I am currently working on a cryogenic system with the design temperature of -105 Deg. C.
I have been asked to take care of the Thermal Bowing phenomenon while analysing this.

Can anyone throw some light on this especially the details of inputs in C-II?

You only have to give the thermal bowing delta temperature in the KAUX menu. You should get this temp. from Process department.

Regarding the physics of the thermal bowing problem, you can check one of my responses in the Pressuve Vessel forum.

Regards

You have find some interesting explanations in this direction:
http://www.pipestress.com/papers/Therm-Insul.pdf
Regards,

Dear Anindya

I had done analysis for cryogenic system with the design temperature of -196 Deg.C in my previous project. I had not fill thermal bowing delta temperature in the KAUX menu as recommended by you. Our lines were properly insulated. I had no available process data on that regards.
Can you please elaborate what could be possible bowing delta temperature for operating temp -196 deg C. & while analyzing the system what kind of typical supporting arrangement to be provided for the system.

Regards

Habib

Thermal Bowing temperature defined in Caesar is analysed by CII as differential temperature euqal to temp defind in Kaux. Top and Bottom surface of pipe will have differential temp (Vertical pipe donot have thermal bowing)

One more thing need to be takne care while doing therma bowing is this activity takes place when system donot operate at its normal temp (Otherwise Thermal bowing would havenot taken place)hence for stress analysis purpose you need to have in my openion middle temp of Normal operating and Ambient.

Naveen

Habib:

Possibility of thermal bowing has to be informed by process department along with the temperature differential to be considered.I agree with you that most of the time this information is not available( the temperature part ).

We cannot and should not do any analysis without process input.So write to them. Do not guess anything.

Hold down support is generally recommended.

Regards

Anindya

Once again I am working with cryogenic System. Temperature range is upto-170 deg C & some process lines & cold flare lines are falling on that range. Project is in initial stage. I asked process people about thermal bowing temperature. They said that Process do not provide that temperature.

1) If I not at all consider thermal bowing temperature how much it is going to effect piping system?

2) You mention "Possibility of thermal bowing has to be informed by process department "

Which process line & what temperature range generally fall on that category ?

3)"Hold down support is generally recommended"

If I do not get thermal bowing temperature
Should I put all hold down support or alternate hold down support.

If I get bowing temperature can I put hold down support only where upward movement is there
or in general it is to be provided for safe side.

Thanks & regards

Habib

My responses:

1) Cannot be quantified.

2)Process department has to mention this as a note in the Line Designation table( LDT) for the specific lines.It is "their job".As a thumbrule lines with slope and other partially filed lines,large diameter lines, blowdown lines are potential cases. Again, it is upto the process department .Also kindly ask the people who have told you that "process department does not provide the information" a question "which department does ?". I presume their reply may be "pipe stress".

3)If you don't get the data , assume some value. Mark an e-mail or an inter-department memorandum as to what you have considered and let others ( process/projects )agree /disgaree to that.I would recommend using "guide with hold downs" instead of conventional guides at the guide locations.Involve your bosses in getting the data.Your lone effort may not be enough.

Regards

I have a small doubt in this.
In case of lines fully filled, the thermal bowing case will be an occasional one. Then in such a situation dont you think that providing hold downs is something not advisable.
I hope you people got the doubt!!!!!!!

For lines prone to Thermal bowing, to the extent I know , it is not an occasional event.

Regards

Dear Sir,
Thanks for the reply.
But my doubt was, if we have a system where it is not partially filled, ok. In case of fully filled lines, during start up the pipe will be gradually filled to 100%. During this period the lower portion of the pipe will be at lower temp than the upper half and once it is full the temp will nearly be same.
Thats why i was of the opinion that it is an occasional case.
Sir please correct me if I am wrong.

You are right.One example is the Vacuum Transfer lines in Crude Distillation units.There it indeed is an occasional case.

But for this specific system, certain other considerations like two phase flow has to be considered which may require use of sway braces.

Regards