Pressure Regulators For Specialty Gases

Selecting the right regulator for handling a specialty gas product is critical to maintaining the overall purity of the gas stream at the point of use. Ordinary industrial regulators are constructed of materials that may not be compatible with many specialty gases. Air Liquide Australia is able to provide the best equipment for a given application and/or advice on the features and benefits to look for in specialty gas equipment.

Materials in construction

It is important that all materials of construction in a specialty gas regulator (the “wetted surface” ) are compatible with the gas stream it is in contact with during use. Most regulators are made from stainless steel or brass but some are made from aluminium. Aluminium should not be used for oxygen or most corrosive gases. For higher purity gases, stainless steel is generally recommended. For inert gases, brass is often used.

For most specialty gas products regulators made from machined bar stock are recommended over forged body regulators. Forged body regulators have wetted surfaces that are much rougher than machined bodies and those surfaces can trap trace components in the gas stream. Brass regulators may also be either chrome or electroless nickel-plated.

In basic terms, gases that are corrosive or containing corrosive species of gas eg. SO₂, H₂S, Cl etc, require the use of stainless steel equipment. Non corrosive gases can be used satisfactorily with brass bodied regulators. Stainless steel is also the first choice when using the ultra pure grades of gases (>99.999%).

The other materials used to construct a regulator are also important. The diaphragm and gauges as well as parts like seats, seals and other wetted surfaces should be compatible with the respective gas service. Stainless steel diaphragms are recommended for most specialty gas regulators.

Neoprene diaphragms such as those used on industrial regulators should not be used. Check the compatibility chart to determine which materials are safe to be in contact with the particular gas service.

Single-Stage or Dual-Stage Regulators

There are some important differences between single stage and dual stage regulators. Single stage regulators drop the pressure to a lower pressure in a single step. Because the inlet pressure changes as a cylinder of gas is consumed, the outlet pressure on a single stage regulator changes. For many laboratory applications, a constant gas delivery pressure is required and dual stage regulators are recommended.

Dual stage regulators differ from single stage regulators in that the inlet pressure is first dropped to a consistent lower pressure and that pressure is then regulated to the desired outlet pressure. Because there is much less drift in outlet pressure for dual stage regulators, they are recommended for most specialty applications