Technical Committee on Explosion Protection Systems (EXL-AAA)€¦ · Technical Committee on Explosion Protection Systems (EXL-AAA) M E M O R A N D U M DATE: March 13, 2012 TO: Principal

Technical Committee on Explosion Protection Systems (EXL-AAA)

MEMORANDUM

DATE: March 13, 2012 TO: Principal and Alternate Members of the Technical Committee on Explosion

Protection Systems (EXL-AAA) FROM: Jon Hart, Associate Fire Protection Engineer/NFPA Staff Liaison SUBJECT: AGENDA PACKAGE– NFPA 67 + 68 ROC Meeting (Fall 2012) ________________________________________________________________________ Enclosed is the agenda for the Report on Comments (ROC) meeting for NFPA 67, Guideline on

Explosion Protection for Gaseous Mixtures in Pipe Systems, and NFPA 68, Standard on

Explosion Protection by Deflagration Venting, which will be held on Tuesday, March 27th

through Thursday, March 29th, 2012 in Charleston, South Carolina. Please review the

attached comments in advance, and if you have alternate suggestions, please come prepared with

proposed language and respective substantiation.

If you have any technical questions prior to the meeting, please do not hesitate to contact me at:

Office: (617) 984-7470 Email: [email protected]

For administrative questions, please contact Elena Carroll at (617) 984-7952.

I look forward to working with everyone.

mailto:[email protected]

Technical Committee on Explosion Protection Systems

(EXL-AAA) NFPA 67 + 68 ROC Meeting (Fall 2012 Cycle)

Tuesday, March 27, 2012, - Thursday, March 29, 2012

Sheraton Charleston Airport Hotel 4770 Goer Drive, Charleston, SC

AGENDA

Tuesday, March 27, 2012

1. Call to Order – 1:00 PM

2. Introductions and Attendance

3. Review Agenda

4. Committee Member Status and Update of Membership Roster

5. NFPA Staff Liaison Presentation

6. Approval of Previous Meeting Minutes

7. Chairman Comments

8. Act on Public Comments and Committee Comments

a. NFPA 68 Chapter 7 and Gas-related issues

b. NFPA 67 public comments flexible depending on supporter attendance

9. Adjourn Meeting – ca. 5:30 PM

Wednesday, March 28, 2012

1. Call to Order – 8:00 AM

2. Continue Action on Comments

a. Complete NFPA 68 Gas comments

b. NFPA 67 public comments flexible depending on supporter attendance

c. NFPA 68 Dust comments

3. Adjourn Meeting- ca. 5:30 PM





Thursday, March 29, 2012

1. Call to Order – 8:00 AM

2. Complete Action on Public Comments

3. Complete Action on Committee Comments

4. Adjourn Meeting – 5:00 pm

Please submit requests for additional agenda items to the chair at least seven days prior to

the meeting.

Please notify the chair and staff liaison as soon as possible if you plan to introduce any

committee proposals at the meeting.

Address List No PhoneExplosion Protection Systems EXL-AAA

Barry D. Chase03/12/2012

EXL-AAA

Samuel A. Rodgers

ChairHoneywell, Inc.15801 Woods Edge RoadColonial Heights, VA 23834

U 4/1/1996EXL-AAA

Luke S. Morrison

SecretaryProfessional Loss Control Inc.PO Box 162Fredericton, NB E3B 4Y9 CanadaAlternate: Martin P. Clouthier

SE 1/1/1987

EXL-AAA

Michael Davies

PrincipalPROTEGOIndustriestrassellBraunschweig, D-38110 Denmark

M 1/14/2005EXL-AAA

Todd A. Dillon

PrincipalXL Global Asset Protection Services1620 Winton AvenueLakewood, OH 44107Alternate: Paul F. Hart

I 7/16/2003

EXL-AAA

Alexi I. Dimopoulos

PrincipalExxonMobil CorporationEMRE, Safety, Risk and Fire Protection3225 Gallows Road, Room 3A1511Fairfax, VA 22037-0001American Petroleum Institute

U 4/15/2004EXL-AAA

Henry L. Febo, Jr.

PrincipalFM GlobalEngineering Standards1151 Boston-Providence TurnpikePO Box 9102Norwood, MA 02062-9102Alternate: John A. LeBlanc

I 8/5/2009

EXL-AAA

Robert J. Feldkamp

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

M 7/29/2005EXL-AAA

Larry D. Floyd

PrincipalBASF/Ciba Specialty Chemicals Corporation1379 Ciba RoadMcIntosh, AL 36553

U 7/29/2005

EXL-AAA

Joseph P. Gillis

Principal29 Hyder StreetWestboro, MA 01581

SE 10/1/1980EXL-AAA

John E. Going

PrincipalFike Corporation704 South 10th StreetBlue Springs, MO 64015Alternate: Jef Snoeys

M 9/30/2004

EXL-AAA

Stanley S. Grossel

PrincipalProcess Safety & Design Consultant4 Marble Court, Unit 9Clifton, NJ 07013-2212

SE 1/1/1983EXL-AAA

Dan A. Guaricci

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

M 7/1/1991

EXL-AAA

Michael D. Hard

PrincipalHard Fire Suppression Systems, Inc.4645 Westerville Road, Suite AColumbus, OH 43231-6050Fire Suppression Systems AssociationAlternate: Kirk W. Humbrecht

IM 10/1/1994EXL-AAA

David D. Herrmann

PrincipalE. I. DuPont de Nemours & Company1007 Market Street, (D12016)Wilmington, DE 19898Alternate: Thomas C. Scherpa

U 10/10/1997

1



EXL-AAA

Alfonso F. Ibarreta

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

SE 3/4/2009EXL-AAA

David C. Kirby

PrincipalBaker Engineering & Risk Consultants, Inc.1560 Clearview HeightsCharleston, WV 25312Alternate: James Kelly Thomas

SE 1/1/1983

EXL-AAA

Steven A. McCoy

PrincipalCorn Products/National StarchPO Box 1084Indianapolis, IN 46206NFPA Industrial Fire Protection Section

U 10/10/1997EXL-AAA

James O. Paavola

PrincipalDTE Energy/Detroit Edison Company2000 Second Ave., Room 421 GODetroit, MI 48226

U 1/10/2002

EXL-AAA

Stefan Penno

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

M 11/2/2006EXL-AAA

Mitchel L. Rooker

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

M 10/10/1997

EXL-AAA

Joseph A. Senecal

PrincipalUTC/Kidde-Fenwal, Inc.400 Main StreetAshland, MA 01721Alternate: Randal R. Davis

M 1/1/1989EXL-AAA

Cleveland B. Skinker

PrincipalBechtel Power Corporation5275 Westview DriveFrederick, MD 21703-8306

SE 3/4/2009

EXL-AAA

Bill Stevenson

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

M 7/22/1999EXL-AAA

David R. Stottmann

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

M 11/2/2006

EXL-AAA

Stephen M. Stuart

PrincipalHylant Group2401 West Big Beaver Road, Suite 400Troy, MI 48084

I 7/24/1998EXL-AAA

Erdem A. Ural

PrincipalLoss Prevention Science & Technologies, Inc.810 Washington Street, Suite 4Stoughton, MA 02072

SE 1/16/1998

EXL-AAA

Robert G. Zalosh

PrincipalFirexplo20 Rockland StreetWellesley, MA 02481

SE 1/1/1991EXL-AAA

Eric R. Johnson

Voting AlternateSavannah River Nuclear Solutions, LLCSavannah River SiteBldg. 235-11H, Room 10Aiken, SC 29808Voting Alt. to Savannah River Nuclear Rep.

