Lurmark Pneumatic Boom Section Shutoff Valve won't shut.

[DrWazzock]

On my old Bateman Hi Lo sprayer manifold we have 4 air operated Lurmark boom section shutoff valves.
Over the years I have had a few problems with these valves failing to close particularly at higher spraying pressures.
They do close if you switch the spray pump off for a couple of seconds to drop the spray pressure. They stay closed when you put the pump back on. so this is a work around.
What I have done with some success is added washers to pack the closing spring tighter to the air piston but even this measure does not seem to be working now and I cannot understand why. With the valve off the sprayer in the vice it takes a hell of a lot of force to open the valve against the spring. The air pressure achieves this on the sprayer so why the heck won't the spring close the valve when the air pressure is vented to close the valve?
Baffled by this. They work at say 2 barg spraying pressure but one won't close when working at 4 barg spraying pressure. Must be something to do with the spray fluid pressure acting on the valve but can't work out how and what's gone wrong. Am I tightening the air cylinders on too tightly and maybe crushing the valve stem seals too tight round the stem?

 

[davidroberts30]

Cheapest fix.....buy a 2nd set of nozzles so you dont have to spray at 4 bar...

 

[DrWazzock]

Cheapest fix.....buy a 2nd set of nozzles so you dont have to spray at 4 bar...

Lower pressures help the valves close but one particular valve won’t even close at 3 barg. I need high pressure for fine spray on the beet.
It didn’t help that one of the valves blew out of the manifold while I was fiddling with it. Was testing with clean water fortunately but was completely soaked through by the time I’d climbed down the ladder. I bought a cheap secondhand replacement that my dealer kindly found in his scrap heap. The threads are good so it stays in the manifold but it too won’t close at any sort of reasonable spraying pressure yet I can’t see anything wrong with it. I have swapped to control air lines over and they work fine.
It’s something to do with valve. Wonder if they have been fitted wrong way round by previous owner?

 

[DrWazzock]

Mystery solved. I was assuming the LH valve on the manifold controls the LH boom. Wrong. The pipes cross over going back. So I have been stripping down and adjusting a perfectly good valve while the duff one sits there untouched, then wondering why there is no improvement. What a fool.

 

[Exfarmer]

Mystery solved. I was assuming the LH valve on the manifold controls the LH boom. Wrong. The pipes cross over going back. So I have been stripping down and adjusting a perfectly good valve while the duff one sits there untouched, then wondering why there is no improvement. What a fool.

We have all been there

 

[fieldfarmer]

Mystery solved. I was assuming the LH valve on the manifold controls the LH boom. Wrong. The pipes cross over going back. So I have been stripping down and adjusting a perfectly good valve while the duff one sits there untouched, then wondering why there is no improvement. What a fool.

After a fairly sh1t day, thanks for making me laugh. ( sorry).