Piping - Effective Force (Pressure and Temperature)

[JT100]

The majority of my experience is related to subsea pipelines so excuse me if this question is obvious. Now for a pipeline if I want to consider the effective force I generally have two options, the fully restrained force (made up of end cap, thermal and poisson effect forces) or if I am looking at the unrestrained section then the maximum force possible is the weight of the pipeline x effective axial friction coefficient. I am currently looking at a topsides piping unit and need the force/moments at several points in the pipework, obviously I can do a sense check on my model for the forces at anchors/supports and can check displacement plots to see if its behaving as expected but how can I check that the effective force away from supports is realistic? Apologies if missing something obvious here.

 

[BigInch]

If these are forces imparted to the supports and the supports are vertical, the maximum horizontal force is weight x friction. That is the force on the support, which is equal and opposite as the axial load in the pipe as well. If movement is not enough to slip on the support, the horizontal the force at the support will be the force required to displace the support by the amount of thermal growth of the pipe at that point of support; ie on a vertical column support with no bracing it would be = 3 EI delta/height^3. Delta being the calculated thermal growth.

I had a hard time interpreting your question, hope that was the answer.

We are more connected to everyone in the world than we've ever been before, except to the person sitting next to us. Lisa Gansky

 

[BigInch]

I answered considering thermal growth only, not including pressure contraction. If there is internal pressure, subtract the pressure contraction in the axial direction from the thermal growth and repeat the above method.

We are more connected to everyone in the world than we've ever been before, except to the person sitting next to us. Lisa Gansky

 

[JT100]

Thanks Big Inch, I was looking for a way to calculate the forces away from supports. Say I have piping routed between two supports, anchored at one and guided at the other. How can I calculate the effective force due to pressure and temperature mid way along the piping (between the supports)?

 

[ione]

You have to consider that forces act just on the anchors.

Consider

1. the force due to pressure Fp = P*A (where P is the internal pressure and A is the pipe cross sectional area)
2. the force due to friction Ff = M*f (where M is the weight of the pipe and f the friction coefficient)
3. force related to change of direction Fcd = 2*A*rho*v^2*sin(alpha/2)/g (where rho is the fluid density, v is the fluid velocity, alpha is the turning angle of the pipe, g is the acceleration f gravity)


Take a glance to the link below too

http://www.engineeringtoolbox.com/forces-pipe-bends-d_968.html

 

[BigInch]

Same as I said above, if it slips, its the static friction force at each support, if not slipping, the force is found from the linear growth applied as a deflection on the support, then you calculate the load producing that deflection from that displacement. The axial load imparted to the pipe at that point is equal and opposite.

Guides do not restrain in the axial direction (thermal growth), so no axial load component is produced there.

Loads from fluid changing direction are applied as point loads at the point of direction change and reactions calculated considering the pipe as a structure.

We are more connected to everyone in the world than we've ever been before, except to the person sitting next to us. Lisa Gansky