Insulation of flare headers in crude oil production plant

[hmoto]

Hi
I work in a crude production plant and I was asked the other day about "reInsulating the flare headers after their regular maintence was over". I have about 2yrs exp in this field & i am running around in circles trying to figure this one out.
No one quite remembers why we need to insulate the headers, it seems insulation is a solution to a problem no one remembers.

the location I work in is a desert & hot and dry, so i don't quite get why we need insulation
I appreaicate any input on this
thanks

 

[22082002]

Generally flare header is designed for a case, say 50-70% release of all PSV's in the unit. There can be a case, where plant is under fire(It's actaully section under fire, if you need to go in further details, it involves fire circle and hydrocarbon release analysis) or loss of power/cooling water, where in the hot material is released into flare.
The resulting mixture is usually at high temperature, and we need to have personal protection for that condition, so that, even if sombody touches it, he can feel max temp of 60°C.


In refineries, if suddenly material is relaesed,(in nights/winter) the temperature can be low enough to lead to cocondensation of hydrocarbon liquid, so the line will be sloped to drain the condensing liquid towards the surge drums.

 

[rbcoulter]

There are other reasons why insulation is done besides freeze protection:

1. Protect equipment from structure failure in the event of a fire.

2. Protect employees from burns.

3. Minimize condensation in the lines (Doesn't it get cold at night in the desert?)

4. Help maintain process temperature constant for performance reasons,

etc.

 

[tad123]

Acoustic insulation is another possibility if you have a change of blowing down through this flare header. Especially, if you have a sonic flare it will create a lot of noise.
TAD123

 

[leofig62]

Another possibility is JT (Joules-Thompson) effect due to high and sudden change in relief pressure (dowstream the PSV). he header can get extremelly cold.

Is there a scrubber or knock-out drum in the header. If so, insulation might be required upstream of it.

Good luck,

Leo.

 

[Flareman]

In addition to the good response above, if you check the design conditions for the flare, you may get a guide. It's quite likely that one of the major relief cases is a hot flow of a narrow composition which has the possibility of condensation at normal conditions. If you have a header full of hot vapor which can go to [almost] a single dew point, it doesn't self regulate against vapor presure in a flare header as it would in a closed vesel and you can suddenly have a header of vapor becoming a teaspoon of liquid. That pulls an enormous potential vaccuum which can suck in air at the flare tip end (whoops big bang potential!!). Insulation helps to slow down the cooling and give the process the opportunity to equalise by having the hot vapor displaced by other incoming vapors which will remain as vapor. Of course, insulation alone doesn't guard against the problem, which needs some other monitoring and purge control to pick up the duty but it could be one of the features of the design to avoid this problem.

David

 

[hmoto]

Thanks for all the respones, I will be calling a brainstroming session this week with some of the process engrs. I will keep u all updated on what we narrowed it down to.

thanks again for all ur input