An integral part of any flare system supply is the associated pilot, ignition and flame detection system. With the exception of a few flare applications, the recommended method of igniting a flare is through the use of pilot burner(s). API 537 provides guidance on the required number of pilots required for a given flare tip diameter, however the flare vendor will typically confirm this requirement as part of the overall system design. The ignition system is used to light the pilot burner and pilot flame verification is required to confirm status and thus reliability of the system.
The pilot burner is essentially a robust premixed burner unit designed to provide a stable flame for igniting the waste gas exiting the flare tip and features three main components, the venturi or mixer, gas jet or orifice and the burner nozzle. The design specification of the pilot burner is such that it must be reliably ignited, provide a stable flame (source of ignition) in extreme weather conditions, as well as being durable.
Careful consideration should be given to the location of the ignition system with respect to access as well as the cable and pilot gas routing
In order to light the pilot burner and in turn the flare tip, an ignition system is required. Ignition of the premixed gas at the pilot burner nozzle is the most reliable arrangement and can be achieved by flame or spark. A number of different ignition systems are available, the most common being:
- Flame Front Generator ‘fire ball’ type
- Electronic Spark Ignition
- Ballistic Ignition
- ‘Very Pistol’/Signal Gun
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In order confirm the reliability of the flare system, it is important to verify the ignition source (i.e. the pilot flame). Generally positioned at high elevations (stack, derrick structure, boom or tower), the flare tip and pilot burners are inaccessible during operation which makes flame verification difficult without use of dedicated flame monitoring system. Thermocouple flame detection, flame ionisation and optical scanning are some of the more common methods utilised. The feed back loop from these systems is used to raise an alarm if the flare / ignition system fails or to initiate a re-ignition sequence within an automated ignition system.