The connection and purging of a double-stage pressure regulator connects a cylinder of high pressure vector gas (up to 200 bar) to a gas analyser (GC or microGC). Correctly performed, this operation removes air and moisture from the line, in order to preserve the initial purity of the gas (Helium, Argon, Hydrogen). A rigorous protocol protects operators, preserves equipment and guarantees the accuracy of chromatographic analyses.
In gas chromatography, the quality of the analysis depends in part on the regulator. Poor assembly or incomplete purging pollutes the carrier gas. As a result, your columns are damaged and your measurements are distorted.
Here's the step by step guide from the experts Chemlys to secure your installation, from the carrier gas bottle to the analyser.
Step 1: Pre-Safety Precautions and Cylinder Setup
Before handling high-pressure gas equipment, ensure laboratory safety protocols are strictly met:
Secure Mounting: Always attach the bottle under pressure to a solid support with a strap.
Environmental Safety: The cylinder shall be kept away from sources of excessive heat, fire, corrosive products and the risk of mechanical damage. Access must be restricted to authorized personnel.
Clear Access: Never place a bottle in the passageways or evacuation corridors.
Step 2: Connecting the Pressure Regulator
Anatomy of a regulator for vector gases: Identification of pressure gauges, clamping wheel and location of the seal before connection.
Inspect Connections
Initial Knob Setting: Completely unscrew the regulator adjustment screw (closed position), then re-screw it by about 1 turn (open position). This tip avoids the reflux of the air contained in the regulator to the bottle when opening.
Alignment and clamping - Depending on your gas standard specification, two main mounting types are encountered:
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A. Handwheel Connection with Integrated O-Ring : Designed for tool-free manual connection, this system presses on the knuckle ring (the clamping force) to attach the regulator's tail to the bottle tap. Sealing is ensured by compression of the integrated O-ring. Ensure that the seal is present, verify that it is clean and intact. Align the pressure regulator in the gas outlet axis and screw the steering wheel firmly by hand only. Never use tools (pin or key) or damage the joint or thread.
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B. Hexagonal Nut Connection with Flat Sealing Washer : Used for configurations requiring a higher mechanical clamping torque, this assembly requires a renewable flat joint at each cylinder change. Place a new flat joint at the bottom of the stretcher's tail. Engage the hexagonal nut in hand on the first threads to avoid damaging the screw step, then complete the clamping with a a properly sized open-end wrench. Avoid over-torquing, which deforms or shears the flat gasket.
Critical Safety Identification: Threading Standards
To prevent any risk of assignment error when connecting to a cylinder, the pressure regulator is strictly categorised according to the nature of the gas delivered:
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Type C Regulators (Inert / Neutral Gases): Intended for neutral gases of which our vector gases are part (Argon, Azote, Helium, CO2), this connection is made with a Features standard right-hand threads classic. The nut clamping is clockwise (to the right).
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Type E Regulators (Flammable Gases): Designed specifically for flammable gases (such as hydrogen or methane), it is essential to use a Features left-hand threads (not inverse) where the clamping is performed in the counterclockwise direction (to the left).
Visual Identification:
How to identify a pressure regulator step by step at a glance? The connecting nut of a Type E pressure regulator systematically has Type E nuts feature notched outer grooves cut into the hex faces. engraved on its sides. If you see these external grooves on the nut, don't push to the right: the reversal of the screwing direction is a vital mechanical concealer designed to prevent the accidental connection of a combustible gas to an inert network.
Visual identification of Type E pressure regulator for flammable gases (hexagonal split nut or specific steering wheel, surrounded in blue) against conventional Type C models (rounded in purple) for neutral gases.
⚠️ Essential Operational Hazards
Never stand directly in front of the gas outlet. In case of malfunction or malfunction, the pressure can cause serious injury.
Never leave directly a free tube connected to the regulator. Accidental overpressure in an unconnected tube may cause an effect « whipping » Very dangerous.
Step 3: Dual-Stage Regulator Purging (Step-by-Step)
The purging allows to drive the trapped air into the connection during connection.
- Pressurize the Cavity Briefly open the main cylinder valve a quarter-turn, then close it immediately.
- The input gauge (HP) indicates the pressure of the cylinder (up to 200 bar).
- The output gauge (BP) indicates the set pressure (up to 10 bar).
