8N Hydraulic pressure

rickdude · Jul 27, 2015

How much pressure is required in the 3 Pt lift system to lift an 800 lb load? From what I have read 800 Lbs is about the max an 8N could lift without bringing the front wheels off the
ground. The reason I ask is in line with using an aux pump to supply live hydraulics through the test port fitting, as in how much pressure is actually required for normal lift use. What
would happen if the aux pump used only put out 1000 or 1200 psi, would the lift be super slow, or not work at all? If the relief valve cracks at 1500 psi then an aux pump would be
running in bypass most of the time if it supplied more than 1500 psi. Has anyone run a pressure gauge on their aux pump while using the lift?

old · Jul 27, 2015

Many factors come into play on something like that. A pump does not make pressure the cylinder it feeds is what causes the pressure. The pump does make flow so how many GPM the pump is make a difference as to how fast things get lifted an the pressure relief valve does the regulating of how much pressure the system can build up to. The factory pump is a low GPM pump so if say the live pump you put on is an 8GPM pump the lift will in fact come up a whole lot faster

rickdude · Jul 27, 2015

If I understand the system correctly with an aux belt driven gear type pump it would be pushing fluid through the relief valve all the time, and would give you 1500 PSI or whatever the valve is set to crack at. Once the control lever moves to put a demand on the system the lift moves using fluid from the 1500 psi stream then goes back into bypass once the lift reaches the set position.
Can anyone confirm, or am I out to lunch.

ZANE · Jul 27, 2015

Wrong!
The lift when in neutral position has no pressure on the relief valve. When the lift is at a given height the exhaust valve is partially open allowing just enough flow to bypass to maintain that position.

The relief valve is there to prevent over pressurizing the system. If the relief valve were not functioning and closed the pump would burst or a gasket would blow. Same thing if there is a shock load such as that 800 pound bouncing. Even with a good relief valve the pump could burst or blow a gasket etc. Don't ever even try to carry an 800 pound load such as big roll of hay. Lifting it is one thing, carrying it is another.

Zane

old · Jul 27, 2015

No it would not be pushing fluid by the relief all the time but yes if over what the relief is set at it would when it had demand for pressure to build up

rickdude · Jul 27, 2015

Ok, thanks for the correction Zane. To go back to my original question, what kind of pressure would an aux pump put out under normal working conditions with a 3 pt lift?

TheOldHokie · Jul 27, 2015

(quoted from post at 15:41:12 07/27/15) Ok, thanks for the correction Zane. To go back to my original question, what kind of pressure would an aux pump put out under normal working conditions with a 3 pt lift?

Depends on how you have it plumbed.

For the 3pt lift the pressure is limited by the internal relief valve setting of 1500 PSI. In other words the external hydraulic pump will never produce more than that at the 3pt lift cylinder.

For an external valve installed upstream of the test port the relief setting is whatever the external valve is set at. If the external valve is set to 2000 PSI then that is the maximum your external cylinder will see and the 3pt wioll still be limuited to 1500 PSI. Likewise if you have the externakl valve set at 1000 PSI that will have priority over the internal relief valve and the 3pt will never see more than 1000 PSI.

TOH

TheOldHokie · Jul 27, 2015

(quoted from post at 13:44:39 07/27/15) Many factors come into play on something like that. A pump does not make pressure the cylinder it feeds is what causes the pressure. The pump does make flow so how many GPM the pump is make a difference as to how fast things get lifted an the pressure relief valve does the regulating of how much pressure the system can build up to. The factory pump is a low GPM pump so if say the live pump you put on is an 8GPM pump the lift will in fact come up a whole lot faster

If you send 8 GPM to the test port not only will the lift come up faster you won't get it to go down. The maximum the exhaust valve in the OEM pump can handle is roughly 3 GPM. More than that will cause significant back pressure in the lift circuit that will hold it in the raised position even with the lift control fully down.....

TOH

8N Hydraulic pressure

rickdude

Member

old

Well-known Member

rickdude

Member

ZANE

Well-known Member

old

Well-known Member

rickdude

Member

TheOldHokie

Well-known Member

TheOldHokie

Well-known Member

Similar threads