Ripping with Hyd Top Link

[Rowski]

Not sure about this if this is what CCI meant. A shock load in hydraulic system on the tractor side of the pilot valve, from the FEL or other remote operated device. The shock loads on the cylinder side of the pilot valve should not make the cylinder move. Kind of like a diode in an electrical system.

 

[Glenn9643]

On the Prince page you referenced, in the small print is tells you the pilot ratio is 4:1.
Here is a link to another mfgr indicating 4:1 pilot ratio with varying available crack pressures: http://www.normanequipment.com/downloads/Snap_Tite_catalog.pdf

Seems to me that the amount of pressure required to allow flow of fluid increases with the load on the cylinder, which would make sense.
This is another mfgr description that may help:
http://www.hydraforce.com/Directnl/Dir-pdf/4-250-1.pdf

 

[JerryG]

A regular pilot operated check valve such as the one on a HTL has nothing to do with shock load in the cylinder. The pilot pressure does have to be able to compensate for system variance such as surges. If another valve in the system is operated the system with have a surge of some amount. This surge or variance is one of the things that the pilot is adjusted for. In Mark’s example of 500 pounds of pilot pressure, when the valve is moved that operates the cylinder in question, the line pressure must build to 500 pounds of pressure before the pilot will open the check and let the fluid flow the move the cyl

 

[HayDR]

Jerry's explanation is the most concise. Guys, Don't make it too hard or we all will get a headache and we'll have to send for Nomad..LOL. Maybe JimMC can shed some light on the subject since he is the engineer and I'm just a barnyard engineer.

 

[JimMc]

Just got in from a family wedding, so I may not make much sense, but here goes.

The easy way to look at this is that until the pilot operated check valve sees "X"psi on the intake side of the cylinder, it does not open the exhaust side of the cylinder and allow fluid to exit that side. (It is important to block the exhaust side when attempting to hold a given position because with the intake only blocked, the cylinder can still move by pulling a vacuum (negative pressure) on the intake side. This is really a bad thing as contaminants can be pulled into the system and seals can be damaged by the generation of a great enough vacuum.) This means that there must be pressure from outside of the cylinder (which normally would only come from the operator opening a valve) before the cylinder can move. The "dual" part is important because in a 2 way cylinder either port can be the intake or exhaust, depending on which way you're trying to move the rod.

The whole idea is to isolate the hydraulic pressures inside the cylinder caused by forces trying to extend or retract the rod and only allow movement when the operator wants it. Clear as mud now - right? /forums/images/graemlins/laugh.gif