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Venting of atmospheric and low-pressure storage tanks ISO 28300/API 2000

Simon Maier Regional Manger Europe 7.12.2017

© Braunschweiger Flammenfilter GmbH 2

Agenda

Why conservation vents do not function as Flame Arresters 1

Emission Reduction through breathing loss minimization 2

Storage Tanks with Pressure / Vacuum Relief Valves and Flame Arresters 3

International Standard: Venting of atmospheric and low-pressure storage tanks ISO 28300

EN 14015

Annex L

API 2000

5th edition

TRbF 20

API 2000

6th/7th edition

ISO 28300 Petroleum, petrochemical and natural gas

industries – Venting of atmospheric and low-pressure

storage tanks

Background and development of ISO 28300 Standard

• ISO 28300 was mainly developed based on the API 2000 standard 1998 6th Edition, the EN 14015 Standard Annex L and the German TRbF 20

• Contradiction towards the venting requirements for normal venting

• Contradiction towards the use of vents as flame arresters Committee goal: This standard shall consider all state of the art knowledge concerning tank venting and safety and provide best practice to the user

Why conservation vents do not function as flame arresters:

API 2000 5th Edition 1998 (old version not valid any more): A flame arrester is not considered necessary for use in conjunction with a pressure vacuum valve venting to atmosphere because flame speeds are less than vapor velocities across the seat of the pressure vacuum valve TRbF 20 (German standard): Clearly calls for flame arresters for tanks that contain liquids that can create an explosive atmosphere Factory Mutual (Insurance and approval company) Requires installation of flame arresters on tanks which store liquids with a flash point at or below 43 ◦C or on tanks which heat the stored liquid to its flash point

Conclusion for ISO 28300 committee regarding atmospheric explosion protection of storage tanks:

Research work is needed due to contradicting standards and opinions

ISO 16852 shall apply as test standard

Two types of test are needed:

• A) atmospheric deflagration test

• B) continuous burn test

Atmospheric Deflagration - Test set-up

1 ignition source 2 plastic bag Ø 1,2 m, length 2,5m foil

thickness >0,05 mm 3 conservation vent 4 explosion proof container 5 mixture inlet with shut-off valve 6 mixture outlet 7 bursting diaphragm

atmospheric deflagration test of end-of-line flame arrester as described in ISO 16852 part 7.3.2.1.

High Velocity Burning - Test set-up

1 continuous flame 2 pressure vacuum valve 3 explosion proof container 4 mixture inlet 5 bursting diaphragm 7 pilot flame 10 shut-off valve

atmospheric deflagration test of end-of-line flame arrester as described in ISO 16852 part 9.2.

Example Methanol: (ignitable temperature range is within normal storage conditions)

Vapor pressure: 30 kPa LFL: 5.5 vol% UFL: 26.5 vol%

0

5

10

15

20

25

30

35

40

0 5 10 15 20 25 30 35 40 45

Vapo

r Con

cent

ratio

n in

Vol

.%

Temperature of Liquid Methanol in degree Celcisus

Explosion hazard of Methanol

UFL = 26.5

LFL = 5.5

Ignitable Temperature Range

Recommendation of ISO 28300 regarding explosion prevention:

• Different tank selection • Inert gas blanketing • Flame arresters • Pressure vacuum valves: “Testing has demonstrated that a flame can propagate through a pressure vacuum valve and into the vapour space of the tank. Tests have shown that ignition of a PV's relief stream (possibly due to a lighting strike) can result in a flash back to the PV with enough overpressure to lift the vacuum pallet causing the flame to enter the tank's vapour space. Other tests have shown that under low flow conditions a flame can propagate though the pressure side of the PV, ..”

Emission Reduction through breathing loss minimization (VDI 3479*)

“The Function of the P/V Vent is to keep the vapor space closed during variations in the atmospheric pressure and/or temperature decrease in spite of pertinent

changes of gas volume and pressure, until that time when a technically admissible low or high pressure is reached”

Goal: avoid intake of ambient air and discharge of product/air mixture

* Forschungsbericht 225 “Kohlenwasserstoff – Emissionen aus Festdachtanks – Vergleich von Berechnungsformeln unter besonderer Berücksichtigung der VDI Richtlinie 3479, Hamburg, February 1985

Main influence factor of emission reduction for hydrocarbon vapors

a) Upper and lower set pressure of vents (set pressure & set

vacuum) b) Temperature difference within the vapor space of the tank c) Hydrocarbon concentration of the hydrocarbon/air mixture in the

vapor space (vapor pressure)

Vent valves in acc. to API Standard 2000 with 100% overpressure

Vent Valves with 10% Technology difference from set pressure

(Start open) to opening pressure (full open)

PVRV 100% vs. 10% Lift Tech.

