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Modelling of line which changes from B31.1 to B31.3 in Caesar II

Modelling of line which changes from B31.1 to B31.3 in Caesar II

Hi Everyone,

I have to analyze a steam line which starts inside a power plant and goes to an upgrader. The power plant is designed to B31.1, but the upgrader design code is B31.3 At some point close to border I have to make code change. I'm planning to install 6 DOF anchor point at location and build line from Power Plant to the anchor to comply with B31.1 and after anchor to B31.3. Doing this will simplify and split my line into two and make analysis simple. I would provide anchor restrains to my structural group that they will design it accordingly.

Do you have any advise or any other methods I can look into?

Thanks in advance,

RE: Modelling of line which changes from B31.1 to B31.3 in Caesar II

Why not simply make the split where there is little or no movement predicted for the system and forgo the anchor entirely.

RE: Modelling of line which changes from B31.1 to B31.3 in Caesar II


Yes, it could have been a solution. However, it was made a big mistake in the beginning of process when code of construction has been determined...

Someone (I do not know who) has decided that the power plant outdoor piping shall be designed and build to ASME B31.3 code because this code has impact test provisions for design temperatures below -20F/-29C (All indoor piping is designed to ASME B31.1). This decision has been made even without considering that all outdoor piping is insulated and heat traced, and also considering medium flowing inside pipes (steam, condensate, water, compressed air, Light Oil #2).

I have tried to explain that this is not right approach and all those piping should have been design to B31.1 in it should have been sufficient even for ambient outdoor temperatures of -50F/-46C. I tried many things to explain this:
1. The owner can only set code of construction and fluid service. The owner is a small investment company and person in charge seems have no clue what I was talking about.
2. I tried to explain that design temperature is a mean metal temperature and based on B31.3 it shall be fluid temperature when lines are insulated.
3. I tried to explain that fluid inside pipe will freeze at any temperature below +32F/0C and it won't help even if you make line from impacted tested material and welding procedures. You have to drain lines in case of emergency (lost of power or pump).
4. I tried to explain what is theory behind impact testing, and why we still can use non impact tested materials in our plant using clause which permits reduction of minimum temperature without any success.
I was told that it was made a such decision. Material was already purchased and there is nothing we can do about it.

Here I am designing a line which turns from B31.1 into B31.3 when it crosses a wall...

RE: Modelling of line which changes from B31.1 to B31.3 in Caesar II

What a mess. Check with the local authorities to see if that would be acceptable.

RE: Modelling of line which changes from B31.1 to B31.3 in Caesar II


Our local authorities usually do not step in to point out these inconsistencies leaving it to the owner and EPCM company to sort it out. Of course it would be acceptable if the owner decides and EPCM company accepts (or vise versa).
I was hired to deal with regulatory approvals and confirm design to local regulations and practices. My hands are tied what I can and can't do. I can't go to State Safety Manager and tell him that whoever made this decision is an idiot. People will not understand me.

The main issue is EPCM company is located in a warm place. They do not have lots of experience in projects in cold climates and have misunderstanding of MDMT, impact test requirements and do not understand difference between B31.1 and B31.3 codes.


RE: Modelling of line which changes from B31.1 to B31.3 in Caesar II

Tell them to get their insurance adjuster out there to have a look and see if he will agree to insure the installation as it is. You should not be changing codes for what essentially remains the exact same system.

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