressors with appropriatedispersion nozzles, and a control panel. Explosion isolation is often used in conjunction with these systemsto minimize the potential for flame propagation from the protected enclosure. Explosion suppressionsystems can be used when the combustible products are toxic and can be used irrespective of the locationof the protected enclosure.

Explosion suppression systems typically use dry chemicals (sodium bicarbonate or monoammoniumphosphate) or water as suppressants. Injection of a suppressant into the propagating flame front of theincipient explosion reduces the temperature of the combustible material below a level necessary to sustaincombustion. Thermal quenching (heat absorption) is the principal mechanism utilized by explosionsuppressants.

Explosion suppression systems often utilize methods such as paired detectors, detector voting, andvibration isolation devices to reduce the possibility of inadvertent activations. To aid in the investigation of asystem activation, an indicating device denoting the actuating detector is sometimes used.

Explosion suppression systems have been applied in volumes from 0.2 m3 to 1500 m3 (7.1 ft3 to 52,972

ft3) and against a wide variety of combustible materials.

For additional information on the design of explosion suppression systems, see the SFPE Handbook ofFire Protection , 5th edition, Chapter 44, Clean Agent Total Flooding Fire Extinguishing Systems.


Chapter 44 of the SFPE Handbook of Fire Protection Engineering provides additional information on the design of explosion suppression systems.



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Page 165 of 187

Public Input No. 28-NFPA 69-2017 [ Section No. A.10.1 ]

A.10.1

Explosion suppression systems mitigate the hazardous effects of a deflagration within a protectedenclosure by detecting the deflagration in the early stages of formation (incipient) and extinguishing thefireball before the pressure exceeds the pressure resistance of the enclosure. An explosion suppressionsystem typically consists of explosion detectors, high rate discharge (HRD) suppressors with appropriatedispersion nozzles, and a control panel. Explosion isolation is often used in conjunction with these systemsto minimize the potential for flame propagation from the protected enclosure. Explosion suppressionsystems can be used when the combustible products are toxic and can be used irrespective of the locationof the protected enclosure.

Explosion suppression systems typically use dry chemicals (sodium bicarbonate or monoammoniumphosphate) or water as suppressants. Injection of a suppressant into the propagating flame front of theincipient explosion reduces the temperature of the combustible material below a level necessary to sustaincombustion. Thermal quenching (heat absorption) is the principal mechanism utilized by explosionsuppressants.

Explosion suppression systems often utilize methods such as paired detectors, detector voting, andvibration isolation devices to reduce the possibility of inadvertent activations. To aid in the investigation of asystem activation, an indicating device denoting the actuating detector is sometimes used.

Explosion suppression systems have been applied in volumes from 0.2 m3 to 1500 m3 (7.1 ft3 to 52,972

ft3) and against a wide variety of combustible materials.

Princple of explosion suppression System and components involved to be explained in detail withsketch as attached



Typical_Suppression_Sketch.pdf Typical sketch only. The intent is identify the critical components


The reader should be made aware of what typical components are involved in suppression system.


Submitter Full Name: Venkateswara Bhamidipati

Organization: Powder Process Solutions

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Page 166 of 187


A.10.8.1

The agent can suppression agent and if any escaping gases/contaminants/parts not isolated andreleased from detonators can introduce contamination or chemical hazards when used in combination withcertain process chemicals or materials of construction. The choice of agent should include an evaluation ofall potential adverse interactions between the agent and process. A chemical interaction matrix, forexample, the NOAA Reactivity Worksheet, is an excellent tool to use as a part of this evaluation.


As there may be a possibility of release of additional gases, plastic/metal parts that trigger the agent into the system.


Submitter Full Name: Venkateswara Bhamidipati

Organization: Powder Process Solutions

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Page 167 of 187

Public Input No. 32-NFPA 69-2017 [ New Section after B.7 ]

B.8 Limiting Oxygen Concentration for Fuel Mixtures

See proposed TIA 1212 for text of new section


Provide new annex material which offers guidance and example calculations on how to estimate the LOC for a fuel or a fuel mixture using established methods. The method is only applicable for nitrogen diluent and is not presently recommended for mixtures containing any component with a UFL greater than 75 mol% in air.




