Dual rising mains

[MUJ1299]

Anybody know of a calculator that determines pump flow rates, velocities and head losses when using 2 rising mains of differing sizes? For example a Stage 1 140mm RM will be installed for a pump rate of 13 L/s and 7 years later an additional RM will be installed for up to 34 L/s mallowing possible use of either or both RM's depending on flows required - I can't get my head around the differing velocities and head losses - can it equalise in the system?

 

[LittleInch]

You really need to sketch this out so we can understand what you're talking about, but it sounds like some sort of parallel or twin lines. Then your only common points are the pressure / head at the common points where they start or end.

If you have different sizes of pipe, you will find the larger one takes flow in much larger proportion than you might think.

any simple flow calculation off the web will give you answers based on either flow to find pressure drop or pressure drop to find flow for wholly liquid filled lines.

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

 

[bimr]

It is statement of conservation of energy. The flow will adjust automatically so that the head loss in each branch pipe will be the same. See the text.