Valve Sealing Problem
Need a little help/advise. So I took my Selph valve and decided to make a larger one piece stem. Bored out the body to .3125″ and made a nice one piece stem at .309″. Put a .250″ hole in it which you can slide the condor stem in it until it hits the tophat. Everything was good until I put it in a tank and tried to fill it. Valve leaks and emptys tank out in less then a minuite. No mater how I made the stem seal it leaked the same. You can grab the tophat and change the leak but when you let go it is still leaking the same. I compared it to my Blod valve and the tophat on it you can wiggle a little also. Only thing I can think is I need to make the stem OD a little larger, say .311″. I make the stem seals out of acetal and even tried derlrin just to see if it would work because it is softer. Made sure the back of valve is good by facing it of and scotch brighting it so it is perfect and nice and smooth. I’m kinda puzzled. I have made new stem seals for my blod valve a couple of times with no problems. Anybody have any ideas before I waste another 4 hours trying to get it to work. Thanks
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Thanks yeah I looked it up on macmaster Carr. How does it compare to asetal? I made the same piece for my blod valve with no problems. Old stem was .275″ and new is .309″. It only changes if you push tophat left of right and makes it leak less when you do. Old stem is smaller. I never even tried the valve before. I just desided to open this one up more and see what happens.
High Density Polyethylene
http://www.tapplastics.com/shop/product.php?pid=529&
Starboard spec sheet:
http://www.tapplastics.com/uploads/pdf/StarBoard-sell-sheet.pdf
Do you think that because the stem is so fat that it makes it harder for the end to seal because it has less room to move around and seat? I’m thinking that because you say the seal appears to change as you rotate the stem. Have you tried to put the old stem back in and does it seat properly?
This is your old Selph valve that I did this to. I’m using asetal. What material are you talking about? I tried delrin which is softer with same result. I even made it cone shape. I have to get my compressor back together because I used all my air. Then I will try some more. Also talked to Tim and he said bring it by and he will get it to seal.
I take it you are running a spring in there like the Selph valve?
I second the “more taper at the contact face”, you may also have a harder version of the hdpe that the original.
I know that NSF cutting board (as in restaurant supply) HDPE is harder than Tap Plastics HDPE and Tap Plastic StarBoard (uv quality and colored HDPE) is a bit different (softer perhaps) than the white Tap Plastics HDPE…
I would think softer HDPE would provide a better seal.
Do you have a hardness tester, what does the white say compared to the beige?
I have a couple different white HDPE samples and some black StarBoard HDPE…
Try giving it more taper and match the degree on the part it touches and Polish the hell out of it an use the DeLeon then hold the valve so the stem is free and smack it with hammer. It will pinch it in just a little and make a grove then it should seal I’d think oh an Polish the delron AP its super slick be for u smack it
Here’s some pic’s
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Acetal/Delrin…
Specific gravity (ASTM D 792) : 1.42
Tensile strength, Ultimate (ASTM D 638) : 10,000 p.s.i.
Flexural strength (ASTM D 790) : 14,300 p.s.i.
Flexural modulus (ASTM D 790) : 3.8x 10~5 p.s.i.
Water absorption – 24 hours (ASTM D 570) : 0.25%
Water absorption – saturation (ASTM D 570) : 0.90%
Density (ASTM D 792) : 0.0513 lb/inch~3
HDPE/Starboard
Tensile Strength (PSI) ASTM D638 4100
Flexural Modulus (PSI) ASTM D790 180,000
Screw Holding Strength (lbs.) ASTM D1761 425
Water Absorption (7day) ASTM D570 .05%
Weight (lb./Cubic Inch) .034
Looks like Acetal/Delrin is harder than HDPE… But who know if that will work better, intuitively I would think it would, saofter being able to conform to provide a better seal…
I never used the valve and only remember maybe one seat that didn’t seal on the Selph, have heard of more issues with improper seating on the standard hi-flo valves…