Scubapro Mk5 question
- Thread starter Decotek
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axxel57
Contributor
The part number for both springs is different.
The tension of a spring for an unbalanced (piston) 1st and a balanced 1st should be different, because in a balanced 1st the spring has to withstand more pressure than in an unbalanced 1st, where the tank pressure works against the piston.
I'll check this afternoon......
The tension of a spring for an unbalanced (piston) 1st and a balanced 1st should be different, because in a balanced 1st the spring has to withstand more pressure than in an unbalanced 1st, where the tank pressure works against the piston.
I'll check this afternoon......
halocline
Contributor
I’d be very interested in trying it; I’m always on the look out for MK5 and MK10 springs that have some life left in them. My usual issue is low IP. I always have to use the ‘+’ seats and I still frequently come up around 125 PSI. It’s not the worst thing, but I’d to get them a little higher. It sounds like the MK2 spring might be even worse, though.
axxel57
Contributor
Okay, the springs are quite different in length and the thickness of the wire.
I tested a MK2 Plus and a Mk5 DIN with 5LP ports.
Both had an IP of 136psi at full tank.
I put the spring of the MK5 into the MK2, and, surprise surprise, the IP dropped to 108psi!
I would have expected the opposite, but obviously has the longer piston of the MK5 and the fact that the valve is balanced a different effect than I would have expected.
The MK2 Spring fits perfect into the MK5 body and the IP increased by 18psi to 154psi.
So it seems to be an option to use the MK2 spring in a MK5 1st.
If I find time I will conduct tomorrow a Flow Test to make sure that higher flow is not dropping the dynamic IP too much.
Anyway, it never crossed my mind to use a MK2 spring in one of my many MK5s when the IP was pretty low.
So thanks for the question........
I tested a MK2 Plus and a Mk5 DIN with 5LP ports.
Both had an IP of 136psi at full tank.
I put the spring of the MK5 into the MK2, and, surprise surprise, the IP dropped to 108psi!
I would have expected the opposite, but obviously has the longer piston of the MK5 and the fact that the valve is balanced a different effect than I would have expected.
The MK2 Spring fits perfect into the MK5 body and the IP increased by 18psi to 154psi.
So it seems to be an option to use the MK2 spring in a MK5 1st.
If I find time I will conduct tomorrow a Flow Test to make sure that higher flow is not dropping the dynamic IP too much.
Anyway, it never crossed my mind to use a MK2 spring in one of my many MK5s when the IP was pretty low.
So thanks for the question........
axxel57
Contributor
Just conducted the Flow Test with the MK5 with MK2 (Plus) spring.
I always conduct the Flow Tests at 600psi tank pressure ( worse case scenario).
Starting with a static IP of 140psi, at 5 SCFM the dynamic IP dropped to 128psi, at 7,5 SCFM to 126psi, and stayed there also at 10 SCFM and finally 12,5 SCFM.
That means that at depth equivalents of 120-200-300 and 380 feet the MK5 with the MK2 spring maintains a dynamic IP of at least 126psi, which is completely acceptable.
I checked some more old MK2 springs, most of them produced a static IP of a bit more than 150psi (152-156psi), one had only 148psi, so it seems to depend on the condition.
Interesting the whole thing anyway.........
I always conduct the Flow Tests at 600psi tank pressure ( worse case scenario).
Starting with a static IP of 140psi, at 5 SCFM the dynamic IP dropped to 128psi, at 7,5 SCFM to 126psi, and stayed there also at 10 SCFM and finally 12,5 SCFM.
That means that at depth equivalents of 120-200-300 and 380 feet the MK5 with the MK2 spring maintains a dynamic IP of at least 126psi, which is completely acceptable.
I checked some more old MK2 springs, most of them produced a static IP of a bit more than 150psi (152-156psi), one had only 148psi, so it seems to depend on the condition.
Interesting the whole thing anyway.........
interesting.....
If the spring fits into the allotted space, produces the required IP range and does not coil bind under maximum travel (compression) then I would think it okay to use.
I've found an engineering shop with a spring test machine. They're happy to test a range of springs for me (beer economy at work) and give me the spring rates. Hopefully I can then cross reference to a specialist spring supplier...........
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