U 10/18/2011

2



EXL-AAA

Geof Brazier

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

M 3/21/2006EXL-AAA

Martin P. Clouthier

AlternateProfessional Loss Control Inc.PO Box 162Fredericton, NS E3B 4Y9 CanadaPrincipal: Luke S. Morrison

SE 10/27/2005

EXL-AAA

Randal R. Davis

AlternateUTC/Kidde-Fenwal, Inc.400 Main StreetAshland, MA 01721Principal: Joseph A. Senecal

M 7/14/2004EXL-AAA

Paul F. Hart

AlternateXL Global Asset Protection Services18257 Martin AvenueHomewood, IL 60430Principal: Todd A. Dillon

I 4/4/1997

EXL-AAA

Kirk W. Humbrecht

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

IM 7/19/2002EXL-AAA

Edward L. Jones

AlternateNordson Corporation300 Nordson Drive, M/S 44Amherst, OH 44001Principal: Robert J. Feldkamp

M 7/29/2005

EXL-AAA

Jason Krbec

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

M 10/18/2011EXL-AAA

John A. LeBlanc

AlternateFM Global1151 Boston-Providence TurnpikePO Box 9102Norwood, MA 02062-9102Principal: Henry L. Febo, Jr.

I 8/5/2009

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 01760Principal: Alfonso F. Ibarreta

SE 10/20/2010EXL-AAA

Thomas C. Scherpa

AlternateThe DuPont Company, Inc.71 Valley RoadSullivan, NH 03445Principal: David D. Herrmann

U 8/9/2011

EXL-AAA

Jef Snoeys

AlternateFike CorporationToekomstlaan 52Herentals, B-2200 BelgiumPrincipal: John E. Going

M 3/21/2006EXL-AAA

James Kelly Thomas

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

SE 8/9/2011

3



EXL-AAA

Franz Alfert

Nonvoting MemberInburex ConsultingAugust-Thyssen-Str.1Hamm, D-59067 Germany

SE 7/29/2005EXL-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

Harry Verakis

Nonvoting MemberUS Department of LaborMine Safety & Health AdministrationApproval & Certification CenterIndustrial Park Road, Box 251Triadelphia, WV 26059

E 1/1/1977

EXL-AAA

Richard F. Schwab

Member Emeritus79 Aspen DriveBasking Ridge, NJ 07920-1975

SE 1/1/1991EXL-AAA

Barry D. Chase

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

3/1/2012

4

Monday 3 12, Monday

Explosion Protection SystemsEXL-AAAName Representation Class Office

Distribution by %

Company

Todd A. Dillon XL Global Asset Protection Services I Principal

Henry L. Febo, Jr. FM Global I Principal

Stephen M. Stuart Hylant Group I Principal

3Voting Number Percent 11%

Michael D. Hard Hard Fire Suppression Systems, Inc. Fire IM Principal


Michael Davies PROTEGO M Principal

Robert J. Feldkamp Nordson Corporation M Principal

John E. Going Fike Corporation M Principal

Dan A. Guaricci ATEX Explosion Protection, L.P. M Principal

Stefan Penno Rembe GmbH Safety & Control M Principal

Mitchel L. Rooker BS&B Safety Systems, LLC M Principal

Joseph A. Senecal UTC/Kidde-Fenwal, Inc. M Principal

Bill Stevenson CV Technology, Inc. M Principal

David R. Stottmann ST Storage M Principal


Luke S. Morrison Professional Loss Control Inc. SE Secretary

Joseph P. Gillis SE Principal

Stanley S. Grossel Process Safety & Design Consultant SE Principal

Alfonso F. Ibarreta Exponent, Inc. SE Principal

David C. Kirby Baker Engineering & RiskConsultants, Inc.

SE Principal

Cleveland B. Skinker Bechtel Power Corporation SE Principal

Erdem A. Ural Loss Prevention Science &Technologies, Inc.

SE Principal

Robert G. Zalosh Firexplo SE Principal


Explosion Protection SystemsEXL-AAAName Representation Class Office

Distribution by %

Company

Samuel A. Rodgers Honeywell, Inc. U Chair

Alexi I. Dimopoulos ExxonMobil Corporation American U Principal

Larry D. Floyd BASF/Ciba Specialty ChemicalsCorporation

U Principal

David D. Herrmann E. I. DuPont de Nemours & Company U Principal

Steven A. McCoy Corn Products/National Starch NFPA U Principal

James O. Paavola DTE Energy/Detroit Edison Company U Principal

Eric R. Johnson Savannah River Nuclear Solutions,LLC

U Voting Alternate


28Total Voting Number

ROP MEETING MINUTES


August 15‐17, 2011

NFPA Headquarters, Quincy, MA

1. Call to order

The Fall 2012 ROP meeting of the Technical Committee on Explosion Protection Systems at NFPA Headquarters was called to order by Chairman Sam Rodgers on August 15, 2011 at 12:30 pm.

2. Introduction of Committee Members

Self introductions of members were completed. Those present are indicated below:

Fall 2012 ROP Meeting Attendance

NAME REPRESENTING

Rodgers, Samuel – Chair Honeywell, Inc.

Davies, Michael – Principal PROTEGO Inc.

Febo, Henry – Principal FM Global

Going, John – Principal Fike Corporation

Ibarreta, Alfonso – Principal Exponent, Inc.

Rooker, Mitchel – Principal BS&B Safety Systems, LLC

Senecal, Joseph – Principal UTC

Stevenson, Bill – Principal CV Technology, Inc.

Stuart, Stephen – Principal Hylant Group

Ural, Erdem – Principal Loss Prevention Science and Technologies

Zalosh, Robert – Principal Firexplo

Brazier, Geof – Alternate BS&B Safety Systems, LLC

Thomas, Kelly – Alternate Baker Engineering and Risk Consultants, Inc.

Hinske, Raymond – Guest API‐ Exxon Mobil

Hart, Jonathan – Staff Liaison NFPA

3. Announcements

Jonathan Hart reviewed NFPA’s meeting procedures. An introduction to the revised NFPA Regulations that will affect the Committee in its next cycle and in the revision of NFPA 69 was given and a review on how to access committee information from the “Doc Info” pages was

presented. The key remaining dates for the revision cycle of NFPA 67 and 68 were published in the meeting agenda package as follows:

Date for Mailing TC Ballots September 9, 2011

Receipt of TC Ballots by September 30, 2011

ROP Published and Posted December 23, 2011

Comment Closing Date March 2, 2012

Final Date for ROC Meeting May 4, 2012

Ballots Mailed to TC before May 18, 2012

ROC Published August 24, 2012

Intent to Make a Motion Closing (NITMAM) October 5, 2012

Issuance of Consent Document (No NITMAMs) November 27, 2012

NFPA Annual Meeting (Las Vegas) June 2013

Issuance of Document with NITMAM August 1, 2013

4. Approval of Minutes The minutes of the May 2007 committee meeting in PTB Headquarters Braunschweig, Germany as well

as the June 2011 Pre‐ROP meeting minutes in Quincy were approved.

5. Gas Task Group Presentation Bob Zalosh presented the work that had been completed by the gas task group and then detailed how the feedback from the Pre‐ROP meeting had been taken to produce the latest proposed gas venting equation. 5. Action on Proposals The committee acted on thirty‐three public proposals. Sixteen additional committee proposals were generated and acted upon. 6. Old Business There was no old business to discuss. 7. New Business There was no new business discussed. 8. Adjournment The meeting was adjourned at 4:00 pm on August 17, 2011.

August 25, 2011 Windows Live Meeting 1. The continuation of the ROP meeting to act on Committee Proposal 4 was called to order by

Chairman, Sam Rodgers at 1 pm. 2. Attendance for the conference call/ Windows Live meeting is indicated below:

Rodgers, Samuel – Chair Honeywell, Inc.

