Snuffing Steam for Fired Heater

[sshep]

A new plant being built on this site has a fairly small hot oil system with a fired heater. This is a natural gas fired, forced draft, cylindrical heater- already built but not yet in service. The design did not include fire box snuffing steam, and now the question has come up as to whether this is needed.

My previous experience has been whatever was already existing on the sites where I work- this has been a mix. Sometimes there was a snuffing steam station, sometimes not; sometimes purge steam, sometimes not. The only mention of snuffing steam that I can find in API Std 560 is in section 15 about purge steam, which states that purge steam and snuffing steam may share the same firebox connections (minimum 2ea 3/4" coupling). Our firebox has 2ea 2" purge steam connections as standard, but these are just blanked off. Neither purge steam (restart interlocks) or snuffing steam (typically a manual station) is provided. No other standards (including NFPA 85) address snuffing steam, although I did get some standard layout piping recommendations on an internet site. Purge steam is not an issue because there is a burner management system that addresses restart interlocks. My question is only with respect to snuffing steam- i.e. how one would suppress a firebox fire (or not).

My question is: do any of you know any standard or practice which addresses snuffing steam requirements for a fired heater? I will also take any advice or applicable experience on this issue.

best wishes always,
sshep

 

[0707]

Snuffing steam is a safety concern and is more dependent of good practices HAZOP analysis rather than specific standards

“Snuffing steam connections are supplied by the heater manufacturers, generally in the combustion chamber and header boxes.
The control point or snuffing steam manifold is generally located at least 15 meters away from the heater, is supplied by a live steam header and is ready for instantaneous use. Smothering lines should be free from low pockets and should be so arranged as to have all drains grouped near the manifold.
Collected condensate (apart from freezing and blocking lines) can, when blown into a hot furnace, result in serious damage. (Low points should be drilled 10 mm diameter or provided with spring opening auto-drain valves).”

For more information go to

http://www.red-bag.com/cms/index.php?section=71

luis marques

 

[JLSeagull]

I worked offshore with a fired incinerator to eliminate acid gas and many gas turbines. Four of the gas turbines were GE LM-2500 (27,000 hp) compressors with waste heat recovery units to provide hot-oil for the amine, TEG, water generator, etc. The platform had no steam. Among my concerns was the potential failure of the tubes - thus pouring hot-oil (Dowtherm Q) into the turbine exhaust. I kinda thought that snuffing steam could be a good thing in that event. However, snuffing steam was not in the cards for that offshore application. We had a stack thermocouple instead.

I swim pretty well.

 

[popovic]

As per my experience with fired heaters, snuffing steam should be included in this design; for example, to estinguish firebox fire in case of a hot oil tube rapture,.
Normally, steam impingement on the tubes and fibre blanket or refractory should be avoided.
As you mentioned there is no need for a heater steam purge, since air for forced draft is provided. Air is a better solution particularly in a case of a heater with ceramic fiber blanket.