Single-Stage vs Two-Stage – There are two basic types of regulators. Duration of gas usage helps to identify whether a single-stage or two-stage regulator provides the best service. A single-stage regulator is a good performer for short duration gas usage. It reduces the cylinder pressure to the delivery or outlet pressure in one step. This type of regulator is recommended when precise control of the delivery pressure is not required because delivery pressure variations will occur with decreasing cylinder pressure.

A two-stage regulator provides better performance for long duration gas usage. It reduces the cylinder pressure to a working level in two steps. The cylinder pressure is reduced by the first stage to a preset intermediate level, which is then fed to the inlet of the second stage. Since the inlet pressure to the second stage is so regulated, the delivery pressure (manually set by means of the adjusting handle) is unaffected by changes in the cylinder pressure. Thus, the two-stage pressure regulators provide precise control of the gas being consumed. A two-stage regulator performs best when it is attached to the cylinder and adjusted to the desired reduced pressure, and then remains in service until the cylinder is ready for change out.

Materials of Construction – A regulator must be constructed with materials compatible with the intended gas service and application. When selecting your regulator, you should first consider the wetted materials (those that will come in contact with the gas). Typical materials used for regulator construction are:

• Noncorrosive: Aluminum, Brass, Stainless Steel, Buna-N, PCTFE, Neoprene, Teflon®, Viton®, Nylon.
• Corrosive : Aluminum, Stainless Steel, Monel®, Nickel, PCTFE, Teflon.

The ideal construction for high-purity gas service is a regulator that has a stainless steel diaphragm. They are none contaminating and assure satisfactory use for all applications of noncorrosive and mildly corrosive gases.

Gauges – Generally single and two-stage regulators are equipped with two gauges a cylinder or inlet pressure gauge and a delivery or outlet pressure gauge. The cylinder pressure gauge has the higher pressure range and is located adjacent to the inlet port. The delivery pressure gauge of the lower pressure range is located adjacent to the outlet port.

The actual pressure gauge range is usually greater than the pressure range for which the regulator is rated. For example, a regulator that has a delivery pressure range of 1–50 psig (0.1–3 bar) will typically be supplied with a 0–60 psig (0–4 bar) delivery pressure gauge. This ensures that the rise in delivery pressure as a result of the regulator’s supply pressure effect will not exceed the gauge pressure range.

Not all cylinder regulators have two gauges. A line regulator is typically provided with a single gauge that monitors the outlet pressure or reduced pressure. This gauge is usually situated in the 12 o’clock position. Regulators designed for liquefied gases may not have a cylinder pressure gauge because the cylinder pressure varies only with temperature as long as liquid is present in
the cylinder.

Pressure Regulators: Maintenance
Regulator maintenance is an important part of maximizing your system’s performance and extending the service life of system components. A maintenance schedule is the frequency at which recommended maintenance operations should be performed. Adherence to a maintenance schedule should result in minimizing downtime due to regulator failure as well as enhancing safety in the work area. Regulator service defines the gas service in which the regulator is installed in terms of its corrosive nature. There are three categories: noncorrosive, mildly corrosive and corrosive. Establishing the category a regulator fits into can be difficult. Consult your Representative.

Recommended Schedule – This schedule should be used as a general guide. Be sure to follow the manufacturer instructions supplied with your regulator.

1. More frequent overhaul or replacement may be required for regulators installed in a corrosive ambient environment.

* If diaphragms are neoprene or another elastomer, they may dry out and require more frequent replacement.

** If regulators are not properly installed and used, or if a poor grade of gas is used, or if purging is not properly done, overhaul and/or replacement may be required more frequently than indicated.

+ For regulators used in toxic or corrosive gas applications, care should be taken to ensure proper precautions.

NA Not applicable