Mod for hydraulic pump?

[Tchamp]

I have a 2001 PT 2422 that has the Subaru engine 25 hp. It came new with the 22 hp but since was upgraded.

My auxillary pto - steering pump assembly is a 8 gpm 2500 psi gear pump.
My question is when I replace the pump assembly which is weak, I am thinking of putting a 10 gpm 2500 psi pump to replace the old. The difference in the required hp for the 10 gpm on the new pump is 3 hp which I already have from the new 25 hp Subaru. The attachments from Power Trac are rated from 8- 12 gpm.
I shouldn’t have to worry about power loss for the rest of the machine since it was running on 22 hp from the factory.

I’m thinking that I can upgrade my pump, and in return have better flow for a more diverse attachments from the aftermarket, brush hog, stump grinder, etc and have better results from that which I already have since the pumps on the attachments are rated for 8-12 gpm.

Am I thinking on the right track? Looking for any input before I do this in about 2 weeks. The only downside I can think of is when starting the motor i may have to put a higher amp battery and or a high output starter to spin it over faster.

 

[agjones]

You may have considered /some any of the following already...

For baseline comparison, you might want to check w Terry the cost to rebuild/swap the existing pump.

Confirm that the 2001 22hp version used 2500psi as the working pressure. 2000psi is also possible.

In general, you seem on the right track, consider: that more flow will produce more heat (potential power loss) in the hydraulic system and the stall point on that engine is hovering over your head anytime you are working close to max psi.

The mini skidsteer standard, 10 gpm@3000psi things like dingos use with engines in a similar power curve perform well. They generally give up travel for power.

 

[Tchamp]

You may have considered /some any of the following already...

For baseline comparison, you might want to check w Terry the cost to rebuild/swap the existing pump.

Confirm that the 2001 22hp version used 2500psi as the working pressure. 2000psi is also possible.

In general, you seem on the right track, consider: that more flow will produce more heat (potential power loss) in the hydraulic system and the stall point on that engine is hovering over your head anytime you are working close to max psi.

The mini skidsteer standard, 10 gpm@3000psi things like dingos use with engines in a similar power curve perform well. They generally give up travel for power.

I hav thought about the heating issue and am going to install a larger oil cooler to compliment the other one that is on there as well. My oil capacity is only 5 gal on this unit so I really want to keep the oil cool .

I have confirmed with terry and he said that I could probably run up to a 12 gpm pump as long as I was willing to trade off the speed . I chose 10 gpm because I didn’t think I would be losing any of the speed it was originally designed for. But I am liking the idea of more POWER lol

 

[agjones]

Sounds good. Smart to add cooling capacity, especially in Georgia!

Increased flow on that circuit is faster tool speed (work), your force remains limited to 2500 psi.

 

[Tchamp]

Sounds good. Smart to add cooling capacity, especially in Georgia!

Increased flow on that circuit is faster tool speed (work), your force remains limited to 2500 psi.

Yes, I can adjust the pressure settings up some if I choose but don’t think it’s necessary. I will have to reset them because when I was diagnosing the pump I actually tried to increase The max pressure on the check valves so they aren’t spot on at 2500 now I don’t know where they are because the pumps max output was 1500 psi. I could adjust the pressure down on them but it stopped at 1500 with the pressure regulator check valvewhen I adjusted them upward. I also switched them around to see if it would make a difference which it did not.

 

[BigDaddyEureka]

+1 on agreeing that you're on the right track thinking this through. The only thing that hasn't been discussed is "tank turns" - or how often the total volume of the tank flows through working system per unit time. If your tank turns get too low then heat will build up even faster. You've thought of an improved cooler - an excellent idea! - and in general PT tends to run fairly large tank turns so you're probably going to do fine.

A very coarse rule of thumb is that for a high duty cycle machine like a medium wheel loader, you want your tank turns between 5 and 10 per minute. If you get down to 3 you either need a VERY large and effective cooler relative to the system volume or you need to reduce the duty cycle somehow to give the cooler time to catch up and manage the total thermal mass in the tank / system. If you get below 1.5 you run the risk of temperature-related cavitation due to boiling the oil in the circuit before it reaches the cooler. THIS IS NOT GOOD, and booger to troubleshoot, and to be avoided at all costs. More than 10 tank turns / minute is nice, but sometimes excessive and can be a problem in low ambient conditions (far north, Siberia, etc.) because you never really get the machine up to operating temperature and the thick oil isn't great for certain pumps.

Probably more than you wanted, but thought i'd offer what I know. Seems like you're on the right track so far!

 

[agjones]

+1 on agreeing that you're on the right track thinking this through. The only thing that hasn't been discussed is "tank turns" - or how often the total volume of the tank flows through working system per unit time. If your tank turns get too low then heat will build up even faster. You've thought of an improved cooler - an excellent idea! - and in general PT tends to run fairly large tank turns so you're probably going to do fine.

A very coarse rule of thumb is that for a high duty cycle machine like a medium wheel loader, you want your tank turns between 5 and 10 per minute. If you get down to 3 you either need a VERY large and effective cooler relative to the system volume or you need to reduce the duty cycle somehow to give the cooler time to catch up and manage the total thermal mass in the tank / system. If you get below 1.5 you run the risk of temperature-related cavitation due to boiling the oil in the circuit before it reaches the cooler. THIS IS NOT GOOD, and booger to troubleshoot, and to be avoided at all costs. More than 10 tank turns / minute is nice, but sometimes excessive and can be a problem in low ambient conditions (far north, Siberia, etc.) because you never really get the machine up to operating temperature and the thick oil isn't great for certain pumps.

Probably more than you wanted, but thought i'd offer what I know. Seems like you're on the right track so far!

Great info thx for the depth.

 

[Tchamp]

Great info thx for the depth.

Not sure if possible to have the flow you are describing, if my pump is a 10 gpm and I have a 5 gal reservoir then it will only move the fluid through twice in 1 Min Time, am I correct?

I know that the fluids get pretty warm pretty fast on my unit I have, I was attributing it to the weak pump and the small reservoir.

 

[MossRoad]

Not sure if possible to have the flow you are describing, if my pump is a 10 gpm and I have a 5 gal reservoir then it will only move the fluid through twice in 1 Min Time, am I correct?

I know that the fluids get pretty warm pretty fast on my unit I have, I was attributing it to the weak pump and the small reservoir.

You have to remember that you have 2 continuously running PTO pumps (the MAIN PTO and the AUX PTO/STEERING/FEL pumps), PLUS the tram pump.

Whether you're doing any work or not, the pumps are always pumping oil through the system. They cannot be turned off. And they are always generating heat just by friction moving through the systems. Add work to the load, like a brush cutter or mower motor, and the heat starts to build just from the blades pushing air. Then throw some grass or brush resistance to the blades and the heat increases rapidly.

So you can figure the total flow of both your MAIN and AUX PTO pumps into your tank return cycles that are being discussed. I think my MAIN is 8GPM and my AUX is 4GPM, but I'd have to check with Terry to be sure. So that would be 12 GPM through the tank. The tank on my machine is 10 gallons.

I'd need over a 50 gallon tank to get a bit over 4 of these tank turnovers.

 

[MossRoad]

Not sure if possible to have the flow you are describing, if my pump is a 10 gpm and I have a 5 gal reservoir then it will only move the fluid through twice in 1 Min Time, am I correct?

I know that the fluids get pretty warm pretty fast on my unit I have, I was attributing it to the weak pump and the small reservoir.

If you pump 10 gallons through a pump from a 5 gallon reservoir, you're going to drain the tank twice a minute. That is correct math.