Hello everyone. Hoping one of you engineer types can help me calculate total head for an assembly I am working on. I am trying to achieve a specific number at a specific height. I plan to use fittings in a rising helix to create more pressure as the lift is low and puts the pump out of its efficiency curve. If you think you can help, message me and I will provide more details. TIA---Pete
Need help calculating Total Head
- Thread starter boggerdak
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Well you do need some help as there is no need for a "rising helix" to keep a pump in its efficiency curve. If the pump needs to see additional head you can use a valve. Just as well give everybody else the benefit of what it discussed, which is kind of the purpose of forums. Just need depth to the static and pumping water levels as well as flow and pressure needed at the surface?
It appears that you are more concerned about efficiency than flow rate, which is a little strange to me. But adding more piping is far from being the best approach. Just use a valve to throttle the flow, or an orifice after you determine the pressure drop you need.
I am looking to draw water from a platform in a lagoon. The pump has its intake and discharge flange at roughly the same height. I will be setting this approximately 14" below the waterline. It is a submersible pump with a bottom draw. I brought up efficiency because exactly where the total head and efficiency curve cross is where I need to be. The pump will push 350gpm @ 23ft total head. I need 350gpm. Total lift from the 14" below the water line to where the discharge will occur is 86" (72" above the waterline). There will also be approximately 2' of horizontal run at the top. The discharge flange on the pump is 4". I had planned to neck it down to 3" if necessary. Trying to avoid using a valve for throttling as I am looking for simplicity and tamper resistance.
As I am sure you can tell, I am struggling with understanding how to figure this out. Please be gentle....
As I am sure you can tell, I am struggling with understanding how to figure this out. Please be gentle....
Be glad to help. Do you have a pump curve?
Looks like a good pump. As you can see the shaft power goes down as the flow rate drops with more restriction. It is going to try to pump 450 GPM with no more head than you have. All you really need is an orifice plate with the right size hole for 350 GPM. I can do the calculations for that, but it is not easy, Even if you get all the data correct to make the orifice plate the right size, it is easy to miss something. Also, sometimes things change over time. A valve is a variable orifice. You can just close the valve until yo get the 350 GPM you want, even if things change over time. No calculations needed. It doesn't get much simpler than just a valve. As for tamper proof, just taking the handle off the valve after it is set is usually enough. But if you are afraid someone will use a wrench to mess with the valve, hack saw off the stem where the handle fits. Lol!
