Great care must be taken when filling oxygen cylinders due to the inherent dangers, some of which can be fatal. This is why the task should only be performed by specialized medical professionals (specifically Respiratory Therapists), by auxiliary medical professionals (paramedics and firefighters with special training) or those working for medical supply companies who are qualified.
Proper Storage of H Cylinders
-
All oxygen cylinders should be stored in a clean area at room temperature and in a vertical position to keep particulate matter from accumulating around the neck or valve opening. The valve opening should be capped. To "crack" the H cylinder to check pressurization, be sure the cylinder is upright; point the valve opening away from your body and anyone near. If a regulator is already attached to the valve opening, open the valve slowly at first to pressurize the regulator or you may damage the device. Do not use any tool to open an H cylinder but do so by hand. If the valve won't open, the tank is faulty.
Medical Cylinders must have hydrostatic tests performed on them every five years. The date of every test is etched directly onto the bottle. Before filling cylinders, check to be sure they are not due for testing.
Note: most H cylinders used in hospitals are filled from a liquid oxygen storage decanter.
Before Filling HP Cylinders
Check the valve opening for any debris and clear any away
(this is usually accomplished by simply "cracking" the cylinder
forcefully and briefly if any pressure remains within); if debris cannot
easily be removed, tag it as OOS (Out of Service) and report the
cylinder's number to the FAO (Food and Agricultural Organization).
Inspect the cylinder for damage, corrosion, illegal repairs or improper markings. Examine the valve and regulator, if any; be sure they are up to specs and in good condition.
If unsure of the procedure or something happens that you don't expect, stop the procedure and contact your supervisor or other qualified person before continuing. The potential for explosion makes this a very dangerous task if not performed properly.
Inspect the cylinder for damage, corrosion, illegal repairs or improper markings. Examine the valve and regulator, if any; be sure they are up to specs and in good condition.
If unsure of the procedure or something happens that you don't expect, stop the procedure and contact your supervisor or other qualified person before continuing. The potential for explosion makes this a very dangerous task if not performed properly.
Filling a Cylinder from Other HP Cylinders (Trans-Filling)
- Connect the fill valve of the storage unit to the cylinder;
tighten by hand alone. Keeping the cylinder upright, place it in a
shielded container if one is available.
Start filling the empty bottle from a cylinder that has a higher pressure. Open the valve slowly. Once the cylinder valve is fully open, open the fill valve, but only partially, allowing a slow rate of fill (a rate not exceeding 200 PSI per minute, as registered on the pressure gauge) to avoid rupturing the empty bottle or the fill line. You will hear a hissing sound that will stop when the pressures are equalized.
The filling cylinder should never become hot to touch; this indicates too fast a fill rate, though it isn't unusual for the bottle to become slightly warm. If the bottle becomes too warm, close the fill valve and allow it to cool. Remember Boyle's Law: as a warm gas cools within a confined enclosure, pressure will decrease. Try to keep the filling cylinder as cool as possible.
Once the pressure between the tanks equalizes (hissing stops), follow the same steps in reverse to unhook from the first filler bottle and attach the fill valve to the next cylinder with a higher pressure than the one being filled. Repeat this process until the cylinder is filled to 2000 psi.
When done with these steps, close the valve on the filled cylinder, then open the bleed off valve on the cascade line. If using a shield, it is safe to open it at this time and disconnect the fill valve from the recharged bottle.
Cover the cascade valve opening with a plastic cap and store it safely, then fill out the Compressed Air Cascade Usage Chart at the filling station. Before fastening the regulator to the filled bottle, inspect the valve opening for debris. Hand tighten the regulator in place, aim the valve away from you or anyone else and slowly open the valve to check for leaks; check the gauge reading to see if it jibes with the gauge at the filling station. If not, report to your supervisor that the fill gauge may require recalibration. Shut the valve; bleed the pressure from the regulator and remove it from the cylinder, then store the cylinder properly.
Note: Filling the cylinder to its capacity is not possible with trans-filling.
Filling a Cylinder from a Liquid Oxygen Storage Tank (Decant Filling)
To prevent static electricity sparking, rubber soled shoes are required. Due to excessive and rapid freezing likely with liquid decanters, heavy gloves should be worn. Stricter guidelines may call for the use of overalls, eye and ear protection as well. There should be no open flames or smoking within at least 200 feet of the filling station.
Connect the fill valve of the liquid storage unit to the cylinder; tighten by hand alone. Keeping the cylinder upright, place it in a shielded container if one is available. If there is a metal shield, secure the top before filling begins.
Most hospital liquid oxygen storage tanks have no shielded area, but are kept a safe distance from populated areas in case of cylinder explosions, which are very rare but possible.
The filling procedure is basically the same, except that the filler line is equipped with a bleed off valve and should be vented in an open area. Once filling begins, watch for leaks in the line and valves. If any occur, stop the filling procedure before tightening connections or fire may result.