What should I know about using and discharging compressed gas cylinders?

2020-06-17 10:00:43 keepwin

General precautions

When moving tanks, securely fasten them to a suitable tank transporting device. At the site, chain or otherwise secure the tank in place. Remove the valve cap only after the tank has been safely installed then check the tank valve and fixture. Remove any dirt or rust. Grit, dirt, oil or dirty water can cause gas leaks if they get into the tank valve or gas connection.

Never open a damaged valve. Contact your gas supplier for advice.

There are four standard types of tank valve outlets to prevent interchanges of gas handling equipment between incompatible gases. Use only the proper equipment for discharging a particular gas from its tank. Never use homemade adaptors or force connections between the tank valve outlet and gas handling equipment.

Whether a compressed gas is a liquefied, non-liquefied or dissolved gas, the gas supplier can give the best advice on the most suitable gas discharge equipment and the safest way to use it for a specific job.

In general, do not lubricate any tank valves, fittings, or regulator threads, or apply jointing compounds and tape. Use only lubricants and sealants recommended by the gas supplier.

Tanks stored in cold areas may have frozen valves. Use only warm water to thaw the valve or bring the tank into a warm area and allow it to thaw at room temperature.

Use only recommended keys or handwheels to open valves. Never use longer keys or modify keys to increase their leverage. Avoid using even the correct key if it is badly worn. Do not use pipe wrenches or similar tools on handwheels. Any of these practices could easily damage the valve seat or spindle.

Always open valves on all gas discharge equipment slowly. Rapid opening of valves results in rapid compression of the gas in the high-pressure passages leading to the seats. The rapid compression can lead to temperatures high enough to burn out the regulator and valve seats. Many accidents involving oxidizing gases result from burned out regulator and valve seats, usually caused by opening valves too quickly.

Do not use excessive force when opening tank valves--use no more than three quarters of a turn if possible. If a problem develops, the valve can then be closed quickly. Leave keys on tanks when valves are open so the valve can be closed quickly in an emergency. Some tank valves, such as oxygen valves, have double seating. These valves should be fully opened, otherwise they may leak.

Do not use excessive force when opening or closing a tank valve. When closing, turn it just enough to stop the gas flow completely. Never force the valve shut.

Close tank valves when the tank is not actually in use. Do not stop the gas flow from a tank by just backing off on the regulator. Regulators can develop seat leaks, allowing pressure to build up in equipment attached to the regulator. Also if the tank valve is left open, foreign matter can enter the tank if the tank pressure drops lower than the pressure in attached equipment. Close the tank valve first and then close the regulator.

Liquefied Gases

Manual valves are normally used on tanks containing liquefied gases. Special liquid flow regulators are also available. If it is necessary to remove liquid as well as gas from a tank, discuss this with the gas supplier before ordering. Some liquefied gas tanks have eductor tubes which allow the liquid to be withdrawn from the tank. The supplier can provide suitable tanks and special instructions.

Do not remove gas rapidly. The pressure in the tank could drop below the required level. If this happens, or if rapid gas removal is needed, follow the gas supplier's advice.

Non-Liquefied and Dissolved Gases

Use automatic pressure regulators to reduce gas pressure from the high levels in the tank to safe levels for a particular job.

There are two basic types of automatic pressure regulators: single-stage, and double- or two-stage. Generally, two-stage regulators deliver a more constant pressure under more precise conditions than single-stage regulators. Sometimes, manual flow controls are used on non-liquefied gases. Fine flow control can be obtained, but an operator must be present at all times. Manual flow controls do not automatically adjust to pressure buildups in blocked systems.