Four Cylinder Filling Tips

I conduct high pressure cylinder/liquid container/carbon dioxide cylinder filling classes for GAWDA members all across the country. There are four items that I stress during my training classes that, if done, really reduce the chances of fatality or serious injury to our employees and customers.

frangible disc safety and a fusible metal-backed frangible disc safety

This is an example of a frangible disc safety and a fusible metal-backed frangible disc safety.

#1  Hammer test (dead ring) all steel cylinders.
DOT requires all steel cylinders approved to go ten years between requalifications to pass a hammer test prior to each fill. I know of two cylinder failures in the past two years (one fatality and one near miss) that very likely would not have happened if the cylinder had been given a hammer test. Both cylinders were in oxygen service and had water in them when filled. Both cylinders were extremely corroded and pitted on the inside from 100 percent oxygen and 100 percent humidity. Both cylinders had been hydrotested within two years of the failures. Therefore, I now recommend during my training sessions that all steel cylinders be hammer tested prior to filling, not just those approved for ten years.

#2  See through the holes on the safeties on liquefied gas products such as carbon dioxide.
If a fusible metal-backed safety gets installed onto a liquefied gas cylinder, then someone has made a bomb just waiting to go off. Overfill the cylinder or expose it to high temperatures causing the cylinder to go hydrostatic full, and the resulting pressure can rupture the cylinder. If there is nothing wrong with the cylinder, then the failure pressure can be approximately 2.5 to 3.5 times the stamped service pressure. If the cylinder filler will just verify prior to filling that they can see through the holes on the cylinder safety, then they have verified that a fusible metal-backed safety is not installed on the cylinder.

spring-loaded pressure relief device and the bursting disc

Immediately behind the pressure gauge are the spring-loaded pressure relief device and the bursting disc.

#3  Verify that there is a pressure relief device (PRV) on the liquid container before filling.
#4  Verify that there is a bursting disc (BD) on a liquid container before filling.
Numbers 3 and 4 go together. I know of two instances in the past years that removing and plugging the openings where the PRV and BD were resulted in the catastrophic failure of the liquid container. Both cases resulted in near fatalities for three people. In both cases, the container filling people did not see that the safety devices were removed and plugged. Since then, I have continually emphasized that any person filling a liquid container find the pressure gauge and look immediately behind the gauge and ask the very important question: Does it have a PRV and a BD installed?

There are more cylinder filling tips to know and follow to prevent potential problems. These are just four of them that I give special emphasis during the cylinder filling classes. Please verify that your cylinder filling personnel know these four items and use them. You could be saving one of your employees’ or customers’ lives.

Gases and Welding Distributors Association
Michael Dodd GAWDA’s DOT, Security, OSHA &EPA Consultant Michael Dodd is president of MLD Safety Associates in Poplar Bluff, Missouri. Members can reach him at 573-718-2887 and