Davies, Michael – Principal PROTEGO Inc.

Dillon, Todd – Principal XL Global Asset Protection Services

Febo, Henry – Principal FM Global

Feldkamp, Robert – Principal Nordson Corporation

Going, John – Principal Fike Corporation

Grossel, Stanley – Principal Process Safety and Design Consultant

Hard, Michael – Principal Fire Suppression Systems Association

Ibarreta, Alfonso – Principal Exponent, Inc.

Kirby, David – Principal Baker Engineering & Risk Consultants

McCoy, Steven – Principal NFPA Industrial Fire Protection Section

Senecal, Joseph – Principal UTC

Skinker, Cleveland – Principal Bechtel Power Corporation

Stevenson, Bill – Principal CV Technology, Inc.

Stuart, Stephen – Principal Hylant Group

Zalosh, Robert – Principal Firexplo

Brazier, Geof – Alternate BS&B Safety Systems, LLC

Scherpa, Thomas – Alternate The DuPont Company, Inc.

Thomas, Kelly – Alternate Baker Engineering & Risk Consultants

Hart, Jonathan – Staff Liaison NFPA

3. The committee reviewed how Chapter 7 of NFPA 68 will look as proposed with the changes

to the gas venting equations accepted by straw poll at the committee meeting. 4. Committee Proposal 4 was accepted and corresponding committee proposals, generated to

remove references to KG within the annex, were also accepted.

5. The meeting was adjourned at 3 pm. Minutes prepared by: Jonathan Hart, Staff Liaison





Key Dates for the Fall 2012 Revision Cycle

Final Date for ROC Meeting May 4, 2012

Ballots Mailed to TC before May 18, 2012

Ballots Returned By June 1, 2012

ROC Published August 22, 2012

Closing Date for Notice of Intent to Make a Motion (NITMAM) October 5, 2012

Issuance of Consent Document (No NITMAMs) November 27, 2012

NFPA Annual Meeting June 2013

Issuance of Document with NITMAM August 1, 2013

Technical Committee deadlines are in bold.





Staff Liaison Notice

Note from the Staff Liaison

Dear Technical Committee Members:

We are very pleased that you will be participating in the processing of the 2013 Edition

of NFPA 67 and NFPA 68. Development of the Standard would not be possible without the

participation of volunteers like you.

Meeting Preparation Committee members are strongly encouraged to review the published comments prior to the

meeting and to be prepared to act on each item.

Handout materials should be submitted to the chair at least seven days prior to the meeting.

Only one posting of the comments will be made; it will be arranged in section/order and will be

pre-numbered. This will be posted to the NFPA 67 and NFPA 68 Document Information pages

(www.nfpa.org/67 or www.nfpa.org/68) under the “Next Edition” tab. If you have trouble

accessing the website please contact Elena Carroll at [email protected].

Mandatory Materials:

Last edition of the standard

Meeting agenda

Public proposals/comments

Committee Officers' Guide (Chairs)

Roberts’ Rules of Order (Chairs; An abbreviated version may be found in the

Committee Officer’s Guide)

Optional Materials:

NFPA Annual Directory

NFPA Manual of Style

Prepared committee proposals/comments (If applicable)

http://www.nfpa.org/67

http://www.nfpa.org/68

mailto:[email protected]





Regulations and Guiding Documents All committee members are expected to behave in accordance with the Guide for the Conduct of

Participants in the NFPA Codes and Standards Development Process.

All actions during and following the committee meetings will be governed in accordance with

the NFPA Regulations Governing Committee Projects. Failure to comply with these regulations

could result in challenges to the standards-making process. A successful challenge on procedural

grounds could prevent or delay publication of the document.

The style of the document must comply with the Manual of Style for NFPA Technical

Committee Documents.





General Procedures for Meetings

Use of tape recorders or other means capable of producing verbatim transcriptions of any

NFPA Committee Meeting is not permitted.

Attendance at all NFPA Committee Meetings is open. All guests must sign in and

identify their affiliation.

Participation in NFPA Committee Meetings is generally limited to committee members

and NFPA staff. Participation by guests is limited to individuals, who have received prior

approval from the chair to address the committee on a particular item, or who wish to

speak regarding public proposals or comments that they submitted.

The chairman reserves the right to limit the amount of time available for any

presentation.

No interviews will be allowed in the meeting room at any time, including breaks.

All attendees are reminded that formal votes of committee members will be secured by

letter ballot. Voting at this meeting is used to establish a sense of agreement, but only the

results of the formal letter ballot will determine the official action of the committee.

Note to Special Experts: Particular attention is called to Section 3.3(e) of the NFPA

Guide for the Conduct of Participants in the NFPA Codes and Standards Development

Process in the NFPA Directory. This section requires committee members to declare any

interest they may represent, other than their official designation as shown on the

committee roster. This typically occurs when a special expert is retained by and

represents another interest category on a particular subject. If such a situation exists on a

specific issue or issues, the committee member shall declare those interests to the

committee and refrain from voting on any action relating to those issues.

Smoking is not permitted at NFPA Committee Meetings.





Committee Actions All public proposals and comments must be acted upon by the committee. The following actions

are permitted by the Regulations Governing Committee Projects for disposition of comments.

Accept - The committee accepts the proposal or comment. Only editorial changes such as

paragraph and section numbering, and corrections to spelling, capitalization, and

hyphenation may be made.

Reject - The committee rejects the proposal or comment entirely. The committee may

reject any comment that is incomplete, per the NFPA Regulations Governing Committee

Projects.

Accept in Principle - The committee accepts the proposal or comment with revision. The

committee action must indicate the specific revisions to the proposed content, and the

locations of each revision within the proposed wording or the document.

Accept in Part - The committee accepts part of the proposal or comment and rejects the

remainder. Only editorial changes such as paragraph and section numbering, and

corrections to spelling, capitalization, and hyphenation may be made to the accepted

portion. The committee action must indicate the specific parts that were accepted and

rejected.

Accept in Principle in Part - The committee accepts part of the proposal or comment

with revision and rejects the remainder. The committee action must indicate the specific

parts that were accepted and rejected, as well as the nature and location of each revision.

Hold (Comment Stage Only) – The committee holds the comment to be considered as a

proposal during the next revision cycle. One of the following conditions must be met:

(a) The comment introduces a concept that has not had public review by being

included in a related proposal as published in the Report on Proposals.

(b) The comment would change the text proposed by the TC to the point that the TC

would have to restudy the text of the Report on Proposals or other affected parts

of the Document.

(c) The comment would propose something that could not be properly handled within

the time frame for processing the report.





Committee Statements Any proposal or comment that is "Rejected", "Accepted in Principle", "Accepted in Part",

"Accepted in Principle in Part", or “Held” must include a committee statement, preferably of a

technical nature, that provides the reasons for the action.

A committee statement is not required for any proposal or comment that is “Accepted”, but

should be included when the committee’s reasoning differs from the substantiation provided by

the submitter.

Report on Comments – November 2012 NFPA 67_______________________________________________________________________________________________67- Log #2

_______________________________________________________________________________________________Alexi I. Dimopoulos, ExxonMobil Research and Engineering

67-11Revise text to read as follows:

It is recommended to The installation of detonation arresters within the filling andemptying lines of below ground storage vessels should be considered if flammable atmospheres occur in these systemsduring routine operation. unless it can be assured that these lines are filled with liquid during operation all times. In thisapplication in-line detonation arresters are recommended as the ignition source (i.e. pump) is likely to be pretty far awayfrom the vessel which has to be protected. For systems which may contain flammable mixtures for non-routineoperations such as commissioning and decommissioning, the selection of mitigation strategies should commensuratewith risk. The addition of Detonation Arresters should undergo a Process Hazard Assessment to ensure the use of thedevice does not introduce a new risk (i.e. plugged vent or process lines which could result in equipment overpressure).

