if anyone has time to read and look at my question and give me advice it will be great:)))

According to specification for stress analysis under Temperature definitions is like this:

P1=55 bar
Tope=55°c
Tdesign max=95 °c
Tdesign min=-46 °c (during edepressurization)

Tinstalation=5°C for hot lines and 85°C for cold lines.

In Caesar temperature input I fill 3 temmperature:
T1=Tope
T2=Tdesign max
T3=Tdesign min

I have doubt what to put for ambient temperature for caesar. Default temp is 21°c.

You need to find the ambient tempertaure during installation. I think the 5 degree C can be your ambient temp. Put this number on the Special Execution Parameters under Environment.

Regards

This is text from specification.

Tope=55
Tope.max - not applicable
Tdes.max =95
Tdes.min =-46
Tupset -not applicable
Tinst - plant installation temperature defined in basis of design doc.

than in specification is

Tins(installation or base temp) shall be assumed to be 5°C for hot and 85°for cold lines.

It is not clear to me plant installation temp defined in basis of design doc and Tins=5 and 85. Is it the same items. Generally does ambient temp is Tinstalation temp.

Em I right if I perform two separate calculation for Tdesign max with Tinst=5 and calculation with Tdesign min with Tinst.=85


In that case I can not check stress from Tdesignmin to Tdesignmax.

Set up your temp like below for two cases and compare which one is the worst;

T1=55 (normal operating)
T2=95 (design maximum)
T3=-46 (minimum design)
Ambient =5

T1=55 (normal operating)
T2=95 (design maximum)
T3=-46 (minimum design)
Ambient =85

I would expect first case gives the worst result. your expansion stress range for exetrem case would be L2-l3.

Regards

Two cases,two separate calculation files.

Thanks

To me, you must be having a broad classification as Hot lines and Cold lines in your stress critical line list.
Your installation temperature is more or less your ambient temperature. I appreciate the wise decision of selecting extreme temperature for both hot and cold lines.( Low ambient for hot lines, High ambient for cryo Lines)

Prepare 2 seperate CFG files, One for hot lines system (Ambient 5 degree) and another for cold lines system (Ambient 85 degree).Use them wisely with the type of lines in that perticular system.

As it is evident that we calculate the Expansion Stress range for any system and not the stress at a perticular temperature. So a system with ambient +85 and operating temp just +10 (Absolute Range = 75 degree)is far more critical than a system with ambient +8 and operating temp +55(Absolute Range = 47 degree).

And you dont need to run your system any time with both the ambient temperature(5/85) to check severity of stresses. Just calcualte the absolute difference in design/Operating temp with ambient (5 / 85) and select the case with higher temperature differential for your analysis.Say for instance the case with Absolute range 75 degree shown in above paragraph is severe case.

hope my point is clear. Comments are welcome

KemalK,

I'm somewhat agree with STC but u no need to preapare so many load cases for this calc, basis of design most of times they are in genral it applicable according to process and operating conditions,
as you are checking for worst case in min design condition (i.e. T3= -46deg C) that is suffiecent to check the stresses in stress range condition; as per my knowledege your load cases should be

T1 =55, (OPE)
T2 =95, (MAX)
T3 =-46, (MIN)

I found the ambient temp is quite a sensitive to nozzle load calculation where pipe connects into vessel or pump. Otherwise, no need to look at two ambient cases, as the expasion stress will cover the whole range.

Case 1 Tinst = 85 and DT= -46-(+85)=131

Case 2 Tinst = 5 and DT= 95-(+5)=85

For my calculation i will setup like this

Special Execution Parameters under Environment---i will put 85

T1 =55, (OPE)
T2 =95, (MAX)
T3 =-46, (MIN)

Em I right.

For me it is strange to install pipe on 85°C.

Yes I agree with you. 85 degree C is stange figure for the ambient temp, but it gives worse result than 5 degree C for the support load or any nozzle load check.

For the strss check, your extreme case comes from L2-L3 [(w+p1+t2)-(w+p1+t3)=141 degree C], so the change of ambient temp (85 or 5) will not affect your stress.

So final conclusion is i a will not make mistake if i put ambient temp 85 T1, T2 and T3 as we already discussed in the posts above.

You know client has the last decision. Bigger loads on vessels nozzles means more money for vessel production...maybe usage of hangers etc etc.

I just explore line list and also critical line list. There is no classification hot and cold lines. Actually system is always hot lies. Fluid inside pipe is some kind of gas under high pressure. During accident situation vessels will be depressurized. Only in that situation temperature will be -46 for short period of time.

Hi Kemal

I would suggest to take T1=55deg; T2=100deg; T3=-45deg and ambient=5deg. why?
in design basis if you carefully see, it should be mentioned that installation temperature 5deg for hot lines and 80deg for cold lines (cryogenic or lines operating below ambient temperature). for me, the best practical option is consider 5deg if you analyse non cryogenic line. for your gas line, obviously its non cryogenic. you may not have hot or cold insulation also if i am right.
moreover imagine/foresee the practical situation. your line may get fabricated or installed in a summer day at say 21deg to 40 deg ambient condition or winter at 5deg. thats why they give 5deg as ambient for hotlines (worst/min possible ambient since the line will be hot in operation). after installation they charge the line and it gradually experience temperature to 55 to 100 at worst case. after charging and stabilization of line depressurization may occure at pressure control station in case of accident or any abnormal operation. ie, line may go to -45deg. now see, the possible maximum DT is 5deg to either 55deg (ope) or at worst case 5deg to 100deg. it may never be installation temperature to -45deg. with the above said temperature settings and load cases accordingly you address all the temperature changes in the lifetime of your line.
you may consider 85deg as installation if your line will directly depressurize to -45 deg immediately after installation (ie, even before charging the line with gas or any startup after a long shutdown of line for maintenance or repair). your process guy can bet his salary that its practically impossible.
sorry for the long write-up...!!!! i just thought of giving a picture of practical situation. hope it clarifies your query.
i welcome any experienced guy's view on this. i might have missed some points or my understanding may lack some more informations. our forum has many experienced guys who have helped me before.

Thanks a lot shan. your post is very hopeful for me. you right i do not have cryogenic operating lines. so for my analysis i have to use the highest differential temperature for hot lines (acc.to specification for stress analysis) and that is 95-5. Ambient temp has to be 5°c.