7 replies to this topic

[jprocess]

Dear All:
Please find attached a PFD of a condensate stabilisation unit.
As can be seen the separator with tag: 20-V-103 (off-gas compressor suction drum) is a special kind of separator with top flanged head type.
I do not know why basic engineer has been considered this kind of separator?
In general what can be the application of flanged head separators?
Thanks in advance.

Attached Files

•  SpecialSeparator.pdf   87.61KB   90 downloads

[Art Montemayor]

The only reason(s) for using a vessel body flange (or other access opening) on a process vessel - especially a vapor-liquid separator - is due to the need to gain access to the internals of the vessel.

In almost every case, the reason is that someone (the client, the design engineer, the project engineer, the project manager, etc.) deemed it necessary because the separator has internals that need inspection and, sometimes, replacement. This is particularly true if a mesh pad is used inside the separator.

A body flange can be a pain in the backside for operating personnel - mostly due to constant leaks. That's why it is so important to make smart and strategic decisions early at the process design stage as to whether the trade-offs are worth the bother of specifying vanes or mesh pads in process vessels - especially large vessels that require human access in confined spaces.

I refuse to install internals that require inspection and maintenance in process vessels unless I definitely require them or have to have them due to a mandate or process requirement. I simply do not like the idea of having to pass on an order to another human being to enter a confined process space. It's always a calculated risk, in my opinion.

[jprocess]

Dear Art:
We have lots of 2 and 3 phase separators in our NGL plant and except a few of them, the others have demister but only the previousely mentioned separator is flanged type.So I doubt that easy access for maintanance be the reason!

[Art Montemayor]

Jprocess:

You asked: "In general what can be the application of flanged head separators?"

You also failed to tell us the fluid(s) involved, the capacity, the materials of construction, the temperature & pressure, and the manufacturer.

I responded with my opinion, based on my experience in designing, building, specifying, installing, operating, and purchasing 2-phase separators - many of them specifically for applications as compressor suction separators. I know from personal experience with such separators as Peerless, Wright-Austin, Armstrong, etc. that body flange construction is more expensive than none. The reason manufacturers have told me in the past is to achieve internal access.

Now, you respond with: "I doubt that easy access for maintanance be the reason!" -- OK. I give up. What is your answer to your question? Perhaps you know the answer. Was this a "test" question that I flunked? I was unaware that we could only contribute answers or opinions that you are in agreement with.

[jprocess]

Dear Art:
If I know the answer or have an idea I will say in my post that let us share our ideas similar to my plot plan topic.
But for this topic I do not know about the concept behind of mentioned configuration.
About your statement:
"The reason manufacturers have told me in the past is to achieve internal access."
I did not mean that I refuse this idea,but as I said in my earlier post I doubt that this idea be the reason becasuse we have lots of other separators with demister but none of them is flanged type!
Here are some additional data:
Operating Pressure: 7.5 barg
Operating Temperature: 52 °C
Outlet vapor stream:
Flow> 426 kg/hr
Mainly composed of c1,c2.c3 and h2s
Density: 14.51 kg/m3
The project in its engineering stage so there is no vendor data yet.

[pleckner]

@JP:

You're getting into a bad habbit of asking the Forum questions that should be answered by the engineer doing the design. We are not in the mind of the design engineer nor are we able to ask him/her the reasons why he/she does the things he/she does.

Art is correct in that the reason for the top of a vessel to be flanged is for easy access, which is misleading because having to dismantle a lot of pipe to pull the flange is not easy. And these type of vessels are usually pretty small so that there may not be enough room on the top head to put a proper manway.

[jprocess]

Dear Phil:
Thanks a lot for your reply.
Let me clarify about your statement more:

@JP:

You're getting into a bad habbit of asking the Forum questions that should be answered by the engineer doing the design. We are not in the mind of the design engineer nor are we able to ask him/her the reasons why he/she does the things he/she does.

We have not access to basic engineer company because that company do not exist in real world now.The documents are related to 5 years ago.But my goal is not to ask these questions from the members instead of basic engineer.I make these topics including the related docs because I think that these cases are interesting and special and have the potential of discussion and useful points.This is the human nature that special and new subjects attract him.

Art is correct in that the reason for the top of a vessel to be flanged is for easy access, which is misleading because having to dismantle a lot of pipe to pull the flange is not easy. And these type of vessels are usually pretty small so that there may not be enough room on the top head to put a proper manway.

I again repeat that I respect Mr.Monemayor's idea.
The idea of manway can be logical Thank you!

[pleckner]

A good response.

Then you must put into your post that you ran across an issue from documents x years ago and would like some opinions because there is no "original" designer to consult with. If you do this, then we can approach your issues differently and not have to make assumptions about why you are asking certain questions. As Art keeps telling everyone, it all about communications and giving us details and back ground information.