- Air evacuation : The exit being slightly open, you must hear a leaking whistle and see HP pressure gradually decrease while the bottle is closed. (If the leak is not audible or too large, adjust the steering wheel).
- Repeat Cycles : Perform this press-and-bleed sequence 3 to 5 consecutive times to sweep air out of the inlet fitting.
- Set Working Pressure : Unscrew the regulator adjustment knob completely, then fully open the main cylinder valve.
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- The HP gauge will display stable cylinder pressure.
- The BP gauge shall indicate 0 bar (closed adjustment rod).
Pressure regulator leak check
Pass the probe of an electronic leak detector over all critical areas (nuts, teflonated fittings, etc.).
Detectable gases: H2, Helium, Argon.
Little or no detectable gases: Azote (N2) is not easily detected by electronic probe because of its air content. For this gas, perform a pressure retention test.
Note by the expert Chemlys : Leaks at the regulator are mainly due to defective joints or damaged threads. To guarantee you total safety, all the pressure regulators provided by Chemlys undergo an individual seal check in the workshop before dispatch.
WARNING: Never use liquid bubble leak detectors (e.g., Snoop®) on analytical gas lines! Surfactant liquids leach into tubing via back-diffusion, permanently poisoning MEMS detectors, Micro GC injectors, and capillary column stationary phases. Always use an electronic leak detector.
4. Gas analyser connection
Choosing the pipe (Tube 1⁄8"): use only clean tubes. Be careful with cutting chips or dust.
The choice of material depends on the configuration of your laboratory:
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316L Stainless Steel Tubing: Rigid, highly recommended for permanent laboratory setups. Cut cleanly using a dedicated roller tube cutter.
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Copper Tubing: Flexible, suitable for mobile test carts. Coil excess length neatly to absorb vibration. It cuts with a pipe cutters. The excess length can be wound in turns to reduce congestion.
Compression Fitting Swagging (Swagelok / VICI)
- Cut the 1⁄8" tube very clearly and make sure that the the final 5 cm are perfectly straight..
- Slide in order on the tube: the nut, the counterferule, then the ferrule, allowing it to pass 1 cm of exposed tubing at the end. (Note: Front and back ferrules may be separate, as with Swagelok®or integrated, as with VICI® fittings).).
- Insert the tube into the pressure regulator's BP connection and screw the nut by hand.
- Swagging/Tightening: Using two 7/16" flat keys (one to hold the connector, the other to tighten the nut), perform tighten the nut 1/2 turn from finger-tight while holding the tube seated.
Caution: Over-tightening crushes the tubing ID and permanently damages fitting threads.
Connection of the analyser under gas flow
- Prepare the second end of the 1⁄8" tube (cut + nut + counterferule + ferule).
- Adjust the regulator knob to establish a tiny purge flow (outlet pressure
Why this step? Making the connection under gas flow allows to expel dust and remove residual air from the tube. - Insert the tube into the analyser gas input and screw by hand, then press 1⁄2 turn with the 7/16" keys.
- The LP delivery gauge will register backpressure as the circuit seals.
- Service pressure adjustment: Adjust the final delivery pressure to instrument specifications
(e.g.: For MicroGC Fusion, the recommended pressure is 5.5 bar / 80 psi).
Step 5: Final Verification and Leak Troubleshooting
Once the circuit is under pressure, close the pressure regulator valve: the inlet and outlet pressures must remain perfectly stable.
Make the final check with the electronic leak detector on all nuts and fittings.
What to do in case of a leak on the ferrules?
Incremental Tightening: Perform a light 1⁄8 extra turn on the nut with the two flat keys until the leak disappears.
Preventive replacement: If you feel an abnormal resistance to tightening or the nut grin, do not insist. Replace the nut and its set of ferrules immediately to avoid damaging the threads of the instrument.
Expertise Chemlys for your gas installations
A compromised carrier gas delivery system is the primary cause of baseline noise, ghost peaks, and detector downtime on GC and MicroGC analytical equipment.
Gas analysis specialist, Chemlys accompany you in:
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- Selection of high-precision pressure regulators and automated manifold panels.
- Supply of certified ultra-clean tubing, SilcoNert® treated lines, and Swagelok® / VICI® fittings.
- Installation, qualification and maintenance of your analytical equipment.
