The main function of a gas train is to regulate fuel pressure, where in the event of a safety failure its role is to shut off the gas flow.

It also controls the high/low pressure parameters, and it filters the fuel to prevent impurities from entering the equipment and damaging or blocking it.

In this blog article you can learn about the function of each of the component parts.

Article content:
Furnace gas train components
How Nutec Bickley can assist you

Furnace gas train components


The typical arrangement of a furnace gas train lines up in the following order:

  • Manual shut-off valve
  • Sediment trap
  • Filter
  • Pressure gauges
  • Main regulator
  • Relief valve
  • Low gas pressure switch
  • Safety valve (single or double)
  • High gas pressure switch
  • Manual shut-off valve (again)

Component 1: Manual shut-off valve

Shuts off the gas supply when not needed or during maintenance; on request, it can include a Lock-out Tag-out (LOTO) device.

Component 2: Sediment trap

A section of pipework designed to trap solids and prevent them from contaminating equipment.

Component 3: Filter

Removes any dirt contained in the fuel or the pipe itself. It can be mesh or a filter element.

Component 4: Pressure gauges

These measure the inlet pressure, and help the starter to adjust the pressure regulator.

Component 5: Main regulator

Adjusts and regulates the outlet pressure. Maintains control of inlet pressure, outlet pressure and the desired flow.

Component 6: Relief valve

This sits after the main regulator, so that in the event of overpressure the line is depressurized and excess pressure is vented to atmosphere to avoid damage to the equipment.

Component 7: Low gas pressure switch

This is a Normally Open contact that closes on sensing gas pressure. It is part of the electrical safety circuit. Its role is to ensure that there is sufficient gas pressure to operate properly.

Component 8: Safety valve (single or double)

Located at the end of the electrical safety circuit. These are Normally Closed valves: this means that since they are not powered, they are closed. In the event of a problem in the electrical safety circuit, this type of valve stops receiving electrical power and closes immediately, cutting off the fuel supply.

Component 9: High gas pressure switch

Closed contact that opens when the gas pressure exceeds the setpoint pressure. Its function is to ensure that the fuel pressure does not exceed a set maximum.

Component 10: Manual shut-off valve – final

Its main function is to carry out air tightness tests on the safety valve. It also serves to shut off the gas supply if it is not needed, or during maintenance tasks.

How Nutec Bickley can assist you


We can help you in various ways with your systems:

1.- We check that everything is working properly in your gas train: valves, pressure switches, etc.

2.- We carry out a review to ensure that your gas train complies with NFPA 86 standards; we also help you with the modifications necessary to bring you into compliance.

3.- We perform the annual leak test on your valves in line with the NFPA 86 standard (reference NFPA 86–2003 Edition Paragraph A.7.7.2.4 for leak test procedure).

4.- We hold spare parts covering the various leading brands on the market.

At Nutec Bickley we are industrial furnace specialists. Contact our expert advisers so they can let you know about all the solutions that we have for you.

Author: Hilario Zavala, Combustion and Control Specialist

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