Forces on Valve chambers 1

[Maher K]

I have a valve inside a concrete valve chamber. Upstream the valve there is a dismantling joint that connects the valve to a flanged pipe which have a puddle flange at the place where it intersects with the wall of the chamber. The same is on the downstream side of the valve without having a dismantling joint.
When the valve is closed, a force is generated along the direction of the pipe which depends can be calculated by multiplying the column of water (water pressure) by the cross sectional area of the valve.
As far as I know, the use of a puddle flange at the locations where the pipe intersects with the walls of the chamber is to ensure a watertight and pressure-tight seal.
Now the question is this, is the generated force/thrust transferred to the walls of the chamber? If yes, is it on the upstream wall only or distributed equally between the upstream and downstream walls? I am concerned whether I have to take into design any force when designing the walls of the chamber

 

[Maher K]

The numbers are correct. I'm getting large numbers when checking the stability. Water table is 0.5 m below ground level. I'm getting that I need wing walls from each side not less than 2 meters from each side.

 

[1503-44]

High water table will make this design tricky. It is not indicative of the best soils. Buoyancy forces will not help friction. Will you need piles to resist these high loads? I would look to trying to direct bury in soil without a vault. Your soil report will be key to selecting the best design option.

Your pipe will be subject to uplift from buoyant forces, esp when empty. I don't see concrete weight coating on your pipe detail. What gives there?

It is time to tell us everything you know now instead of by this little by little disclosure. It appears that you have a difficult design and, if you want good advice, that only comes after you provide good and reasonably complete info.

My best advice at this time is find a different place to put this valve.

“What I told you was true ... from a certain point of view.” - Obi-Wan Kenobi, "Return of the Jedi"

 

[LittleInch]

What exactly is the pipe material and pipe to pipe jointing mechanism being used here? Push fit / low axial constraint or welded / flanged / high capacity axial restraints?

If your pipe will take the axial load then ditch the cheap and cheerful puddle flange and use a flexible coupling suggested earlier.

If it won't then you're really trying to build a large anchor bloc capable of handling several hundred tonnes of force.

Which is it?

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

 

[saikee119]

The numbers are correct. I'm getting large numbers when checking the stability. Water table is 0.5 m below ground level. I'm getting that I need wing walls from each side not less than 2 meters from each side.

Just give you an idea of a similar pipeline 2x1.6m dia case for comparision. Haven't got time to verify if the flow rate was for one line or two but the rated flow is 11,370m3/h and the rated pressure is 25 barg (transient pressure is higher but no data). A typical section of the anchor block is depicted below.

Please note the width is over 28m for two lines of 1.6m diameter combined into one block which weight over 3000 tons. Also the design is a remedial work after the bell spigot joint came off when a valve was shut so there was an element of overdesign to make sure the submission could be passed quickly. The above block is for above ground installation but the sketch also show the existing opposite side change direction from below ground to above ground arrangement.

If your design were primary based on using the passisve resistance of the soil then 2m wing wall on both side would make sense. In generally the resistance is just the combined weight of the foundation, pipework, valve, water and all fixings times coefficient of soil friction (at the base of pit) plus any passive resistance of the soil on the areas of your valve pit hard press against the soil. You current valve pit looks too light and may do with a larger dimension as well as a thicker base, as you need to transfer first the hydraulic force from the valve to its foundation and the from foundation to the wing walls through the box structure of the valave pit.

 

[1503-44]

I'd tend to look at something like taking all thrust loads with a separate anchor block structure handling either tension or compression in the pipe between that and the valve, on the right side of your vault detail and building more of a typical vault adjacent to it on the left side. The construction would have much cleaner lines and form work and be easier and faster, if you can manage to keep all those thrust loads in the valve, piping and anchor wall and completely out of the vault walls.

I don't like the high angles risers above, as it introduces upward thrusts and overturning moments. It is extremely important to have long runs of as straight as possible pipe on both sides of anchors, otherwise all those thrust loads add significant bending load to those goosenecks which carry into the connections and valve inside the offset section of pipe.

“What I told you was true ... from a certain point of view.” - Obi-Wan Kenobi, "Return of the Jedi"