1. GRPE ISO GROUP MEETING, MUNICH, JANUARY 22th, 2003 GAS CYLINDERS USE OF PRESSURE RELIEF DEVICES Hervé BARTHELEMY AIR LIQUIDE PARIS

2. 2 PRD – FIRE PROTECTION ISO/CD/15869-1 REQUIRES USE OF THERMALLY ACTIVATED PRD This type of PRD is the only one which allows gas pressure release in case of fire even at low pressure Some fully wrapped cylinders behave very badly during standard bonfire tests if not protected with PRD

3. 3 CYLINDER – CARBON FIBER - PLASTIC LINER SERVICE PRESSURE : 3 000 PSI

4. 4 CYLINDER – CARBON FIBER - PLASTIC LINER FRAGMENTATION AFTER 100 s EXPOSURE TO STANDARD BONFIRE TEST SERVICE PRESSURE : 3 000 PSI

5. 5 PRD – FIRE PROTECTION SITUATION WITH INDUSTRIAL CYLINDERS (SINGLE, BUNDLE/PACK OR ON TRAILER) Several millions are in used In Europe : PRD not required by regulation and not used In North America : PRD required by regulation. For H 2, the industry decides to use bursting disk back up with a fusible plug (to avoid unexpected release of gas)

6. 6 RISK ANALYSIS 1)IN CASE OF FIRE / RISK OF CYLINDERS BURST SHORTLY AFTER THE FIRE 2)RISK OF GAS RELEASE – H 2 IS EXTREMELY FLAMMABLE H 2 : 70,5 % (LFL = 4 % ; UFL = 74,5 %) CH 4 : 10 % (LFL = 5 % ; UFL = 15 %) The minimum energy for igniting H 2 in air is 10 times lower than CH 4 The flammability range of H 2 in air is much bigger than CH 4 TWO RISKS SHALL BE CONSIDERED

7. 7 ACCIDENT WITH AN HYDROGEN BUNDLE (1985) LEAK DUE TO FAILURE OF A NUT

8. 8 ACCIDENT WITH AN HYDROGEN BUNDLE (1985) VUE OF THE FIRE DAMAGE THE FILLING CENTER WAS SEVERELY BURNED

9. 9 ACCIDENT IN STOCKHOLM (1983) – HYDROGEN LEAK THE EXPLOSION CONSECUTIVE TO THE HYDROGEN LEAK LEADS TO SEVERE DESTRUCTION IN A BIG AVENUE

10. 10 ACCIDENT IN STOCKHOLM (1983) – HYDROGEN LEAK BUNDLES – 18 CYLINDERS – 50 L/200 bar (about 180 m 3 H 2 )

11. 11 GENERAL CONSIDERATIONS AVOIDANCE OF GAS RELEASE It is better to contain the gas in cylinder as much and as long as possible. Consequently, the use of PRD shall be limited.

12. 12 INCIDENTS : FIRE RESULTING FROM GAS LEAKAGES A batch of 120 hydrogen cylinders was being vented. Gas issuing from one cylinder ignited and this in turn ignited the gas issuing from the other cylinders. Operator suffered burns. An operator of the H 2 supplier had to replace all valves on the hydrogen tubes. A fire occurred. Operator suffered burns. Material damage. Residual gas at the end of the vent pipe from six acetylene cylinders caught fire. No injury, no damage. When de-valving a silane cylinder a yellow flame was seen to envelop the valve and spanner head. No injury or damage. Six cylinders filled with acetylene had to be emptied because they were blowing off acetone. The escaping acetylene ignited. No injury. Little material damage.

13. 13 INCIDENTS : FIRE RESULTING FROM GAS LEAKAGES When disconnecting the pigtail from a silane cylinder there was a sudden flame which injured the operator’s hand. For periodic inspection acetylene cylinders were being emptied. When the cylinder valve was opened a mixture of acetone and acetylene escaped violently and ignited. Only material damages to cylinders. A client was transporting an oxygen cylinder in his own vehicle, with the windows closed, when a fault in the electrical system started a fire. A leaking cylinder valve was suspected. The driver, who could not release the safety belt, was killed. During maintenance of a monosilane installation, a sealing got lost. Monosilane escaped and ignited spontaneously. Safety check after maintenance must be improved.

14. 14 INCIDENTS : FIRE DUE TO INDUE FAILURE OF PRD Acetylene cylinders with melt plugs were vented in a faulty manner to the atmosphere. A fire started, spreading to the other cylinders. The personnel and the fire brigade succeeded in confining the fire to a group of 7 cylinders which were destroyed. While welding on a higher floor, molten slag falling on C 2 H 2 cylinders stored on another floor caught fire when fusible material melted and released acetylene (2 separate instances). Sparks from a cutting torch melted the fusible on an acetylene cylinder in a car service centre leading to a large fire that destroyed part of the garage. A small fire in the vicinity of a C 2 H 2 cylinder may have led to the softening of the fusible plug material in an acetylene cylinder. The escaping gas caught fire and destroyed a small shop. Cylinder in service. Fire of C 2 H 2 cylinders – Regulation not properly followed. Fusible plug melted.

15. 15 INCIDENTS : CYLINDERS INVOLVED IN A FIRE The halls at a subcontractor burned. 85 full and 190 empty cylinders containing flammable and toxic gases were stored in one of the halls. Halls completely destroyed. In fire occurred in the acetylene storage station. No injury. Total loss of acetylene station, damage to adjacent LOX and LIN vaporizers and piping. Total loss of cylinder argon storage. A gas cabinet with a 10 % PH3/balance He cylinder caught fire. Damage gas cabinet As a metal workshop a fire occurred, 18 welding gas cylinders were stored and burst including one high pressure oxygen cylinder, one Ar/CO 2 cylinder, one acetylene cylinder showed bulge. 18 cylinders to be taken out of service.

16. 16 GENERAL CONSIDERATIONS - Many severe fires result from unexpected gas release. - Several severe fires result from undue failure of C 2 H 2 fusible plugs. - Cylinders involved in fire : none of the reported incidents led to facilities or injuries. Fire itself in a severe hazard – PRD will not help.

17. 17 PROPOSAL 1)Full Metal (Type 1) and HW (Type 2) – Good behaviour in Fire Fail after a time long enough No need of PRD directly on the cylinders. 2)Fully Wrapped cylinders Thermally activated device is required, if cylinders cannot resist 5 min. in a « Standard fire » (Note ISO 11119 requires only 2 min.). 3)For every type, the car manufacturer will decide the use (or not) and the type of PRD to protect the full system.