Material compatibility between the gas being used and the materials of construction of the regulator is essential. Regulator components that come in contact with the gas stream called "wetted surfaces" must be compatible with the gas being used. Depending on the environment the regulator is being operated in, external materials of construction must be considered as well. Smith Equipment manufactures a wide variety of regulators from various materials to meet most any application. For more information on materials compatibility please refer to the "Material Compatibility Reference" located below.

Types of inlet connections (CGA connections) are determined by the type of gas being used. You can determine what CGA connection you need by locating the gas you will be using in the "Regulator CGA Connections guide located below.

The higher the purity grade of gas selected, the more "diffusion resistant" the system components need to be. Maintaining gas stream purity is directly related to the materials of construction in the equipment selected. For example when high purity gas is required, regulators with non-stainless steel diaphragms should not be used. Elastomeric (rubber based) diaphragms tend to absorb and outgas which may compromise the gas purity. Regulators with stainless steel metal to metal diaphragms prevent particulates from being absorbed and later diffused into the gas stream maintaining gas purity. To define the grade of regulator purity required, consider the following as a guide:

GENERAL PURPOSE REGULATORS- Are recommended for use with non-corrosive and non-hazardous pure and mixed gas applications where elastomeric outgassing is not critical. These regulators are not recommend for analytical or high purity applications. Typical applications included general laboratory or plant use. These regulators contain a self resetting safety relief valve vented to atmosphere to protect downstream equipment from over-pressurization and are available with optional needle valves.

HIGH PURITY ANALYTICAL REGULATORS- Are recommended for use with non-corrosive pure and mixed gas application. Typical applications include gas management of analytical instrumentation, chromatographic carrier gas, and process gas regulation. These units minimize outgassing and inboard diffusion through the use of stainless steel convoluted diaphragms and high purity seats and seal rings. These regulators contain a self resetting safety relief valve vented to atmosphere to protect downstream equipment from over-pressurization and are available with optional needle valves.

HIGH PURITY REGULATORS- Are recommended for use with non-corrosive pure and mixed gas application. Typical applications include gas management of analytical instrumentation, chromatographic carrier gas, and process gas regulation. These units minimize outgassing and inboard diffusion through the use of stainless steel convoluted diaphragms, high purity seats and seal rings. These regulators may be fitted with optional captured safety relief vents to safely vent away hazardous gasses and protect downstream equipment from over-pressurization in the event the diaphragm failures. Optional packless diaphragm valves are also available for these regulators.

HIGH PURITY CORROSION RESISTANT REGULATORS- Are recommended for use with mildly corrosive and non-corrosive gas applications. The stainless steel convoluted metal to metal diaphragm seal provides superior leak performance and eliminates the need for seal rings. The metal to metal seal eliminates outgassing and inboard diffusion in the gas stream. These regulators may be fitted with optional captured relief vents to safely vent away hazardous gasses and protect downstream equipment from over-pressurization in the event of a diaphragm failure. Optional packless diaphragm valves are also available for these regulators.

DELUXE CORROSION REGULATORS- Are recommended to control the pressure of highly corrosive and reactive gasses. All wetted surfaces of the deluxe corrosive service regulators are constructed of Monel, Inconel or PCTFE materials and are protected by two sintered Monel filters. These regulators are recommended for use with halogen gases.

Single stage regulators reduce pressure by passing through one pressure reducing valve area in a single step to deliver a pressure within a specific range. Regulators designed in this way will show a slight increase in delivery pressure as the cylinder pressure falls during use. This phenomenon is known as decay/rise. This reduced inlet pressure provides less force against the regulator valve causing it to open wider resulting in increased pressure. If constant pressure is required, periodic adjustment of the regulator is required as the cylinder pressure is reduced. Two stage or dual stage regulators perform the same function as single stage regulators however; they are actually two regulators in the same housing. In two stage regulators delivery pressure remains constant as the cylinder pressure decreases. Greater accuracy in pressure control is maintained because the pressure is reduced by passing through two pressure reducing valves instead of one. The first stage reduces the incoming high pressure down from 3,000 psi to around 200-300 psi. The second stage is adjustable and reduces the remaining pressure down to the desired working pressure. Because the inlet pressure on the second stage is relatively stable from the first stage, two stage regulators maintain stable delivery pressure and do not require periodic adjustment as the cylinder pressure decreases.

In summary a single stage regulator will automatically increase outlet pressure as the cylinder pressure drops. A two stage regulator outlet pressure will remain constant when the cylinder pressure drops.

Specific outlet connections are determined by the gasses used as well as application and down stream requirements. Most regulators are available with or without outlet fittings and are configured at the time of ordering. Smith Equipment offers a wide variety of outlet fittings including standard hose fittings, needle valves, diaphragm valves, and tube fittings. Refer to the available options shown on the catalog page for the specific regulator chosen. Other options and accessories are also available as listed on specific regulator pages.