feed water heaters skirt

[mech212]

When our supplier provides the drawing of high pressure and low pressure feedwater heaters , there is a part of shell called skirt , its position is after tubesheet in LP heater and its position is at steam inlet in HP heater , so what is the skirt ? IS it a part of shell ? what is its function and why its position differes from LP and HP heaters ? ( I didn't find such information in books or on the internet )

 

[MFJewell]

If I remember right, it is usually a different material than the shell and is to take up thermal expansion. Can you post the drawings?

 

[MJCronin]

1) "there is a part of shell called skirt " ... Yep,we know ... pressure vessels and HXs have been built with skirts for the past 80 - 100 years. Is this your first project dealing with heat exchangers or pressure vessels ?

2) The function of the skirt on a vertical axis HX is to support the component. Customarily, it is NOT part of the pressure retaining boundary and therefor NOT part of the shell.

3) Are these all vertical axis feedwater heaters ? That is a bit unusual for modern power plants, most typically they are horizontal axis. Why wont you share the drawings with us, so that this discussion can have some meaning ?

4) For various thermal design reasons, it is not unusual to have different supporting schemes for HP and LP feedwater heaters. We will never know unless you make the drawings available to others ....

4) Where is this plant located and what are the governing codes and standards ?

MJCronin
Sr. Process Engineer

 

[MJCronin]

http://cr4.globalspec.com/thread/35841/Designing-Supports-for-Pressure-Vessels

Many threads on eng-tips regarding PV skirts and skirt designs .....

http://www.eng-tips.com/viewthread.cfm?qid=174230

If there are skirt openings for process piping connections, there must be a careful evaluation for strength ...

MJCronin
Sr. Process Engineer

 

[mech212]

I can't put drawings as it is confidential to my company if they discover there are penalties ,, the skirt is not the part that support the pressure vessels as saddles but it is a shell , which mean the drawing is divided shell part 1 welded to shell part 2 welded to skirt and then welded to shell part 3 and son on , so actually it is a shell but I don't know why it is not called a shell but called skirt ?

 

[JStephen]

Some terms just don't have real exact definitions. I find myself using lug, clip, gusset, and similar terms in a variety of different applications, and "skirt" is potentially vague as well. It could imply a cone shape, a covering, etc. It's possible that other manufacturers of similar items use a different term for it.

"some part resembling or suggesting the skirt of a garment, as the flared lip of a bell or a protective and ornamental cloth strip covering the legs of furniture, baseboard (def 1), apron (def 13), a flat horizontal brace set immediately beneath the seat of a chair, chest of drawers, or the like, to strengthen the legs, a flat brace or support immediately beneath a tabletop."

 

[SnTMan]

mech212, I don't know much of anything about feedwater heaters, but I'd suggest you look at the metallurgy. It is possible the skirt is intended to field weld into a condenser without needing PWHT.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[MJCronin]

mech 212....

Well, I for one am still confused about what you are talking about .... Does everyone else understand ?

Confidential, confidential .... oh yes, yes yes ...

However, I guess that it would be impossible for you to take up a bit of paper and sketch exactly what it is that you are trying to describe. Sometimes this is the only way for others to understand the issue ....

You don't have to reveal the client's name on the sketch ....

MJCronin
Sr. Process Engineer

 

[TGS4]

I'm with MJCronin on this. You've asked for help, using non-standard terminology, and yet you can't help yourself in the slightest by providing a sketch? If it's that confidential, then you shouldn't have asked it here, at all. You should have asked internal to your organization from folks that are within your confidentiality realm.

 

[MFJewell]

Shell and skirt are standard terminology for horizontal feedwater heaters used in fossil and nuclear plants. I have seen it used many times from different manufacturers on their specifications, drawings, and datasheets. I just don't recall what the skirt actually does and since I no longer work at the utilities I used to work at, I can't access those drawings or specs to make an educated guess (though I did take a stab at it above).

 

[MJCronin]

https://play.google.com/store/books...gclsrc=aw.ds&dclid=CJCrqoXBstcCFY3HwAodcocJ9Q

MJCronin
Sr. Process Engineer