Scubapro MK15 servicing question

[bada3003]

First, thanks to everyone, especially awap and halocline, whose comments help me a lot.

An update. The missing piston o-ring arrived from the seller today. More on the seller below. theoringstore.com sent me a note saying that they'll ship the EPDM/polyurethane o-rings March 7, so proceeded to service with the items in the now completed service kit. Can always swap out the PU ones with their EPDM counterpart later.

Replaced all the o-rings and parts provided in the kit. So it's essentially all the components marked "Annual Replacement" in the schematic plus a couple of other items (copper retaining ring and washer which came in the kit). One exception: I did not replace the HP seat. More on this below. Applied a good amount of christolube, especially to the dynamic o-rings. Dry tested it and the ambient chamber air leak is gone!

Some additional notes:

Breathing from a 2nd-stage seems normal but again it's dry testing so has to be taken with a grain of salt. IP reads 130 PSI which falls within the general operating range but there seems to be a "performance problem". I think it's called IP recovery (but could be wrong) where after a breath of air from the 2nd-stage IP drops to 120 and takes about 7-9 seconds to reach and stabilize at 130. Does not exceed 130. Have only read the 1st stage related chapters of Wolfinger and Harlow's books so will need to read up on the more subtle performance related issues in the later chapters.

I did not replace the HP seat, one because it "looked not worn" (probably a mistake), and two, halocline mentioned something about the HP seat not being the most easy part to get. The HP seat does have some sign of wear (scratch-like marks near the center indentation), so may just replace it as the one from the seller seems pristine, especially if it has anything to do with the "IP recovery" issue mentioned above.

A couple of notes on the seller. I did not mention anything specific about the seller in my posts since I took the seller's word that the kit was from scubapro, experience teaches that rushing to judgment is littered with mistakes, and the seller had 100% review rating on ebay (as I do as a buyer). Also, all the comments on the shelf life and quality concerns of o-rings (I did manage to read all of awap's long but informative SP o-ring thread, eventually) made me think that what appeared to be "used" parts may stem from 16+ years of sitting on a shelf/parts inventory somewhere. The seller included an additional, very supple piston stem o-ring in addition to the missing piston o-ring which was a nice touch. Anyhow I left the seller a positive review.

There is a point to the long-winded seller comment: on the package containing the missing o-ring, I noticed the sender's name which looked familiar but couldn't place it. Only a couple of hours later while servicing the regulator did it occur to me to check the author names of the two books mentioned above. The seller was one of them. It's a small world and I'm glad that I did not jump to conclusions initially.

 

[ams511]

Where can you get Oceanic after market seats/kits?

Trident dealers should be able to get you seats for the Oceanic clone of the MK-5. They may also sell HP seats for the diaphragm regs, I am not sure as it has been a while since I looked at their catalog. You can also purchase kits from NESS.

---------- Post added February 26th, 2014 at 08:59 PM ----------

There is a point to the long-winded seller comment: on the package containing the missing o-ring, I noticed the sender's name which looked familiar but couldn't place it. Only a couple of hours later while servicing the regulator did it occur to me to check the author names of the two books mentioned above. The seller was one of them. It's a small world and I'm glad that I did not jump to conclusions initially.

Yes, Wolfinger's wife is Bigfoot-Daisy, she has been selling inventory for quite some time.

---------- Post added February 26th, 2014 at 09:11 PM ----------

My main targets are my MK25 (new) and MK17 (used but serviced recently) which I would like to be able to service competently.

Ideally to save money your best bet is to standardize on one first and one second. You can keep your tool outlay to a minimum and have only one kit per stage. However, I don't

 

[redacted]

Where can you get Oceanic after market seats/kits?

Is this what you are looking for? Scuba Regulator High Pressure HP Seat Part First Stage Dive A290 | eBay

If not, the seller seems to have quite a few seat in the Trident line.

 

[bada3003]

It'll probably be a month or so before I can test the MK15 under water. Not planning on giving up on it.

My AL 1st stage regs are titan (w/o environmental seal) which I got new and Apeks DST which I got used. Lake Michigan (and some quarries) can reach low 40s at depth ~80-100 ft in places, so getting a couple of cold water regs (mk17 and apeks) for sidemount -- without buying everything new -- to mitigate free flow has been a motivator for the reg service project.

