curious

[jcottons]

i see alot of tnt cylinders without the dpcv (double piloted check valve), are they that big of a deal or does it even matter?

 

[J_J]

Perhaps a check valve is a better way of sealing off cyl leakage than the spool in a valve.

Parker hyd says this: Positive shut-off is provided by a hardened poppet and cage assembly.

Another source says this: USE AND OPERATION
Pilot check valves are used to block the cylinder in both directions. Flow is free in one direction and blocked in the reverse
direction until pilot pressure is applied.

It is just another way for the 3pt setting to stay set and not drift.

It does not prevent the cyl leaking internally.

Depending on load, the pressure must overcome the imposed force/psi caused by the implement to move the cyl .

 

[MtnViewRanch]

i see alot of tnt cylinders without the dpcv (double piloted check valve), are they that big of a deal or does it even matter?

There are positive and negatives to most everything. I personally do not have them on my "TnT" cylinders and do not sell them with any DPOCV. My experience has been that with my cylinders in use that the rod will drift about 1/8"-1/4" in about an hours use. Is that a big deal? Not for me, and not for anyone that is grading and making adjustments every few minutes.

Depending on the type of control valve you may have, but if you have the float position, there are circumstances where it is beneficial to be able to put your hydraulic side link in float mode. If you have the DPOCV, YOU CANNOT DO THIS FUNCTION.

You ask if it is that big of a deal, apparently not. If it was, I would think the the OEM's would have them on their factory "TnT" sets. None of them do as far as I know of. Not JD, not Kubota, not Case, not Massey, not even Cat. Not one of them use the DPOCV on their top and tilt cylinders.

Don't get me wrong, there is a place for their use. I would think in farming, but when it comes to grading, it just is not that big of a deal. If the drifting is excessive, then there is a good chance that the control valve should be either rebuilt or replaced.

 

[SPYDERLK]

There are positive and negatives to most everything.
Depending on the type of control valve you may have, but if you have the float position, there are circumstances where it is beneficial to be able to put your hydraulic side link in float mode. If you have the DPOCV, YOU CANNOT DO THIS FUNCTION.

This is a KEY point. Many, when choosing to have a full function setup could miss this.
larry

 

[MtnViewRanch]

This is a KEY point. Many, when choosing to have a full function setup could miss this.
larry

Many many people have no idea of the possibilities that they can have and what they can do with Top and Tilt hydraulics. I still can't get over how many people have a tilt cylinder and do not have them setup so that they would be able to tilt an equal amount in both directions. :confused2: Now some manufacturers do not build them that way, and on some of the sub cuts it is not practical to have that capability. But in general there is no good reason on a CUT size and bigger tractor to not have the ability to tilt an equal amount to the left and right.

 

[J_J]

DPOC OR LOCK VALVE.

If someone wanted this valve for a reason, maybe safety, it could be installed whenever.

Here is the valve in 1/2 ports and 3/4 ports.

Surplus Center - LOCK VALVE 1/2" NPT 25 GPM 3000 PSI

Surplus Center - LOCK VALVE 3/4" NPT 30 GPM

http://www.surpluscenter.com/adspecs/AS9-5606-75.pdf

Even these valves are not zero leak free. The seating is steel on steel.

 

[oldnslo]

i see alot of tnt cylinders without the dpcv (double piloted check valve), are they that big of a deal or does it even matter?

Typical use of a DPCV is where unwanted cylinder movement is a safety issue.

Examples: Back hoe stabilizers, scissor lift plat forms, etc..

 

[jcottons]

thanks guys!..i hae seen some without (mine has one)..i was just wondering..thanks for all the info. Now i know

 

[J_J]

Well then, when using the T-N-T, does the implement stay where you put it, and if it does, that is what it is supposed to do. Valves can leak, and they say check valves are better.

 

[MtnViewRanch]

Well then, when using the T-N-T, does the implement stay where you put it, and if it does, that is what it is supposed to do. Valves can leak, and they say check valves are better.

A DPOCV hinders all the possibilities that can be had with top and tilt cylinders without the check valves. Yes they move, it is so minute that it just does not really make a difference. If the cylinder moves enough that it causes a problem, then most likely the control valve should be rebuilt or replaced. Yes the DPOCV usually takes care of the drift problem. But by having the check valve, you now give up the ability to have and use a float position. If a persons main use is for farming, then yes get the cylinders with the DPOCV on them. But for about everything else, it just is not that big of a deal. I know that there are many people that disagree with me and that is fine. What I do know is that ALL as far as I can tell OEM machines that offer top and tilt cylinders DO NOT have any DPOCV on their cylinders. Now these cylinders are usually purchased with a tractor that is going to be used for grading. When you are grading, there are situations when you need to use float mode with the side link to get the best possible result. You CAN NOT do this with a cylinder that has a DPOCV. Most landscapers are continuously adjusting the implement to get a good result anyway, so what difference does it really make if the cylinder drifts down 1/16" between adjustments? In reality it makes no difference. But for those that feel that it is a concern or for some where it does present a problem, then by all means they should use a DPOCV.