SP MK25/S600 Freezeups

[tanzer2250]

I have had similar problems. It sounds like the problem was your mk25 first stage not being properly tuned for cold water diving. I am not a technician and have not taken a scubapro regulator course. I have not worked on my own regs. I can only relay my own understanding of things.

My understanding is that the mk25 is not ready out of the box for cold water and needs to be properly adjusted for cold water diving. I am not aware of any cold water kit for the regs. You should contact your LDS or scubapro to have the proper adjustments made, if it wasn't set up for cold water when you purchased it. I also recommend that you make sure that your LDS tech. is actually competent and experienced to make the adjustments and does not just have a certificate hanging on the wall!

I have three mk25 reg. sets, with an s600 as my primary, an R380 as my backup and an R190 for my deco. I have had several double freeflows (s600 and r380), all in fresh water, at depths between 25' and 100'. The common factor seems to be water 42 degrees F and colder.

I recently had all of the regs. overhauled and upgraded to the latest version of the mk25. At the same time, they were tuned for cold water diving. The new ambient chamber cap was added that includes both the antifreeze ridges (supposed to prevent ice creep) and the larger ambient chamber openings (provide greater water flow through the ambient chamber, also to help prevent ice formation). I also believe the pistons were changed to the latest composite version (supposed to help prevent ice formation?). I think these are standard on current mk25s, but I don't know when the change occurred.

The IP for the mk25s was set to the low end of the specification (125 psi) and the cracking effort of the second stages was set to the high end of the specification (s600 - 1.4?; R380 - 1.8?). I am having the LDS check the IP and cracking effort to confirm and record for future annual overhauls. I believe that there may have been other adjustments made, but I do not have a record of what else was actually done and don't want to give an inaccurate report. If there were other adjustments, I want to make sure these are recorded by my LDS as well, so that we don't have to "reinvent the wheel" during the next overhaul. I have tried to get as much info. as I can but service reports don't contain an itemization of all work done and all final settings.

As an aside, wouldn't it be nice if the manufacturers and LDS provided this kind of information on the regs. to the consumers (or at least kept those records for future work and to track problems)!

My understanding is that for cold water diving, the mk25/s600 (or other second stage) needs to be properly adjusted (detuned?) or free flows can occur. I am not sure if adjusting the regs. for cold water ends up taking away the performance benefits of a high performance reg. for both cold water and other diving conditions. So far, I have tried them in 44 degree F. fresh water and did not experience any free flows.

Fortunately, I dive with a GREAT buddy who helped me isolate and try to solve the problems underwater during each freeflow. On each occasion, we could not stop the free flows and had to turn the dives. After one double freeflow at 100', we turned the dive and began to ascend. I began breathing my buddy's primary at about 60' and continued till approx. 25' when I switched to a stage. My buddy dives Poseidons (and recently upgraded to the Extremes) and has never had a problem at any depth on any mix. The Poseidons breathed fine.

As an aside, if anyone has used both Poseidons and Scubapros, I would like to see a comparison of the pros and cons of each. Several of my friends that have a lot more dives than I do tend to dive the Poseidons and swear by them. They are New Jersey wreck divers, not cave divers. If you have any info. on the extremes, I would like to hear about that as well.

For me the jury is still out on the Scubapros. On the one hand, my personal experience is that I have had several free flows in cold water and spent an awful lot of time trying to solve the problems. On the other, I can not ignore that Scubapro is one of the top regulator manufacturers in the world and the mk25/s600 continues to get stellar reviews as one of the top performing regs ever. They apparently have sold a lot of regulators, for a lot of years and to divers that dive in all conditions - including cold/ice diving. I also have to admit that better experienced and more knowledgeable techs at the dive stores that I went to in trying to solve the problems would have probably saved me a lot of trouble. I am continuing to dive them and hope that I won't have any more problems.

 

[Soggy]

Big-t-2538 once bubbled...
Also, how often do you see 38 deg. for any length of time?

Me? Quite often. I think we just broke 40 degrees here.