10 mbar 18 mbar

20 mbar

Valve set pressure to be adjusted

Opening pressure

MAWP

Set Pressure and Vacuum needs to be influenced

(design pressure)

PROTEGO® 10% Technology

Function with lifting cover Function without lifting cover

Difference between Full lift and proportional pallet

© Braunschweiger Flammenfilter GmbH 17

© Braunschweiger Flammenfilter GmbH 18

V

pressure

MAWP

Required flow

P set PROTEGO 10% P close PROTEGO 10%

P set 100%

P close 100%

P set N2 blanketing

Design Problem with 100 % overpressure Technology

8 2

0 10

4 6

8 2

0 10

4 6

Operating range 0 to +4.5”WC

Starting to open +4.5”WC

Full flow 5.0”WC

Blow down to +3.1”WC

Operating range 0 to +2.5”WC

Starting to open +2.5”WC Full flow 5.0”WC

Blow down to +1.8”WC

10% 100%

inches of WC inches of WC

10% vs. 100% Technology

9.78

35.84 %

7.44

51.20 %

5.31

65.17 %

4.32

71.68 %

0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

80.00

Emiss

ion M

assfl

ow (t/

yr) a

nd

% of

Emiss

ion R

educ

tion

1 2 3 4

Calculation Example Fixed Roof Tank with Pressure/Vacuum Vents

100% 40% 10% 0%

Safe protection of storage tanks with Pressure / Vacuum Relief Valves and Flame Arresters

Who knows such an installation?

Many traditional configurations are a safety risk

ISO 16852 requires both flow and flame transmission testing of Pressure Vacuum Relief Valves combined with Flame Arresters but lots of Pressure Vacuum Relief Valves combined with Flame Arresters are not fully tested!

Many traditional configurations are a safety risk

At subsonic flow small pressure losses can impact the lift of a valve pallet quite severely. An increase in the accumulation from set pressure till full-lift is likely.

Many traditional configurations are a safety risk

Placing a Flame Arrester below the Pressure Vacuum Relief Valve leads to: • Additional risk of clogging and hence storage tank collapse • May not be safe if explosions or endurance burning occurs • Flame Arrester element cannot be serviced without losing explosion

mitigation effect • Difficult and lengthy maintenance procedure particularly with larger

sizes

Many traditional configurations are a safety risk

Combining a Flame Arrester with a Pressure Vacuum Relief Valve can lead to reduced flow or even severe chattering in high flow relief scenarios when protection is needed most.

Chattering of combined valve with flame arrester

© Braunschweiger Flammenfilter GmbH 27

© Braunschweiger Flammenfilter GmbH 28

Combined valve with flame arrester

Thank you for the opportunity to present

Excellence in Safety and Evironment

Back up

© Braunschweiger Flammenfilter GmbH 30

Emission reduction with PROTEGO® Over-/Underpressure- Relief Valves

Possible minimum leakage rates (examples) Flange connection Protego Standard ISO 28300 / API 2000 6th edition

over up to bubbles per min cm³/min m³/h bubbles per min cm³/min m³/h 40 25 7,5 0,00045 786 236,6 0,01420

40 100 63 18,9 0,00113 786 236,6 0,01420 100 150 94 28,2 0,00169 786 236,6 0,01420 150 200 125 37,5 0,00225 7866 2360,0 0,14160 200 250 157 47,1 0,00283 7866 2360,0 0,14160 250 300 188 50,4 0,00302 7866 2360,0 0,14160 300 350 220 66,0 0,00396 7866 2360,0 0,14160 350 400 252 75,6 0,00454 7866 2360,0 0,14160 400 500 314 94,2 0,00565 31460 9438,0 0,56628 500 600 376 112,8 0,00677 31460 9438,0 0,56628 600 700 440 132,4 0,00794 31460 9438,0 0,56628

at 90% set pressure at 75% set pressure

PROTEGO - Germany

TÜV-Certified Flow Test Rig

Flow testing of vents according to API 2000/ISO 28300 (TÜV Certified Flow Rig)

1. test medium supply (e.g. blower or fan) 2. calibrated flow measurement device 3. test tank 4. calibrated measuring device for pressure and vacuum 5. (pressure and vacuum measurement may be achieved

with separate instruments) 6. temperature measuring device 7. barometer - measuring device for atmospheric pressure 8. device to be tested 9. pipe-away if fitted 10.atmospheric temperature and dew point measuring

device 11.L = length of connecting pipe (straight pipe nipple)

