General Purpose Regulators
High Purity Regulators
Ultra High Purity Regulators
Basic Line Regulators
High Purity Regulators
High purity systems require equipment that maintain system purity. Elements such as moisture, oxygen and other gaseous vapors present in ambient air may contaminate a high purity gas system. These contaminates enter the system through leaks in connections and when the regulator is removed from the cylinder during cylinder change outs. The different features of a regulator determine the type of service for which it is used. A high purity regulator has different features than a general purpose regulator. The main features that determine regulator suitability for high purity application are body type, seal type and diaphragm type.
Regulator bodies may be of forged or barstock construction. A forged body is formed by casting metal in a mold under pressure. A barstock body is machined out of cold-drawn metal bar. Barstock bodies are used in high purity applications because a low internal volume can be achieved through the machining process. The low internal volume allows for easier purging of contaminates like moisture, oxygen or moisture. Forged body regulators have more dead space and tend to trap moisture and contaminates in these areas making the regulator more difficult to purge.
The cold-drawing process of the barstock body construction produces a metal with a tight grain structure. This tight grain structure prevents the regulator’s internal surfaces from absorbing moisture and contaminants. A more porous grain structure, which collects more contaminants, is found in the internal surfaces of a forged body regulator. These collected contaminants can eventually find their way into the gas system.
Diaphragms may be constructed of elastomers (neoprene, Viton, etc.) or stainless steel. Because they do not absorb and release contaminants, stainless steel diaphragms are used in high purity regulators. When an elastomer diaphragm is exposed to ambient air the diaphragm will absorb contaminants. These contaminants can be released into the gas stream at some point in the future.
The seal between the body of the regulator and the diaphragm is important in maintaining purity. A poor seal creates a leak point through which contaminants can enter the gas system. A metal to metal (metal diaphragm to metal regulator body) seal is the most reliable, leak-free seal. An elastomer diaphragm or elastomer seal can degrade over time creating a leak point in the body of the regulator. These elastomer seals, like elastomer diaphragms, can also absorb contaminants that could be released into the gas stream at a later time.
Dual Stage vs. Single Stage Regulator
Dual stage regulators reduce the source pressure down to the desired delivery pressure in two steps. The advantage of a dual stage regulator is its ability to deliver a constant pressure, even with a decrease in inlet pressure. For example, as a gas cylinder is depleted the cylinder pressure drops. In these conditions a single stage regulator will exhibit decaying inlet characteristics causing the outlet or delivery pressure to increase. The second stage of a dual stage regulator compensates for the decaying inlet pressure and provides a constant outlet pressure. In applications where constant delivery pressure is required a dual stage regulator is recommended.
Single stage regulators accomplish pressure reduction in a single step. Delivery pressure will change as cylinder pressure is depleted. Single stage regulators should only be used in applications where a constant outlet pressure is not critical or can be monitored and adjusted as needed.
Line regulators are single stage regulators that are used to provide point-of-use pressure monitoring and control. A line regulator may be installed near instruments downstream from the source gas and are used to monitor and adjust pressure at the point of use. These regulators are installed directly into gas lines and have a single outlet pressure gauge.
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