I have had my SP MK2/R190 down to 34 degrees in the middle of winter and have never had any troubles. My new MK25/S600 hasn't been in really cold water yet, though....we'll see how it holds up.

 

[sylvester]

I have also seen low temps a few times this year on New Years Day, Mid Jan, and last weekend.

With me moving to Pa in July I am sure I will be in cold water more then I have here in Missouri. So I am trying to relove this issue ASAP, the detuning suggestion makes sense, I am going to my LDS at lunch to talk that opion over with him, because he is also trying to work the issue.

 

[Mverick]

Did you buy the reg from that LDS?

If so, They probably tuned it how they like. After they received them. So they breath easier. And detuned the 250 for your octo to prevent freeflow. Since they all went bad.

Why is an Instructor or DM diving an Air 2 in a class? If a student has problems he has to swap to the Air 2 and give the student his reg. Which creates a big problem with control. He should have had a regular second at the very least. And to be a DIR zealot, which I'm not, the 7ft second to hand off would have been nice. But obviously it wouldn't have helped in this case.

Did you try to adjust your second stage under water? I set mine up with a little free flow. Then twist the knob to stop it. But I haven't touched the ones I'm using now. Same set up from the factory. And didn't have any problem with free flow.

Had your instructor dove there regs before at depth?

I had mine at the same depth and temp you had. Meremet at depth is always around 42. And I dive there on occasion. MK20/G500, MK25/S600, MK20/HP250, TX50/DS4, TX100, Blizzard. None have freeflowed at depth and cold.

Any reg will have problems if not set up properly. And since all three did. I'm betting they had adjusted them wrong.

And I've had mine under ice without problem.

 

[tanzer2250]

If you are moving to PA, you might end up diving the Wabank and Dutch Springs quarries/"man made lakes." Both can get down into the upper 30's/low 40's at various times of the year. We can not always get out off new jersey and it's nice to get a quick dive in without the risk of getting blown out by weather.

If your LDS is not familiar with adjusting the regs for cold water, I recommend that they contact Scubapro or that you find another LDS that is experienced!

By the way, when my s600 free flowed, it would not stop freeflowing, even after turning the adjustment know all the way down and VIVA's to the predive setting.

 

[Mverick]

Oh,
MK20 or MK25's aren't sealed. They are a piston design which is open. While the MK16 and MK18 are sealed. They are a diaphram design. So are the Apeks TX50/ds4, Tx100, that I dive.

 

[sylvester]

No I did not buy my setup from his store, he did service my g250 last time.

I attempted to trun my settings down to min "predive" with no success. About the air II, I am a fan of it. I like it but did not have one then because I was diving my new wing so I attached my G250. The above comment is not intended to start a thread about Air II we all have our prejudices and you are welcome to dislike my or others peoples gear choices.

I ask about the 7' hose because I have heard but cant confirm that it may help with freeze ups?

Also I am not sure what froze? the s600 or mk25? Since the g250 was working flawlessly.

I am going out at lunch to attempt to find a soulition for how to correct. He was going to contact SP, I will address detuning based on what I have read here.

When I get to Pa I will dive the quarrys I have a cpl bookmarked already on my PC. I will be in Carlisle, so the best I can tell is I will be near a few of the sites.

Thanks to all for your help so far, this board is great for this kind of info.

 

[Mverick]

It wasn't a slam on the Air 2. I actually have one also. I don't use it anymore but I have one and used it for a couple of years on my singles rig.

I liked the Air 2 because it is right there. You don't have to search for it. During air sharing I can find it imeadiately. Didn't like it hooked up to the inflator because I had to twist my neck. But It just had to get me to the surface safe.

Now I use a Bungied Second around my neck. Don't have to search for it either. And it's not linked to my BC inflator. I like that better.

What I don't like is an instructor using one while teaching.

Sorry about your problems.

 

[sylvester]

No problem, no blood, no foul.

I will eventually switch to a bungied 2d, but my priority now is fixing my reg. My LDS who worked on my g250 last said he did not tune it down. So I still wonder why it worked and the other failed.

