4 replies to this topic

[Ghasem.Bashiri]

Dear Process Experts
Due to Site temperature and Process requirements I need to use a heating media for a sump (Liquid Caustic) and a Caustic Storage.
Technically I have two solution: Electrical Heater and Steam Coil.
During our HAZOP meeting someone proposed steam coil and better solution without any evidence.
Is there any written code or practice for such selection?
Also I need to know with using steam coil for sump drum which is underground, is there any problem with stream trap in steam (Condensate) return line.
Becasue steam trap can be located in sump with condensate line go up from sump to piperack and condensate collection or steam trap can be installed in ground level and condensate can pushed by steam from sump to steam trap in ground level near sump. Please help me with some pain and gain or strighforward guide.
GB

[Art Montemayor]

Ghasem:

In my opinion, a below-grade sump is a very bad decision for a caustic sump. It is a deadly hazard and a maintenance nightmare. As you have noted, you have a steam trap problem because you have to locate the trap below grade as well.

Your problems are a result of having the stored caustic solution located below grade.

An electric heater is normally not selected for causic heating because of the corrosivity of the fluid and the hazards with its leaks. Caustic solution is a constant containment problem. I have yet to see a caustic solution system that didn’t have leaks – especially around threaded connections. And even flanged and gasketed joints have a tendency to seep out the very dangerous fluid that attacks human tissue without mercy. I would rather employ a steam coil – but in an elevated, secondary contained caustic solution tank.

You may not be allowed to do what I recommend, and that is a major setback, in my opinion, for a safety environment. I simply will not tolerate chemical storage below grade – whether in a drum tank or in a filled sump. Either method is a safety hazard and requires confined space entry for maintenance and that is something that I will fight like a bulldog to avoid in any plant that I work in.

I hope my experience is of some help.

[Gualtiero]

hi GB,
there are regular stops, such as on weekends?
If the site is too low, like some russian site where enviromental temperature is below the 0°C then, some problems arise. If the plan stopped in the weekend, on Monday morning you will probably find the steam trap frozen.
Hot water tracing may be a better solution, if hot water during the weekend is moving at a reasonable temperature.

[vishtech03]

Steam coil with Low pressure steam is the preferred option.The Condensate from Steam trap outlet need not be connected to a Condensate header for recovery.This has to has to be drained due to negative elevation.

[breizh]

Hi ,

You may consider these guidelines from Dow Chemicals:

http://www.dow.com/c...ety/general.htm

http://www.dow.com/c...fety/design.htm

As previously stated Caustic soda is very harmful and special care should be taken !

Hope this helps

Breizh