Effects of internal pressure on pipe supports

[S_a_e]

From my understanding, internal pressure produces no forces on pipe supports.
This is because internal pressure is fully balanced by the tensions in the pipe (hoop stress).

If I want to consider an effect, can I do it by assuming a forced displacement on the clamp stem due to radial expansion of pipe from internal pressure?

Basically I calculate dR, stem deforms by dR/Lstem, and this produces a tension in the stem.
This tension multiplied by stem area is a force.

The only problem I see is that by forcing fixed displacement, deformation will be different depending on the initial length of stem, and so tension will change from stem to stem if they have different lengths.

 

[shvet]

Internal pressure in a pipe support? What design of support - tensioned pipe support?

 

[S_a_e]

I refer to a pipe system that is held in place by pipe supports.

Think of a steel structure skid that supports pipe routing by pipe clamps such as this one:

 

[shvet]

Where is internal pressure on this picture?

 

[S_a_e]

Internal pressure is in the pipe that is being held by this support.
E.g DN200 pipe with 10 bar inside.

My reasoning is that no pressure effects are induced on the clamp, but my question is if they should be somehow evaluated instead (e.g by considering pipe deformation).

 

[1503-44]

Internal pipe pressure may affect loads on hangers. Internal pressure can cause longitudinal movements of pipe and, depending on pipe configuration, might cause loads in all directions.
See Bourdon effect.

https://whatispiping.com/bourdon-effect-true-and-effective-axial-force/

Pressure does change the diameter, but a very, very small amount and can be neglected except in extremely tight, 0 clearance, fit ups.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[S_a_e]

Thanks for your answer 1503-44.

I am aware that pressure can cause movements, which cause stresses in all directions.

My question specifically is, if you can consider for example 10 bar acting downwards on the pipe surface and causing a force on the hanger that is below.

I am 99.9% sure this is not correct, but I am asking you because a colleague wants to calculate the force on the stem of the hanger by multiplying pressure with the surface of the lower half of the clamp

 

[1503-44]

That makes no sense to me.
Pipe internal pressures are contained entirely by hoop stress, therefore they remain inside the pipe wall.

In your case it appears to be that yhe only force on the rod is weight of pipe, insulation and contents of the pipe.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[LittleInch]

Pressure acts in all directions all of the time.

So any force "down" is matched by a force "up"...

So yes, there is a small increase in force on the two bolts you see in the picture you post due to circumferential expansion of the pipe, but NOT on the support itself. the increase in force on the bolts is very small.

you're seriously over thinking this....

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

 

[1503-44]

Better than no thinking at all.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[shvet]

for info

5.2 REACTION FORCES
The discharge piping on pressure relief systems experiences reaction forces (thrust forces) developed by the relief flow in three forms. The force that is usually considered is the quasi-steady state force which is produced when a fluid is discharged from the end of a pipe to the atmosphere. Because closed piping systems under steady flow do not exert a reaction force onto their supports, this force is the only steady state force that is applied to the piping supports.
The second form of the reaction force is the transient reaction force. The magnitude of this force is proportional to the rate of change in the mass flow within the piping. Depending on the relief scenario and pipe segment length, the duration may be of the order of a few milliseconds to several seconds. The transient force is frequently neglected for gas phase relief but can be significant for liquid or twophase relief.
The third form of the reaction force may be an increase in tension within the pipe segment. Usually, the tension used in designing flanges and other joints is based upon the piping “design pressure”. The selected design pressure usually has enough margin such that any increased tension due to flow does not impact the design. This chapter provides methods that the relief systems designer may use to determine whether the additional force produced by the fluid’s momentum is significant.
The relief systems designer needs to be aware how the calculated reaction forces will be used by the structural engineer. If the stresses in the piping supports will be evaluated with a static force analysis, then a dynamic load factor may need to be applied to the forces to account for the structural response. The value of the dynamic load factor depends on the rate at which the force is applied, the duration of the force and the natural frequency of the structure. On the other hand, if a dynamic analysis will be used to evaluate the structural response, then the dynamic load factor is not required. The effect of the dynamic load factor is automatically included in the dynamic analysis. The relief systems designer must convey the magnitude and location of the loads to the structural engineer. If the relief systems designer does not understand how the forces are applied to the piping, then the structural engineer probably won’t understand the situation either.

 

[Snickster]

Like others have said the pressure forces in a pipe is balanced by hoop stress so there is no net force to the supports.