PTO Irrigation Pump Question

Spudm

Member
About a 500 GPM pump running off a 55 hp tractor. Was wondering if running a PTO pump is hard on a tractor? Tractor runs at about 1500 rpm, diesel engine under load. Never had a problem with tractor over heating, but now it does since using that pump a lot a couple of years ago.
 
A lot of people believe that running an internal combustion engine at a constant speed under a constant load for extended periods of time is hard on it. Don't know for sure. I know generator engines don't last long but, I think they are cheap made to start with.
 
The engine doesn't care that it's running a steady speed. A better place to start looking would be a slipping fan belt or a scaled up radiator core. Drain out some coolant until you can see what the tubes look like in the radiator , are they open and clear ? or full of scale and rust ? Hose the out side of the radiator clean from both sides , dust and crud can seal off the airflow through it ....
 
We were pumping serious water with a Kubota a few years back. It starting to overheat almost from the git go. Pulled the side curtains on the engine and it cooled right down nicely.
 
My brother in law and his brothers plus other hired help milk over 600 cows and they pump water from the creek about a mile away sometimes. One year their tractor caught fire and it was a total loss.
 
There were 413 Chryslers that ran under full load on irrigation wells for decades. Valve jobs were needed every few years.

I don't think you should be taxing your 55 hp but there are charts that show you what you need. The amount of head, or lift, is a big factor in the hp requirement. Sorry, I don't have the chart handy.
 
What kind of pressure are you trying to make at 500 gpm? That is what really determines your hp requirements.

Do you have a pump curve for your pump? That would help make your decision, too.

Last, get a Murphy switch system for your tractor- they are a must for such things. Too hot or no oil pressure, and she'll shut down immediately. They can be the difference between happy7 with a tractor on the pump, or dissatisfied.
 
Back when I was a kid, Dad had a very old DC Case on a PTO pump. I would guess we ran it for well over 8 years, pumping 1200 GPM. Little to no pressure. Just enough to get the water up the hill, then it dumped into an irrigation ditch. The pump was an old Fairbanks, I think. Big enough you could get some nice Blue Gill swimming in the ditch. Pretty sure it never burned more then 3/4 gallon of Propane an hour. Only reason we switched, was he put a pivot in.
The next pump was a WD 45 motor, running a Berkly pump. As long as you were up against pressure, like 120 psi, it would run great and cool. Try open discharge, and it would get hot, and burn valves.
 
Another thing we had trouble with, was the bugs plugging up the radiator. Best thing he ever did was drill a well!!!!
 
It should be fine from a PTO perspective, that is what they are made for.

You need to have the pump curve, know pressure and flow to determine HP required.
 
A centrifugal pump will take the most HP at maximum flow, that is why the HP dropped off when you pinched the outlet down.
 
This relates to a vacuum cleaner.

A question for all, does it draw more amps when you stick your hand over the end, or leave it open?
 

David G has it right. If that 500 GPM pump is moving 500 GPM for any length of time it would be a big load for 55 HP. If it were pumping 50 GPMs at 100 psi it would burn hardly any fuel. You should be able to find out how much your nozzles or whatever flow, at a given pressure and then you can tell how heavily you are loading the tractor. 35 years as a firefighter. The problem with tractors on pumps is lack of auto shut down in case of overheat or loss of oil pressure.
 
(quoted from post at 16:24:32 07/25/14) No it wouldn't.

Used to pump 750 gals all summer long with a M off the belt pulley.

Allan

Well Allan perhaps you did but I have to go by my experience in experimentation with different pumps powered with different engines and using a pitot gauge to get GPM measurements within 10 GPMs. Any given pump will pump its full rated flow with only a very small suction lift and short suction intake and very large and short discharge hose/pipe. When you get any length of discharge pipe or hose the friction reduces flow dramatically so GPMs drops equally, reducing the load on the pump.
 
