You bet they do. In Common Myth #30 we discussed gas tubes; how they work and why they are needed. It is imperative that these tubes be removed every time a hydrostatic test is performed.

All internal parts in a pressure vessel are to be removed when conducting a hydrostatic test (NFPA 10 5-5.1.2) so that air cannot be trapped.

Additionally, a complete internal inspection must be performed (NFPA 10 5-5.1.4)

Failure to remove the gas tube will likely cause other problems. Forcing water against the rubber sleeves on the tube at hydrotest pressures will cause the sleeves to tear or will make holes in the sleeve. The tube will be nearly impossible to dry. If the sleeves are torn, dry chemical will back up into the tube, contact the moisture inside, cake and plug the gas tube. If this happens, the extinguisher is likely to fail.

Please make sure any time a cartridge operated extinguisher, wheeled or hand portable, is brought in for testing, the gas tube is removed before testing and examined. Also, exercise care when replacing the tube so that threads are not ruined and the tube is not over tightened and cracked. When in doubt, always consult the manufacturer’s maintenance manual for hydrotest instructions.

Just another reason stored pressure extinguishers are simpler, more reliable and easier to service.