Hydraulic plumbing query.

[oakleaf]

I have installed a valve block on my fertiliser spreader hoist so I can operate it from the ground instead of climbing back into the cab everytime I load in a bag. The feed comes in to the left side of the block from the tractors single acting spool via a 3/8 pipe and returns via a 1/2 inch pipe out the right side of the block to the free return on the tractor.
So I set the spool to pump and the left lever works the jib in and out no problem.

The right lever will raise the boom but it does not go back down when the lever is put in the opposite position. In fact it raises at a slower pace.
Why does it not go down? Have I plumbed it wrong? Any ideas please.

 

[davedb]

That looks like a twin double acting spool block, Is there a bung screwed in that block on the Rh side where another pipe could be put? You may have to put a short pipe from there to the return line to allow the oil to go to return when you push the lever the other way to lower your bag lifter

 

[C.J]

You should have used a single acting slice for the boom.

 

[davedb]

You should have used a single acting slice for the boom.

Yes that’s it put piping it as I say will get round that problem

 

[Stock]

Can you plumb your return in to a free flow port and increase the bore of the pipe?

As the others have said use a single acting spool but you might need to fit a one way restrictor. Most spools don't like restricted returns..........................................

 

[Mursal]

Yes as above or dump the output (not used) from the double acting slice back into the return.
As I have just now read David already explained.

 

[oakleaf]

Thanks for replies.
The valve block was sold as one double and one single but it may be two doubles. I will be back in that yard tomorrow and will check it out for sure.
If it is , probably plumb a line from blanked port into return as suggested by @davedb.

 

[oakleaf]

Can you plumb your return in to a free flow port and increase the bore of the pipe?

As the others have said use a single acting spool but you might need to fit a one way restrictor. Most spools don't like restricted returns..........................................

The return is already plumbed into free flow return on tractor and already is a larger bore than the feed so surely there is no restricted return?

 

[Stock]

Where did you get the valve, would like to see if a schematic of the block was available to check the ports.....................
can you post a larger pix of the manufacturers plate?

 

[oakleaf]

Ok so today I removed the valve and returned to the supplier. Once again they assured me it was a one double and one single block that I had and could offer no explanation of why it wouldnt lower the boom , even blaming the tractor.
Anyway returned home and plumbed in a short pipe teed into return as advised by the experts on here and all is now working as it should.
So once again thank you.

 

[oakleaf]

Where did you get the valve, would like to see if a schematic of the block was available to check the ports.....................
can you post a larger pix of the manufacturers plate?

Photo as requested.

 

[Stock]

http://www.mchc.ie/uploads/catalogues/1704_Hydraulics.pdf
Pg 97 is the closest I can find to yours,the plumbing is correct but the connecting of B2 port to the T port should not be necessary to have it work as a single acting valve............................

 

[Lincsman]

It could be a pure backpressure thing, would it go down when the tractor stopped pumping?

 

[Mr Happy]

I have been sent this info on the valve name plate. but it does mean the valve has the correct spools!

A1 = cylinder spool with spring centre


B1 = single acting spool with spring centre


G = BSP ports


KZ1 = standard lever

Hope it helps

 

[oakleaf]

It could be a pure backpressure thing, would it go down when the tractor stopped pumping?

Yes it would drop when tractor wasnt pumping, however having to climb back into cab to knock out the spool each time I needed to drop the arm would have defeated the point of having the valve block mounted on the crane (as no doubt you are aware).

 

[Lincsman]

Yes it would drop when tractor wasnt pumping, however having to climb back into cab to knock out the spool each time I needed to drop the arm would have defeated the point of having the valve block mounted on the crane (as no doubt you are aware).

I had the same issue with a tractor mounted forklift (remember those?) it would go up if there was nothing on the forks and you moved the lever to down, the cure was a bigger return pipe.

 

[oakleaf]

I had the same issue with a tractor mounted forklift (remember those?) it would go up if there was nothing on the forks and you moved the lever to down, the cure was a bigger return pipe.

Interesting.
Perhaps a 3/4 return pipe would have solved my issue also.
Anyway its sorted now with the extra little pipe so I can live happy ever after or something like that