valves and fittings (pipeline )

[ahmadbazzari]

hi
am a fresh graduated mechanical engineer working at " wast water pumping station " put i became some nervous from some welding and pipeline design basic
so many questions on my head
like ....
1) can we weld two fittings together ?
2) can we weld fittings directly to a valve ?
3) can we weld two valves directly ?
4) what is the allowance distance between any two fittings , any valves , or fittings ( elbow reducer or tee ) between them-self or between them and other valves ?
5) what is the distance between two pump ( one duty and the other is stand by ) ?
6) when i have to make a header between two pump , what is the allowance distance between the upstream and down stream , and suction port and draining port ?
i know that a lot of questions but i hop to help me or at least give me some basic or books to start learning
thank you ^_^

 

[jte]

Hi Ahmad, welcome to Eng-Tips!

Have you tried the search function? Many of your questions can be answered with a little bit of effort on your part.

 

[bimr]

1) can we weld two fittings together ? If the fittings are steel.
2) can we weld fittings directly to a valve ? Not customarily done for maintenance reasons.
3) can we weld two valves directly ? Not customarily done for maintenance reasons.
4) what is the allowance distance between any two fittings , any valves , or fittings ( elbow reducer or tee ) between them-self or between them and other valves ? Usually nothing, unless the disturbance created by the fitting will cause turbulence and affect the other item (flow meter, pump, etc.)
5) what is the distance between two pump ( one duty and the other is stand by ) 3-6 feet clearance from outside pump foundation to outside pump foundation depending on size of pump..
6) when i have to make a header between two pump , what is the allowance distance between the upstream and down stream , and suction port and draining port ? No specific dimension. You probably need 2-3 feet for constructability.
i know that a lot of questions but i hop to help me or at least give me some basic or books to start learning Get a copy of Pump Station Design by Garr Jones.
thank you ^_^

 

[pennpiper]

My opinion:
1) can we weld two fittings together? Yes if they are both Butt Weld fittings
2) can we weld fittings directly to a valve? Yes if the Valve and the fitting are both Butt Weld.
3) can we weld two valves directly? Yes if they are both Butt Weld end valves.
4) what is the allowance distance between any two fittings (0 inches), any valves (0 inches if butt weld or Flange to Flange) , or fittings ( elbow reducer or tee ) between them-self (0 inches) or between them and other valves? (0 inches of fitting make-up)
5) what is the distance between two pump (one duty and the other is stand by)? A lot depends on the size of the pumps, the safety considerations involved (Heat) and the type of pump, but generally 3'-0" (1 meter).
6) when i have to make a header between two pump , what is the allowance distance between the upstream and down stream , and suction port and draining port? Your #6 question is gibberish and is not understood by me. Pleas consider finding a real Piping Designer with the proper experience to do this work.

Sometimes its possible to do all the right things and still get bad results

 

[Alex303]

3 & 4) If using butterfly valves\check valves, particularly wafer installations it is important to check the butterfly disk and check valve flap distance. If you put a wafer check valve directly upstream of another valve the flap will actually be obstructed, same goes for a wafer butterfly. Other valves such as flow control valves may have pilots that stick out within the internal cast flanges which may be an issue. Same goes for non digital flow switches which have a flap that sticks into the pipe. Some other probes may have things that stick into the pipe too. Never assume a valve\probe can be fitted directly against another valve\probe without either knowing the product or looking at the catalogue.

 

[rconner]

All good responses. You have mentioned all these welding questions are for piping in a waste water pump station. Just one more comment in general concerning "welded" piping systems for some such applications. Particularly for any smaller diameter piping, it is obviously difficult to somehow "reach inside" the welded joints and effectively/manually field repair any inside pipe linings involved that may be specified and have been provided by the manufacturer for internal corrosion protection (that are/may be affected by obviously high welding heat). While some might think the answer to this problem is the employment e.g. of various "stainless" steels, that are often structurally thinner and not lined, I believe in practical application it has also been found difficult in some cases to construct durable welded stainless steel piping systems without problematic effects on the metal from the prep, welding operations, and/or service. For welding of even larger diameter lined piping that might allow access, widespread internal lining patching is also not without its contemporary issues, e.g. all the modern (and in many cases prudent) safety rigamerole concerning "confined spaces" etc.
For these and other reasons I believe major (at least municipal) wastewater plants and pump stations have traditionally been constructed with a great deal of the process piping built with essentially shop-prefabricated (according to submitted and approved line drawing layouts/dimensions) and shop-lined (virtually throughout) piping with e.g. flanged and/or (externally) grooved-end joining.