Cylinder Maintenance

Valve Maintenance

If grit, dirt, oil or water get into the cylinder valve then safety and/or quality may be compromised and gas leakage may occur. Before assembling regulators and fittings make sure there are no particles of dirt in the cylinder outlet. If a supply of clean compressed air or nitrogen is available use this to blow out any loose particles of dirt from the valve sockets: N.B. eye protection must be worn during this operation. Where clean compressed air or nitrogen is not available, particles of dirt and residual moisture can be removed by "cracking" open and immediately closing the valve (otherwise known as "snifting").

When "snifting" you must take the following safety precautions:

Wear eye protection
Be sure there is no possible source of ignition in the vicinity; stand clear of the gas stream and on no account deflect the gas stream with the hand or the face.
It is also recommended that in the case of high purity gases such as argon, you dry the outlet of the cylinder valve with a clean cloth before "snifting."

Never "snift" hydrogen as it may ignite spontaneously and never "snift" toxic gases. Instead, carefully inspect the outlet and if there are any signs of dirt, blow it out with a jet of clean compressed air or nitrogen.

If the valve outlet contains oil then do not attempt to use the cylinder and return it to BOC under complaint.

Avoiding Cylinder Contamination: Backflow

Backflow occurs when air enters a cylinder by flowing through an open valve or an empty cylinder.

Safety hazards can be created if contaminants are allowed to pass back into the cylinder. Precautions must be taken to ensure that backflow of liquid or gas does not occur either when the cylinder is in use or when it is in store after being emptied.

Preventative Measures

As soon as the gas is in the cylinder has been used, close the cylinder valve to avoid moisture and other contaminants entering the cylinder.

It is particularly important to ensure that when cylinders are connected to a process in which the process pressure can exceed the cylinder supply pressure adequate precautions are taken to avoid backflow in the cylinder. The following should be observed:

Always close the supply cylinder valve when not in use
Never leave an empty cylinder connected to a process
Never use a cylinder as a receiver for waste gas liquid or other material

Fit Preventative Equipment

Fit a non-return valve or check valve

This is the simplest and cheapest method of preventing backflow, but it must be considered as the minimum requirement. These valves require regular maintenance as particulate matter or corrosive conditions can prevent resealing.

Fit an automatic shut-off/isolation valve

This is activated by a low pressure signal when the supply gas cylinder pressure reaches a level that requires the cylinder to be replaced. An alarm should normally be incorporated into the system to alert the operator.

What to do if your cylinder becomes contaminated

If you know that a cylinder has become contaminated, by whatever means or whatever the contamination, inform BOC Gases. Before the cylinder is returned, make sure that you label the cylinder and provide any relevant information about the known or suspected contamination. This information is required even if the contaminant, such as water, has been emptied out of the cylinder before return.

Please Note:

Never let oil or grease touch your cylinder or fittings. Lubrication of cylinder valves and fittings is highly dangerous as well as being unnecessary. High pressure oxygen will react violently with grease which may explode or ignite violently.
Never use jointing compounds. Do not apply white or read lead, joining compounds or jointing tape to any cylinders, valves and fittings.
Oxygen equipment is at most risk from oil and grease so keep greasy hands, rags and gloves away from any part of the cylinder and fittings.
Normal body oils do not usually matter, though it is a sensible precaution never to touch any surface which is subject to oxygen under pressure.