Pipe loads vs Diameter change

[sprintcar]

Ever have someone get you so confused that you doubt the equations?? I'll post this in both Pump and Piping forums.

Situation ~ Horizontal discharge pump, 135psi (shut head) with 18" dia discharge connected to a 36" long transition spool piece that goes up to 24" diameter system. Static piping flange loads are all under manufacturers allowable limits.

Question ~ To determine the hydraulic loads applied to the flange, I took 135psi and the 18" diameter (assuming a shut head condition)which would apply 34353lbf reacting to 'pull' the pipe off the pump, resisted by the flange bolts.

The confusion lies in the effect of the 24" diameter. My comment(simply stated)was that the spool piece sides resisted forces other than the 18" diameter, but I was told the actual force would be 61000lbf from the 24" diameter pipe. A marker board full of sketches and equations (in metric)and a language barrier prompted me to write you guys for help.

Can anyone provide a brief, clear explanation on this?? Thanks! Keep the wheels on the ground
Bob
showshine@aol.com

 

[johnp]

I agree with you. The pump sees the 18" dia pressure at the pump flange.

At the 24" pipe the full force is exerted, but the reducing sides of the transition spool exert an equal and opposite component of axial force, so the flange only sees the effect of the 18" pipe.

If you had an expansion joint in either the 18" section, or the 24" section then you would have to allow for the added size of the bellows section.

 

[sprintcar]

If we add an expansion joint (sliding type on either side of the diameter transition) that would decouple the rigid piping, what effect would you see regarding the flange load? Keep the wheels on the ground
Bob
showshine@aol.com

 

i want to find and calculation of the presure deop in the pipe which is used in the gas and oil burner.

 

[johnp]

muklo2010 (Visitor) - you need to "start a New Thread" forum378. Otherwise your question will only be seen by a few people.

 

[johnp]

A sliding coupling releases axial and torsional forces. Now the flanges connecting to the sliding joint will see only the frictional component from the joint packings.

The 18" horizontal pump discharge will see the pressure thrust. The pump would be designed to take that thrust.

At the other end you now have 24" of pressure thrust which needs to be anchored somewhere. That means very close to the slip joint you now need a pipe anchor.

The slip joint is not designed to take any bending loads, so the pipe anchor must cater for that. The slip joint also will not take care of any misalignment of pipe and pump.

There doesn't seem to be much sense in providing 2 slip joints. One should be adequate.

 

[sprintcar]

Johnp - THANKS!
This is what I was trying to explain. Basically the piping should be anchored in a manner to remove ALL mechanical forces from the pump, but in reality that rarely happens.
There would only be one slip joint - I meant 'either' side of the coupling.
Do you know any vendors that make large (over 24&quot slip joints with 3 or 4" of axial capability?
You can email direct if you'd like
Thanks again for the clarity check! Keep the wheels on the ground
Bob
showshine@aol.com

 

[johnp]

1 - Try

http://www.pipingtech.com

2 - 3" to 4" axial is a lot of movement. Do you really need that much? It seems a lot more than temperature movement taking place.
2 - An 18" pump is quite big - bigger than anything you would find in an average refinery or processing plant. It would be prudent to get a pump engineer to have a look at your proposed design installation.

 

[sprintcar]

actually - the 4" of axial is for a different design where the flange needs to be moved back instead of using the normal spool piece

Keep the wheels on the ground
Bob
showshine@aol.com

 

[Franko]

See

http://www.cpacl.com/products/slip.htm

Have you found any other manufacturers of slip-joints?