G
George Ghio
- Jan 1, 1970
- 0
OK now.
Hydraulics and the fantasy of Wayne:
A spool valve is a block of steel or iron. It has a hole in it. The
spool resides in this hole.
The hole has annular ports in it. The spool has lands spaced along it.
The spool slides inside the hole, as the spool is moved in one dierction
or the other the lands open and close the annular prots in the body of
the valve.
(See 3.jpg <http://community.webshots.com/album/197368503CupbKm>
This type of valve has a seal at each end of the body. These seals keep
the oil inside the valve (mostly). There are no seals between the
annular ports. If there were they would be damaged by the passage of the
lands on the spool.
There is a constant internal leakage between the spool and the body of
the valve.
If a spool valve is used to extend a piston vertically and then the
valve is returned to its neutral position the internal leakage will
allow the piston to retract. The speed of this downward movement depends
on several factors:
1) The tolerances between the body and spool
2) The viscosity of the oil
3) The temperature of the oil (hot oil gets thiner)
4) The weight on the piston
As can be seen these factors all affect the internal leakage of this
type of valve. It cannot be otherwise because there are no seals between
the annular ports in this type of valve.
The only way to stop the piston fram slowly decending is to use a pilot
opreated check valve. A check valve is a positive seal. A spool valve is
not.
As much as Wayne twists and weasels and makes silly statements about the
pressure relief valve, a spool valve is a constant loss system.
The fact that (nearly) all the losses are due to internal leakage makes
no difference.
Once you return the valve to its neutral position any pressure in the
ports fades away.
This is the nature of spool valves. There is no positive sealing between
the ports.
Have a look at;
http://community.webshots.com/album/197368503CupbKm
I am afraid that Waynes grasp of the mechanics of hydraulics is as
tenuous as his grasp of his solar power system, welding, writing and
fencing.
I am sorry that Wayne can't accept his limitations and insists on
pursuing his nonsense trying to score points here. The fact remains that
he is spreading dangerous misinformation.
This has been a public service safety announcement.
George
Hydraulics and the fantasy of Wayne:
A spool valve is a block of steel or iron. It has a hole in it. The
spool resides in this hole.
The hole has annular ports in it. The spool has lands spaced along it.
The spool slides inside the hole, as the spool is moved in one dierction
or the other the lands open and close the annular prots in the body of
the valve.
(See 3.jpg <http://community.webshots.com/album/197368503CupbKm>
This type of valve has a seal at each end of the body. These seals keep
the oil inside the valve (mostly). There are no seals between the
annular ports. If there were they would be damaged by the passage of the
lands on the spool.
There is a constant internal leakage between the spool and the body of
the valve.
If a spool valve is used to extend a piston vertically and then the
valve is returned to its neutral position the internal leakage will
allow the piston to retract. The speed of this downward movement depends
on several factors:
1) The tolerances between the body and spool
2) The viscosity of the oil
3) The temperature of the oil (hot oil gets thiner)
4) The weight on the piston
As can be seen these factors all affect the internal leakage of this
type of valve. It cannot be otherwise because there are no seals between
the annular ports in this type of valve.
The only way to stop the piston fram slowly decending is to use a pilot
opreated check valve. A check valve is a positive seal. A spool valve is
not.
As much as Wayne twists and weasels and makes silly statements about the
pressure relief valve, a spool valve is a constant loss system.
The fact that (nearly) all the losses are due to internal leakage makes
no difference.
Once you return the valve to its neutral position any pressure in the
ports fades away.
This is the nature of spool valves. There is no positive sealing between
the ports.
Have a look at;
http://community.webshots.com/album/197368503CupbKm
I am afraid that Waynes grasp of the mechanics of hydraulics is as
tenuous as his grasp of his solar power system, welding, writing and
fencing.
I am sorry that Wayne can't accept his limitations and insists on
pursuing his nonsense trying to score points here. The fact remains that
he is spreading dangerous misinformation.
This has been a public service safety announcement.
George