I have been working with the System where the The temp is in the creep range.

I need to take care of Minimum span requirement for the elevated temp lines.

I have gone some references But all in vain as it is part of higher mathematics

So anybody there who can help me to tackle the situation.

Just need authentic equation to calculate the Minimum span required for elevated temp.

Thanks in advance.

I think you are using the wrong term here (i.e.: "Minimum").
The "Minimum" span can 10mm or 1 meter or something else that is very small or close.

Don't you mean the "Maximum" recommended span for pipes at elevated temperatures?
Then if you want answers you need to give us the pipe sizes, pipe wall schedules and the highest Operating Temperatures.

Yes its "Maximium". And thanks for that.

Pipe Size = 16" Sch60

Operating Temp = 750 Deg C

The maximum allowed span will depend on the lesser result from three calculations .... you need to check out limiting bending stresses and mid-span deflections, both are easy to calculate. Then you need to consider local stress at the support points, which depend on the type of shoe, contact area etc. Equations are in Roark.

Remember to include weight of insulation and cladding, which you have not mentioned.

@MoverZ

Thanks.

Yes. I have calculated as you said. But the question is about Creep Deflection.

As my system is at creep range, it has also been considered for creep deflection which ultimately gives me the Maximum Span limit for elevated temp lines. And there i am finding the difficulty.

Have anyone has solved such type of System?

Or if i could find some reference where i can find it, It will be thankful.
Mahesh67

You will need to limit your span stresses exactly as pressure stresses are limited, to retain creep within predictable limits.

Mahesh67,
Sorry for not commenting sooner. I have been away due to a family emergency.

Now to your original question.
Considering the data you have furnished I have two recommendations:

a). If the line is being run/routed by itself (no other lines involved) - 16" Sch 60 Carbon Steel pipe (at elevated temperature) can span 50 feet with 1" +/- deflection.

b). if the line is being run in a pipe rack with other lines then you need to establish the pipe support spacing (25' to 30') that is most economical for all the lines.

Thanks Jop

Can you elaborate it with any reference that you have. As my line doesn't

satisfy either the condition which you told.

May be some authentic calculations will help me further.




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Mahesh67

What do you mean "As my line doesn't satisfy either the condition which you told."

Are you saying:
(a)that your line is not running by it self?
and
(b)it is not running in a pipe rack with other lines?

So what is the story?

I think a span of 50ft is way too large for the conditions given, unless it's some really special material.

Assuming that the pipe is stainless, the highest allowable at 750 deg C would be around 1.9 ksi against an ambient of 16.7 ksi. In addition the Young's modulus will be 19.2E3 ksi against 30.3 ksi cold.

In addition, there is likely to be some heavy insulation and cladding to carry.

Using the usual formulae from Kellogg, a span of around 17ft would be indicated based on above.