Most specialty gases are supplied in cylinders compressed to high pressures. Pressure regulators reduce these high pressures to lower pressures that can be safely used in an operating system. Proper regulator selection is critical for both safety and effectiveness of operating systems.
Many variables are involved in selecting the proper pressure regulator. While certainly not a comprehensive list, the following provides some of the more important considerations. To further assist in making proper regulator selections, refer to our Pure Gas Specifications or Mixed Gas Specifications pages as applicable for recommendations.
Materials used to construct regulators must be compatible with the gas – especially those materials (wetted parts) in contact with the gas. We offer a wide variety of regulators with various materials of construction to help ensure that the correct regulator is available for your needs. Please refer to our Materials Compatibility chart.
Regulators must be designed with vent connectors to permit the attachment of a vent line or disposal system as a precaution, in the unlikely event of a diaphragm failure.
Like all system components, regulators should be selected to protect the purity of the service gas. As an example, regulators with stainless steel diaphragms are recommended for high purity applications because they are more "diffusion-resistant" than those with "rubber-type" diaphragms. For low particulate applications, consideration should be given to selecting regulators with machine welded VCR® connections. Optional helium leak tests also help to ensure the integrity of regulators.
Cylinder regulators as their name implies are connected directly to gas cylinders. Typically offered in both single and two-stage designs, cylinder regulators normally have inlet and delivery pressure gauges.
Line regulators, on the other hand, are used directly in piping systems such as downstream of the manifold or bulk storage vessel. Because inlet pressure in piping systems is normally constant, line regulators are typically single-stage configurations with delivery pressure gauges only.
Single stage regulators reduce pressure in one step as gas is consumed. Dual stage regulators are actually two regulators housed in one body. The first regulator (first stage) is non-adjustable and reduces in-coming pressure to an intermediate setting (typically 250 to 300 psig). The second stage is adjustable and reduces intermediate pressure to final desired delivery pressure. Because the second stage sees only relatively minor inlet pressure changes from the first stage, dual stage regulators maintain steady delivery pressure and do not require periodic adjustment. They are well suited for applications where constant delivery pressure is essential.
Regulators must be able to reduce pressure to levels compatible with the operating system and consistent with process needs. Our extensive line of pressure regulators provides numerous choices with delivery pressure ranges available as low as 0-0.5 psig, or as high as 0-6000 psig.
Regulators must be able to safely handle incoming gas pressure. Here again, a wide selection is available which includes regulators that handle inlet pressures up to 10,000 psig.
Helium leak integrity is a measure of how well a regulator prevents gases from leaking into or out of a regulator body. The measured quantity is expressed as a flow rate such as 1 x 10-9 scc/sec He (1 billionth of a cc/sec). In this case, a helium leak integrity rating of 1 x 10-9 would indicate that the regulator would leak enough gas to fill a cubic centimeter every 33 years. If the rating were 1 x 10-3 the regulator would leak enough gas to fill a cubic centimeter in just 17 minutes.
Helium is used as the test gas because it is chemically inert, it’s easy to detect and it’s an extremely small molecule which allows it to pass through the smallest leak. The lower the helium leak specification, the better the regulator will be at preventing leaks into the atmosphere and minimizing contamination from gases outside the regulator body.
Other criteria for consideration include operating temperature, flow requirements, regulatory issues (e.g. medical regulators manufactured to FDA standards), special applications, design preferences and cost. Call your local representative for further assistance.
Note: Regulators are designed to control pressure. Generally they are supplied with gauges that indicate pressure. Regulators do not measure or control flow unless equipped with devices (such as metering valve or flowmeter) specifically designed for those purposes. Contact your local sales representative to find out more about Praxair’s new line of flow monitoring and flow controlling devices.