I will rig my pony and go back to try and figure out if what ever fix the LDS comes up with works.

He believes tuning it down will suffice to fix it but on principal does not agree with that as a fix. Kinda defeats the purpose of having a high end regulator.

I did look because my wifes reg is only a month old, and hers in the new mk25af model, so a good note is I nly have one to fix/upgrade.

 

[Genesis]

First, the Mk10/Mk20/Mk25 are all relatively similar regulators. The Mk20/25 are identical internally except for the extenral adjustement for IP on the 25, and that can be added by swapping in three parts (or so) to any Mk20.

The first question is "what froze?" Without know that, you know nothing. You can get two different types of freezing, with a couple of subtypes. Let's look at them:

1. First stage, EXTERNAL freeze. Can only happen with an environmentally open (e.g. BP such as Mk10/20/25) first. When gas expands, it cools. The gas expands a LOT coming out of a tank at 3000 psi to an IP of ~140ish psi. If this is the cause turning DOWN the IP is the WRONG thing to do, since adiabatic expansion cooling is proportional to the difference in pressures! SP has tried a LOT of things to attempt to prevent this, including the "TIS" system (basically bushings to insulate chamber so that ice does not form and jam the piston), the new composite piston (ice won't theoretically stick to it), etc. Effective? Maybe. More effective is probably filling the environment chamber with silicone (so there's no water in there, or very little) as silicone won't freeze, but its a hellish mess to deal with when you do overhauls and CAN be one in normal use, since there is a possibility of it leaking out. Diaphram 1sts are generally immune to this. Can cause either a freeflow OR air cut-off, but usually causes a freeflow!

2. First stage, internal freeze. Can happen with ANY first. Tihs is caused by excessive moisture content in the gas in the tank. There is no fix that a reg manufacturer can come up with for this one - the fix is "don't get fills that have excessive moisture in them!" Same deal - you can get either an air cut-off or freeflow, but usually get a freeflow with this.

3. Second stage, external freeze. Can happen with any second. Caused by the moisture in your exhaled breath, or ambient water that gets into the reg (e.g. when you remove it from your mouth underwater) freezing due to the adiabatic expansion and cooling of the incoming gas from your hose. This typically causes a freeflow as it binds up the mechanism.

4. Second stage, INTENRAL freeze. Technically possible for the same reasons that a 1st can freeze this way, but VERY uncommon. Watch out for things like the Apollo "biofilter" though in cold water!

Now, here are some further issues.

1. If you have a first stage freeze freeflow AND you crimp the hose, you risk a hose explosion. The reason your reg is freeflowing is that the seat isn't sealing in the first! If you shut off the outward flow of gas, the pressure in the LP hoses will rise to that of the TANK! This will reliably rupture the LP hose(s), which will then drain your tank REAL FAST. (If you want to see HOW fast, take off one of your LP hoses from its reg and turn on a new tank, then time it - you'll be flabbergasted at how fast the open LP hose will drain your gas!) It is quite dangerous to attempt to control a freeze-up freeflow this way for this reason!

2. A SECOND freeflow can be controlled by crimping the hose, since the 1st is still producing the proper, regulated IP.

The problem is that it is pretty difficult to KNOW which is happening, BUT if BOTH seconds are freeflowing, its probably a first-stage freeze. If only one is, it is PROBABLY a second-stage freeze, BUT, being wrong and attempting to control it with a crimped hose turns a problem into a real emergency.

The best option is to shut down the valve, breathe something else (your buddy's reg, a pony, the other post if you have doubles, etc), begin an abort, and turn it back on after its had a chance to thaw. Oh, and try to figure out what's freezing and how, and either fix the problem or replace the reg with one more suitable.

Detuning is probably NOT the correct answer; it may lower the freezing point by a couple degrees (maybe), but it will NOT "fix" it.

If you are in a situation where this procedure would be unsafe, then you need two first, two seconds, and two supply valves, so you can shut one down and let it warm up.

Oh, BTW, using inflators and other things that increase the rate of gas flow make the probability of a freeze - of any type - go up a LOT. So if you freak in cold water......