iDRY Vacuum Kilns

Sponsors:

Valmet 546 Series 2 Forwarder

Started by Wrenchman, September 06, 2018, 11:39:15 PM

Previous topic - Next topic

0 Members and 1 Guest are viewing this topic.

Wrenchman

Question on the hydraulic valve bank behind the cab...Lately have noticed when lowering the main boom, the speed of it has picked up significantly, all other hydraulic functions have remained at the same speed. Does this sound like a shuttle valve issue?

mike_belben

Does the boom cylinder exhaust all fluid through the valve spool exclusively or does it use a pilot operated dump line direct to tank?


If its all through the spool, look for an adjustable flow control valve somewhere in the boom's work ports and lines.  Typically made from a black oxide finished or plated steel, rectangular block with a knurled dial to crank in and out for adjusting cylinder stroke speed. Usually threaded into valve port.   


No new leaks or other functions acting strange or moving?
Praise The Lord

snowstorm

shuttle valve o rings cause all kinds of strange things to happen. when they go missing. the last o rings i got seem to last much longer. the only sure way to tell is take 1 out

mike_belben

Good point SS. 

A cross leak to tank would definitely do it.
Praise The Lord

barbender

I've never been around a Valmet, so I don't know how they're set up. On Ponsse forwarders, the main boom down function is not powered, the valve just opens and releases pressure. Gravity down. So on our Ponsses, the problem would be in the valve bank and solenoid.
Too many irons in the fire

snowstorm

valmet used a rexroth valve. load sensing pressure compensated with a open center gear pump. with a primary and secondary shuttle valve. after a while the o rings break up whatever there are gone. when this happens all kinds of strange things happen. any weird things happening with a 546    646  its a good place to start. only buy the right o ring and back up from komastu. a plain o ring will not last. i would have to look in my book but i belive it dose have pressure down on the boom maybe 600 psi. if its a 650 xl crane there may be a regeneration valve on the top of the boom. lift psi is around 3000psi. when everything is right they work very well not quite as good as a piston pump. it should lift and swing without slowing either one down

Skeans1

Quote from: snowstorm on September 07, 2018, 11:29:36 AM
valmet used a rexroth valve. load sensing pressure compensated with a open center gear pump. with a primary and secondary shuttle valve. after a while the o rings break up whatever there are gone. when this happens all kinds of strange things happen. any weird things happening with a 546    646  its a good place to start. only buy the right o ring and back up from komastu. a plain o ring will not last. i would have to look in my book but i belive it dose have pressure down on the boom maybe 600 psi. if its a 650 xl crane there may be a regeneration valve on the top of the boom. lift psi is around 3000psi. when everything is right they work very well not quite as good as a piston pump. it should lift and swing without slowing either one down
90 ditron vs 70 ditron o rings?

Wrenchman

I'll have to get into my parts book, see how they come apart. Haven't had the luck of having to take the valves apart since I've owned it. Finishing a job this weekend with it, will have to wait til next week after the machines are moved....and a stop at Roland in Esky to pick up some new o-rings and backers.

SS...it is a 620 XL.

Thank You Sponsors!