Vertical pipe support load

[ttoonnyy]

Hi Guys

I got this question for a vertical pipe, hundreds meter deep for underground mine dewatering.
I'll need to work out the weight to support for the hanger design. No piping engineer to provide the load, unfortunately...
The total pipe weights about 5t and content weights 7t. vertically positioned, lateral controlled every 6 meter.
No expansion, dynamic, water hammer load considerd for now.
For the vertical load, there are 2 supporting options
Option 1
1 hanger hung the pipe from very top, the pump is connected at very bottom.
Therefore will generates a 12t weight for the hanger.
If this is the case, assuming the pipe is strong enough..can the pipe carry 7t content vertically?
Does the content pass whole gravity to the pipe wall through pressure and friction?
I see the reference from Peng engineering ASME mentioned the pipe line load should consider content as line load, not sure if it fits here.
Option 2
1 hanger hung from the very top, and another hanger/support from the very bottom before connecting to pump.
If this is the case, should bottom hanger undertake 60%+ of the total (pipe+content load); the top hanger undertake minimum 50% of the total (pipe+content load)?
Or bottom hanger undertake 7t content + 50% of the pipe load (5t)?


Would appreciated for any comments.
Cheers, Tony

 

[GBTorpenhow]

Need a sketch.

If open to the fluid at the bottom I have a hard time imagining how the weight of the contents could show up as tension in the pipe. Usually the weight of the contents appears as hydrostatic pressure only.

Production/injection well strings are typically supported only at the wellhead as I recall and hang freely into the well so yes, the entire weight of the pipe string can possibly be supported as tension at the top of the string assuming the pipe is strong/thick enough.

Bottom support might be tricky, any compression loads would be probably be undesirable as such a long string would have very low buckling resistance

 

[LittleInch]

It all goes on what is happening at the base of the pipe and the flexibility of the connection to the pump.

I would normally have thought that the end cap force from the weight of the fluid in the pipe would be taken by base support with some sort of fixed support, but maybe not.

contents will not cause a force on the pipe from friction and pressure, but end cap force will have an impact if the pipe is free to move at the base of the shaft.

If you have two supports then it all starts to get a bit complex depending on the level of either thermal expansion between installed condition and operating or strain expansion of the pipe.

In theory the top hanger could then be a spring hanger sized for the weight of the pipe, with a vertical force of 5 tonnes, with the base support being responsible for the fluid weight. But any failure of the top hanger or too much expansion or contraction of the pipe outside the range of the spring hanger could leave the base support supporting it all.

 

[Snickster]

Option 1

The weight of the contents will be transferred to the pipe at the bottom elbow pushing down vertically, plus weight of pipe will be total design weight for the hanger. I don't see any issue with letting pipe hang from a single hanger above with lateral bracing along the pipe as you mentioned. The pipe will stretch downward due to weight of pipe and contents equal to e=S/E where e is % strain. Also there may be some thermal expansion and with one hanger at top of pipe all thermal expansion will be forced downward. Therefore pump nozzle piping needs to be flexible enough to absorb this deflection without overload of pump nozzle. This will be the tricky part.

Option 2

I believe if the bottom support were perfectly rigid then it would feel the entire weight of content load. This is because the only way the top support can feel any load applied at the bottom elbow is due to the pipe stretching in accordance with the equation shown above. If the bottom support is so rigid it does not move at all then the vertical pipe cannot stretch and therefore no load can be felt by the upper support. The bottom support will likely not be absolutely rigid and deflect somewhat under load which will allow the pipe to stretch and transfer some load to the top support depending on the relative stiffnesses of the upper and lower supports. In this case the weight of the pipe will be shared by both the upper and lower supports based on the relative stiffnesses of the supports.

If it were me, I would just design the upper and lower supports for the entire load. 24,000 pounds is not that significant for a pipe support that will make it much larger in size relative to say if you designed it for only 12,000 pounds on each support. It will allow the flexibility to remove say the bottom support if required to service the pump if required.

If there is thermal expansion the upper support will likely need to be a spring support since any thermal expansion should be directed upward away from the pump nozzle with a rigid support at the lower end. In this case although both supports will be designed for full weight plus content load, the upper spring can support will be sized based on the expected actual load it will carry at the deflection expected for determining spring sizing requirements, whereas the structural support that the spring support attaches to should be designed for the total weight of pipe and contents.