Flexible Connection to Skid 2

[jobarr]

I am working on a project where we are installing a new domestic water booster pump skid for a small community. There is existing flanged ductile iron piping that we will be connecting to. Should there be a flexible connection between the booster pump skid suction and discharge lines and the existing flanged ductile iron piping? Or can I do rigid flange-to-flange connections between the existing piping and the skid? The booster pump skid will have 4 inch piping. The existing ductile iron piping is 6 inch. Obviously, I will have to install a reducer to connect the pipes.

I have looked through some previous threads, and it sounds like flexible connections should be avoided when possible since they are a common failure point. However, some threads seem to suggest that flexible connections are suitable for the suction line, but not for the discharge line. These previous threads seem to deal more with the actual connections to the pumps, while I am connecting to a packaged skid system. I am leaning toward not having flexible connections, but I would appreciate some advice. Here is a summary f my questions on this topic:

1. Should I use flexible connections between booster pump skid and existing piping?
2. What would be the reason for using flexible connections (if they are needed)?
3. If flexible connections are needed, what type of flexible connections should be used?

Thank you.

 

[MikeHalloran]

2.1 The skid, or whatever foundation you provide for it, may settle over time.
2.2 If anything on the skid produces vibration, e.g. a piston pump, you may wish to isolate the vibration from everything else.
2.3 Even if it's bolted down, the skid will eventually be hit by a truck or a forklift; you may want to prevent a 'small bump' from becoming a major problem.

3.1 Metal bellows have a limited life.
3.2 Rubber 'compensators' should last longer, but I don't know if they're good for suction service.
3.3 Consider also the sort of flexibility provided by the sort of omega-shaped bent pipe you sometimes see in pipelines or process piping. An alternative would be four elbows with a short spool and two long spools, with flanged slip joints that can rotate a tiny bit without leaking.
3.4 Consider a couple of hoses of appropriate construction.
3.5 It's possible that the existing ductile iron pipe might withstand some displacement from its original position, depending on how it's anchored and supported.

1. See the project spec for guidance, and you decide.



Mike Halloran
Pembroke Pines, FL, USA

 

[Gator]

"omega-shaped bent pipe you sometimes see in pipelines or process piping"

AKA 'expansion loop', in case you want keywords to search with.

 

[BigInch]

Good equipment foundations that do not settle are far better than non-rigid or hose pipe connections, but I guess that depends on how much you like replacing hoses and realigning-leveling equipment.

"Flexibility" can also be provided by proper arrangement of rigid piping.


Technology is stealing American jobs. Stop H1-Bs for robots.

 

[LittleInch]

Should you? Your choice

Reasons?
If your pipe sees a lot of movement or thermal expansion and you don't have an anchor block
If your pipes are not aligned well in any direction
If there's a lot of vibration

What type?
For this size and pressure I would go for either a braided hose or similar flexible pipe.

If this is ductile orion pipe what I'd the joining system? Push fit?
Ate you breaking into the system? You might need to include anchor blocks

A lot will depend on the system and how good your pipe fitters are to get the final tie in right to the nearest mm before you connect to the pump. Pressure rating can come into it as well as cost.

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

 

[jobarr]

Thank you all for your comments. Based on the comments you have provided, and additional research, I am leaning toward installing a single arch Mercer (series 450) expansion joint at the point of connection to the skid. Any thoughts on this approach?

 

[KevinNZ]

We have designed many large pump insulations and always try to avoid expansions loops. The foundations need to be sound and pumps run smooth. We deal with high pressure hot water so carry out a full thermal and EQ stress check and have pipe loops to take loads off the pump nozzles.

 

[BigInch]

What size pump (motor HP) are we talking about here?

Technology is stealing American jobs. Stop H1-Bs for robots.

 

[LittleInch]

Why are you "leaning towards it"? Only when we understand the reasons why it's there can anyone say its Ok or not/

How much movement / angular displacement / axial movement are you expecting?

If it's very low then just hard pipe it but allow enough in the design for site measured lengths in X, Y and Z.

Seems a bit OTT to me for a water booster station...

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