DPOCV supplier

[oldnslo]

Also, I've heard the term "chatter" bandied about in regard to DPOCV's. What causes it, and what's the cure?

And thanks again to you guys for the education. :thumbsup:

"Chatter" comes from the POC loosing pilot pressure. Example: cylinder mounted vertical with rod down with a Load hanging on the rod. Once the check is piloted open the load wil cause the cylinder to "freefall" until pilot pressure is lost. then the POC closes. pilot pressure rebuilds, valve opens and the cycle repeats. In extreme cases the cylinder and load will actually bounce.

Pilot ratio: This can be a can of worms to explain but will give it a try.

ratio (rod up) = Rod End area x MWP
(Cap end area x MWP) - load

MWP = Max Working Pressure

Reverse the formula for rod down applications.


In Rod Down application be very careful if there are large loads being supported. You may require a higher pilot ratio than expected.

Roy

 

[J_J]

I believe they reduce the chatter by either slowing down valve activation, or installing an orifice inline.

 

[oldnslo]

I believe they reduce the chatter by either slowing down valve activation, or installing an orifice inline.

Both will work IF the valve has meter out control. Orifice must also be sized to create enough back pressure to hold the load under all conditions.

Roy

 

[AKKAMAAN]

Ok, but on the Brand PC valve you pointed out (photo one) the pilot port would still have get cracking pressure from the other end of the cylinder, so it would have to be teed into the capped side of the cylinder. Right?

If so, then the single piloted check in photo two would do exactly the same thing, although because the pilot fluid's path is internal, the valve and its external plumbing would still look like the usual top link DPOCV setup (photos three and four). However, the valve itself should naturally be somewhat cheaper than the double version, and only one end of the cylinder would be locked. Correct?

Sorry for the high density of my brain cells on this subject. I've worked in electronics for 50 years, so I can do that in my sleep, but I've only played with hydraulics for a few weeks, and it's like first year algebra to me. :laughing:

This one will do the same as the Brand one....I like this one better...

 

[AKKAMAAN]

"Chatter" comes from the POC loosing pilot pressure. Example: cylinder mounted vertical with rod down with a Load hanging on the rod. Once the check is piloted open the load wil cause the cylinder to "freefall" until pilot pressure is lost. then the POC closes. pilot pressure rebuilds, valve opens and the cycle repeats. In extreme cases the cylinder and load will actually bounce.

Pilot ratio: This can be a can of worms to explain but will give it a try.

ratio (rod up) = Rod End area x MWP
(Cap end area x MWP) - load

MWP = Max Working Pressure

Reverse the formula for rod down applications.


In Rod Down application be very careful if there are large loads being supported. You may require a higher pilot ratio than expected.

Roy

Good post Roy!
Thanks for the extra attention about that!!