Recommendation #3: Fire departments should ensure that when opening a cylinder post valve with the regulator attached, it should be opened slowly and positioned away from the operator and other people.[1][2]
DISCUSSION: The Compressed Gas Association Manual, CGA G-4, Section 4.4.10,[2] recommends the following: Never to permit oxygen to enter the regulator suddenly. Always open the cylinder valve slowly. Stand to one side and not in front of or behind the regulator when opening the cylinder valve. Never use wrenches or tools except those provided or approved by the oxygen regulator manufacturer. Avoid the use of a wrench on valves equipped with handwheels. Never hammer a valve handwheel in attempting to open or to close the valve. If a valve cannot be opened by hand, notify the supplier.
The fast opening of the valve could subject passageways or components to adiabatic compression (rapid compression with an associated rise in gas temperature, potentially to a material’s ignition point), which could result in hot spots and possible ignition of nonmetallic or particulate contaminates. Fast opening of the valve also provides the possibility of particles being forced into the flow path of the regulator. Once the particles are introduced into the flow path, it is also possible that the particles can collide with the filter located underneath the inlet screw or an additional target (Diagram 1). The filter will then act as the target which could result in the ignition of the metal particle.
The regulator should be positioned away from the operator (and other people) when the cylinder valve is opened and to let the regulator pressurize before looking at the gauge. If possible, the cylinder should be positioned upright and placed between the operator and the regulator (regulator barrel pointed away from the operator). This way an operator can open the cylinder valve from arms length away. Operators typically look at the gauge when the cylinder valve is opened. It is recommended that operators not try to read the gauge until the regulator has fully pressurized.
In this incident it is unclear if the victim opened the valve slowly. Test results concluded that the particle ignited in the area of the bronze sintered-inlet filter. Once ignition took place, the aluminum surrounding the filter ignited and released outward, causing injury to the victim. Laboratory tests have concluded that aluminum alloys will readily sustain combustion at pressures as low as 35 pounds per square inch ambient (psia) and produce approximately 10 times the heat of copper alloys when burning.
Recommendation #4: Fire departments should ensure that fire fighters are trained and aware of safe handling procedures pertaining to oxygen systems.[2][3]
DISCUSSION: Fire departments should provide fire fighters with training in safe handling of oxygen resuscitators including operating procedures, maintenance, cleaning, visual inspections, and hazards that can occur. The operation of oxygen resuscitators is not a complicated task; therefore, training is sometimes overlooked. The operators should not only be able to operate oxygen resuscitators, but also know how to care for them and be aware of hazards involved with their use. Fire fighters are sometimes put in complicated situations where they have to administer oxygen to patients in the vicinity of grease, oil, gas, or other dangerous substances. Fire fighters should be trained to know what to do in these complicated situations and understand the proper maintenance procedures as well as when to report that a system needs repair.
Additionally, operators should be instructed to first open the cylinder valve slowly, letting the regulator pressurize, and then fully open the cylinder valve. What often happens is that the operator opens the valve just slightly, then sees the gauge register pressure, and then doesn’t fully open the cylinder valve. Fully opening the cylinder valve has two positive effects: 1) When the valve is not fully opened it can cause deformation of the cylinder seat valve and this has been suspected to be an ignition source; 2) Opening the cylinder valve against the stem gasket (i.e., fully opening and back seating the valve) helps keep oxygen from leaking past the stem gasket during use.[4]
Operators should also use care when installing the inlet gasket. Installation of this gasket is a good way of contaminating the regulator/cylinder valve if the operator’s hands or components are not clean. Care should also be used to tighten the regulator onto the cylinder valve to prevent leakage of oxygen past the seal during use.[4]
To further assist in the understanding of these areas, fire departments can refer to, and follow, the Compressed Gas Association’s CGA G-48 manual and additionally ASTM’s documents regarding training.[3]
- ↑ National Aeronautics and Space Administration [1983]. Design guide for high pressure oxygen systems, Washington, DC, Publication 1113.
National Fire Protection Association [1994]. NFPA 53: Guide on fire hazards in oxygen- enriched atmospheres. Quincy, MA. - ↑ 2.0 2.1 2.2 Compressed Gas Association [1996]. 4.0 High pressure oxygen cylinders. Oxygen CGA G-4. 9th ed. Compressed Gas Association, Inc., 1725 Jefferson Davis Highway, Arlington, VA 22202.
- ↑ 3.0 3.1 Werley BL, ed. [1991]. ASTM Committee G4.05 fire hazards in oxygen systems: ASTM standards technology training coursebook. 2nd ed. Philadelphia, PA. 11. Compressed Gas Association, Inc. CGA P-1, Safe handling of compressed gases in containers. Compressed Gas Association, Inc., 1725 Jefferson Davis Highway, Arlington, VA 22202.
- ↑ 4.0 4.1 Newton, BE., Personal communication regarding the review of NIOSH FACE report 98-F23, January 13,1999.
