How to Choose a Regulator
While all regulators can reduce pressure in a gas system, high purity regulators conform to very exacting standards of pressure control. Below, we discuss some basics of comparison that can help you navigate and choose a regulator that best suits your needs. Our experienced and knowledgeable staff at Freshford gas control equipment would be more than happy to answer any further questions you may have about regulator design and operation.
Single Stage Vs Two Stage
Single-stage regulators reduce pressure in a single step to deliver pressure within a specific range. Regulators designed in this way will show a slight variation in delivery pressure as the cylinder pressure falls during use. For this reason, single-stage regulators are best suited for applications where a constant outlet pressure is not critical. Where an operator can monitor and adjust pressure, or where inlet pressure is constant. Two-stage regulators perform the same function as single-stage regulators. However, delivery pressure remains constant as cylinder pressure decreases. Greater accuracy in pressure control is maintained because the pressure reduction is performed in two steps. Two-stage regulators are recommended for applications requiring constant outlet pressure over the life of a gas cylinder.
Helium Leak Integrity
Helium leak integrity is a measurement 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 10-9cc/sec He ( 1 billionth of a cc/sec). In this case, a Helium Leak integrity rating of 1×10 -9 would indicate that the regulator would leak enough gas to fill one cubic centimetre every 33 years. If the rating were 1×10-3, the regulator would leak enough gas to fill one cubic centimetre in just 17 minutes. Helium is used as the test gas because:
- It is chemically inert
- it is easy to detect
- it is an extremely small molecule with the ability 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 at minimizing contamination from gases outside the body.
Materials of Construction
The materials of construction for a regulator should be selected based on the properties and purity of the gas being used. Regulators from brass, aluminium and 316L stainless steel. Brass is compatible with most of non-reactive gases. A choice of forged body or bar stock construction is available. Forged body regulators are economical; however their internal surface finishes are relatively rough as compared to barstock body regulators. Barstock body regulators have all wetted surfaces machined to a smooth finish, which reduces the possibility of contamination. 316L stainless steel is highly corrosion resistant and is suitable for use with many of the highly corrosive gases in their anhydrous form. Aluminium is an economical lightweight alternative to stainless steel for many of the mildly corrosive gases. Consult your gas supplier to determine suitable materials of construction or get in touch for more information.
Determine the maximum no flow pressure permitted by your system. Locate this pressure on the vertical axles of the chart. If there is no curbe for your specific condition interpolate a curve. Follow the curve to the desire flow rate on the horizontal scale. Read horizontally to the left to determine the corresponding pressure drop. Because flow rate is dependent upon inlet pressure, data is presented at full cylinder pressure 2000 PSIG (137 Bar) partially full 500 PSIG (34 Bar) and nearly empty 200 PSIG (14 Bar).
The diaphragm is a sensing element crucial to the function of the regulator and the purity of gas delivery. Stainless steel diaphragms are corrosion resistant and have low leakage rate characteristics. Neoprene diaphragm may offer more sensitive pressure control but do not offer the gas purity of stainless steel. Coating a neoprene diaphragm with PCTFE enhances gas purity greatly.
While a single or two stage regulator of the appropriate material with suffice in most gas services, some applications require specifically designed regulators. Please contact us for further information or take a look what regulators we have to offer from market leaders Hi-Lo Uk gas equipment and Gas Arc.