Emission per cycle (opening to reseating)

overpressure set pressure mass (opening) mass (reseating) total mass total volumembar kg kg kg m³

full lift 10% 20 0,08 0,32 0,40 0,5

modulated 40% 14 0,51 0,66 1,17 1,4

modulated 100% 11 2,31 1,08 3,39 4,1

0,00

0,50

1,00

1,50

2,00

2,50

3,00

3,50

10% 40% 100%

reseatingopening

Pset,ERV = 18,2 mbarg Pclose,PV = 11,3 mbarg

Pset,N2 = 10,4 mbarg

Opening pressure versus closing pressure

Example: API 650 / EN 14015 Tank with a design pressure of +20 mbarg

Pclose,ERV = 13,5 mbarg

Pset,PV = 14,9 mbarg

(by using 10% technology)

Popen,PV = 16,4 mbarg

Popen,ERV = 20,0 mbarg

Pset,ERV = 10,0 mbarg Pclose,PV = 3,1 mbarg

Pset,N2 = 2,6 mbarg

Opening pressure versus closing pressure

Example: API 650 / EN 14015 Tank with a design pressure of +20 mbarg

Pclose,ERV = 8,0 mbarg

Pset,PV = 3,8 mbarg

(by using 100% technology)

Popen,PV = 7,6 mbarg

Popen,ERV = 20,0 mbarg

Blow Down needs to be considered when sizing

4

2dF

AFpset ⋅==π

4

2DF

AFpreseat ⋅==π

d D d < D

reseatset pp >

Benchmark Report on Vents (leak rate)

Areas where End-of-Line Endurance Burning is likely to occur

end of line deflagration flame

arrester explosive mixture

filling line

flame arrester

outbreathing of explosive gas/air mixture

burning of explosive ignited gas/air mixture

liquid

vapour Endurance Burning:

maximum thermal stress considering 2 heat transfer mechanisms burning situation (convection problem period 1) no burning situation (conduction problem period 2)

The Challenge of Designing Endurance Burning Flame Arresters

Convective Time Period (vapor flow cooling the filter element is present)

Conductive Time Period ( no cooling through vapor flow)

The Challenge of Designing Endurance Burning Flame Arresters

Endurance Burning: 120min no flame transmission red: combustion side blue: protected side black: protected side Test Gas: Ethylene (NEC Group C Vapor)

Temperature Curve for a Successful Endurance Burning Test

Temperature rise during conductive periode

Case 1: Endurance Burning Tested End of Line Arrester applied with a P/V Vent

Endurance Burning: flame transmission after 9 min red: combustion side blue: protected side black: protected side Test Gas: Hexane (NFPA Group D Vapor)

Enclosing heat from P/V – Vent lead to failure

Case 2: Endurance Burning Tested End of Line Arrester applied with „Goose Neck“

Endurance Burning: flame transmission after 16 min red: combustion side green: protected side Test Gas: Hexane (NFPA Group D Vapor)

Factory Mutual Research Approval Guide

Important Demands from Test Standards like FM and European Test Standard ISO 16852, EN 12874 to Assure Chemical Plant Safety

1. Flame Arrester Companies have to be Audited to assure Quality Production 2. Live Field Tests are documented in Test Report which Shows Exact Test

Conditions (c, p, T) 3. Arresters should only be installed according to Test conditions 4. Be aware what is written in the Standards

Design Considerations to lower the likelihood of misapplication

1. Arrester has to be Safe Goal can be achieved if arrester is tested according to ISO 16852, EN 12874 or

FM standard 2. Misapplication has to be avoided Approval report should be requested from Vendor End Of Line Arrester should only have 1 Flange 3. Easy Maintenance has to be assured Goal can be achieved with hingeable Weather hood Flame arrester Elements should be easily accessible

Design solutions with a positive track record

“Investigation of main application failures proved by life field testing of endurance burning tested end of line flame arresters “

Solution:Combination conservation vent/deflagration arrester with hinged weather-hood for endurance

burning

Often typical misapplication for Endurance Burning Protection: Heat trapped above arrester

results in flashback !

Test and Application Standards (EN 12874, ISO 16852, FM) Demand to apply only tested

configurations

Where Do My Storage Tank Losses Come From ?

Storage Tanks Have to Breath

Why Does A Quality Product Result in Vapor Saving?

Leak rate testing according to API 2521

API calls for leak rate testing at 75% of set pressure

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0.9

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0 0.2 0.4 0.6 0.8 1

Tank Pressure oz/sq inch

Leak

rate

[scfh

]Groth

PROTECTOSEAL

PROTEGO

PROTEGO 10%

75 % to set (0.5oz/sqinch)

75 % to set (0.65oz/sqinch)

Point of full open

PROTEGO 6"

PROTEGO 10% 6"

Leak rate testing results company A

company B

Avoid secondary damage from leaking!

Reduce your Explosion Risk from Leaking!

Leak rate testing according to API 2521

API calls for leak rate testing at 75% of set pressure