In reference to the original question, which I did not answer, there should be no harmful effects on your tractor from pumping, you have a different issue.
 
Showcrop,

You are correct with this, because the outlet piping pinches down the outlet and reduces the flow.
 
been many years since school but isn't 1 horse power the amount of energy required to lift 33,000 lbs. of water 1 ft. in 1 minute, less efficiency. have fun playing with numbers, 2.31 ft. is 1 psi and water weighs 8.3 lbs. per gallon
 
(quoted from post at 18:56:38 07/25/14) Back when I was a kid, Dad had a very old DC Case on a PTO pump. I would guess we ran it for well over 8 years, pumping 1200 GPM. Little to no pressure. Just enough to get the water up the hill, then it dumped into an irrigation ditch. The pump was an old Fairbanks, I think. Big enough you could get some nice Blue Gill swimming in the ditch. Pretty sure it never burned more then 3/4 gallon of Propane an hour. Only reason we switched, was he put a pivot in.
The next pump was a WD 45 motor, running a Berkly pump. As long as you were up against pressure, like 120 psi, it would run great and cool. Try open discharge, and it would get hot, and burn valves.

Usually with a centrifugal pump. Throttling the discharge increases the amount of torque required to spin the impeller at the same rpms.
Throttling the intake reduces the torque required to spin the impeller.
Of course if the discharge is blocked or virtually blocked. The centrifugal pump will just whirl the media being pumped. Shaft torque demand will be reduced.
 

As previously stated. If somebody has dumped tap water into the cooling system. A layer of thermal insulating minerals has been added to the inside of the rad.
A fan pulley and belt can "look" fine but be worn and slip. Don't try super tightening the belt. This will tear the water pump bearings and/or the alternator bearings out.
There are many phantom "over heating" problems that are due to a faulty gauge. Or somebody that sees a gauge swung over 2/3 of the way but not in the red. When they are used to seeing the temp gauge just 1/3 of the way over.
Operating the engine at 2/3 speed will reduce cooling airflow .
 
At the pump the gauge is about 100-120 lbs, the main line is uphill about 30-40 ft, and running 20-25 #30 sprinklers through 3 inch pipe 1/4-1/2 mile. If I remember correctly, the gauge at the sprinklers was about a 1/3 of what it read at the pump due to friction loss. I would run the tractor/pump for 90 minutes.
 
We also ran a SC Case on an irrigation well. Ran the belt pulley, pumping just over 1000GPM. Well was only 63 feet deep, and pumping into a ditch. Ran that little tractor for well over 20 years. Pt a set of rings in it once, and ground the valves twice.
 
If I take the 33,000 lbs., and divide it by 60, I would get 550, which is what 1 hp has the value of raising in one second, one ft.
Now if I divide 550 by the gallon weight,(8.3 lbs.),I get 66.3, multiplied by the hp. of the tractor, gives me 3646, my lift figure in feet. This should be the number 55 hp would raise 8.3 lbs or one gallon of water in one second.
Now if I take my lift result of 3646 and multiply it by 10 seconds, my lift would be 36,460 feet in 10 seconds, right?
 
You did not hurt it pumping water, power wise PTO work is PTO work, you could be turning a pump, an ensilage blower or a bush hog and the tractor does not know which is which. Your overheating problem will more than likely be one of the usual suspects, dirt clogging radiator or screen, fan belt wore out, water pump weak, leak etc. I would start by washing out the radiator coils and air passages.
 
David,

It will draw less, less air in the pump to load the impeller.

Here is one I don't understand. A squirrel cage blower, like goes in a central air system... Pull the blower unit out, run it, check the amp load. It will be maxed out, even over amped. Put it back in, providing some back pressure, and the amps drop.

How?
 
Spud, I think there is something to that. More the constant load than constant speed.

In an automotive application, even pulling a heavy load, there are many periods of coasting, which helps with ring and valve guide lubrication.

