4 replies to this topic

[fahrudin]

Dear Engineers,

In early of this month we had faced the problem power failure, called power total black-out in our refinery.
at that time flare pilot had off due to no supply fuel gas to pilot.
normally we use fuel gas from fuel gas drum that has been supply from LPG vaporizer.
but, due to black-out happened, steam supply to LPG vaporizer is lack (Steam system off, boiler trip)
So no supply gas to Fuel Gas drum then No supply fuel gas to flare pilot.

In view of safety matter this is potential serious problem.
Fortunately at that time no unexpected accident happen.

How to keep the flare keep firing.
anyone who have this experinece kindly please share to me

Regards,
Fahrudin

[ankur2061]

Fahrudin,

Two ways of dealing with this problem:

1. Provide a bank of LPG cylinders connected to the flare ignition system as a back-up to the Fuel gas drum

2. All the electrical equipment related to flare ignition / pilots should be on emergency back-up power supply or Uninterrupted Power Supply (UPS).

Hope this helps.

Regards,
Ankur.

[kkala]

Agreeing to Ankur's post (both 1 & 2 should be realized), following may be also worthy of consideration, even though I do not have practical experience.
A. Mentioned switch to LPG from cylinders should be automatically implemented, e.g. at low fuel gas flow or pressure (so this control should be able to operate in general power failure).
B1. Normally there is requirement by design for flare pilots to remain on (lit) in total power failure. Try looking into the power failure case having occurred, to trace whether such a requirement exists in the design and why it has been inactive -- restore it before deciding on new modifications.
B2. Existing vaporizer is understood to send into fuel gas drum, so fuel gas can be supplied to pilot for a few minutes (t) after power failure, until pressure in the drum reaches its minimum acceptable value. This time (t) can increase by increasing the capacity of fuel gas drum (e.g. by another drum in parallel), so that there is enough time for operator to start LPG vaporization by e.g. electricity (connected to backup power supply) instead of steam. Or to bypass vaporizer connecting directly upstream to the gas phase of LPG storage, which will auto refrigerate rather slowly.
C. Look into load shedding and steam shedding schedule of the refinery, with an intent to give a higher priority to (α) steam feeding vaporizer (β) electricity to pilot panel and its controls (e.g. spark to light pilot, UPS to check pilot flame, etc).
D. General power failure can occur once every (say) 10 years (according to local information), resulting in heavy release of hydrocarbon gases into air. If flare is non burning, results may be indeed catastrophic (e.g. vapor cloud explosion) in addition to environmental damage.

[fahrudin]

Dear Mr. Ankur & Kkala.
Thank you very much for your sharing, it's very helpful for me.
I think the simple way is juct connect the bank of LPG cylinder to pilot gas.

Regards,
Fahrudin

[kkala]

I think the simple way is juct connect the bank of LPG cylinder to pilot gas.

Also connecting fuel gas line to the gas phase of LPG storage (supposing it is pressure storage), that is bypassing vaporizer, might be another practical way, depending on how long this gas supply could last.
Any option should be implemented automatically (for a quick response in general power failure) and this may render situation a bit complicated, since it has to assure operation in power failure (power / instrument air supply to be backed-up).