Pilot Flame Monitoring for Elevated Flare 2

[cmarbry]

Exploring the different technologies for pilot flame detection. Does anyone have real-world experience with the following?:
1) thermocouples (retractable or not)
2) ionization/rectification
3) UV
4) IR
5) acoustic

The downfalls of each are pretty obvious - access to TC's and ionization electrodes during operation and interference for UV, IR, and acoustic.

So, my questions is - despite these limitations what has been most sucessful for you?

The flare system I'm working on is for a gas processing facility. It will be combusting hydrocarbons (C6 and lighter) from emergecy flaring and PSV's.

Thanks,
Clay

 

[Flareman]

Cmarbry
Wow, ask an easy question why don't you!!!

Could write a book on this.

Thermocouples - most common method, long experience so most record of problems. Most problems come in the associated connections and wiring because it's not been designed for the high temperatures. Don't use regular wire in conduit in hot zones, make sure the tails are heat resisting, use mineral insulated stainless or inconel sheaths, use thermowells, all wiring connections in hot zones with SS MIMS. Shop made wiring nds (not site made), double protect everything from the flame lick.
Only measure the pilot flame, not everything else.

Accessibility poor so get it right for at least a 5 year span.
Pilots and thermocouples can be mounted together on a guide track. helps for in-service maintenance but is a pain to design (and get down ?) because of the potentially long runs and the need to handle piping and wiring as the pilot moves.
Thermocouples can be "poked" up a long tube. Tend to sag out of place over time and not read the flame, difficult to keep straight during fitting, may need special tools.

Relatively short stacks can be fitted with a canting device to get the pilots and the thermocouple down in one piece. tailor made solution

Have done all the above

Ionization - hate it. great idea in an enclosed environment but susceptible to wet, dirt, rust, shorts and uses High tension ignition.
Stay with High Energy ignition if you want direct lighting. Works in water and soot!!??
But needs activation with (a thermocouple?)

UV - stay away sun light activated

IR remote optical fairly common these days. Benefit is remote mount. Drawbacks are remote mount sees fog and mist before it sees the flame. Distance limited. may not see the pilot because something on the tip is in the way, may really see the main flame most of the time (if you care), can't see individual pilots without individual devices

Acoustic - only one manufacturer uses, My view .. gimmick..
The theory is there but I'm not convinced on the practice
relies on acoustic filters to "find" the tone emitted from a specific device. Distance and roughness attenuation in a pipe are concerns (site tuning ?)

So there
Good luck
David

http://www.flareman.com

 

[JLSeagull]

When can we expect to buy the book?

 

[roca]

Interesting
I have the same issues right now on an offshore facility.
The norm is thermocouples – one per pilot.
We have specified thermocouples and the suppliers are guaranteeing 2 years life – could last 5 but will only commit to 2. Whereas the tip is guaranteed for 10 years minimum. If they fail they won’t be changed out as it’s a major shutdown to allow access to the tip.
Responses to use of IR have been mixed – some believe it is not effective on its own and thermocouples should also be used.
Acoustic – only John Zinc make it. I’ve learnt its not so good and is susceptible to all kinds of interference and seems to be only really suitable for leak detection around flanges of high pressure systems etc.
CCTV + sophisticated software is highly reliable to the extent it now seems to be the method of choice of most clients for open path fire detection – check out Groveley on the net. Only problem is where to site the camera to view all pilots.FLame ionisation is only used with electronic ignition - we are using the traditional FFG.

 

[Chentronics]

Hi Roca,

You may wish to consider the reliability of the ignition source as well. Chentronics Corporation offers a diagnostic exciter that detects igniter tip (spark plug) wear. The system detects "skipping" of energy release (from the exciter) and closes a set of contacts to let the operator know the plug is about to fail (the plug is still working). This proactive indication of failure can prevent a lot of frustration.

For more info:

http://www.chentronics.com