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Page 168 of 187

Public Input No. 10-NFPA 69-2016 [ Section No. C.1 ]



Page 169 of 187

Replace table with attached

C.1 General.



Page 170 of 187

Table C.1(a) and Table C.1(b) provide values for limiting oxidant concentration (LOC) using nitrogen,carbon dioxide, and inert dust as the diluent. Table C.1(a) provides LOC values for flammable gases, andTable C.1(b) provides data for combustible dust suspensions.

Table C.1(a) Limiting Oxidant Concentrations for Flammable Gases When Nitrogen or Carbon Dioxide AreUsed as Diluents

Gas/Vapor

Adjusted LOC

(Volume % O2 Above Which

Deflagration Can Take Place) per7.2.3

Reference*

Original LOC

(Volume % O2 Above

Which DeflagrationCan

Take Place)

N2–Air

MixtureCO2–Air Mixture

N2–Air

Mixture

CO2–Air

Mixture

Methane 10.0 12.5 1 12.0 14.5

Ethane 9.0 11.5 1 11.0 13.5

Propane 9.5 12.5 1 11.5 14.5

n-Butane 10.0 12.5 1 12.0 14.5

n-Butyl acetate 9.0 — 9 9.0 —

Isobutane 10.0 13.0 1 12.0 15.0

n-Pentane 10.0 12.5 1 12.0 14.5

Isopentane 10.0 12.5 2 12.0 14.5

n-Hexane 10.0 12.5 1 12.0 14.5

n-Heptane 9.5 12.5 2 11.5 14.5

Ethanol 8.7 — 9 8.7 —

Ethylene 8.0 9.5 1 10.0 11.5

Propylene 9.5 12.0 1 11.5 14.0

1-Butene 9.5 12.0 1 11.5 14.0

Isobutylene 10.0 13.0 4 12.0 15.0

Butadiene 8.5 11.0 1 10.5 13.0

3-Methyl-1-butene 9.5 12.0 4 11.5 14.0

Benzene 10.1 12.0 1, 7 11.4 14.0

Toluene 9.5 — 7, 9 9.5 —

Styrene 9.0 — 7 9.0 —

Ethylbenzene 9.0 — 7 9.0 —

Vinyltoluene 9.0 — 7 9.0 —

Divinylbenzene 8.5 — 7 8.5 —

Diethylbenzene 8.5 — 7 8.5 —

Cyclopropane 9.5 12.0 1 11.5 14.0

Gasoline

(73/100) 10.0 13.0 2 12.0 15.0

(100/130) 10.0 13.0 2 12.0 15.0

(115/145) 10.0 12.5 2 12.0 14.5

Kerosene 8.0 (150°C) 11.0 (150°C) 510.0

(150°C)13.0

(150°C)

JP-1 fuel 8.5 (150°C) 12.0 (150°C) 210.5

(150°C)14.0

(150°C)



Page 171 of 187

Gas/Vapor

Adjusted LOC



Reference*

Original LOC

(Volume % O2 Above


Take Place)

N2–Air


N2–Air

Mixture

CO2–Air

Mixture

JP-3 fuel 10.0 12.5 2 12.0 14.5

JP-4 fuel 9.5 12.5 2 11.5 14.5

Natural gas (Pittsburgh) 10.0 12.5 1 12.0 14.5

n-Butyl chloride 12.0 — 3 14.0 —

10.0 (100°C) — 312.0

(100°C)—

Methylene chloride17.0 (30°C)

15.0 (100°C)

—

—

3

3

19.0 (30°C)

17.0(100°C)

—

—

Ethylene dichloride11.0

9.5 (100°C)

—

—

3

3

13.0

11.5 (100°C)

—

—

1,1,1-Trichloroethane 12.0 — 3 14.0 —

Trichloroethylene 7.0 (100°C) — 3 9.0 (100°C) —

Acetone 9.5 12.0 4 11.5 14.0

n-Butanol NA 14.5 (150°C) 4 NA16.5

(150°C)

