A flare that suddenly vibrates and roars may have a simple control fault rather than a mechanical one. On a service call to a UK landfill, a flare with bad vibration and noise was traced to a temperature display that had been knocked out of its clips. Without a reading, the combustion air louvres stayed open and the flare drew in too much cooling air. This post explains the fault, and what regular servicing is meant to prevent.

The problem

The site reported bad vibration and noise from a 1,000 m³/h enclosed flare. On arrival the engineer found the flare shut down, but power was on at the panel. The temperature display was blank.

The diagnosis

The display had not been clipped in correctly. Refitting it cleared the problem and the flare started with no vibration or noise. The probable cause was the mains supply being connected in the panel over the weekend, which knocked the display out of position.

That explains the symptoms. On start-up the louvres opened correctly under the timer control, but never closed again, because the temperature loop that should have closed them had no signal. Too much cooling air then entered the chamber, causing the vibration and noise. The lesson is that in a flare with automatic temperature control, a lost signal is a mechanical problem as well as an electrical one.

What the service arrangement looks like

The operator, via its consultants, asked for servicing of a flare that had not been serviced since it began operating. The proposal:

• Quarterly visits, each completed within one day on site.
• Extra time charged at hourly rates, with expenses if overnight stay is needed.
• An initial inspection at the first visit, since there was no service history.
• Parts included in the contract limited to flame arrester gaskets and status lamp bulbs.
• Response within 24 hours on weekdays for written notifications, with an emergency call-out arrangement.
• A report with each quarterly invoice.

The contract runs for a minimum of twelve months, with four weeks’ notice to end it, and places duties on the customer: use the equipment correctly, do operator checks, tell the supplier promptly about faults, keep records and allow access.

What to consider for your own site

1. Check displays and connectors after electrical work.
2. Do not ignore a blank display. Investigate before restarting.
3. Service from day one. A flare not serviced since commissioning will need an inspection first.
4. Know what a service contract excludes. Repairs and parts beyond the listed items are charged separately.
5. Keep records of usage and performance for your permit. See LFTGN05.

FAQ

Why would a flare vibrate?

One cause is too much combustion air entering the chamber when the louvres fail to close.

How often should a flare be serviced?

This contract specified quarterly visits.

Flare behaving oddly?

Describe the symptoms. See also a modulating valve failure case.