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.
Eng-Tips is the largest engineering community on the Internet
Intelligent Work Forums for Engineering Professionals
Flexible Coupling in Pump Suction 2
- Thread starter DGrayPPD
- Start date
1.17"is not strain relief, it severe misalignment,I would be looking for A better option.
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.)
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.)
- Thread starter
- #3
LittleInch
Petroleum
If the round purple circles under the pipes are the piles or are supports which won't settle like the tank will then a couple of flexible joints in that single leg or just a single length of Braided hose should be enough.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
- Thread starter
- #5
-
1
- #6
I would put two flex joint in the common horizontal run before the elbow. But,I would use ball-type joints rather than rubber or metal bellows joints. We use these on crude booster pumps connected to pipelines that have a lot of movement.
Johnny Pellin
Johnny Pellin
QualityTime
Civil/Environmental
Remember that flexible couplings are not to be used under negative pressure situations.
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.
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.
-
1
- Thread starter
- #8
SandCounter
Mechanical
Flexible couplings can be, and are used on pump suctions if rated for vacuum. If rubber, they will have steel wire embedded to hold the form under vacuum. I always just cheat and call a flexible coupling company and get them to select it (and quote it) based on my specifications. They will want to know max vacuum, axial travel, radial travel, angular travel, flange rating and bolting spec. They will also want to know if you want tie rods.
I used to count sand. Now I don't count at all.
I used to count sand. Now I don't count at all.
LittleInch
Petroleum
I would go for something a little longer (2-3D)given the amount of vertical movement, but otherwise looks good to me.
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.
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.
MikeHalloran
Mechanical
Bellows, metal or not, don't do well under external pressure; they buckle and fail.
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
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
QualityTime
Civil/Environmental
Hi All:
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.
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.
MikeHalloran
Mechanical
QT, if the pipe is fully supported by some sort of bed, why does it need the piles?
Mike Halloran
Pembroke Pines, FL, USA
Mike Halloran
Pembroke Pines, FL, USA
QualityTime
Civil/Environmental
QT, if the pipe is fully supported by some sort of bed, why does it need the piles?
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
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
MikeHalloran
Mechanical
... and a pipe support next to the gate valve would stop the tank from settling, for how long?
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
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
QualityTime
Civil/Environmental
The pipe support is to prevent the pipe from settling...not the tank LOL. The flex coupling takess the differential movement
MikeHalloran
Mechanical
Given a little sleep, I think I misremembered the limitations of bellows, i.e., they do okay with external pressure, less so with internal pressure. Mea culpa.
Mike Halloran
Pembroke Pines, FL, USA
Mike Halloran
Pembroke Pines, FL, USA
- Thread starter
- #20
What is everyone's opinion on using 2 of these, one at either end of the straight run, to give flexibility? Same parameters apply with settlement.
- Status
Similar threads
