Rexarc Liquid Flashback Arresters Models 3 to 150

Hydraulic flashback arresters for fuel gas distribution lines

The Rexarc liquid flashback arrester range protects the main gas supply of a fuel gas piping system from reverse flow and flashback. Rexarc designed the arresters in accordance with NFPA 51 and ASME requirements, for acetylene, hydrogen, LPG, propylene and natural gas. Fuel gas enters through the inlet connection and passes three safety devices: a reverse-flow check valve, a charge of Rexarc flashback arrester (FBA) fluid that acts as the flame-arresting medium and extinguishes the flame front, and an integral safety relief valve that vents flammable gas through user-installed vent piping.

Rexarc states that hydraulic arresters create little flow resistance, resulting in no loss of pressure, and that they are built to last with no annual replacement. After any flashback event the arrester must be removed from service and replaced.

Technical specifications

The #100 inlet pipe connection must extend above the top of the arrester. Weights are dry weights for planning only.

Installation, filling and maintenance

The arrester is installed vertically with access for inspection, using fittings and piping the same size as the service line, with inlet and outlet shutoff valves for maintenance. Vent piping must be at least the relief valve outlet size, must carry no valves or restrictions, must be independently supported, and ends in a downward-facing elbow at a safe outdoor location. After leak testing with inert gas the unit is purged, then filled with Rexarc FBA fluid to the bottom of the fill port threads, and the fluid must be kept above minus 34 C (minus 30 F). The manual calls for a weekly fluid level check in the first month, monthly leak inspection, and annual relief valve test and fluid replacement. Darkening, charring, particles or odour change in the fluid can indicate a flashback.

Choosing the model

Pick the model from the required flow and operating pressure in the table: the #10HP is the 200 psi version and the #150 is a flanged unit for 15 psi service. Confirm the gas, line size, relief valve set pressure and vent routing, and use only Rexarc-approved FBA fluid. The sizes are dimensioned in the manual for planning only; verify the load before lifting.

How Rexarc liquid flashback arresters Models 3 to 150 work

A flashback is a flame that runs backward through a fuel gas line, towards the gas supply. A liquid arrester stops it with three safety devices. A check valve blocks reverse flow of gas. A charge of Rexarc flashback arrester fluid forms a barrier that cools the flame front and puts it out. If pressure builds up inside, an integral relief valve lets the flammable gas out through vent piping that the user installs. Gas coming in from the inlet bubbles through the fluid on its way to the outlet, which does not cause a noticeable pressure drop.

Where Models 3 to 150 are used

• Fuel gas distribution lines for welding and cutting.
• Acetylene, hydrogen, LPG, propylene and natural gas piping.
• Manifold stations and the main gas supply in workshops.
• Plants that follow NFPA 51 for oxy-fuel gas systems.

Selection checklist for Models 3 to 150

• Model from #100 to #150, picked by the flow in SCFH, from 100 up to 15,000.
• Inlet and outlet size, from 3/4 in NPT up to a 4 in Class 150 flange.
• Vent outlet size, because the vent pipe must be at least as large as the relief outlet.
• Operating pressure: 2, 10, 15 or 40 psi, or 200 psi for the #10HP, and 15 psi for the #150.
• The gas used, such as acetylene, hydrogen or LPG.
• Fluid quantity and dry weight, for the support.
• Place for the vent piping, which should end in a safe outdoor location.
• Inlet and outlet shutoff valves for maintenance.

Installation, filling and maintenance notes

Install the arrester upright, where it can be reached for inspection, with piping of the same size as the service line. The vent line must carry no valves, must be supported on its own and must end in a downward elbow outdoors. After a leak test with inert gas, purge the unit, then fill it with the Rexarc FBA fluid to the level stated in the manual. Keep the fluid above the minimum temperature in the manual. Check the fluid level and the leaks at the intervals the manual gives, and test the relief valve each year.

Requesting a quotation for Rexarc Models 3 to 150

Send the gas, the flow, the pressure and the pipe size. Seven Star LLC serves industrial customers in Oman and the GCC and replies with a quotation based on the information provided.

After a flashback event

If a flashback happens, the arrester must be taken out of service and replaced. Find the cause of the flashback before the system runs again.

Fluid condition

Darkening or charring of the fluid shows that the arrester has been exposed to heat. Replace the fluid at the intervals set by the maker, and use only the specified fluid.

Records and inspection

Keep the model, the fill date and the inspection results with the gas system file.

Documents and quotation

The Rexarc liquid flashback arrester installation, operation and maintenance manual (1-39-0462) is attached under Datasheets & Documents. See related equipment in our Oxy-Fuel Cutting Equipment category.

For a quotation, send the model, gas, flow, operating pressure and line size.