The MK15 is an excellent regulator, I wouldn't give up on it. You just need the special snap ring pliers and the kits are not as easy to find as other SP kits. But as an example I found someone with seats that sold me five for $5 each, I figure that should last me a few decades, by which time either me or all the oceans, or both, will be dead anyways. There's a cheery thought!

Once you get done with this reg you should have no problem with the MK25, it's pretty similar. The MK17 is a bit different and there's a tool that's helpful. The AL stuff is quite straightforward, herman makes a handy installation tool, and there's great support in the vintage dive community, assuming your AL stuff is the titan or legend and follows the old 1st stage design leading back to the doublehose regs.

---------- Post added February 27th, 2014 at 05:00 PM ----------

Yea, me neither. My last reg is a HOG DS1 w/ environmental seal which I got new. A tad over $200 w/ 2nd stage, 7 foot hose, and DIN-to-yoke converter in a package deal. Beautiful reg and breathes super nice. Can't believe how well priced it is given its apparent quality. And you can get the service kit from the company. And O2 serviced/ready out-of-the-box if I'm not mistaken. I still like my MK25/S600 the best but probably for sentimental reasons. The MK25 and HOG DS1 will be tagging along for a cavern course in FL in a few weeks.

Ideally to save money your best bet is to standardize on one first and one second. You can keep your tool outlay to a minimum and have only one kit per stage. However, I don't

 

[ams511]

Can't believe how well priced it is given its apparent quality.

I bought a set of switchbacks as an impulse purchase and I would say they are the same quality of my Apeks ATX-50s. The dive industry runs on ignorance and bullsh!t. If you look at the Apeks line the TX-20 is the base reg to get a TX-40 you add a metal slug for heat transfer, to get a TX-50 you add a knob. Scubapro does the same, the S550 is just a S600 without the knob, but a S600 sold at a much higher price point than the 550. So in scuba you really don't get what you pay for.

 

[bada3003]

I've been learning as well. There are detailed posts about the history of Apeks (cosmetic relabeling), cosmetic differences between primary 2nd stage and octo's, etc. Like in many sports sectors, maybe 90% is marketing hype and finding the 10% that's meaningful becomes the task at hand. Go to tenniswarehouse.com and check out racquet reviews. Full of, kindly put, BS. Same goes with golf. With scuba, I'm finding there's a bit more grounding though. The physiology stuff is still clouded in pseudo-science (it seems there's just not enough hard core research done since the 60s when space exploration took center stage), but the one area I'm finding has reasonable (as far as I can make out) solid footing is regulator servicing/repair. The two books by Wolfinger and Harlow are very well written and strike a chord w.r.t. their motivations. They also let me to embark on this DIY/DIR path. And super expertise by folks on scubaboard.com who've accumulated tons of experience.

I bought a set of switchbacks as an impulse purchase and I would say they are the same quality of my Apeks ATX-50s. The dive industry runs on ignorance and bullsh!t. If you look at the Apeks line the TX-20 is the base reg to get a TX-40 you add a metal slug for heat transfer, to get a TX-50 you add a knob. Scubapro does the same, the S550 is just a S600 without the knob, but a S600 sold at a much higher price point than the 550. So in scuba you really don't get what you pay for.

 

[halocline]

Breathing from a 2nd-stage seems normal but again it's dry testing so has to be taken with a grain of salt. IP reads 130 PSI which falls within the general operating range but there seems to be a "performance problem". I think it's called IP recovery (but could be wrong) where after a breath of air from the 2nd-stage IP drops to 120 and takes about 7-9 seconds to reach and stabilize at 130. Does not exceed 130.

I did not replace the HP seat

IP 130 is fine. When you take a deep breath or purge, the IP gauge will swing down and then should swing back up quickly when you stop the airflow. It should lock up at IP quickly and consistently. Don't worry about the apparent 10 PSI dip; there are lots of reasons why your IP gauge could indicate that when the actual drop is far less. For example, there are venturi forces in the turret that likely cause low pressure areas in adjacent ports, which is where your IP gauge is connected. I had a long conversation with Peter Wolfinger about this once, I was surprised how little he knew about it. I suspect when he worked for SP they had much more accurate ways of measuring IP during inhalation.

