Heaters on KO drum 1

[Teresek]

The heaters in the boot of the flare KO drum on "my" platform are currently out of operation.

I have tried to find out if the heaters are defined as a part of the security system (we are discussing weather they can be removed permanently or not). In the Engineering Manual the purpose of the heaters is described as follows: "Electric heaters are located in the boot of the drum to heat cold liquid prior to pumping (maintain minimum temp of 5 deg Celcius). " From this, it seems like the heaters are a pump protection (to protect the drains pump on the KO drum liquid outlet).

On the other hand, what if wax, ice, etc blocks the outlet to the level instrumentation. If this happens, the level will "freeze" and we will no longer be able to detect HH liquid level. This will be a very critical situation.

In my seek for answers I have looked to several other platforms. The size of the heaters vary a lot, from a few kW to 3x50kW on "my" platform.

To summarize:
Does anyone know if the KO drum heaters are defined as a part of the security system?
Does anyone know any sizing rules for KO drum heaters?

 

[monaco8774]

KO drum heaters are generally there to stop either waxing problems or to keep viscosity low enough to satisfy your KO drum pumps. If you have a sump the normal level bridles can get plugged by wax but in 15 year of operations support on 25 different rigs, I have never seen it, Ususally the majority of what is in the flare drum is water unless you have either a big carry over or foaming problem or you have a continuous dump from drains or other sources of crude oil. Much more common is sand plugging teh bridles for which you should have routines for checking bridles.

The sizing basis is to maintain a temperature above the cloud point of your crude (you should have this from crude assays). Since the crude if it enters should already be above the cloud point (or else you wouldnt be processing it properly) you need to know what the ambient worst case temperature is and then just supply sufficient to compensate for heat losses to ambient from say 5C above cloud point. In other words Q=hADT, h is your heat loss coefficient, A the surface area of wetted vessel, DT =(T cloud+5- T ambient)

Note some people use the pour point instead of the wax apearance temperature this is usually much lower and is when the crude basically doesnt flow.

Note if your cloud point or wax apearance temperature is below ambient you dont need any heating

 

[MortenA]

You cross posted this in "chemical engineering other topics" i think it was. With regards to the safety issue/reference to standards you could also see my reply here.

Best regards

Morten

 

[JJPellin]

This is an interesting question. Unfortunately, I am not going to be helpful in answering the question. I am a rotating machinery engineer and so my interest tends to focus on the pump. However, long ago, I was a project engineer. One of the projects I had was the installation of a heater in a flare KO drum. This particular drum actually had two sources of heat. There was a steam coil coming in from the end, supported in a track several inches off the bottom. And the bottom 1/3 or so of the drum was steam traced and insulated on the outside. I assumed that the steam tracing was there to keep the contents from freezing (or setting up) so they could be pumped out. But I assumed that the bayonet heater from the end was there to vaporize light hydrocarbon so that it would pass down the flare to the recovery compressors. There would be more value in recovery of the light hydrocarbon in the compressors rather than pumping it to slop with the liquid (which is usually mostly water). I don't recall if the steam coil heater was normally in service or if they only turned it on if they had an event that would dump light hydrocarbon into the flare. It looks as if my assumptions may have been false.