Carbon disulfide 3.0 5.5 4 5.0 7.5

Carbon monoxide 3.5 3.5 4 5.5 5.5

Ethanol 8.5 11.0 4 10.5 13.0

2-Ethyl butanol 7.5 (150°C) — 4 9.5 (150°C) —

Ethyl ether 8.5 11.0 4 10.5 13.0

Hydrogen 3.0 3.2 4 5.0 5.2

Hydrogen sulfide 5.5 9.5 4 7.5 11.5

Isobutyl acetate 9.1 — 9 9.1 —

Isobutyl alcohol 9.1 — 9 9.1 —

Isobutyl formate 10.5 13.0 4 12.5 15.0

Isopropyl acetate 8.8 — 9 8.8 —

Isopropyl alcohol 9.5 — 10 9.5 —

Methanol 8.0 10.0 4 10.0 12.0

Methyl acetate 9.0 11.5 4 11.0 13.5

Propylene oxide 5.8 — 8 7.8 —

Methyl ether 8.5 11.0 4 10.5 13.0

Methyl formate 8.0 10.5 4 10.0 12.5

Methyl ethyl ketone 9.0 11.5 4 11.0 13.5

n-Propyl acetate 10.1 — 10 10.1 —

n-Propyl alcohol 8.6 — 9 8.6 —

UDMH (dimethyl-hydrazine)

5.0 — 6 7.0 —

Vinyl chloride 13.4 — 7 13.4 —



Page 172 of 187

Gas/Vapor

Adjusted LOC



Reference*

Original LOC

(Volume % O2 Above


Take Place)

N2–Air


N2–Air

Mixture

CO2–Air

Mixture

Vinylidiene chloride 15.0 — 7 15.0 —

Notes:

1. See 7.7.2 for the required oxygen level in equipment.

2. Data were determined by laboratory experiment conducted at atmospheric temperature and pressure.Vapor–air–inert gas samples were placed in explosion tubes and ignited by electric spark or pilot flame.

*References:

1. J. F. Coward and G. W. Jones (1952).

2. G. W. Jones, M. G. Zabetakis, J. K. Richmond, G. S. Scott, and A. L. Furno (1954).

3. J. M. Kuchta, A. L. Furno, A. Bartkowiak, and G. H. Martindill (1968).

4. M. G. Zabetakis (1965).

5. M. G. Zabetakis and B. H. Rosen (1957).

6. Unpublished data, U.S. Bureau of Mines.

7. Unpublished data, Dow Chemical Co.

8. U.S. Bureau of Mines.

9. L. G. Britton (2002).

10. Unpublished data, Dow Chemical Co., 2002.

Table C.1(b) Limiting Oxidant Concentrations for Combustible Dust Suspensions When Using Nitrogen asa Diluent

Dust

Median Particle

Diameter byMass

(μm)

LOC (Volume % O2 Above Which Deflagration

Can

Take Place),

N2–Air Mixture

Cellulosic Materials

Cellulose 22 9

Cellulose 51 11

Wood flour 27 10

Food and Feed

Pea flour 25 15

Corn starch 17 9

Waste from malted barley 25 11

Rye flour 29 13

Starch derivative 24 14

Wheat flour 60 11

Coals

Brown coal 42 12

Brown coal 63 12

Brown coal 66 12



Page 173 of 187

Dust

Median Particle

Diameter byMass

(μm)

