When we talk about ignition logic, we are referring to the steps we need to follow to safely ignite a furnace in order to avoid explosions or unforeseen events.

Every device/system has a start-up procedure, and in the case of an industrial furnace this entails the fulfillment of certain requirements.

These requirements are regulated by various standards around the world; so, at Nutec Bickley, we are concerned with complying with the standard that exists in the country/region where the equipment will be installed (Mexico, USA, Canada, Europe, etc).

Discover below exactly what you should check in each part of your equipment, in preparation for ignition, in order to operate as safely as possible.

Article content:
Safety limits/protocol
Flame relays
Burner ignition

Safety limits/protocol

Safety limits are the conditions that the furnace must meet at all times to operate safely. They are different in each locality (although generally very similar to one another) so we advise you to focus initially on complying with local regulations.

To ignite your furnace, the first thing to do is check that the safety line is observed in order to facilitate purging of the furnace. Then open the gas valve and light the burners; this is normally done automatically when the purge is finished.

If at any time any of the safety conditions are no longer met, the burners should be shut off and the main gas valve closed.

Flame relays

We have a flame relay for each burner to ensure that throughout the process no burner goes out and as a consequence causes an unsafe situation with the gas valve open.

Flame relays govern the opening of the gas valve, triggering of the burner’s ignition spark, and checking that the flame does not go out. In the event of failing to detect the presence of a flame, they will automatically close the valve.

Burner ignition

It is highly recommended to ignite burners on low fire so that in the event of the burner not lighting the accumulation of gas inside is smaller.

It is also easier to light a burner on low fire and, once properly lit, to enable high fire. Subsequently, depending on the temperature control, the intensity of the flame will vary in high fire mode.


If the burner does not light, the flame relay will direct the gas valve to close and will activate a fault indicator for the attention of the operator.

There are several reasons why the burner may not light properly:

  • Dirty photocells
  • Incorrect air/gas ratio
  • Carbon-fouled spark plug
  • Insufficient gas reaching the burner
  • Damaged components

To operate safely we advise the following:

  • Purge the furnace again if no burner ignites in the combustion chamber.
  • The maximum time that the furnace can safely continue operation without burners being lit is deemed to be such that the lower explosive limit reaches 25%.
  • You should verify that all components are working properly.


At Nutec Bickley we have over 40 years of experience manufacturing industrial furnaces. We understand and apply international safety standards. Contact our advisers to review your procedures and help you achieve optimal operation.

Author: Pedro Espinosa – Head of Electrical Engineering and Control

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