Hydrolic Valves Open Center

[Wern]

As kennyd noted, I hope my problem is a lesson for you all. The main problem is the service and support for this Chinese product.
In my case it is KPX Tractor as the supplier. Not only did I never got a reply from these folks, they charged my Visa in Dec. 2006 for a 9 bucket I ordered. As of today, Sep. 23,07, I am still waiting for delivery.
On Aug. 29, 07 I gave them a deadline for a reply until Sept. 20, 07 after which I will take legal action. In spite of 2 reminders in that period, no reply.
If the valve sets (2 of them) are the problem, then hands off Chinese Backhoes !
But in any case, hands of KPX Tractor !!

 

[Wern]

Although a spoken word cannot be taken back, I want to take back the last line of my last thread. I got this morning Sep.24,07 a call from KPX with the promise to comply with all my requests. I don't know why KPX never responded before, maybe my requests never reached the right person. I am hopeful for a good resolution and I keep you posted.

 

[jimmysisson]

Maybe someone from, or acquainted with, KPX saw your posts! If so, good.
Jim

 

[Wern]

We have disassembled the valve set and found that the ports for oil return where closed. So it seems that I have a closed Center Valve Set on a system which requires a Open Center for continuous flow.

I am trying now to get the right parts; Endplate and Inlet Section (called header in my attachment).
Not an easy task, because the supplier has problems identifying the parts. . But at least I am getting a response and it seems they are now trying hard to help me fix this problem.

I also found that John Deere has a valve set which can be changed from open to close center by replacing a bolt on the endplate. I have a similar bolt on the side of the endplate and wonder if my valve set has the same provision.
So, I am not sure how long it will take to get the right parts and when I can push myself to start working on this again , but I will report once I get this equipment working.

A lesson, next time I think twice before buying complex tractor attachments. I could have saved myself a lot of work and aggravation and possible even money by subcontracting all the work I had in mind with this backhoe!!

 

[Wern]

Just for the records, I am still waiting on reply from KPX. I don't know whether they will or can replace these endplates. No response to my 4 e-mails.

 

[Wayne County Hose]

This is a two pressure system valve, allowing the use of two separate system pressures in one valve.

An open center valve will port fluid back to tank in neutral, when you move the spool in either direction, you port fluid to the work ports. A closed center system holds the fluid at the spool under pressure until the spool is moved, then porting pressurized fluid to the work ports.

I don't know if this can be done on your valve. Many closed center valves are converted to open center by removing a plug and installing a line from there back to tank/

Also, take those q.d.'s off of the suction side of the pump. Never, ever, install a q.d. on the suction side of a pump. They create turbulence and are a flow restrictor making your 1" line act more like a 3/4" line with turbulence. Also, if your q.d. develops a leak, you won't know until your pump aerates and pukes.

 

[Wern]

Wayne,

What is a q.d. ?

Sal from my local hydrolics shop showed me some valve sets with a plug to convert close to open loop, as you explained. But this is unfortunately not possible on my set. If you look at the endplate on my attachments you can see the return pass is closed. We considered drilling a hole, but we could not find a path to the return line.

Wern

 

[shaley]

QD = Quick Disconnects

 

[Wern]

Well, it seems that the pump too big is part of the problem.
After assembly and testing of the valve set the stalling engine problem was gone. If I run the pump at idle I get smooth operation on all cylinders. Of course there is no power under these conditions. So, I guess a smaller pump would let me operate at higher RPM to get the power to operate the backhoe.
There must have been an other problem in the valve set which disappeared after dis/assembly. In order to test the valve set I had to study the hydraulic schematic. A hydraulic Eng. explained me how to read the schematic. I made and attached a drawing which helps to understand how these valves operate and facilitate testing.
Thanks to all of you who helped me solving the problem.

 

[biggerten]

Well, it seems that the pump too big is part of the problem.
After assembly and testing of the valve set the stalling engine problem was gone. If I run the pump at idle I get smooth operation on all cylinders. Of course there is no power under these conditions. So, I guess a smaller pump would let me operate at higher RPM to get the power to operate the backhoe.
There must have been an other problem in the valve set which disappeared after dis/assembly. In order to test the valve set I had to study the hydraulic schematic. A hydraulic Eng. explained me how to read the schematic. I made and attached a drawing which helps to understand how these valves operate and facilitate testing.
Thanks to all of you who helped me solving the problem.

I have an LW-7 back hoe, and have it powered by a Prince 7A pump, same pump as yours, lower flow rate (7 gpm). Works fine, valves are open center.