Industry experience indicates that for most industrial applications the wholesale addition of detonationarrestors is unnecessary introducing additional complexity and potentially new hazards in process equipment for littledemonstrated reduction in risk. The risk of plugged vents and process lines which may result in over pressures and aloss of containment could present a far greater risk to a facility than the explosion risk. The application of FlameArresters and Detonation Arresters should be risk based considering routine and non-routine operation, and equipmentfailure modes.

Note - pumps are not likely ignition sources as the pump is not likely to be operating if the line contains vapor.

_______________________________________________________________________________________________67- Log #3



In order to prevent exceeding the MAWP and MAWV of the vessel, a vent pipe to atmosphere is typicallyinstalled. The installation of detonation arrester should be considered if flammable atmospheres occur in these systemsduring routine operation. This vent pipe should be protected with a detonation arrester. Alternatively, an end-of-lineflame arrester can be installed if the length of the vent line is short enough so that the run-up distance from the possibleignition source, which is likely to occur at the end of the vent line, is smaller than the tested L/D ratio of the end-of-lineflame arrester. For systems which may contain flammable mixtures for non-routine operations such as commissioningand decommissioning, the selection of mitigation strategies should commensurate with risk. The addition of DetonationArresters should undergo a Process Hazard Assessment to ensure the inclusion of the device does not introduce a newrisk (i.e. plugged vent or process lines which could result in equipment overpressure.

Figure 10.2.1 shows one method of a typical safeguarding concept with flame and detonation arresters for anabove-ground storage tank containing flammable liquids utilizing flame and detonation arresters. The filling andemptying line is secured with liquid seals. The figure shows a vessel that is connected to a closed system for vaporbalancing and is additionally equipped with end of line pressure vacuum valves with integrated flame arresters.

Industry experience indicates that for most industrial applications the wholesale addition of detonationarrestors is unnecessary introducing additional complexity and potentially new hazards in process equipment for littledemonstrated reduction in risk. The risk of plugged vents and process lines which may result in over pressure and a lossof containment could present a far greater risk to a facility than the explosion risk. The application of Flame Arrestersand Detonation Arresters should be risk based considering routine and non-routine operation, and equipment failuremodes.

1Printed on 3/13/2012


_______________________________________________________________________________________________Harold Dinsmore, John Zink Company, LLC


In the following the assumption is made that flammableliquids are stored and processed and the vapors are recovered by a carbon, adsorption unit. The internal area of thestorage vessels, process vessels and piping is defined as zone O. To avoid hot spotting resulting from adsorption heatrelease, the vapor concentration is, brought down to 50% below LFL. This measure, if controlled properly, is the primarymeasure for explosion prevention. Additional explosion isolation measures are needed as the carbon adsorption vesselsare not designed explosion pressure proof and during the regenerative cycles it cannot be assured that the vapor airmixture will remain below 50% of LFL. For this reason. secondary measures in the form of flame arresters arerecommended for enhancing safety. It is recognized that this protection strategy may not be practical for all vaporrecovery applications which use carbon adsorption processes. An example of an application for which the statedprotection strategy would not be appropriate would be those applications where vapor recovery units with vacuumregenerated carbon adsorption beds are used to process feedstreams which have relatively high hydrocarbon vaporconcentration as would be typical of evaporative hydrocarbon vapor emissions resulting from the storage and/or filling oftransports at liquid product bulk distribution terminals. Therefore, for those types of applications, alternative safetyprotection strategies which have been demonstrated to be effective by the suppliers of these systems, are acceptable.

John Zink Company strongly objects to the proposed protective strategy for carbon adsorption units aspresented in paragraphs 10.4 and 10.4.1 because if this strategy was required, if would effectively eliminate vaporcontrol technology which has been used around the world for the past 35 years in bulk product distribution and storageterminals as the standard for vapor recovery of evaporative hydrocarbon vapor emissions. There are many differentapplications where carbon adsorption is used. The process as depicted in Figure 10.4.1 appears to be a conventionalsolvent recovery system which is characterized by passing an air stream containing a low concentration of hydrocarbonsolvent vapor through beds of activated carbon which are used to purify the air by adsorption of the hydrocarbonsolvent. The carbon beds are typically regenerated by introducing steam into the carbon beds. The steam desorbs thesolvent and it along with the desorbed solvent are condensed together using a suitable coolant. The condensed solventis then decanted from the steam condensate for recovery. While the protective strategy as proposed in Section 10.4may be appropriate for this type of application, it is not appropriate, or even feasible, for other types of applications andcarbon adsorption processes For example, the ADAB™ process, which my company manufactures, is principallyapplied to the recovery of evaporative hydrocarbon vapor emissions vented from transports (trucks, rail cars, barges andships) when those -l transports are being loaded with volatile organic liquids (e.g. gasoline loading). In the ADAB™process a mixed air and I hydrocarbon vapor stream containing a relatively high concentration of hydrocarbon is passedthrough beds of activated carbon where hydrocarbon vapor is adsorbed by the carbon allowing the purified air to bevented to the atmosphere. With this process, the carbon beds are regenerated for re-use by taking them off stream andpulling a vacuum on the bed with a mechanical vacuum pump. The desorbed hydrocarbon vapors discharging thevacuum pump are then recovered by absorption into a circulating absorption fluid which normally is the liquid from whichthe vapors were evaporated during the loading process.

The following comments are relative to the ADAB™ process:1) There are an estimated 3,000 ADAB™ systems in operation around the world with an excellent track record of safe

performance dating back for over 35 years and 300 million hours of run time. Because of the excellent reputation forreliability, recovery efficiency, and safety these systems have become the standard for evaporative hydrocarbon vaporemission recovery at bulk distribution terminals around the world .

2) Inlet air dilution of the vapor feedstream to 50% of LEL is definitely not recommended as this would not becompatible with the ADAB™ process. The applicability of the ADAB™ process is dependent upon the ability to processrelatively concentrated vapor feedstreams. Typically feedstreams to this process contain 10-50 volume % hydrocarbonvapor and are normally above the UFL. To require dilution of the vapor feedstream to 50% of the LEL would requirehuge quantities of air. For example, with a vapor feedstream containing 50 vol. % hydrocarbon vapor concentration,approximately 60 volumes of dilution air would be required for everyone volume of inlet vapor in order to attain the 50%LEL requirement. This dilution would not only significantly drive up system cost to handle all the dilution air, but wouldhave the effect of significantly reducing the adsorption capacity of the activated carbon to the extent that the processwould no longer be a viable vapor emission control alternative

3) John Zink company does agree that a detonation arrestor may be desired in the vapor feedstream piping between


Report on Comments – November 2012 NFPA 67the Vapor Recovery Unit and the transport loading operation however, we do not believe it is justified to install additionalarrestors in the vapor feed or vent piping from each adsorber vessel. In most ADAB applications, the vapor feed streamis caused to flow through the carbon beds without the need for a vapor blower simply by allowing a small back pressureto build in the transports as they are being filled. The additional arrestors would add significant pressure drop throughthe system such that blowers would have to be provided to move the vapors through the vapor recovery system toprevent too much back pressure in the transports being loaded. Further, the carbon beds are passive devices withoutmoving parts. They are filled with either granules or pellets of activated carbon, typically 2 to 4 mm in diameter. Thismedia acts as a flame arrestor and prevents passage of a flame front through the beds. Further, there are other provenmeans that have been used by the suppliers of this type of equipment to safely address the rare. potential for carbonbed hot spots. John Zink Company, for example, provides deeply imbedded temperature sensors in each carbon bed todetect an abnormal rise in temperature. These temperature detectors provide the means to automatically shutdown thesystem in a safe mode isolating each carbon bed by closing both inlet and outlet valves. The carbon bed temperature isthen reduced to normal levels by employing a special carbon bed cool-down procedure provided by the supplier. It isimportant to realize that should a carbon bed high temperature excursion occur, the carbon bed does not burst intoflames or explode, instead there is a gradual temperature rise that develops over an extended time period of hours oreven several days of operation. This gives plenty of time for the problem to be recognized and corrective action to takeplace. For that reason, the additional safety equipment suggested by Section 10.4 including the "extinguishing system"connected to each carbon bed is not required for safe system operation.