The 7-9 seconds until lock up is not good. I bet your gauge is showing an initial drop, then quick recovery to a pressure somewhere below 130, then a slow climb back to 130, is that correct? The probable reason for this is that you did not replace the seat, and so it is engraved with the profile of the piston edge from before. When you put it back together, the piston edge contacts the seat in a slightly different spot and you end up with a sloppy lock up. You could try leaving it pressurized overnight, tapping the purge a few hundred times over the course of a few hours, and see if the piston re-seats itself securely. It probably won't.

Replacing the seat and making sure there are no scratches or imperfections on the piston edge are really important parts of rebuilding one of these. Once the seat is installed and the reg pressurized, you shouldn't take it apart again. Some folks have been able to remove the seat retainer while leaving the seat in it, and have it go back in close enough to the same orientation so that the piston locks up in the original engraving. I haven't had much luck in that regard.

 

[Peter69_56]

Thanks everyone for the links, time to go do some searching.

 

[bada3003]

Yes, it's as you described. Whether I purge or breath from the 2nd stage, after the 2nd stage closes, IP reaches 120 PSI "immediately" but then climbs gradually to 130 at which it stabilizes. None of my newly bought 1st stages (titan, mk25, hog ds1) have that issue: they all "immediately" reach their set IP then stay there. The same goes for the used mk17 which was serviced 4 months back. My used Apeks DST, however, has a similar problem as the mk15. It immediately reaches 130, then slowly climbs to 135 at which it stabilizes. A difference is that the PSI gap is smaller. I will try replacing the HP seat in the mk15 and see if that makes a difference.

One other thing: I omitted an issue that I encountered when servicing the mk15 in the earlier update. When reassembling the reg, I found that part #22 in the schematic (swivel o-ring, 01-050-161) was missing both in the reg and the SP service kit. Since the original leak was not emanating from the ambient chamber ports, I ignored the missing swivel o-ring issue. Also, it missing both in the reg and the service kit made me think that maybe it's not essential (or mk15's design has evolved which obviated the part). The swivel o-ring shows up as an annual replacement part and common sense seems to indicate that it is needed for proper sealing of the LP port side IP chamber. I mention it because of your comments about venturi forces in the turret and their potential impact on IP measurement.

IP 130 is fine. When you take a deep breath or purge, the IP gauge will swing down and then should swing back up quickly when you stop the airflow. It should lock up at IP quickly and consistently. Don't worry about the apparent 10 PSI dip; there are lots of reasons why your IP gauge could indicate that when the actual drop is far less. For example, there are venturi forces in the turret that likely cause low pressure areas in adjacent ports, which is where your IP gauge is connected. I had a long conversation with Peter Wolfinger about this once, I was surprised how little he knew about it. I suspect when he worked for SP they had much more accurate ways of measuring IP during inhalation.

The 7-9 seconds until lock up is not good. I bet your gauge is showing an initial drop, then quick recovery to a pressure somewhere below 130, then a slow climb back to 130, is that correct? The probable reason for this is that you did not replace the seat, and so it is engraved with the profile of the piston edge from before. When you put it back together, the piston edge contacts the seat in a slightly different spot and you end up with a sloppy lock up. You could try leaving it pressurized overnight, tapping the purge a few hundred times over the course of a few hours, and see if the piston re-seats itself securely. It probably won't.

Replacing the seat and making sure there are no scratches or imperfections on the piston edge are really important parts of rebuilding one of these. Once the seat is installed and the reg pressurized, you shouldn't take it apart again. Some folks have been able to remove the seat retainer while leaving the seat in it, and have it go back in close enough to the same orientation so that the piston locks up in the original engraving. I haven't had much luck in that regard.

 

[redacted]

One other thing: I omitted an issue that I encountered when servicing the mk15 in the earlier update. When reassembling the reg, I found that part #22 in the schematic (swivel o-ring, 01-050-161) was missing both in the reg and the SP service kit. Since the original leak was not emanating from the ambient chamber ports, I ignored the missing swivel o-ring issue. Also, it missing both in the reg and the service kit made me think that maybe it's not essential (or mk15's design has evolved which obviated the part). The swivel o-ring shows up as an annual replacement part and common sense seems to indicate that it is needed for proper sealing of the LP port side IP chamber. I mention it because of your comments about venturi forces in the turret and their potential impact on IP measurement.

If that o-ring is missing, the 1st stage would never lock up. It is essential.