LOC (Volume % O2 Above Which Deflagration

Can

Take Place),

N2–Air Mixture

Brown coal briquette dust 51 15

Bituminous coal 17 14

Plastics, Resins, Rubber

Resin <63 10

Rubber powder 95 11

Polyacrylonitrile 26 10

Polyethylene, h.p. 26 10

Pharmaceuticals, Pesticides

Amino- phenazone <10 9

Methionine <10 12

Intermediate Products,Additives

Barium stearate <63 13

Benzoyl peroxide 59 10

Bisphenol A 34 9

Cadmium laurate <63 14

Cadmium stearate <63 12

Calcium stearate <63 12

Methyl cellulose 70 10

Dimethyl terephthalate 27 9

Ferrocene 95 7

Bistrimethyl- silyl-urea 65 9

Naphthalic acid anhydride 16 12

2-Naphthol <30 9

Paraform- aldehyde 23 6

Pentaerythritol <10 11

Metals, Alloys

Aluminum 22 5

Calcium/ aluminum alloy 22 6

Ferrosilicon magnesium alloy 17 7

Ferrosilicon alloy 21 12

Magnesium alloy 21 3

Other Inorganic Products

Soot <10 12

Soot 13 12

Soot 16 12

Others

Bentonite derivative 43 12

Source: R. K. Eckhoff, Dust Explosions in the Process Industries, 2003.

Note: The data came from 1 m3 and 20 L chambers using strong chemical igniters.




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Issued_TIA_69-14-1.docx TIA 69-14-1





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NFPA® 69


2014 Edition


TIA 14-1

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Public Input No. 4-NFPA 69-2015 [ Chapter H ]

Annex H Informational References

H.1 Referenced Publications.

The documents or portions thereof listed in this annex are referenced within the informational sections ofthis standard and are not part of the requirements of this document unless also listed in Chapter 2 for otherreasons.

H.1.1 NFPA Publications.


NFPA 51B, Standard for Fire Prevention During Welding, Cutting, and Other Hot Work, 2014 edition.



Fire Protection Guide to Hazardous Materials, 14th edition, 2010.

H.1.2 Other Publications.

H.1.2.1 AIChE Publications.

American Institute of Chemical Engineers, Three Park Avenue, New York, NY 10016-5991.

AIChE Center for Chemical Process Safety, Guidelines for Hazard Evaluation Procedures, Wiley, New York,1992.

H.1.2.2 ANSI Publications.

American National Standards Institute, Inc., 25 West 43rd Street, 4th Floor, New York, NY 10036.

ANSI/ISA 84.00.01, Parts 13, Functional Safety: Safety Instrumented Systems for the Process IndustrySector, 2004.

H.1.2.3 API Publications.

American Petroleum Institute, 1220 L Street, NW, Washington, DC 20005.

API 2000 STD 2000 , Venting Atmospheric and Low-Pressure Storage Tanks Nonrefrigerated andRefrigerated , 4th 7 th edition, 1992 2014 .

API 2016 API RP 2016 , Guidelines and Procedures for Entering and Cleaning Petroleum Storage Tanks,2001, reapproved 2006 .

H.1.2.4 ASME Publications.

American Society of Mechanical Engineers, Three ASME International , Two Park Avenue, New York,NY 10016-5990.

ASME Boiler and Pressure Vessel Code, 2007 2015 .



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H.1.2.5 ASTM Publications.


ASTM E 1226 E1226 , Standard Test Method for Explosibility of Dust Clouds, 2010 2012a .

ASTM E 1491 E1491 , Standard Test Method for Minimum Autoignition Temperatures of Dust Clouds,2006, reapproved 2012 .

ASTM E 1515 E1515 , Standard Test Method for Minimum Explosible Concentration of Combustible Dusts,2003 2014 .

ASTM E 2019 E2019 , Standard Test Method for Minimum Ignition Energy of a Dust Cloud in Air, 2003,reapproved 2013 .

ASTM E 2021 E2021 , Standard Test Method for Hot-Surface Ignition Temperature of Dust Layers, 20062015 .

ASTM E 2079 E2079 , Standard Test Methods for Limiting Oxygen (Oxidant) Concentration in Gases andVapors, 2007, reapproved 2013 .

ASTM WK 1680, Test Method for Limiting Oxygen (Oxidant) Concentration of Combustible Dust Clouds,unpublished draft.

H.1.2.6 CEN Publications.

European Committee for Standardization, 36 rue de Stassart, B-1050 CEN-CENELEC ManagementCentre, Avenue Marnix 17 , B- 1000 Brussels, Belgium.