Put an automotive engine in a marine application, it will be needing a rebuild in 1500 hours or so. Put the same engine in a car or truck, it will last 10 times as long!
 
(quoted from post at 17:20:32 07/25/14) Showcrop,

You are correct with this, because the outlet piping pinches down the outlet and reduces the flow.

Actually it is not so much "pinching down" as friction loss which is a function of distance.
 

Tis the difference between light duty and heavy duty applications.
My truck in round numbers has 160,000 miles and 4,600hrs. Doesn't burn oil and no discernible power loss when towing. It has spent most of it's life making an average of 45HP out of it's potential 300HP.
150hrs sounds awful short even at redline and full throttle. Those engines must have been souped up and maybe even ran on regular gas when they should have had premium.
You can take a GM marine crate engine and wail the tar out of them at full throttle racing around and towing. As long as they don't knock, have clean air and some oil in them. They will run for thousands of hours.
 
It could be either a cooling problem or it could too much load for your tractor. That can not be determined from the information provided. I did a quick Google search for water pump horsepower and found a lot of good sites with online calculators.

I used one online calculator from Washington State University:
120psi pressure
500 GPM flow rate
75 percent pump efficiency =
46.6 brake horsepower.
That would be about 85 percent of your tractor's maximum power, about the maximum continuous load you would want on a 55HP tractor. That is a pretty good match if everything is at face value.

Now into the details:

Are you actually moving 500GPM at 120psi? If 500GPM is the maximum GPM rating of the pump at almost no pressure, you could actually be moving much less flow at 120psi, requiring much less power.

Is your pump rated for 120 psi or more? If it isn't you might be in a less efficient range for the pump, requiring more HP. The pump curves for your model pump would be very helpful. They should be in the operators manual, or from the manufacturer.

Is your tractor rated at 55 PTOHP at the 1500 RPMs you are running it? If the tractor is rated 55 HP at 2500 rpm, a somewhat lower HP at 2100 RPM standard PTO speed, and it is throttled down to run at 1500 RPM, then it would be overloaded trying to turn an actual 46 HP load at only 1500 RPM.

More detailed info would help.

If you have 40 psi at the sprinklers, the 30 to 40 foot rise is 13 to 18 psi, so your friction losses are between 40 to 60 psi, about half your power requirement. Can you take any low cost steps to reduce your friction losses?
 
(quoted from post at 12:02:28 07/26/14) It could be either a cooling problem or it could too much load for your tractor. That can not be determined from the information provided. I did a quick Google search for water pump horsepower and found a lot of good sites with online calculators.

I used one online calculator from Washington State University:
120psi pressure
500 GPM flow rate
75 percent pump efficiency =
46.6 brake horsepower.
That would be about 85 percent of your tractor's maximum power, about the maximum continuous load you would want on a 55HP tractor. That is a pretty good match if everything is at face value.

Now into the details:

Are you actually moving 500GPM at 120psi? If 500GPM is the maximum GPM rating of the pump at almost no pressure, you could actually be moving much less flow at 120psi, requiring much less power.

Is your pump rated for 120 psi or more? If it isn't you might be in a less efficient range for the pump, requiring more HP. The pump curves for your model pump would be very helpful. They should be in the operators manual, or from the manufacturer.

Is your tractor rated at 55 PTOHP at the 1500 RPMs you are running it? If the tractor is rated 55 HP at 2500 rpm, a somewhat lower HP at 2100 RPM standard PTO speed, and it is throttled down to run at 1500 RPM, then it would be overloaded trying to turn an actual 46 HP load at only 1500 RPM.

More detailed info would help.

If you have 40 psi at the sprinklers, the 30 to 40 foot rise is 13 to 18 psi, so your friction losses are between 40 to 60 psi, about half your power requirement. Can you take any low cost steps to reduce your friction losses?

Decreasing friction loss would increase gallonage which will increase the HP requirement. The tractor has been able in the past to handle the job because of the amount of friction loss.
 

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