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Too large of a pilot valve?

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Unread postAuthor: Technician1002 » Sun May 24, 2009 10:39 am

dewey-1 wrote:
Technician1002 wrote:
dewey-1 wrote:I agree with jrrdw.

I have used a 1 inch sprinkler to pilot a 1.5 inch sprinkler valve.
I had to because the blow gun was to restrictive on the larger valve.

Look here;

http://www.spudfiles.com/forums/viewtop ... tml#127106


I don't.

The blow gun was the hint the equalization leakage is high. Too high.


Tech this is why I am confused.

I made the statement of a restrictive blow gun on my cannon.
It has nothing to do with resrictive blowgun on his! He never even stated that.

I thought you were stating that I also had a bad or messed up main valve
because of your reference to "blow gun was the hint"

I could have used a ball valve but they are inconvenient and ugly for the purpose I wanted. That is to have a trigger handle.


I was referencing the very original post. No blow gun was mentioned but it is in the photo of the cannon in the original link in the very original post.
Image

To make matters worse, there is an elbow in both the pilot for the sprinkler valve and an elbow on the discharge of the sprinkler valve. I made a guess to the addition of the latter made a change in operation. I may be completely off base on this one. Too many variables and much confusion on which elbow. In providing the back pressure to the sprinkler valve, I was referencing the PVC one on the left.
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Unread postAuthor: dewey-1 » Sun May 24, 2009 11:01 am

Tech;
I do concur with you that he may have more of a piston problem than anything.

He is using a 3/8" fitting that screws into the sprinkler valve and I am thinking that there are two possibilities for a sprinkler problem.

1. The fitting is so large in diameter it is preventing the spring from sitting its original position against the valve's lid. In other word the spring is being compressed such that it takes more air pressure to attempt to crack the valve diaphragm. To much spring pressure!

2. The fitting is interfering with the actual diaphragm such that it cannot
open all the way.

Hopefully deathbyDWV can tell us what he actually found so others can benefit from this discussion. (Including me!)
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Unread postAuthor: Technician1002 » Sun May 24, 2009 11:14 am

dewey-1 wrote:Tech;
I do concur with you that he may have more of a piston problem than anything.

He is using a 3/8" fitting that screws into the sprinkler valve and I am thinking that there are two possibilities for a sprinkler problem.

1. The fitting is so large in diameter it is preventing the spring from sitting its original position against the valve's lid. In other word the spring is being compressed such that it takes more air pressure to attempt to crack the valve diaphragm. To much spring pressure!

2. The fitting is interfering with the actual diaphragm such that it cannot
open all the way.

Hopefully deathbyDWV can tell us what he actually found so others can benefit from this discussion. (Including me!)


The other item mentioned is that the main piston valve may require a lower pilot pressure the sprinkler provides if it is just sizzleing like a pop off just before lifting and keeping the pressure too high. The PVC elbow may be helping the diaphragm lift which is the point I was making.
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