Valve leak down

[J_J]

Any oil at cold temperatures will not flow as fast as when hot, and on a driven pump, the oil will heat up quickly. Pressure in a system is caused by some kind of resistance to the pump, whether it is a closed valve, a cylinder, or a motor. The pressure will vary as you use the system. An example of a system with the pump running max rpm and very little pressure, would be the PTO pump. When not in use, the fluid is pumped through the on/off valve and back to tank. Very little pressure would be generated. Now if the PTO valve were switched on, and you had a hydraulic motor is the circuit, the motor becomes the resistance, and the pressure will develop as you control the flow. In my case, I use a lever to vary the PTO speed. Some of you have a solenoid to activate the PTO, and you can't regulate the speed except by changing the speed on the engine. I was surprised at the pressure on the lift arms when raising them with no load. My gage read very low pressure. As soon as you pick up a heavy load, the pressure climbs up close to max. You will also get spikes that may go above the rated pressure when things are suddenly changed.

 

[J_J]

Any oil at cold temperatures will not flow as fast as when hot, and on a driven pump, the oil will heat up quickly. Pressure in a system is caused by some kind of resistance to the pump, whether it is a closed valve, a cylinder, or a motor. The pressure will vary as you use the system. An example of a system with the pump running max rpm and very little pressure, would be the PTO pump. When not in use, the fluid is pumped through the on/off valve and back to tank. Very little pressure would be generated. Now if the PTO valve were switched on, and you had a hydraulic motor is the circuit, the motor becomes the resistance, and the pressure will develop as you control the flow. In my case, I use a lever to vary the PTO speed. Some of you have a solenoid to activate the PTO, and you can't regulate the speed except by changing the speed on the engine. I was surprised at the pressure on the lift arms when raising them with no load. My gage read very low pressure. As soon as you pick up a heavy load, the pressure climbs up close to max. You will also get spikes that may go above the rated pressure when things are suddenly changed.

 

[KentT]

</font><font color="blue" class="small">( So you see a big difference using 20W50 when you changed out. I will have to consider that. Guess there would be no added pressure according to J.J with the thicker oil. I would think it would be harder on the pumps, especially during colder weather?. Since I will be going to a 6 ply tire soon, I could sure use the extra torque.
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That's why the use of synthetic instead of Dino. 15W50 synthetic is likely no "harder" to pump when cold than 10W30 or 10W40 dino oil. The real difference is when it is hot... which is EXACTLY what you're looking for. With no oil cooler, I'd think the difference would be even more noticeable on a PT-180... but I have no firsthand experience. /forums/images/graemlins/wink.gif

 

[KentT]

</font><font color="blue" class="small">( So you see a big difference using 20W50 when you changed out. I will have to consider that. Guess there would be no added pressure according to J.J with the thicker oil. I would think it would be harder on the pumps, especially during colder weather?. Since I will be going to a 6 ply tire soon, I could sure use the extra torque.
)</font>
That's why the use of synthetic instead of Dino. 15W50 synthetic is likely no "harder" to pump when cold than 10W30 or 10W40 dino oil. The real difference is when it is hot... which is EXACTLY what you're looking for. With no oil cooler, I'd think the difference would be even more noticeable on a PT-180... but I have no firsthand experience. /forums/images/graemlins/wink.gif

 

[Barryh]

On the synthetic verses dino, those were exactly my thoughts knowing I have no oil cooler. The only thing undecided as of yet is Amsoil over Mobil 1 and the cost. Anywho, I know this has been hashed out before. I don't want to take away from the valve topic. Thanks for your insight on the difference in performance.

 

[Barryh]

On the synthetic verses dino, those were exactly my thoughts knowing I have no oil cooler. The only thing undecided as of yet is Amsoil over Mobil 1 and the cost. Anywho, I know this has been hashed out before. I don't want to take away from the valve topic. Thanks for your insight on the difference in performance.

 

[Barryh]

Thanks for clearing that up. More good information to log away. /forums/images/graemlins/smirk.gif

 

[Barryh]

Thanks for clearing that up. More good information to log away. /forums/images/graemlins/smirk.gif

 

[Spiffy]

</font><font color="blue" class="small">( <font color="red"> Whether the leak down happens over minutes hours or weeks, I don't see any difference in safety. </font>

Your right but, I must admit it's nice when working with heavy objects, to be able to take things in and out of the bucket, or off of the forks with the machine off that is. Guess I need to constantly keep in mind sudden let down in pressure could result in a broker leg or worse. Good topic for safty concerns.
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Exactly! Unless the leak down occurs over seconds (in which case hydraulic control would be really annoying), I can't see where they can claim the leak down as a safety issue. So I'd like to be able to have the bucket or forks where I left them - even if I want to finish unloading after lunch!

 

[Spiffy]

</font><font color="blue" class="small">( <font color="red"> Whether the leak down happens over minutes hours or weeks, I don't see any difference in safety. </font>

Your right but, I must admit it's nice when working with heavy objects, to be able to take things in and out of the bucket, or off of the forks with the machine off that is. Guess I need to constantly keep in mind sudden let down in pressure could result in a broker leg or worse. Good topic for safty concerns.
)</font>

Exactly! Unless the leak down occurs over seconds (in which case hydraulic control would be really annoying), I can't see where they can claim the leak down as a safety issue. So I'd like to be able to have the bucket or forks where I left them - even if I want to finish unloading after lunch!