ASME B31.4 Wind Load 2

[marchieV]

I just want to know the criteria for wind load for pipeline under ASME B31.4...

Beacause it is indicated in the ASME B31.4 : "401.2.3.2 Wind Loads. Wind loads shall be considered in the design of above grade pipelines. Refer to ASCE 7 for the application of wind loads."

Does it mean all pipe size be subjected for wind load?
What criteria should I consider as per pipe size? Thank you in advance for the reply.

Sincerely,
marchie

 

[LittleInch]

Yes all pipe sizes.

You're looking at horizontal forces from wind load and possibly vortex induced vibration from long spans.

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[marchieV]

LittleInch,

Thank you for your reply.

Also, I want to ask regarding expansion loop... When the thermal displacement of the inside bends exceeded the allowable displacement (based on Pipe PRO software), does it mean the pipeline needs additional loop?
I am doing stress analysis for revamp/replacement of pipeline for different material (from CS to be replaced by SS) and different Design Temp. (from 65degC it will become 90degC now)?
I came up with a conclusion of adding expansion loop since the displacement and design temperature of the new line is higher than the old line.
Please give some advice regarding this matter. Thank you in advance.

Sincerely,
marchie

 

[LittleInch]

It's pretty rare for a pipeline to B 31.4 to be laid on sleepers above ground. Not unheard of but rare. If it's above ground why not use B 31.3 design - much more applicable to this type of thing. Why is it not buried? Pretty difficult to pig an AG line with expansion loops and if you can't pig it it's not a pipeline in my view - just a long bit of piping....

In general yes, if the design temp is higher, then it will expand more and hence probably need more expansion loops.

Having said that, at 90C you'll find equal difficulties burying this. Is it insulated as well?

Beware of SMYS de-rating of stainless at those sort of temperatures. The software might not recognize it unless you tell it.

How long, what size, what pressure?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[marchieV]

LittleInch,

The propose code was ASME B31.4 and that was already as per client specification.

The whole system is about approximately 21km.If you mean is anchor to anchor it is about 200meters while the loop was designed every 100meters. But the problem is the temperature was changed from 65deg C to 90deg C
that is why I am having trouble in the design of the loop due to lack of space with existing pipeline.

Sy is automaticaly generated by Caesar II.
8" NPS, 3.96MPA, 90deg C.

Sincerely,
marchie

 

[LittleInch]

Wow, that's some length of a/g pipework. Where is this thing?

Well I'm not surprised you're having trouble - change a key parameter like temperature that much and you won't be able to make it fit into an existing system designed for a much lower temperature.

Was the client expecting miracles?

How much is it predicted to move compared to maximum amount? Is it just movement that is large or are stresses also too high?

IF just movement it may just need some extra long shoes....


Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[marchieV]

The clients are expecting the same result but I already explain to them the impact of increasing the temperature. Also the temperature was set by the Process group that is why I don't have any justification to say so.

Based on my research 110mm is the maximum for such temperature and size but my pipeline moves upto 133mm.
That is why the system is also stress-over in all bends.

Additionaly, I have a hard time to solve the non-converging issue in the Caesar II program.

Sincerely,
marchie

 

[pennpiper]

marchieV,
You wrote:"I am doing stress analysis for revamp/replacement of pipeline for different material (from CS to be replaced by SS) and different Design Temp. (from 65degC it will become 90degC now)?"

Why are you using the Design Temperature for the Stress calculations for expansions and Loop sizing?

The Design Temperature is a theoretical temperature which the line will never see. I suggest you consider using the Maximum Operating Temperature. I think you might get better results.

Sometimes its possible to do all the right things and still get bad results

 

[LittleInch]

Ok, Client expecting miracles.

All you can do is write a report saying that the bends are all overstressed and movement is unacceptable and send it in with a recommendation for what needs to be done.

If they want to ignore physics that's their problem, not yours. Just analyse it.

At 8" and 21km long, what's the temperature drop or is it trace heated?

The only other option is to do a pre-heat of the pipe sections and then clamp them in place in their extended state but allow the expansion to occur at a free end before welding the next section which has also been pre-stressed. This is what they do with some of the hot bitumen lines in Canada, but isn't easy as you need to flow hot water through the lines or somehow heat it up and then rapidly clamp it before welding it to the next bit without letting the tension go....

Doing that for 21 km will be a right pain, but might get you your get out of jail free card....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[racookpe1978]

How high above ground is the pipe intended to be? After all, if the loops are horizontal (not vertical) then there could be justification for a near-zero wind load - but snow and ice increase!

Look, if he is changing metal, you have to "rebuild" the pipeline - so it doesn't exist as-is right now, so you just need to specify every loop is twice the offset length they currently have drawn.

 

[KevinNZ]

LittleInch

Cold/hot pull does not change the thermal stress range, so in B31.1 and B31.3 there no credit for this. Is B31.4 different?

 

[LittleInch]

Don't know to be honest, but I gather the issue is overstress at the bends and maximum displacement not stress range. Stress range is normally more to do with fatigue and weld issues no?

Anyway, it's just an idea for the OP to try and see what happens.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.