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  #11  
Old 11-04-2012, 12:49 PM
mrsteve mrsteve is offline
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Quote:
Originally Posted by White Gardens View Post
Agreed. The "dome" section of the rubber probably aids the rubber in opening and closing of the valve.

Guessing that the thinner mesh area is where the rubber is allowed to flex.


.....
I'm not an expert on the material, but it looks like the mesh material is the same throughout the old one. The manufactured one certainly has the mesh. I'd like to say all went well with the rebuild, but I still have an issue to look at next week. Once under pressure it worked fine for several cycles, then decided to stay open. I'm looking at the valve (Richdel 205) that they are using to port off the water as a possible cause. May be that it doesn't want to close under the low flow from the exhaust tube. I'm going to verify that it will close at the valve by capping the exhaust flow, then proceed from there. I knew this was bad news from the beginning, but I'm determined to finish even if it means cutting it out and installing an electric valve.
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  #12  
Old 11-04-2012, 01:12 PM
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Quote:
Originally Posted by Kiril View Post
I'm gonna bet the mesh material on the old diaphragm plays an integral part in the opening and closing of the valve.
"cloth-inserted" rubber material is widely available on the web, except for some of the thinnest stuff we saw in valves.
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  #13  
Old 11-04-2012, 03:42 PM
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Quote:
Originally Posted by mrsteve View Post
....Once under pressure it worked fine for several cycles, then decided to stay open......
Make sure there isn't any corrosion build-up on the brass parts with close tolerances, as they could prevent closing. Also, you might try a stronger spring above the diaphragm assembly. Increasing the spring force was always a cheesy fix for a valve having closing problems.
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  #14  
Old 11-05-2012, 03:26 PM
mrsteve mrsteve is offline
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To recap the newly rebuilt valve decided to stick on. So today I took the exhaust tubing loose at the valve and capped the flow. Valve goes off like it should. Went to the porting electric valve about 100' away and capped the line ahead of the electric valve. Hydraulic valve goes on and off like it should. On when I remove the cap and off when I put it back on. So this tells me the Richdel 205 is not closing under the low flow from the exhaust tubing. It's not much more than a trickle (maybe the tubing is getting squeezed somewhere along the path). I cut out the 205 and put in a Rain Bird PEB and ran a netafim solid hose from the valve into the flower bed for the water I'm porting off. Had to dial the flow control down, but it does close. Which in turn closes the hydraulic valve. Great success finally.

Without meaning to be a prick I feel as though I need to address the stronger spring comment. Isn't it all about water pressure. The upper chamber has more pressure which keeps the seat closed. The spring may assist the travel , but it's differential pressure that closes or opens the valve. This hydraulic valve doesn't have a spring at all. The water ports up thru the stem to build pressure on top of the diaphragm to close the valve (pin type). I have left out springs before on the Wethermatic bass valves by mistake and they still work (I've learned to put everything on the valve box lid now, so it all gets back in). I always felt the spring sort of kept the diaphragm from wedging itself against the top on opening. Please correct me if I'm wrong on this.
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  #15  
Old 11-05-2012, 06:37 PM
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The spring can matter. The pictured hydraulic valve has a screen on the diaphragm assembly, which is indicative of a normally-closed valve. That would mean the pressure above the diaphragm would equal that below the diaphragm, so it isn't water pressure that would close the valve. It would be the fact that the upper-chamber diaphragm area is greater than the area of the diaphragm assembly where the seat washer is. The hydraulic force is a function of the surface area the pressure is acting against. The difference in surface area translates to a force that holds the valve closed.

When a diaphragm valve gets stuck wide open, the pressure is just about equal on both sides of the diaphragm, over areas that are just about equal on both sides of the diaphragm, and all the while the rushing water itself presents some additional force in the way of its momentum. A flow control can make all the difference here, because introducing a slight pressure drop creates less hydraulic force on the inlet side of the valve diaphragm, and the valve can close. Absent a flow control, and absent any spring force inherent in a flexible diaphragm itself, it becomes the job of the valve spring to provide a force that allows the valve to close.

Class dismissed.
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  #16  
Old 11-05-2012, 06:58 PM
mrsteve mrsteve is offline
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I see what your saying, it's still differential not spring tension that ultimately causes the valve to seal. The spring and or flow control are aids. Thank you for the lesson.
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  #17  
Old 11-05-2012, 07:38 PM
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It's easy to forget that pressure and force are two different things.

One example of a valve that absolutely depends on the diaphragm being the spring force is the Greenlawn angle valve, with its thick urethane diaphragm. Also, the infamous Toro Flo-Pro valve began its unhappy existence without a diaphragm spring, only to see one a few years later.
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  #18  
Old 11-05-2012, 11:45 PM
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Quote:
Originally Posted by mrsteve View Post
To recap the newly rebuilt valve decided to stick on. So today I took the exhaust tubing loose at the valve and capped the flow. Valve goes off like it should. Went to the porting electric valve about 100' away and capped the line ahead of the electric valve. Hydraulic valve goes on and off like it should. On when I remove the cap and off when I put it back on. So this tells me the Richdel 205 is not closing under the low flow from the exhaust tubing. It's not much more than a trickle (maybe the tubing is getting squeezed somewhere along the path). I cut out the 205 and put in a Rain Bird PEB and ran a netafim solid hose from the valve into the flower bed for the water I'm porting off. Had to dial the flow control down, but it does close. Which in turn closes the hydraulic valve. Great success finally.

Without meaning to be a prick I feel as though I need to address the stronger spring comment. Isn't it all about water pressure. The upper chamber has more pressure which keeps the seat closed. The spring may assist the travel , but it's differential pressure that closes or opens the valve. This hydraulic valve doesn't have a spring at all. The water ports up thru the stem to build pressure on top of the diaphragm to close the valve (pin type). I have left out springs before on the Wethermatic bass valves by mistake and they still work (I've learned to put everything on the valve box lid now, so it all gets back in). I always felt the spring sort of kept the diaphragm from wedging itself against the top on opening. Please correct me if I'm wrong on this.
The old hydraulic stuff intrigues me. So whats the needs for the RB PEB, is that to bleed off the pressure on the hydraulic ends of things so that the hydraulic valve can open?
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  #19  
Old 11-06-2012, 06:30 AM
mrsteve mrsteve is offline
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Yes. The valve with no influence is closed. The electric valve just relives the water from the upper chamber allowing the valve to open. Using the PEB makes it electrically actuated. You have a constant flow (trickle) of water from the upper chamber when the valve is open, so the water is sent into the flower bed. One thing about this particular valve is, when it starts to fail it will bypass water out of a port in the body. This helps you locate the valve since there are no wires to trace. On this job I had two leaks, one at the curb (lowest head) and one where the valve was.
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  #20  
Old 11-06-2012, 08:47 AM
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Toro still makes an 'actuator' for these normally-closed valves. Of course, it is with barbed inlets that connect to their 1/8-inch ID control tubing.
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