Can you overload a hydraulic pump?

[Shadow_storm56]

Simple question that I'm pretty sure I know the awnser to but I wanted to check anyway. Say your tractors hydraulic pump puts out 20GPM, You are running multiple hydraulic motor that can easily pull over that if running at full speed. So as a result your pump is outputting it's max flow for extended periods. Aside from overheating is there any risk to damaging the pump? Thanks!

 

[BruceP]

I would think that max PRESSURE would generate heat and could damage pump.... max FLOW would not harm the pump.

Beware that some hydraulic pumps are far more complicated... they have 'feedback' which regulates flow/pressure at the distribution point so the implements 'share' appropriately without inadvertent movement nor undue wear on the pump.

For example: If running a mower on 3pt hitch. The mower requires lots of FLOW... but when you change the height of the hitch, you may not want to mower to loose speed.

 

[Shadow_storm56]

I would think that max PRESSURE would generate heat and could damage pump.... max FLOW would not harm the pump.

Beware that some hydraulic pumps are far more complicated... they have 'feedback' which regulates flow/pressure at the distribution point so the implements 'share' appropriately without inadvertent movement.

For example: If running a mower on 3pt hitch. The mower requires lots of FLOW... but when you change the height of the hitch, you may not want to mower to loose speed.

This has manual flow regulators, for the 2 aux hydraulics. But it does have some stuff like that. The steering, the loader and the 3 point all have priority over the rear aux ports. So if you have a hydraulic motor running on the back and move your loader then the loader acts completely normal but the motor on the back will slow or even stop for a second.

Also that's good, I have a specialized manure spreader that has 2 hydraulic motors, one for the side thrower chain and a really big and slow one for the bed chain. Both at full speed can pull 30gpm total but the bed chain runs at about half or less speed so it will essentially talk the tractors full 20gpm to run it. It was an old crank style manure spreader for the bed chain that we converted to hydraulic. The crank styles just blow apart.

 

[ruger1980]

The pumps cannot produce more "flow" than their maximum displacement at any specific rpm.
Hydraulic circuits have some sort of protection built in. It could be a simple pressure relief valve, a pressure compensator or limiter or one any number of other pump regulation devices. Running at maximum output can shorten the life of a pump compared to running at partial load just like running any device at full load.

Running with either contaminated, aerated, insufficient, overheated, or fluid of to low a viscosity will cause more damage than running heavily loaded.

But we really don't have much detail on you're hydraulic circuit. Is this an OEM design or something someone has created?

 

[North Idaho Wolfman]

Say your tractors hydraulic pump puts out 20GPM, You are running multiple hydraulic motor that can easily pull over that if running at full speed!

Won't /cant happen, the only damage your going to do is to the equipment motor or the equipment itself.
Like Ruger said you tractor can't produce more GPM than it's rated for.
In fact most produce less, and if your looking at your tractors overall GPM, usable won't be that because other systems will take away from the total.

Motor loads also create a lot of heat, and without the proper flow they create more heat thus damaging it and possibly the tractor if it gets too high, or the implement will simply not work, or work up to it's potential.

 

[North Idaho Wolfman]

Running at maximum output can shorten the life of a pump compared to running at partial load just like running any device at full load.

Open systems run at full GPM output all the time.

 

[Shadow_storm56]

Won't /cant happen, the only damage your going to do is to the equipment motor or the equipment itself.
Like Ruger said you tractor can't produce more GPM than it's rated for.
In fact most produce less, and if your looking at your tractors overall GPM, usable won't be that because other systems will take away from the total.

Motor loads also create a lot of heat, and without the proper flow they create more heat thus damaging it and possibly the tractor if it gets too high, or the implement will simply not work, or work up to it's potential.

Yea motor loads do produce heat I'm aware, it's on a spreader so theres cooling time between loads.

 

[Shadow_storm56]

All good and helpful replies so thanks

 

[ruger1980]

Open systems run at full GPM output all the time. ]

Not necessarily true. We manufacture equipment with open center systems that only flow what is needed to satisfy the functions activated. There many types of systems out there.