EN 12874:2001, Flame Arresters— Performance Requirements, Test Methods and Limits for Use, 2001.(Superseded by BS EN ISO 16852)

BS EN 14034-4, Determination of Explosion Characteristics of Dust Clouds , - Part 4: Determination ofthe Limiting Oxygen Concentration LOC of Dust Clouds, 2004 5th edition, 2005, amendment 1, 2011 .

BS EN ISO 16852, Flame arresters— Performance requirements, test methods and limits for use, ISO16852:2008, including Cor 1:2008 and Cor 2:2009 2011 ; German version EN ISO 16852:2010.

H.1.2.7 FM Global Publications.

FM Global, 270 Central Avenue, P.O. Box 7500, Johnston, RI 02919-4923 .

FM Global Loss Prevention Data Sheet 7-76, “Prevention and Mitigation of Combustible Dust Explosionsand Fire,” January 2012.

H.1.2.8 IEC Publications.

International Electrotechnical Commission, 3, rue de Varembé, P.O. Box 131, CH-1211 Geneva 20,Switzerland.

IEC 61511, Functional Safety — Safety Instrumented Systems for the Process Industry Sector, 2003.

H.1.2.9 Military Specifications.

Department of Defense Single Stock Point, Document Automation and Production Service DLA DocumentServices , Building 4/D, 700 Robbins Avenue, Philadelphia, PA 19111-5094.

MIL-B-87162A, Military Specification: Baffle Material, Explosion Suppression, Expanded Aluminum Mesh,for Aircraft Fuel Tanks, 1994. (Cancelled No S/S document 15-Oct-2004)

MIL-C DTL -5541F , Chemical Conversion Coatings on Aluminum and Aluminum Alloys, 2006.

MIL-DTL-83054C, Detailed Specification Baffle and Inserting Material, Aircraft Fuel Tank, 2003.(Transformed on 03-Nov-2009 into QPL in the QPD)

MIL-PRF-87260A (USAF), Performance Specification, Foam Material, Explosion Suppression, InherentlyElectrostatically Conductive, for Aircraft Fuel Tanks, 1998. (Transformed on 27-Apr-2007 into QPL in theQPD)

H.1.2.10 NOAA Publications.

National Oceanic and Atmospheric Administration, (NOAA), 14th Street and Constitution Avenue, NW,Washington, DC 20230.

NOAA Reactivity Worksheet, April 2007.



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H.1.2.11 SAE Publications.

Society of Automotive Engineers SAE International , 400 Commonwealth Drive, Warrendale, PA 15096.

SAE AIR 4170A, Reticulated Polyurethane Foam Explosion Suppression Material for Fuel Systems and DryBays, 1998, reaffirmed 2007 .

H.1.2.12 U.S. Government Publications.

U.S. Government Printing Publishing Office, 732 North Capitol Street, NW, Washington, DC20402 20401-0001 .




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H.1.2.13 Other Publications.



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Bartknecht, W., Explosions: Course, Prevention, Protection, Springer-Verlag, Heidelberg, 1989.

Barton, J. (Editor), Dust Explosion Prevention and Protection — A Practical Guide. Gulf ProfessionalPublishing, Houston, TX, 2002.

Britton, L. G., “Using Heats of Oxidation to Evaluate Flammability Hazards,” Process Safety Progress,20(1), 31–54, March 2002.

Chatrathi, K., and J. Going, “Pipe and Duct Deflagrations Associated with Incinerators,” Process SafetyProgress, 15(4), 237, 1996.

Chatrathi, K., J. Going, and W. Grandestaff, “Flame Propagation in Industrial Scale Piping,” Process SafetyProgress, 20(4), 286–294, 2001.

Coward, J. F., and G. W. Jones, “Limits of Flammability of Gases and Vapors,” Bulletin 503, U.S. Bureau ofMines, Pittsburgh, PA, 1952.

Eckhoff, R. K., Dust Explosions in the Process Industries, Butterworth-Heinemann, Oxford, England, 2003.

Förster, H., Flame Arrester Testing and Qualification in Europe, Proceedings of the 10th InternationalSymposium on Loss Prevention and Safety Promotion in the Process Industries, Stockholm, Sweden,19–21 June 2001a.

