Step: 1: Pressure or Flow
Do you require a pressure regulator or a flow regulator?
All high-pressure regulators are designed to accept incoming pressure of 150bar+ from the cylinder. This makes them a high-pressure regulator. But what do you require on the outlet of the regulator. What does your instrument/analyser/GC require? Pressure or flow?
Typically, a gas detection instrument will require flow (0.5l/min) where a gas analyser may require pressure at 1 or 2 bar. The instrument, analyser or GC will dictate what is required.
Once this is determined then we can continue.
(For more info read our blog Calibration Gas Flow & Pressure with Specialty Gas Regulators)
Step 2: What is the outlet flow rate or pressure requirement?
Specific flow rates or pressures may be required for a specific instrument or analyser.
Determining that level will allow us to select a regulator with the correct outlet requirements or a variable range which includes the value required.
Many regulators have specific flow rates which are fixed, while others have a selection of flow rates. A continuous flow regulator will provide the required flow rate required by the instrument. In cases where the analyser has an internal pump then an on-demand flow regulator will provide the flow once a vacuum is placed on the regulator.
(For more information read our blog on Best Practice for Gas Detection Instruments with Internal Pumps)
All pressure regulators have outlet ranges such as 0-1.5bar, 0-3.5bar or 0-10bar. Select the range which matches your requirement. If your analyser requires 2 bar then select the 0-3.5bar range.
Step 3: Gas type and concentration:
The gas mixture or gas type will determine the material requirement of the regulator. It is also important when selecting other materials such as tubing.
(For more information read our blog Selecting Compatible Materials for Calibrating Gas Detection Instruments.)
Highly corrosive gases such as chlorine, ammonia, nitrogen dioxide, hydrogen cyanide require stainless steel regulators.
Hydrogen sulphide and sulphur dioxide can use nickel plated brass if the concentration is below 50ppm. Higher concentrations of H2S and SO2 require stainless steel.
Non corrosive gas mixtures such as CO, CO2, O2 and most hydrocarbons would require brass. It is important not to use nickel plated brass for high concentrations of carbon monoxide, as CO and nickel are incompatible and can form tetracarbonylnickel.
Where high purity gas concentrations are used with highly corrosive gases, purging systems are recommended.
Step 4: What inlet connector do you require? Flow or Pressure Regulators
The gas type or gas mixture will dictate what valve type is on the gas cylinder. Australian (AS), British (BS) or North American (CGA) standards are typical depending upon where the gas mixture was manufactured. The inlet connector on the regulator must match the gas cylinder valve. You must determine what type of valve is on the cylinder, whether that is an old cylinder or a new cylinder. The material of the valve and regulator will be dependent upon the gas type.
Inlet connectors can be changed to match the gas mixture if required.
Step 5: Do you require a single or dual stage regulator (pressure regulators only)
The outlet pressure of a specialty gas regulator has an inverse relationship to the gas volume in the cylinder. As the gas volume decreases the outlet pressure increases.
Do you require a constant outlet pressure throughout the use of your analyser? Often analysis may take some time to complete so the analyser is left unattended.
If you require a constant pressure being delivered to your analyser then a dual stage regulator is required. The dual stage regulator corrects for the increase in outlet pressure and maintains the pressure at the selected valve. As per step 2, if you require a 2 bar continuous outlet pressure you would select a dual stage regulator with the range 0-3.5bar and set the value to 2 bar.
If an increase in outlet pressure is not important then a single stage regulator would be appropriate for your application. In the case of a 0-3.5bar range regulator the highest outlet pressure would be 3.5bar.
Single and dual stage regulators are available for all types of materials of pressure regulators.
Step 6: What type of outlet connection do you require? Pressure regulators only
Most flow regulators have a hose barb connection for low pressure tubing.
All pressure specialty regulators have a ¼” NPT Female outlet. Many different outlet connectors are available to connector to your gas distribution system.
Select the outlet connector to meet your requirements.
- Pressure or Flow
- What pressure or flow
- What gas type and concentration
- What inlet connector
- Single or dual stage
- What outlet connector