Pipe supports Allowable loads 1

[Johnrem]

Hi every specialist;

Our stress group gave me loads on a support.The support is fixed stool at elbow type. Elevation is 1.2m from BOP (bottom of pipe), pipe stool is 4" SCH 40.
Do someone have any idea how to calculate allowable loads of such kind of supports?

Thanks

 

[JedClampett]

You could go into the AISC Manual for Steel Contruction and get allowable bending moment and axial load for a 4 inch pipe column.
Or you could ask someone in your office who's done this before how they did it.
The second method will give you more confidence in your design.

 

[weab]

I don't understand your question - a sketch would be helpful.

 

[Johnrem]

Many thanks;

I attach this time a drawing showing two cases of using pipe stool support. Case where stool will be welded to steel structure and case where stool needs a fondation.
My question is as follows: What will be the allowable loads (horizontal, vertical and moments if any) that this type of support can sustain in both cases ?
Pipe stool= 4" Sch 40, Elevation H=1.2m

Let us start from case of weleded stool to structure.

 

[Bagman2524]

Just design it as a cantilever and use your basic P/A and Mc/I formulas.

 

[westheimer1234]

Your question seem too basic.
Are you in Piping department or Structural department?
If you are in Piping, give that loads to the structural department for them to design the stanchion, base plate and foundation.
Dont forget the windload of the pipe.

 

[weab]

That's what our office might call a "dummy leg".

I agree with West. With regard to moment, axial, and shear, if you add some of one you can add less of another. If you can't intuitively know that this will work, a structural engineer should look at this, especially with the shape of the weld.

 

[Johnrem]

West;
Can you provide the basic formula?

 

[westheimer1234]

P/A + Mc/I

Ask a favor from Structural Department since they will design the stanchion anyway. It will only take them less than 5 mins to design the "dummmy leg".

Piping Department usually has a standard for pipe supports.

 

[Johnrem]

Do you have any sample of this kind of piping support with its allowable loads calculation sheet?

We dont have structural department, I have to fixe this issue by my self.

 

[westheimer1234]

0.6 Fy > P/A + M/Sx

P= vertical load
A= area of pipe
M = moment equals horizontal load x height of support
Sx = section modulus of pipe
Fy = yield stress of pipe

 

[westheimer1234]

oopps
it should be

fa/Fa + fb/Fb < 1.0

maybe experts can comment if 0.6Fy was conservative
as Fa for your case.

 

[Johnrem]

what are fa, fb, Fa abd Fb in you last explanation?

 

[Ussuri]

Allowable and actual axial and bending stresses

 

[Johnrem]

not clear, can you explain one by one:
fa is......
fb is......
Fa is ......
Fb is .......

thank u

 

[BAretired]

fa is axial stress = P/A
fb is bending stress = M/S
Fa is allowable axial stress (varies according to height)
Fb is allowable bending stress = 0.6 Fy

Pipe produced in accordance with ASTM A53 comes in two grades with a yield strength of 205 MPa (30,000 psi) and 240 MPa (35,000 psi) respectively. Unless you know differently, use the lesser of these values.

Will the supported pipe be in an exterior environment? If so there will be wind loads and temperature effects to consider. The axial capacity of the stanchion varies according to its height.

It is not prudent to rely on an answer from this forum to use on the job. You should obtain the advice of a structural engineer as you do not seem to have even a slight grasp of the factors involved.

BA

 

[par060]

hey you guys are giving away the secret handshake....

 

[paddingtongreen]

Sorry to throw water on this fire, but that elbow is bound to rotate, perhaps about all three axes, the piping does peculiar things when it heats and when it cools, especially when it turns corners. Piping moments could add to the moments due to the orthogonal forces on the support.

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[Ussuri]

Surely the loads the OP was given are as a result of a piping stress analysis? So it is entirely possible that they loads he was presented with are in all 6DOF.

But, if his pipers are anything like our pipers he needs to be careful. Our pipers have a way of coming up with loads that just cant be accomodated reasonably. We moan, they move the supports/change the conditions and everyone is happy.

 

[paddingtongreen]

6DOF was my thinking too. Given that the OP had to ask the question, that would make the advice given, dangerous.
"A little knowledge can be a dangerous thing"

Michael.
Timing has a lot to do with the outcome of a rain dance.