Förster, H., Flame Arresters — The new standard and its consequences, Proceedings of the InternationalESMG Symposium, Part 2: Industrial Explosion Protection, Nürnberg, Germany, 27–29 March 2001b.

Förster, H., and C. Kersten, Investigation of Deflagrations and Detonations in Pipes and Flame Arresters byHigh Speed Framing, 4th International Symposium on Hazards, Prevention and Mitigation of IndustrialExplosions, Bourges, France, 21–25 October 2002.

Green, D. W., and R. H. Perry, Chemical Engineering Handbook, 7th ed., Wiley, New York, 1997.

Grossel, S. S., Detonation and Deflagration Flame Arresters, Wiley, New York, May 2002.

Hattwig, M., and H. Steen, Handbook of Explosion Prevention and Protection, Wiley–VCH Verlag GmbH &Co., Weinheim, Germany, 2004.

Heidermann, T., and M. Davies, In-Line Flame Arrester Application Limits and Matrix Concept for ProcessPlant Safety from Flash Back of Thermal Combustion Units, Proceedings of the 40th Annual LossPrevention Symposium, Global Congress on Process Safety AIChE Spring National Meeting, Orlando, FL,April 24–27, 2006.

Jo, Young-Do and K-S. Park, “Minimum Amount of Flammable Gas for Explosion within a Confined Space,”Process Safety Progress, v 23, 2004.

Jones, G. W., M. G. Zabetakis, J. K. Richmond, G. S. Scott, and A. L. Furno, Research on the FlammabilityCharacteristics of Aircraft Fuels, Wright Air Development Center, Wright-Patterson AFB, OH, TechnicalReport 52-35, Supplement I, 57 pp., 1954.

Ketchum, D. E., J. K. Thomas, and Q. A Baker, Loss of Inerting Due to Multiple Exhaust Vents, paperpresented at the 39th Annual Loss Prevention Symposium, Atlanta, GA, April 10–15, 2005.

Kondo, S., K. Takizawa, A. Takahashi, and K. Tokuhashi, Extended Le Chatelier's formula and nitrogendilution effect on the flammability limits,” Fire Safety Journal, Elsevier, 41, 406–417, 2006.

Kondo, S., K. Takizawa, A. Takahashi, K. Tokuhashi, and A. Sekiya, “A study on flammability limits of fuelmixtures,” Journal of Hazardous Materials, Elsevier, 155, 440–448, 2008.

Kuchta, J. M., Bulletin 680, U.S. Bureau of Mines, Pittsburgh, PA, 1985.

Kuchta, J. M., A. L. Furno, A. Bartkowiak, and G. H. Martindill, Effect of Pressure and Temperature onFlammability Limits of Chlorinated Combustibles in Oxygen-Nitrogen and Nitrogen Tetroxide-NitrogenAtmospheres, Journal of Chemical and Engineering Data, Vol. 13, No. 3, p. 421, July 1968 (AmericanChemical Society, Washington, D.C.).

Ma, T., “A thermal theory for estimating the flammable limits of a mixture,” Fire Safety Journal, Elsevier, 46,558–567, 2011.

Moore, P., and D. Spring, Design of Explosion Isolation Barriers, IChemE Symposium Series No. 150, pp.1–20, 2004.

Ogle, R., “Explosion Hazard Analysis for an Enclosure Partially Filled With a Flammable Gas,” ProcessSafety Progress, v 18, 1999.



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Roser, M., A. Vogl, S. Radandt, W. Malalasekera, and R. Parkin, “Investigations of Flame Front Propagationbetween Interconnected Process Vessels,” J Loss Prevention Process Industries, 12 , 421–436, 1999.

Senecal, J.A., “Flame extinguishing in the cup-burner by inert gases,” Fire Safety Journal, Elsevier, 40,579–591, 2005.

Siwek, R., and P. E. Moore, “Design Practice for Extinguishing Barrier Systems,” Process Safety Progress,16(4), 219, 1997.

Szego, A., K. Premji, and R. Appleyard, Evaluation of Explosafe Explosion Suppression System for AircraftFuel Tank Protection, Air Force Report AFWAL-TR-2043, AD A093125, 1980.

