Apeks DST 5 port orientation on doubles for cave diving

[v-v]

@v-v if you damage that amount of stuff, you have SERIOUSLY screwed up. You have to be going very fast and hit the rock at just the right angle. I have never heard of any damage like that being done to a DST.

Now, for what matters to you.
Parts 3/4/5/6 are in both regulators and are the actual diaphragm that makes the regulator work
Part 1 and 24 are the same thing and are the spring pressure adjustment screws that determine your IP.

When you change a UST to a DST, or US4 to DS4, you remove parts 1 and 2, and replace them with parts 24 and 23 *pretty sure part 1 and 24 are the same part number*.
Part 28 is the outer retaining cap, 27 is the actual sealing diaphragm. 26 is a sticker, and 25 is a pressure transmitter that presses on part 4 and makes it depth compensating.

For all intents and purposes it's a solid block of brass. You aren't going to damage it, and in a cave there is exactly a 0% chance that you'll rip the exposed diaphragm.

Great, thank you very much, those are the (reassuring) answers I was looking for!

 

[tbone1004]

Yeah, so since I have the sealed version (28 to 23) my question is, what happens if I scratch/cut/break element (27) and maybe (26, 25) since they're also quite exposed?
If I lost the 1st stage, then I'm probably right to worry of facing the diaphragm outward / forward and should better keep it inwards. No?

it's something like 1/8" thick silicone. You aren't going to scratch/cut/break that diaphragm. I've never heard of that happening before.
26 is a sticker, so that is irrelevant
25 is a really thick piece of plastic that is for all intents and purposes stationary and is not exposed. You won't break it.

Hypothetically, if you cut the silicone diaphragm, the chamber will fill with water and the regulator will become unsealed. It will function perfectly fine, but you will want to remove the cap to clean it after the dive. Again though, I've never heard of one of those getting compromised in the middle of the dive from external factors. I have had one extrude, but the regulator had IP creep so that was a regulator failure and had nothing to do with environmental factors

 

[JohnnyC]

You're WAAAAAAAYYYYY overthinking this. Rig them like normal and don't worry about it.

 

[divad]

Here's a picture of an Apeks DST knock-off with environmental seal:

 

[divad]

On three different regulators I just measured, the environmentally sealed ones are only a scant 3/8" longer. Or, not worth quibbling about.

 

[jadairiii]

There is a good reason to remove the environmental seals, effectively turning a DST into a UST, if you ever plan on diving those regs deep. I've had freeflows as shallow as 240' due to the IP issue.

For more details, read deep diving regulators

Odd, never heard or seen this happen. My original Tech instructor only used the DST's, my mix instructor only used the DST's and I went exclusively to DST/DS4 in '99. Of that group, never saw it happen (with thousands of dives deep on those regulators by those 2 guys). I also know a lot of WKPP guys that have used them deep without issue. Add to that, both of those unnamed instructors, maintenance was not a "high priority" with them.

Now, I am not doubting you here, but, I would not immediately go and condemn the seal if I had free-flow deep. Plus, I'm having a hard time trying to figure out how the plunger/seal would give too much "feedback" at depth? (I read the article linked)

Add to that, the linked article seems to say the issue is with those first stages and AIR 2's? And the author claims his first choice 1st stage is the Mares MR22? Mares?

 

[tbone1004]

@jadairiii it depends on how aggressive the second stages are set. If they are backed off enough, you can plan for it with IP and cracking effort settings, but it's not ideal

 

[rsingler]

There is a good reason to remove the environmental seals, effectively turning a DST into a UST, if you ever plan on diving those regs deep. I've had freeflows as shallow as 240' due to the IP issue.

For more details, read deep diving regulators

I'm sorry, but this article makes some blanket statements that are just not correct. And the fact that the author is from "scuba engineering" lends credence that he shouldn't have, based on what I read there.
For example, this whole "overboost" argument is incorrectly argued. And his "chart" computing the degree of overboost does not differentiate by manufacturer or design. That's just wrong!
The real reason overboost might occur is not due to the relative diameters of the force transmitter plunger, but rather due to the relative diameters of the main and environmental diaphragms. And in some designs, the opposite is true: since the environmental diaphragm is smaller than the main diaphragm, the added absolute IP rise with depth is less than with an unsealed.
Temperature factors aside, the main reason that freeflow at depth is more common is due to the increased Venturi effect of denser gas at depth on the second stage. That is easily tuned out.
And to say that sealed regs might get colder than wet regs completely ignores the fact that it doesn't matter if your reg is colder than freezing if there's no water inside to freeze! I'm not so sure that even the temp difference is true with the most critical components, because where the adiabatic cooling occurs is a dry area in both designs.
The ONLY thing he said that I agree with is the minor point that an upstream Jetstream design will freeflow at a tank pressure below 200 psi. If you're at depth with an ascent constraint with a tank below 200 psi, you've got other problems, I'd say. This argument is typical of the Poseidon haters, who conveniently ignore the superb performance and certification of this design at extreme depth.

My point? The Internet is a dangerous place to get your information.

@Luis H , care to comment on the article referred to above?

 

[taimen]

And the author claims his first choice 1st stage is the Mares MR22? Mares?

What is wrong with Mares, performance-wise?

 

[jadairiii]

What is wrong with Mares, performance-wise?

Nothing "wrong" with the MR22, but internally it is pretty much the MR12 (second gen). And I own 2 MR12III's, not my choice of a tech regulator, but that is me.

I rebuild all my regulators, I just prefer the Apeks, like the way they are built, their internals, everything, and I have owned just about every major brand regulator over the years.