_______________________________________________________________________________________________67- Log #4



Strategies to control explosion hazards in carbon absorptionunits is application specific and can include concentration control, Flame and Detonation Arresters, instrumentedinterlocks, and equipment which can contain explosion overpressures. The protective strategy highlighted in this sectionand Figure 10.4.1 is applicable to a specific application and may not be suitable for all industrial applications. In theexample provided In the following the assumption is made that flammable liquids are stored and processed and thevapors are recovered by a carbon adsorption unit. The internal area of the storage vessels, process vessels and pipingis defined as zone 0 To avoid hot spotting resulting from adsorption heat release, The vapor concentration is reducedbrought down to 50% below LFL to avoid hot spotting resulting from adsorption heat release. This measure, if controlledproperly, is the primary measure for explosion prevention. Additional explosion isolation measures are needed as thecarbon adsorption vessels are not designed explosion pressure proof and during the regenerative cycles it cannot beassured that the vapor air mixture will remain below 50% of LFL. For this reason secondary measures in the form offlame arresters are recommended for enhancing safety.

The protective strategy for carbon adsorption systems noted in paragraph 10.4 and Figure 10.4.1promotes the concept that the primary method for mitigation of the risk is dilution of the flammable gas to less than 50%.This is design strategy is impractical for many applications including hydrocarbon adsorption/absorption (ADAB)systems commonly used for hydrocarbon recovery in fuel terminal loading operations. Additionally the flame anddetonation arrestor configurations promoted by Figure 10.4.1 could not be applied as noted in an ADAB system as thepressure drop associated with the multiple Flame and Detonation arresters would make the operation of ADAB systemstechnically infeasible. Equivalent protection is provided through instrumentation and inherent design features whichprevent excessive adsorption heat release and the selective use of Flame and Detonation arresters. These systemshave a long record of safe operation. The committee should add additional language to Section 10.4.1 to emphasizethat the strategy to control explosion hazards in carbon absorption units is application specific and can includeconcentration control, Flame and Detonation Arresters, instrumented interlocks, equipment which can contain explosionoverpressures, etc. The protective strategy highlighted in Section 10.4 and Figure 10.4.1 is applicable to a specificapplication and may not be suitable for all industrial applications.



_______________________________________________________________________________________________James F. Koch, The Dow Chemical Company


3.3.2 Combustible Dust. A finely divided combustible particulate solid that presents a flash fire hazard or explosionhazard when suspended in air or the process specific oxidizing medium over a range of concentrations.

This is the definition for a combustible dust from the NFPA 654 ROP. Why not use this? Creatinganother definition serves no meaningful purpose and will only cause confusion. In addition, elaborating on flash fireconcerns, which was given in the committee statement as an area where the definition was incomplete, makes no sensein the context of this standard which covers deflagration venting. Flash fire scenarios, while important, are notaddressed in this standard and adding additional wording around flash fires in this standard is inappropriate. If anythingis mentioned, the reader of the standard should be pointed to NFPA 654, where flash fires are addressed. I would alsopropose to either add the annex information from NFPA 654 or point the reader to that for reference.

_______________________________________________________________________________________________68- Log #16

_______________________________________________________________________________________________Laurence G. Britton, MATRIC


An ignitable heterogeneous mixture, comprising gas with suspended particulate solid orliquid, in which the total flammable gas concentration is >= 10% LFL and the total suspended particulate concentrationis >= 10% MEC", usually used to describe mixtures of flammable gas plus suspended dust where the latter is close to,or above its MEC".

(1) A hybrid mixture must be otherwise it has no importance. By adding the word "ignitable"one does away with the arbitrary and unsupportable requirement of needing the percentage sum (%LFL+%MEC) equal50. Per the NFPA 68 ROP proposed definition one could have a "hybrid mixture" comprising 10% LFL (~900 ppm) ofstyrene plus 40% MEC (12 gm/cu-m) of polystyrene (MEC = 30 g/cu-m) which isn't anywhere near ignitable let alonedeserving of some "special hazard" status. (2) Hybrid mixtures are all heterogeneous so this should be in the definition.(3) The "10% of flammable limit" definition is arbitrary but does the job of eliminating the need to consider gasconcentrations below about 500 ppm. Note that 10% LFL for C7-C10 hydrocarbons is typically 500-900 ppm. I wrote"Short Communication: Estimating the Minimum Ignition Energy of Hybrid Mixtures" (Process Safety Progress, Vol. 17,No. 2 (1998) pp. 124-126) showing that flammable gas at less than about 50% LFL normally has little effect on dust MIE(and presumably burning velocity, which is related to MIE). My revised definition doesn't use this 50% criterion but themore conservative 10% number from the NFPA 68 ROP. (4) The gas concentration usually defines the hazard and theusual circumstance (gas plus dust close to or above its MEC) should be mentioned. These revisions address H. Febo’snegative ROP comment.




68-10Delete 6.5.7.

Adding requirements to address wind loading per proposed 6.5.7, while an important designconsideration, does not impact the safe operation of the vent and should not be included in this standard. It onlyimpacts the life of the vent. There are instances where it is not appropriate to design for the expected wind loading. Anexample is areas where hurricanes are possible. Process vessels will be designed for the wind loading during ahurricane, but any explosions vents will most likely not be. This is because processes are shut down when a hurricaneis approaching. After the hurricane is past, the process will be inspected before start-up. If the vent has failed, a newone will be installed. Adding a separate design wind loading for a vent will only lead to confusion in the equipmentspecification process and possibly lead to the wrong wind loading being used for the process vessel.

_______________________________________________________________________________________________68- Log #1

_______________________________________________________________________________________________Samuel A. Rodgers, Honeywell, Inc.

68-11Renumber current Figure 6.8.3(c) as Figure 6.8.3(d) and replace current Figure 6.8.3(c) with

modified Figure 6.8.3(c), see below.

******Insert Figure 6.8.3(c) Here******

Modify statement 6.8.3(d) as follows:d) The vent discharge duct cross-sectional area is everywhere less than or equal to 1.5 times the total manifolded vent

area (see Figure 6.8.3(d))

******Insert Figure 6.8.3(d) Here******

The current Figure 6.8.3(c) does not show the comparison between an acceptable and anunacceptable manifolded vent discharge duct. The suggested modification for Figure 6.8.3(d) is relevant to modulardust collector construction, which is the more typical application.


68_F2012_ROC_Log #1_Figure 6.8.3(c)_Rec

Figure 6.8.3(c) Example Manifolded Vent Duct with Single Inlet Perimeter (without Branch Connections)

Permitted

68_F2012_ROC_Log #1_Figure 6.8.3(d)_Rec

Figure 6.8.3(d) Example Range of Vent Duct Area for Manifolded Vent Duct


_______________________________________________________________________________________________John E. Going, Fike Corporation


Vent ducts and nozzles, with total lengths of less than one hydraulic diameter, relative to the calculated vent area,irrespective of the duct area, shall not require a correction to increase the vent area.

