I have 12 MK25s. It is time to service them and I can get 11 of them to lock-up at 140 psig, which is where I like to put them. However, I have 1 that when set at 140, it will creep over the next 5 minutes to 145 psig and stop. Before I throw another piston or HP seat at it, at what point am I just obsessing over it? Opinions or suggestions. I do not see anything that could be causing this problem from looking at both the seat and the piston edge. Any chance the spring under the HP seat could be the problem with it always wanting to go the 145 psig? Thanks!
IP creep-when to repair and when to ignore
- Thread starter jchance
- Start date
Please register or login
Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.
Benefits of registering include
- Ability to post and comment on topics and discussions.
- A Free photo gallery to share your dive photos with the world.
- You can make this box go away
- Messages
- 20,643
- Reaction score
- 15,133
- # of dives
- I'm a Fish!
Important to note the difference between IP creep and IP drift. IP drift is what that reg is exhibiting. As long as it locks up, it's fine. Some more cycling and it will likely stabilize.
5 psi over the length of the ip is not a problem if it stops or locks up as tbone says
snowdog61
Contributor
likely fine but obviously keep an eye on it. Had the same issue with MK20 with updated composite piston - lasted almost 2 yr/200 dives before it finally lost its lock. Inspection showed micro scratches across the edge. There's an excellent post on micropolishing the sealing surface (rsingler I believe). Did that and now it locks up solid with less than 1psi drift. Of course right after the rebuild I picked up a pair of Ti Atomics and this reg is now a backup......
halocline
Contributor
No, drift is when the reg locks up at slightly different IP each time you cycle it. This is definitely creep; it starts at 140 and creeps to 145 over a few minutes.
5 PSI of creep over 5 minutes on a MK25 is not a problem, but I'd keep an eye on it. Sometimes as the seat breaks in it goes away, but sometimes it just gets worse.
Have a look at this: How to restore a Piston Regulator that has IP creep
- Messages
- 20,643
- Reaction score
- 15,133
- # of dives
- I'm a Fish!
@halocline my understanding was creep was when it wouldn't stop and drift was when it had the "setpoint" then would drift up a few psi but lock up once it got there.
snowdog61
Contributor
I'd say it's just semantics - anything over a few psi from initial lock up point and you're not talking about o'ring movement but actual bypass flow between the seat and the piston/orifice. It may eventually seat - drifting say 5-7 psi and be fine for a long while (in my case with my wife's set went almost 200 dives) or it may never fully seat. Respiration rate makes a good bit of these a non-issue (the drift rate is so slow you never get into a free-flow condition on the 2nd because you are pulling the IP back down through breathing) but all need to be monitored to ensure the initial lock point and drift rate is stable. Your piston edge/seat interface has issues and will need to be addressed at some point. When the drift/creep overtakes the breathing rate and you start to free flow, cranking down on the cracking pressure is only masking the problem - that creep/drift rate will never get any better. This is the number one reason to own an IP gage and use it regularly. You will be informed as to when you need to simply adjust your 2nd or rebuild your set. Once the seat/piston/orifice have taken their set, the lower limit of drift/creep is determined. Wear/debris across that interface will gradually show itself via the changing IP rate - and never for the better.
I don't think there is any actual semantic difference in this instance between "creep" and "drift" and I don't think anyone has determined a generally accepted difference by convention for use in scuba. But you got me curious enough to dig around in my service manuals for an example of actual MFGR wording, as I knew at least one of my brands specifies a limit.
That one MFGR's wording is that MP creep at 3,000psi should be 5psi max within 5-15 seconds of cycling the purge.
I checked a couple of other brands and did NOT find an allowed spec for drift or creep. (Did not check everything at my disposal, just wanted a sample.)
Before you creeps drift too far off-see SP Bulletin 242.
Similar threads
