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OT - Starving or Over Pressuring a Transfer Pump

redlee

Titanium
Joined
Apr 2, 2009
Location
Beaver County Alb. Canada
I have a 3" Transfer pump and want to swage it down to 1" for watering, any problems anyone knows of?
Intake is 3" and Im just concerned about pressure build up in the casing,and or "Frothing" inside the casing! The case will always have water, but will it harm it?
Thanks.
 
I have a 3" Transfer pump and want to swage it down to 1" for watering, any problems anyone knows of?
Intake is 3" and Im just concerned about pressure build up in the casing,and or "Frothing" inside the casing! The case will always have water, but will it harm it?
Thanks.

I would want a pressure regulation circuit to recirculate and bleed to maintain a desireable pressure. Is there a pressure rating in the pump?
For example a few shop machine coolant delivery systems I have worked on had a pressure regulator and a ball valve to adjust pressure where the coolant returned to the resivoir. Obviously close down ball valve a little for more pressure. I would run 3" out of your pump for a few feet before necking it down to 1" to reduce turbulance.
 
Your pressure will be limited by pump design. If it is capable of high pressures and is overly restricted then damage will result. Low head pumps will be able to pump against a restriction without problems due to their clearances. A pump capable pressures exceeding 50 lbs or so should have a relief back to the tank or water source, not to the pump intake where the pumped water will just recirculate. Any fire engine can easily boil water in the pump with destructive damage if cooler water is not supplied. If your pumps is a low head model then no problem.
 
You didn't mention how much horsepower, if it's electric, and the pump type.

I'm going to assume that it is a typical gas powered transfer pump. These are almost always centrifugal pumps with a fairly low max head pressure.

If what I assumed is true, then running the pump with a restricted outlet is fine. Just keep the minimum discharge flow high enough that the water discharge temperature s not above 100C. Most centrifugal pumps can tolerate dead heading as long as the liquid in the pump chamber does not exceed the boiling point.

Restricting the suction side can be potentially harmful since you are putting the pump into cavitation if the inlet restriction is less then the outlet restriction. The inlet and outlet restriction limitation is a function of actual flow, not just the orifice diameter. In your application, throttling the engine back would also be good and potentially save some fuel.

Turbine pumps and regenerative pumps do not like to be dead headed. They usually have a substantial max head pressure and have a strong tendency to create a lot of heat if operated at less than normal design outlet flow.
 
Need to know the "type" of pump (centrifugal, diaphragm, gear, impeller . . .????).
Brand name and model number might give us a clue.
 
You could look up the curve for that pump and see if it will work at all for your application. I'm guessing you need a higher head.
 

I'm a little confused. Your original post said that it was a 3" pump. Now it's a 2" pump?

I'm not certain if what you proposed will harm your pump, however, I do know how to avoid the risk.

I would set it up so the pump sees full flow. Also, assuming that the pump is drawing from a pond or such (not "pressure fed").

Assuming that it's a 2" pump, and using nominal numbers (you can look up the actual diameters of the materials that you're using), (2" dia. = 3.14sq") - (1" dia. = .785sq") = (1.732" dia. = 2.355sq"). So, plumb the pump output for 2" with a Tee fitting. Reduce one branch to 1" for your watering hose. On the other output branch, implement a 1.732" dia. orifice followed by a return hose to the pond. You can easily implement an orifice by trapping a disk, inside a coupling between two nipples. With that set-up, ≈60% of rated capacity will always be returned to the pond. If you want to change the pressure in the watering system, change the orifice diameter. The pump will be operating in "nominal" environment.
 
I'm a little confused. Your original post said that it was a 3" pump. Now it's a 2" pump?

I'm not certain if what you proposed will harm your pump, however, I do know how to avoid the risk.

I would set it up so the pump sees full flow. Also, assuming that the pump is drawing from a pond or such (not "pressure fed").

Assuming that it's a 2" pump, and using nominal numbers (you can look up the actual diameters of the materials that you're using), (2" dia. = 3.14sq") - (1" dia. = .785sq") = (1.732" dia. = 2.355sq"). So, plumb the pump output for 2" with a Tee fitting. Reduce one branch to 1" for your watering hose. On the other output branch, implement a 1.732" dia. orifice followed by a return hose to the pond. You can easily implement an orifice by trapping a disk, inside a coupling between two nipples. With that set-up, ≈60% of rated capacity will always be returned to the pond. If you want to change the pressure in the watering system, change the orifice diameter. The pump will be operating in "nominal" environment.

Thanks, I just posted a link of the kind of pump I had because the question was asked.
Didn't think it would matter what size it was, because the same problem would exist with any size of the same kind of pump.
Im pumping from a tank on a trailer for tree watering, I have enough stuff to maintain and didnt want to go and buy an appropriate pump for the job.
 
I wouldn't bother with a pump for tree watering. gravity and big pipe should be almost as fast. Say three or four inch pipe with a pvc ball valve. Think water truck for construction sites.
Bill D.
 








 
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