What would be more accurate is to say fixed displacement pumps will flow a fixed amount in relationship to its speed.

 

[GreensvilleJay]

simple answer ...no....
a 20 GPM pump will max out at 20 GPM.

It was explained to me this way...

Say you've got 20, $1 bills in your pocket. It doesn't matter how many times you pull them out, or how many at a time, you've ONLY got $20.

 

[BAP]

Hit wrong button

 

[Tx Jim]

Open systems run at full GPM output all the time. ]

Not necessarily true. We manufacture equipment with open center systems that only flow what is needed to satisfy the functions activated. There many types of systems out there.

What would be more accurate is to say fixed displacement pumps will flow a fixed amount in relationship to its speed.

May I ask what type equipment you manufacture & what is different about type of OC hyd system you utilize?

 

[ruger1980]

Well the company I work for manufactures construction equipment. But I have worked on many different types and brands of equipment in my past. Most modern hydraulic excavators use an open center system utilizing variable displacements pumps with some sort of pump regulation to control output to the main control valve.
Basically two variable displacement axial piston pumps running at minimum displacement with that flow running through the main control valve and back to tank. Once a function is activated then pump regulation increases flow in accordance to demand. The systems are much more complicated than what you would see on your tractor

There are other types of systems but this has been the most popular for most small to large sixed excavators I have worked on. Compact excavators can be very different though.

 

[North Idaho Wolfman]

Open systems run at full GPM output all the time. ]

Not necessarily true. We manufacture equipment with open center systems that only flow what is needed to satisfy the functions activated. There many types of systems out there.

What would be more accurate is to say fixed displacement pumps will flow a fixed amount in relationship to its speed.

KUBOTA tractors use an simple open center pump system, so it flows full all the time, but yes it is in relation to motor speed, as that is what is driving the pump.
I know there are other systems out there, but the conversation and my answer is based on the use not all other equipment systems available.

 

[lugbolt]

pressure is restriction to flow

pressure=heat if you run continually at, say 20gpm at, say, 3000 engine rpm and 2500 psi continually you better have a way to cool that fluid. Hydraulic motors are real good at cooking hydraulic fluid!

secondly the gpm rating is at a certain pressure. As time goes on and components wear, the gpm rating will drop off. Essentially they produce their rated gpm at certain pressure when brand new and performance drops off from there. There are two tests for a hydraulic system that are important. flow and pressure. They kinda go together in a similar fashion as horsepower and torque and people argue about those all the time. Good way to start a war!

to the op heat is going to be the biggest enemy.

If your motors pull more than the pump pumps, they will be weaker and slower than they should be and the fluid will get hot quick. cooler is your friend.....I wish I coulda got the place I used to work for to push putting coolers on SVL's but no....all they wanted was the sale.

 

[whitetiger]

Simple question that I'm pretty sure I know the awnser to but I wanted to check anyway. Say your tractors hydraulic pump puts out 20GPM, You are running multiple hydraulic motor that can easily pull over that if running at full speed. So as a result your pump is outputting it's max flow for extended periods. Aside from overheating is there any risk to damaging the pump? Thanks!

I keep seeing this comment about a hydraulic motor "pulling" hydraulic oil. If the motor could pull oil, it would not need a pump to supply it. The motor is just a restriction to the flow and it gets what the pump can supply, no more.

 

[GreensvilleJay]

re: hydraulic motor that can easily pull

hmmm that's got me thinking.. consider a motor driving say a bushhog blade or a spreader beater blade. There's a LOT of inertia in the rotating blade so how do they protect the motor when you close off the control valve feeding the oil to the motor. Since no more oil can flow in-out,but the shaft is still spinning.
I'm assuming bypass system ?
I know some 'units' can be used either as motor OR pump, leads to more hmmmms.

 

[ruger1980]

A lot depends on the design of the system but usually they will incorporate an anti-cavitation or check valve that will allow the oil to recirculate to eliminate or at least reduce the cavitation that can occur.