HenrikBP
Contributor
This thread needed a bump so my dive buddies can find it.
H
H
Regulator checklist and inspection
- Thread starter Couv
- Start date
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Bubbletrubble
Contributor
@HenrikBP: This thread should be made a sticky. Perhaps a mod could do this...
HenrikBP
Contributor
In step 7, what should be the pressure drop when the air is flowing, namely in SP MK20?
Here is an updated check list (Rev-7) with a helpful note from Herman (one of the Unusual Suspects) re: IP and balanced/unbalanced first stages.
Regulator inspection checklist
7. To locate a leak, the definite answer comes by submerging all parts of the regulator in a water tub or similar container. Check the first stage, the second stages, the pressure gauge, and all the hoses with special attention to all the fittings. Check around any hose connections as well as all around the first stage and out the mouthpiece of all second stages for small bubbles.
LeadTurn_SD
Contributor
Carlos,
Do you mean how much should the IP normally drop on a Mk20 during inhalation?
Your post quoted a section of the checklist that was unrelated to your question, so I'm not sure what you are asking.
I think one of the Scubapro guru's can answer that (I'm not sure how much IP drop is normal for that reg).
Best wishes.
Do you mean how much should the IP normally drop on a Mk20 during inhalation?
Your post quoted a section of the checklist that was unrelated to your question, so I'm not sure what you are asking.
I think one of the Scubapro guru's can answer that (I'm not sure how much IP drop is normal for that reg).
Best wishes.
If you mean step 6, checking IP, then yes it should drop some. I am nowhere near a SP guru but making an educated guess on a MK-20 I would think would be in the 5-10 psi range, depending on how much flow you have....a full on freeflow with both seconds is one going to be more than a normal breath.
halocline
Contributor
I have found that IP drop on the few MK20s I've worked on is very dependent on the piston type; it drops more with that crummy brass-tipped piston. With the composite piston the drop using my IP gauge on a 22" LP inflator hose is less than 10 PSI with a healthy purge and the recovery is immediate.
There are complications to judging 1st stage performance by the IP drop. For example, my MK2 drops less than either my MK15 or my MK10s, and it's a much lower flow 1st stage, so you'd think the opposite would be the case. I believe the differences in measurement are due to differences in venturi effect and general geometry of the LP area of the 1st stage. Of course, any comparison between two 1st stages would have to be done with the same 2nd stage, because the 2nd stage (and to an extent, the tank valve) is the weak link in terms of flow.
I also suspect that IP gauges vary considerably in their reaction time and sensitivity to movement, and probably an inline gauge right at the 2nd stage junction would be a better indicator than a gauge on the LP inflator hose. Honestly, I'm not sure measuring the drop in the way we normally do tells us much about the capabilities of the 1st stage.
When I was trying to figure out why my IP gauge was acting the way it did on my various 1st stages, I tried hooking up 2 balanced/adjustables that have very forceful purges to the same 1st stage, and simultaneously pushing both purges. That led to some interesting results; the MK15 which had prior dropped more than the MK2 had an initial big drop, then leveled off to about 10PSI under IP, while the MK2 dropped more than 20PSI.
I still think the tank valve is usually the bottleneck for flow, especially when the tank gets low.
There are complications to judging 1st stage performance by the IP drop. For example, my MK2 drops less than either my MK15 or my MK10s, and it's a much lower flow 1st stage, so you'd think the opposite would be the case. I believe the differences in measurement are due to differences in venturi effect and general geometry of the LP area of the 1st stage. Of course, any comparison between two 1st stages would have to be done with the same 2nd stage, because the 2nd stage (and to an extent, the tank valve) is the weak link in terms of flow.
I also suspect that IP gauges vary considerably in their reaction time and sensitivity to movement, and probably an inline gauge right at the 2nd stage junction would be a better indicator than a gauge on the LP inflator hose. Honestly, I'm not sure measuring the drop in the way we normally do tells us much about the capabilities of the 1st stage.
When I was trying to figure out why my IP gauge was acting the way it did on my various 1st stages, I tried hooking up 2 balanced/adjustables that have very forceful purges to the same 1st stage, and simultaneously pushing both purges. That led to some interesting results; the MK15 which had prior dropped more than the MK2 had an initial big drop, then leveled off to about 10PSI under IP, while the MK2 dropped more than 20PSI.
I still think the tank valve is usually the bottleneck for flow, especially when the tank gets low.
blue steal
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bump so I can find it.
John_B
Grasshopper
Reiterating the question from the first post.
Could a MOD please make this thread a sticky?
Could a MOD please make this thread a sticky?
OP
John,
This thread was a Sticky for a while, but because there was conflicting information "the powers that be" decided to downgrade it's status. I think if we could take the latest revision-in a single locked out post, it would better serve the purpose. Even though my name is in the OP position there have been a quite a few folks here who contributed: LuisH, Mattboy, Awap, DA Aquamaster, Herman and lots of others I stole ideas from.
c
This thread was a Sticky for a while, but because there was conflicting information "the powers that be" decided to downgrade it's status. I think if we could take the latest revision-in a single locked out post, it would better serve the purpose. Even though my name is in the OP position there have been a quite a few folks here who contributed: LuisH, Mattboy, Awap, DA Aquamaster, Herman and lots of others I stole ideas from.
c
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