Flexible Coupling in Pump Suction
Flexible Coupling in Pump Suction
(OP)
Is it acceptable to use a flexible coupling in a pump suction line that runs from a fire water storage tank to a pump house which sits on a separate foundation? We expect the tank to settle .65" initially and another 1.17" over 5 years and the pump house foundation is on piles so it will not settle. I seem to get conflicting answers when doing research. NFPA 20 shows using flexible couplings for strain relief, while other sites say to route my flexibility in the line. My opinion is that if NFPA 20 is ok with it, then I am ok with it. Unfortunately it is too late to make changes to the suction line, but will 2 flexible couplings in the straight run out of the tank be sufficient to handle the settlement? Any opinions would be greatly appreciated.





RE: Flexible Coupling in Pump Suction
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: Flexible Coupling in Pump Suction
Here is a picture of the line
RE: Flexible Coupling in Pump Suction
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Flexible Coupling in Pump Suction
RE: Flexible Coupling in Pump Suction
Johnny Pellin
RE: Flexible Coupling in Pump Suction
I assume the yard piping is not settling. It is the foundation of the water tank that is settling.
What JJP is suggesting is correct. This peice of pipe should be in a accessible concrete vault to allow the joint to work as the storage tank settles. You need to consider a detail to prevent shearing of the pipes between the vault and the spigot cast into the foundation wall of the sotrage tank.
RE: Flexible Coupling in Pump Suction
RE: Flexible Coupling in Pump Suction
I used to count sand. Now I don't count at all.
RE: Flexible Coupling in Pump Suction
Come on guys, this is a fire water inlet pipe connection dropping just over an inch over what looks like several feet of pipe.
No need for anything fancy here...
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Flexible Coupling in Pump Suction
I'd go with Dresser couplings, which are not strictly ball type joints but do allow a few degrees of misalignment, at either end of the longish leg between the tank valve and the tee.
Mike Halloran
Pembroke Pines, FL, USA
RE: Flexible Coupling in Pump Suction
The differential movement is all at the wall of the storage tank...not spread out along the length of the connecting pipe (which has bedding underneath supporting the pipe). All the pipe shear and movement is at the wall. JJP's suggestion or DGrayDDp's suggestion is the way to go if you can achieve that type of movement. If this water is potable in any way I would go with the latter.
RE: Flexible Coupling in Pump Suction
RE: Flexible Coupling in Pump Suction
Mike Halloran
Pembroke Pines, FL, USA
RE: Flexible Coupling in Pump Suction
Good point.
If you take a look at the drawing everything is hard flanged or welded. If there was a diferential settlement of 0.6"-1.1" at the storage tank you are putting one hell of a twist on the piping if the soil is truly that liquid. The pipe would bend and would crack somewhere. I would think that is one hell of a lot of stress on that pipe. I would think that you would want to prevent that
There should be a pile pipe support close to the gate valve
RE: Flexible Coupling in Pump Suction
Better, IMHO, to put a flex coupling of some kind next to the gate valve, and another one next to the tee.
I stand by my advice about the bellows.
Mike Halloran
Pembroke Pines, FL, USA
RE: Flexible Coupling in Pump Suction
RE: Flexible Coupling in Pump Suction
Mike Halloran
Pembroke Pines, FL, USA
RE: Flexible Coupling in Pump Suction
RE: Flexible Coupling in Pump Suction
http://www.victaulic.com/en/products-services/prod...
RE: Flexible Coupling in Pump Suction
RE: Flexible Coupling in Pump Suction
Mike Halloran
Pembroke Pines, FL, USA
RE: Flexible Coupling in Pump Suction
RE: Flexible Coupling in Pump Suction
RE: Flexible Coupling in Pump Suction
RE: Flexible Coupling in Pump Suction
No need to complicate things here.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Flexible Coupling in Pump Suction
The best way to use a hose as an alignment tool is as a replacement for an elbow.
RE: Flexible Coupling in Pump Suction
Yes, I believe such an arrangement would be suitable, with the joints you originally proposed. You would need to support the straight run of pipe adjacent to each flexible joint, with supports incorporating integral height adjustment so you can follow the tank down.
I'm guessing that the pipe from the tank is about 12", but the joint datasheet should identify the lateral or angular displacement it can handle.
The Victaulic Style 233 joints look all right, but my concern would be the (perhaps long term) ability to maintain a proper seal on the outside surface of the CS pipework.
I'm not familiar with the ball-type joint proposed by Johnny Pellin, but feel it may be a little over the top for this application.
RE: Flexible Coupling in Pump Suction
Only reason I proposed the victaulic couplings are because the stress engineer is having second thoughts about the flexible hose. What you do not see in the original picture is that there will be a catwalk crossover (width will be more than likely 3'-0") close to the valve for accessibility reasons. The valve is 14" and the stem is projected to be quite tall. Due to the catwalk, the thought was that placing the flexible hose underneath it could create issues if for some reason the hose ever needed to be replaced and maintence could not get to it comfortably. However, placing it outside the catwalk would create too much load on the 14" tank nozzle. So the victaulic couplings were suggested as an alternative with one presumably close to the tee and another close to the edge of the proposed catwalk.