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PostPosted: Thu Jan 01, 2015 1:36 pm 
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Joined: Wed Feb 17, 2010 6:04 pm
Posts: 841
Location: Nova Scotia
Gippeto wrote:
Figuring out how something works by looking at it is how I earned my bread for 25+yrs...sometimes I take that for granted.

A lot of double speak, bs and odd terminology in the article, but will do my best to be clear...

Very small hole in the valve stem is a vent...(can just be seen below and to the left of center of the o-ring) stem is partially hollow. Small piece of rod slides inside of valve stem.

Piston assembly on the right is secured to the body by the screw.

Valve "hat" is hollow...slides over top of piston assembly...uses the urethane seal shown...lower force holding valve closed requires softer material to seal.

The piston area being vented to atmosphere, the net effect is a reduction in surface area for pressure within the valve to push on...resulting in lower opening force.

During the shot cycle, pressure bleeds through the hole in the valve stem, past the rod to the piston assembly and adds a considerable amount of closing force. Once shot cycle is completed, this would then vent back to atmosphere...rod would slow the venting, helping hold the valve closed during early (higher force) hammer bounce events. Rod diameter could be tweaked to adjust fill rate/closing force, but would also effect on the venting end...

HTH,

Al

Is this a similar principle to the way a solenoid actuated water valve operates, being able to open a valve against water pressure with just a small thrust of the solenoid valve piston? The water valves also use a very small vent hole to equalize pressure on both sides of the diaphragm.


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PostPosted: Thu Jan 01, 2015 2:40 pm 
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Joined: Sat Nov 03, 2007 4:19 pm
Posts: 8976
Location: Coalmont BC
Ahhhh.... think I finally saw it.... it appears to be roughly lined up with the exhaust port in the valve body?.... so it would be at atmospheric between shots but at pressure during the shot....

Didn't realize the hole I the stem was large enough for the rod (leaky check valve) to fit inside the stem.... so no, it wouldn't affect the lift....

Gradually beginning to understand it.... pretty sophisticated bit of engineering, eh?....

Bob

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PostPosted: Thu Jan 01, 2015 2:53 pm 
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Joined: Tue Jun 03, 2008 5:46 pm
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Location: Canada
Diaphragm sprinkler valve uses differential force to open...uses the water as pressure source. The solenoid vent is used to create the differential by venting the side with larger exposed surface area (top).

Bear with me..day three of the flu and the drugs MAY be kicking in. 8)

Image

Diaphragm let's say has a diameter of 4"...giving area of roughly 12 in.sq and some change. Port diameter on the inlet side that the diaphragm seals against has a diameter of 2"...giving area of roughly 3 in.sq and change.

Say we have 50psi water pressure....12in.sq x 50 psi = 600 lbs force trying to hold valve shut. 3 in.sq x 50 psi = 150 lbs force trying to open the valve...net force is 450 lbs holding valve closed.

Vent off the pressure from the large side, and the net force reverses direction..valve opens. Close the vent (solenoid) and a small bypass allows the top (larger area) side to re-pressurize. With both sides of the diaphragm now equally exposed to pressure, the spring closes the valve....as down stream pressure drops, force differential takes over again.

Hope that makes some sort of sense. :rolleyes:


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PostPosted: Fri Jan 02, 2015 1:51 pm 
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Joined: Sun Feb 10, 2013 1:16 pm
Posts: 1787
Thanks Al, that's a big help. I hadn't seen the hole in the stem either. It makes more sense now you've pointed it out. I had been imagining the hole on the high pressure side, which just confused me.

That's an amazing design. I love the idea of tackling anti-bounce from the valve side.


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