The purpose of the change is to clarify that the basis of the hydraulic diameter metric is the calculated,not installed vent area. For example, a calculated vent area of 16 ft2 would lead to an acceptable duct of 4 ft, but if 36 ft2

were installed, the duct would be allowed to be 6 ft without penalty. I am not sure what is intended; alternate wordingcould be “relative to the installed vent area”

_______________________________________________________________________________________________68- Log #10


68-11None provided.

The requirement 6.8.4 c is confusing. The listed requirement would lead one to believe that a ventduct cross sectional area less than the vent area is acceptable and that isn’t true. This is somewhat remedied by theequation given in the figure, but this requirement is not explicitly stated here. What is wrong with having a vent ductarea greater than 1.5 X the vent area? Did you possibly mean that the vent duct area should be >= to 1.5X the ventarea?

_______________________________________________________________________________________________68- Log #8


68-13Add a new Section 6.9.5 prior to the current Section 6.9.5 and renumber as follows:

If the process material has a "Degree of Health Hazard" (Health Hazard Rating) of 3 or 4 according to NFPA704, deflagration venting through flame-arresting and particulate retention devices shall not be permitted insidebuildings.

Combustible dust is not completely oxidized during a vented deflagration. Vented material comprisesunburned dust, oxidized combustion products, plus partially burned "decomposition" products. Vent relief devices openat a small fraction of the 6-10 atmosphere overpressures produced by typical confined dust deflagrations and themaximum amount of unburned material is released when the ignition source is farthest from the vent. Unburned dust isalways released during venting and a cloud of dust plus various products can travel large distances from the ventedenclosure. Even with a flame-arresting and particulate retention device installed on the vent closure, some dust willescape into the surrounding area. Alternative methods of explosion prevention or protection should be applied for "highlytoxic" combustible dusts, taking into consideration the potential for personnel exposure to released material during orafter the event. Consideration of the most appropriate means of explosion protection should include environmentalimpact even if a "toxic" dust does not meet the "highly toxic" criteria in this Standard.

While an assessment of the risk of venting inside a building is required by Section 6.9.4, the acutetoxic hazard presented by the quantities of dust which might penetrate the particulate retention element should beevaluated according to the recognized methodology of NFPA 704.



_______________________________________________________________________________________________Timothy J. Myers, Exponent, Inc.

68-24Delete paragraph 8.2.6.8 and annex material A.8.2.6.8.

As stated in the original proposal, no basis has been provided for the 70% penalty factor that can bereviewed by TC members. It has been communicated to me that this correction factor is based upon modeling of the1999 Jahn Foundry explosion in Springfield, MA and explosion venting analysis contained in the Joint FoundryExplosion Investigation Team Report (Joint Foundry Report). This report does not describe explosion venting analysis. Notably, the KSt values of the virgin resin dust contained in the report were based upon testing performed at the OSHASalt Lake Laboratory using the USBM 20-L vessel, which is known to produce a KSt that is significantly lower than theASTM E1226 method. The Joint Foundry Report lists a KSt value of 51 bar-m/s for the resin and 25 bar-m/s forPittsburgh coal. Those values should not be used for evaluating explosion venting using the NFPA 68 methodology;values obtained using the ASTM E1226 method should be used. If this 70% safety factor is based upon calculationsusing OSHA’s values, the analysis is not correct. I participated in the investigation of the incident and collected samplesof virgin resin powder and accumulations of resin powder in duct work and submitted those samples for testing atKidde-Fenwal in Holliston, MA. I personally observed this testing and it was performed in accordance with ASTME1226. That testing found a KSt of 241 bar-m/s for virgin phenolic resin, 179 bar-m/s for material that had accumulatedin ductwork, and 124 bar-m/s for Pittsburgh coal. As expected, the virgin phenolic resin and Pittsburgh coal values areapproximately 5 times higher than those measured by OSHA. If the analysis that forms the basis of the 70% penaltyfactor is based upon OSHA test results, rather than ASTM E1226 results, a 70% penalty factor would not be required.

Note: Supporting material is available for review at NFPA Headquarters.

_______________________________________________________________________________________________68- Log #11


68-26, 68-25Revise text to read as follows:

For hinged panels, multiply the right side of equation 8.2.8 by 1.1.There is a tremendous amount of conservatism already built into vent sizing. This includes using

worst case values of the deflagration index when measuring it for a particular material. It is also always assumed thatthis worst case condition exists in a process vessel, when in reality it usually does not. Fine tuning the vent area toaccount for a 3% difference in round vs. rectangular translating panels makes absolutely no sense. In fact, vents forprocess vessels come in standard sizes. It is very unusual that a vent area calculation will come out to have the exactvent area of a standard vent panel. In that case, the next larger or maybe even a couple of sizes larger panel will beinstalled. (Standard sizes, 24 inch for example, of vents are stock items and are usually much cheaper than a vent thatmay be available, but needs to be a special run, 20 inch for example.) This more than accounts for the 3% differencebetween a round or rectangular vent. Addition of this requirement overly complicates the standard and adds no value.Increasing the vent area for a hinged panel appears appropriate. It does, however, seem inappropriate to account forthe difference between round and rectangular vents. Why not just say to increase the vent area by 10% if the type ofpanel used is hinged? This is more than adequate given the accuracy of these calculations.





8.4.1 …..or less than -0.2 bar (-20 kPa) remove this text*8.4.2 When the initial pressure is less than -0.2 bar (-20 kPa), Equations 8.4.1 shall be permitted to be used withoutthe conditions listed in 8.4.1A.8.4.2 Many processes which operate under vacuum conditions will require protection by venting. The use ofEquation 8.4.1 has been evaluated for its’ applicability to sub ambient operating conditions (<-0.2 bar). Comparison ofthe calculated vent areas using 8.4.1 was made to areas calculated using 8.2.2 assuming Pinit was 0.0. A variety ofPinit, Pstat, Pred and Kst conditions were evaluated. Generally, the use of 8.2.2 gave vent areas equal to or less that8.4.1 and thus conservative. In a few conditions associated with high Kst’s, 8.4.1 gave vent areas less that found by8.2.2 by 5-10%. Since the deflagration could start at atmospheric as well as subambient pressure, it is recommendedthat both calculations be performed and the larger area used.

Allows the user to know that vent area calculations may be performed for subambient conditions butthat the possibility of an atmospheric deflagration must be considered. Allows the application of venting to subambientconditions without the restriction of M being less than MT. Allows the use of vent ducting.

_______________________________________________________________________________________________68- Log #4


68-28Modify the form of Equation 8.4.1 to indicate it as a ratio to the basic vent area, similar to the other

vent area adjustment methods.The method for sub or elevated initial pressure is the only one of the various methods that is not

formulated as a ratio to the basic vent area. The suggested modification will make the application of the sub or elevatedpressure correction consistent with the other adjustment methods. This change coordinates with the submitter’scomment to update Table 8.5.10.

_______________________________________________________________________________________________68- Log #3


68-18Update Table 8.5.10.

******Insert Table 8.5.10 Here******

Table 8.5.10 should be modified to include sub-atmospheric initial pressure and also more clearlyindicate the limitations on application of the models.