Zabetakis, M. G., Flammability Characteristics of Combustible Gases and Vapors, Bulletin 627, U.S. Bureauof Mines, Pittsburgh, PA, 1965.

Zabetakis, M. G., and B. H. Rosen, Considerations Involved in Handling Kerosine, Proceedings, API, Vol.37, Sec. III, 1957, p. 296.

H.2 Informational References.

The following documents or portions thereof are listed here as informational resources only. They are not apart of the requirements of this document.

Aluminum Association AA TEAL1 , International Alloy Designations and Chemical Composition Limits forWrought Aluminum and Wrought Aluminum Alloys, Alexandria, VA, April 2006 February , AluminumAssociation Standard 2009.

ANSI/AA H35.1 / H35. 1 1M , Alloy and Temper Designation System for Aluminum, Aluminum Association,Alexandria, VA, 2006 2013 .

Brenn- und Explosions-Kenngrossen von Stauben, Berufsgenossenschaftliches Institut fur Arbeitssicherheit(BIA) Bergbau-Versuchsstrecke, Institut fur Explosionsschutz und Sprengtechnik, Sonderdruck dersicherheitstechnischen.

Noronha, J. A., J. T. Merry, and W. C. Reid, Deflagration Pressure Containment for Vessel Safety Design,Plant/Operations Progress, Vol. 1, No. 1, American Institute of Chemical Engineers, New York, NY, January1982.

Pineau, J. P., Mechanisms of the Propagation of Dust Explosions in Elongated Vessels, Seminar Course onDust Explosion Venting, London, October 1987.

Schuber, G., Rotary Valves for Explosion Isolation: Approval Without Testing, European Information Centrefor Explosion Protection–International Symposium, Antwerp, Belgium, September 1989.

VDI Richtlinie 3673, Verein Deutscher Ingenieure-Kommission Reinhalting der Luft, Dusseldorf, VDI VerlagGmbH, Dusseldorf, 1979 and 1983.

Zabetakis, M. G., Gasfreeing of Cargo Tanks, Information Circular 7994, U.S. Bureau of Mines, Pittsburgh,PA, 1961.

H.3 References for Extracts in Informational Sections. (Reserved)


Referenced current SDO names, addresses, standard names, numbers, and editions.



Public Input No. 3-NFPA 69-2015[Chapter 2]

Referenced current SDO names, addresses, standard names,numbers, and editions.


Submitter Full Name: Aaron Adamczyk

Organization: [ Not Specified ]

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Public Input No. 19-NFPA 69-2016 [ Section No. H.1.2.5 ]

H.1.2.5 ASTM Publications.


ASTM E 1226 E1226 , Standard Test Method for Explosibility of Dust Clouds, 2010 2012a .

ASTM E 1491 E1491 , Standard Test Method for Minimum Autoignition Temperatures of Dust Clouds, 2006(2012) .

ASTM E 1515 E1515 , Standard Test Method for Minimum Explosible Concentration of Combustible Dusts,2003 2014 .

ASTM E 2019 E2019 , Standard Test Method for Minimum Ignition Energy of a Dust Cloud in Air, 2003(2013) .

ASTM E 2021 E2021 , Standard Test Method for Hot-Surface Ignition Temperature of Dust Layers,2006 2015 .

ASTM E 2079 E2079 , Standard Test Methods for Limiting Oxygen (Oxidant) Concentration in Gases andVapors, 2007 (2013) .

ASTM WK 1680 E2931 , Standard Test Method for Limiting Oxygen (Oxidant) Concentration ofCombustible Dust Clouds , unpublished draft. (2013)


date updates and standard replacing the unpublished draft



Public Input No. 20-NFPA 69-2016 [Section No. A.3.3.25]




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Documents

TECHNICAL COMMITTEE ON EXPLOSION PROTECTION …...NFPA 69 First Draft and NFPA 68 Second Draft Meeting Agenda . January 24-26, 2017 8:00 AM - 5:00 PM EST ... Jason Krbec CV Technology,