Downhill Pumping

[challenger_84]

Hello,

I am designing a sanitary sewer force main which involves pumping below a creek and the outfall elevation is lower than the pump station. This will be an interim condition as a new WWTP is being designed and the force main will be rerouted in 5-10 years.I have not come across this issue before but have researched downhill pumping on this forum and through various online sources and believe the best route will be to keep the line full to avoid issues with constantly filling and emptying the line. I have researched back-pressure sustaining valves as well as an actuated plug valves and I would prefer to go with the former to minimize the system complexity but understand this will require more energy since the pumps will be forced to pump against the head loss across the valve.

I am writing to gain feedback from folks who may have designed or analysed a system like this. Specifically, I am looking for help to analyse the back pressure sustaining valve and determining the corresponding TDH. I have attached a spreadsheet with the project information as well as profiles for the various conditions.

I understand this topic had been discussed at length and any tips or recommendations would be greatly appreciated.

Sincerely

Challenger_84

 

[LittleInch]

Well it depends on how much you want to spend and how much services are available at the far end.

A simple fixed back pressure valve would add about 20m head to maintain a full pipe at all flows from zero upwards.

A more complex variable control valve varying the back pressure depending on flow rate would reduce this to probably 4-5m, but needs a controller, flow measurement from somewhere.

How much this is worth to you depends on how often you are flowing and what the energy costs are, but 5-10 years is a long time.

Or it could work with a simple pump on/ pump off signal with an actuated valve to open / close.

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