154.11

11

154.11

max34

34

0

redstat

effectiveeffective

initialstat

v

vep

P

PP

P

PP

A

A

68_Log #4_Eq #1_F2012_Rec

68_F2012_ROC_Log #3_Table 8.5.10_Rec

Table 8.5.10 Combination Rules and Limitations for NFPA 68 Dust Models

Model Application Vent Ducts 0.8 < Pintial < 1.2 bar-abs

1 < L/D < 6 Allow turbulence Panel Density < 40 kg/m2 Allow partial volume No elevated or sub-atmospheric pressure (calculate vent duct effect last)

Partial Volume 0.8 < Pinitial < 1.2 bar-abs 1 < L/D < 6 Allow turbulence Panel Density < 40 kg/m2 Allow vent ducts No elevated or sub-atmospheric pressure (calculate vent duct effect last)

Panel Inertia 0.8 < Pinitial < 1.2 bar-abs 1 < L/D < 6 Allow turbulence Allow partial volume Allow vent ducts No elevated or sub-atmospheric pressure (calculate vent duct effect last)

Elevated or Sub-Atmospheric Pressure 1.2 < Pinitial < 5 bar-abs or Pinitial < 0.8 bar-abs 1 < L/D < 6 Turbulence (vaxial and vtan) < 20 m/sec Panel Density < MT and < 40 kg/m2 Full volume, no partial volume No vent ducts (calculate elevated/sub-atmospheric pressure effect last)




It shall be permitted to remove the volume occupied by the filter elements provided the filter elements would notobstruct the free flow of hot gases, unburned material, and flame during a deflagration. Methods for achieving thisobjective include but are not limited to:1.(a)* Separate the vent closure from the filters, usually by locating the vent closure below the filters for standard

vertical filters, but other configurations include, horizontal cartridges, pleated flat panel filters etc. that could have side ortop venting. The principle of separation of vent closure from filters shall be maintained regardless of filter design andorientation if this methodology is used.2.(b)* Shorten or remove a row of filters that are nearest to the vent closure such that the area normal to and between

the filters and the vent closure equals or exceeds the vent closure area. In this case a restraining bar shall be installedto hold back the filters preventing them from being deflected toward and obstructing the free flow of hot gases, unburnedmaterial, or flame through the vent during a deflagration.

Where the volume occupied by the filter elements is removed according to Section 8.7.1, the method forcalculating the volume occupied by the filters is dependent on the distance between the filters as follows andsummarized in Table 8.7.2:(a) For round or elliptical cross section filters where the distance between the outer perimeters does not exceed the

radius (or the minimus) of the filters, the volume can be calculated as a block to include the space between the filters.(b) For round or elliptical cross section filters where the distance between the outer perimeters is greater than the

radius (or the minimus) of the filters, the volume can be calculated as the volume of each filter multiplied by the totalnumber of filters.(c) For flat panel filters, calculate the volume of each filter and multiply by the total number of filters. Calculating the

volume as a block is not permitted for flat panel filters.

******Insert Table 8.7.2 Here******

Where the requirements of Section 8.7.1 are not met, Locate the vent closure adjacent to the filter elementsby calculating calculate the total dirty volume of the enclosure on the dirty side of the tube sheet and includeing thevolume occupied by the filters. In this case a method to restrain the filters to prevent them from being deflected towardand obstructing the free flow of hot gases, unburned material, or flame through the vent during a deflagration shall berequired.

Renumber existing Section 8.7.2 as Section 8.7.4, and so on.The method for calculating the volume occupied by the filters is dependent on the distance between the

filters. For round or elliptical cross section filters where the tangential distance does not exceed the radius (or theminimus) of the filters the volume can be calculated as a block to include the space between the filters. If the distance isgreater, then calculate the volume of each filter and multiply by the total number of filters. For flat panel or pleated filters,if the distance between filters does not exceed the thickness of one filter then the volume can be calculated as a block toinclude the space between filters. If the distand is greater, then calculate dht volume of each filter and multiply by thetotal number of filters.

One way to provide a clear path is to separate the vent closure from the filter elements. FigureA.8.7.1(a)(1) shows the vent closure below the filter elements for standard vertical bags, while Figure A.8.7.1(a)(2)shows the vent closure equivalently separated for horizontal cartridges by locating the vent area under the cartridges(Version 1) or to the side (Version 2). The figures provided here are representative of current practices.

******Insert Figure A.8.7.1(a)(1) Here******


Report on Comments – November 2012 NFPA 68

******Insert Figure A.8.7.1(a)(2) Here******

Another approach to provide a clear path is to provide a flow area equivalent to the vent area immediatelyadjacent to the vent. Figures A.8.7.1(b)(1) and A.8.7.1(b)(2) show a side view and plan view, respectively, for verticalelements. Figures A.8.7.1(b)(3) and A.8.7.1(b)(4) show an end view and side view, respectively, for Version 1 of thehorizontal elements while Figure A.8.7.1(b)(5) shows an end view for Version 2 of the horizontal elements.

******Insert Figure A.8.7.1(b)(1) Here******





Figure A.8.7.3, in comparison to Figures A.8.7.1(a)(1) and A.8.7.1(b)(1) shows a situation for vertical elementswhere neither separation nor clear path is provided. A similar situation can exist for horizontal elements.

******Insert Figure A.8.7.3 Here******

Log CP-12 appropriately suggests that there are more design options where the filter element volumecan be subtracted from the dirty-side volume and that the figures should be annex material.


68_F2012_ROC_Log #2_Table 8.7.2_Rec

Table 8.7.2 Filter Element Spacing Criteria

S < r, Subtract Filter Volume as a Block

Spacing, S

Radius, r

S

S

S

S > r, Subtract Individual Filter Volume

Sr

No Flat Panel Guidance Available for Block ‐ Limited to

Subtraction of Individual Filter

Volumes

S

Square Pitch Triangular Pitch Flat Panel

Square Pitch Triangular Pitch Flat Panel

68_F2012_ROC_Log #2_Figure A.8.7.1(a)(1)_Rec

Figure A.8.7.1(a)(1) Vent Area Separated from Vertical Filter Elements

Vent

Clean Exhaust Plenum

68_F2012_ROC_Log #2_Figure A.8.7.1(a)(2)_Rec

Figure A.8.7.1(a)(2) Vent Area Separated from Horizontal Filter Elements

VentClean Exh

aust P

lenum

OR

Version 1 Version 2

68_F2012_ROC_Log #2_Figure A.8.7.1(b)(1)_Rec

Figure A.8.7.1(b)(1) Free Area Normal to Vent for Vertical Filter Elements – Side View


Vent

Restraint for Full Length Bags/Cartridges


Figure A.8.7.1(b)(2) Free Area Normal to Vent for Vertical Filter Elements – Plan View

Vent Width or Diameter, W

Vent Height or Diameter, D

Full Length Bag

Shortened or Removed Bag

Bag Restraint for Full Length Bags

Clear Path to Vent


Figure A.8.7.1(b)(3) Free Area Normal to Vent for Horizontal Filter Elements – Version 1 End View

Full Length Cartridge

Shortened or Removed Cartridge

D

Vent Height or Diameter, D

Restraint for Full Length Bags/Cartridges, if needed

Clear Path to Vent


Figure A.8.7.1(b)(4) Free Area Normal to Vent for Horizontal Filter Elements – Version 1 Side View

Clean

Exhau

st Plenum

D

W



Vent

W

Vent

D

Clear Path to Vent


Figure A.8.7.1(b)(5) Free Area Normal to Vent for Horizontal Filter Elements – Version 2 End View



Restraint for Full Length Bags/Cartridges, if needed

W

Vent

W

DD

Clear Path to Vent

68_F2012_ROC_Log #2_Figure A.8.7.3_Rec

Figure A.8.7.3 Insufficient Separation for Vertical Filter Elements

Vent




68-34Modify the proposal on bucket elevators and include a summary table of vent spacing distances as

well as modification in the case of using plastic buckets.

* Bucket elevators shall be classified as single casing (single leg) or double casing (twin leg) designs.A single casing design has buckets moving both upward and downward within the same casing. A double

casing design has one casing enclosing the buckets as they move upward and another casing enclosing the buckets asthey move downward.

The boot of a bucket elevator is the inlet section at the lower elevation while the head is the outlet section atthe higher elevation.

Vent areas shall be not less than the cross sectional area of each leg and at a minimum shall be fitted both atthe head and as close to the boot as practicable.

Where a vent is not installed directly on the boot, a vent shall be installed on each casing at a distance from theboot less than or equal to the smaller of 6 meters or the additional vent spacing distance per Table 8.8.3.1.

The owner/operator shall be permitted to choose a design Pred of either 0.5 or 1.0 barg.Additional vents shall be installed in each casing at center-to-center spacing distance along the elevator axis

based on the bucket elevator classification, KSt of the material being handled and design Pred as in Table 8.8.3.2.

******Insert Table 8.8.3.2 Here******

Changing from metal to plastic buckets has been demonstrated to increase the explosion pressures,attributed to lower heat adsorption. It is recommended to increase the corresponding elevator design Pred of 0.5 or 1.0barg in Table 8.8.3.2 as in Table A.8.8.3.2 when plastic buckets are used.

******Insert Table A.8.8.3.2 Here******

* At each vent location, the total vent area shall be not less than the cross-sectional area of each leg.Vent area can be located on the bucket face, the sides, or both as suitable for the installation.

Vent closures shall have Pstat less than or equal to 0.1 bar (note: as low as possible).See below.

The method for sub or elevated initial pressure is the only one of the various methods that is not formulated as a ratioto the basic vent area. The suggested modification will make the application of the sub or elevated pressure correctionconsistent with the other adjustment methods. This change coordinates with the submitter’s comment to update Table8.5.10.A tabular representation of the vent spacing criteria is clearer for the user. Vent spacing for single casing elevators

was modified for consistency with Holbrow, et al. The following graph was used to determine vent spacing for doublecasing elevators, based on Holbrow, et al.

******Insert Figure 11 Here******

The recommendation of VDI-2263 Blatt 8.1 is proposed to address identified higher pressures when plastic buckets areused in place of metal.References:


Report on Comments – November 2012 NFPA 68[1] VDI 2263 Blatt 8.1: Staubbrände und Staubexplosionen; Gefahren, Beurteilung, Schutzmaßnahmen; Brand- und

Explosionschutz an Elevatoren (Dust fires and dust explosions; Hazards, Assessment, Protective measures; Fire andexplosion protection on elevators). Verein Deutscher Ingenieure, Berlin: Beuth Verlag, 2011.[2] Holbrow, P., Lunn, G.A. & Tyldesley, A. Explosion venting of bucket elevators. Journal of Loss Prevention in the

Process Industries 15, 10 (2002).


68_F2012_ROC_Log #5_Table 8.8.3.2_Rec

Table 8.8.3.2 Additional Vent Spacing

KSt, bar-m/sec For Pred =0.5 barg, Spacing (meters)

Pred = 1.0 barg, Spacing (meters)

Double Casing (twin-leg) <100 None required None required

100 - 150 10 19

151 - 175 4 8

176 - 200 3 4

>200 N/A 3

Single Casing (single-leg) <100 None required None required

100-150 7 14

151 - 175 4 5

176 - 200 3 4

>200 N/A 3

68_F2012_ROC_Log #5_Table A.8.8.3.2_Rec

Table A.8.8.3.2 Enclosure Strength Adjustment for Plastic Buckets [1]

KSt, bar-m/sec Percent Increase

<100 20%

100-150 35%

151-200 50%

68_F2012_ROC_Log #5_Figure 11_Rec

68 for 176-200 KSt

68 for 151-175 KSt

68 for 100-150 KSt




8.10.1 Where bin vents (air material separators) are installed in common with silo or any other storage vessel theyshall be protected as follows:a) The protected volume shall be calculated as the sum of the volume of the silo and the volume of the collector in

accordance with 8.7b) The L/D of the combination shall be calculated based on the dimensions of the silo alone in accordance with 6.4c) Vent panels shall be located on the silo top surface or on the side walls above the maximum level of the contents of

the silod) It shall be permitted to locate all or a portion of the venting on the bin vent surface in accordance with the following

proportions:

Av,bin vent ≤ Abin vent

Av,silo=Av,total – Av, bin vent

where:Av,total is the total vent area calculated for the bin vent – silo combinationAv,silo is the actual explosion venting area installed on the siloAv,bin vent is the vent area of the bin vent/collectorAbin vent is the total flow area between the bin vent and the silo based on the dimension of the connection between the binvent and the silo.

A.8.10 A bin vent is an air material separator attached to a larger storage vessel but not provided with a physicalseparation between the two. The collected dust is returned directly to the large storage vessel.

The proposed Av,bin vent equation in 8.10 d) is too restrictive. It does not allow placing the entire ventarea on the bin vent. Having the entire vent area installed on the bin vent is acceptable in some situations. It can beacceptable to install the entire vent area on the bin vent if the flow area of the direct connection between the bin ventand the silo is greater than or equal to the vent area installed on the bin vent. If this is the case, then the path betweenthe bin and the bin vent will not restrict flow to the explosion vents.

See the sketch below for an example.

***INSERT ARTWORK 68_L12_FIG_S HERE***

In this situation, the bin vent is directly connected to the silo. There is no cone or narrow transition section to restrictflow area between the bin vent and the silo. The total amount of vent area that can be installed on the bin vent is lessthan or equal to the flow area between the bin vent and the silo. For example, if the flange connecting the bin vent to thesilo is a 3 foot x 3 foot rectangular flange then up to 9 ft2 vent area could be installed on the bin vent to vent the silo/binvent combination. Typical situations that might allow installing the entire vent area on the bin vent include systems werethe silo is relatively small with respect to the bin vent and/or when the dust being processed has a relatively low Kstvalue.


68/L12/S/F2012/ROC

Silo

Bin Vent Vent Panel

Flow Area here must be greater than or equal to vent area installed on the bin vent filter.




Such a vent shall may be tethered. Tethering, when used, should be shown to be effective by appropriate testing.It seems that there is a conflict between the new definition of Translating Vent, Sections 3.3.35.1,

10.3.2.1, 10.3.1.3. and 10.4. The definition permits fragmentation but only suggests tethering. Section 10.3.1.3 probablydoesn’t apply (closures..swing outward), but it does states that “Materials than tend to fragment and act as shrapnelshall not be used.” Section 10.3.2.1 which addresses the fasteners requires tethering when personnel may be struck byflying vent closures. Section 10.4 particularly the annex, describes restraints.I am not sure of the level of conflict but wanted to at least raise the issue.

_______________________________________________________________________________________________68- Log #15

_______________________________________________________________________________________________Martin P. Clouthier, Professional Loss Control Inc.

68-34NFPA standards for certain types of facilities may not require deflagration venting for bucket

elevators that meet criteria, such as low belt speed or large buckets. The exemptions allowed in these standards areoccupancy-specific, and reflect industry risk acceptance rather than the assertion that a deflagration is not possibleunder the stated conditions.

Certain occupancy-specific NFPA standards allow exceptions to the requirement of deflagrationventing for bucket elevators (e.g., NFPA 61 states that the “exemption is based on reports that low belt speeds withlarge buckets substantially reduce dust concentrations”). Although not explicitly stated, the exemptions seem to bebased on industry risk acceptance, rather than absence of loss history. An explanation in the annex of NFPA 68 wouldallow users to understand the reason for inconsistent requirements between NFPA 68 and occupancy standards.
