Regulator Performance With Increasing Depth

[Fishpie]

...the SuperFlow is (almost) identical to the old metal USD 2nd's minus the adjustment knob.

 

[muddiver]

Thanks for the schematic.

It is a classic downstream design which appears to use an o-ring as the LP seat. Interesting. And then it has the additional spring with mechanical adjuster similar to the newer Oceanic Deltas. The older Deltas had the 2 springs with one spring adjusting pressure on the downstream end of the poppet. The newer Deltas have a contraption that looks something like the KM adjustment tube but perhaps a bit more complex. I don't see as many o-rings in this KM contraption, but I do see something called a piston that makes me think there may be a chamber inside that adjustment tube. I would like to better understand what is going on inside there. It is clearly more parts than you need to simply apply more spring force to the end of the poppet.

Edit: After looking at the schematic a bit more, that o-ring must be the seal between the inlet nipple (tube) and the case. So, an LP seat must be integral to the inlet valve (poppet).

The seat is integral to the inlet valve. Typically the valve is replaced when you service the regulator because it comes with the set attached the rebuild kit.

The piston is nothing more than a spacer between the adjustment spring and the valve spring. It's not like you can but two springs up aginst each other. No chambers, just a tube with an O-ring seal for the adjustment shaft.

It is really a simple regulator. I don't know what you mean by "more parts than you need to simply apply more spring force"? The valve spring rides on the piston, which rides on the adjustment spring. The spacer is there to givethe adjustment shaft some thing to spin aginst without torquing the spring. That's all.

 

[redacted]

The seat is integral to the inlet valve. Typically the valve is replaced when you service the regulator because it comes with the set attached the rebuild kit.

The piston is nothing more than a spacer between the adjustment spring and the valve spring. It's not like you can but two springs up aginst each other. No chambers, just a tube with an O-ring seal for the adjustment shaft.

It is really a simple regulator. I don't know what you mean by "more parts than you need to simply apply more spring force"? The valve spring rides on the piston, which rides on the adjustment spring. The spacer is there to givethe adjustment shaft some thing to spin aginst without torquing the spring. That's all.

I believe I am beginning to understand the design. In the KM, The piston (4) is exerting force directly on the inlet valve (25) or the lock nut that is screwed onto it. The adjustment tube must be fixed in the body. So operating the adjustment knob (10) effects the force exerted by the adjustment spring (5). So increasing the force on the adjustment spring increases the force of the seat against the orifice with no effect or perhaps a slight decrease in the force applied by the main spring (26).

If that is basically correct, then the Oceanic design is functionally the same but they threw in an extra o-ring or two that appear to function not as seals but as a way to control alignment. That was throwing me off a bit as I was trying to see them as seals.

What I do not understand is the advantage of this relatively complex design over the adjustable barrel poppet design such as the Scubapro 109 which employs a single spring. I suspect the K-M/Oceanic design allows for finer adjustments by using a light spring as the adjustor spring so larger changes in the position of the adjustment knob results in smaller changes of actual force on the LP seat. But I do have to wonder how this creates a useful performance advantage other than perhaps easier fine adjustments.

 

[c5diver]

i recently had my mr42 serviced and had the dry CWD kit added and i think it breathes better now than it did without. but it could be the servicing.

 

[Akimbo]

...the SuperFlow is (almost) identical to the old metal USD 2nd's minus the adjustment knob.

The original Kirby-Morgan regulators were modified USD regulators. The band mask design was sold or licensed (I don't recall which) to US Divers in the early 1970s. I understand rights to the Kirby-Morgan name was held by USD, which is why it was Diving Systems International when Bev Morgan started the company back up in the mid 1970s. I don’t know how they got the name back, but everybody called the gear Kirbys or Kirby-Morgans anyway. The regulators they now manufacture are functionally identical except for many refinements that include larger ports.

My interpretation of events was that a small-scale Dial-a-Breath adjustment was incorporated into some high-end Scuba regulators in the early 1980s as much for prestige as function. The purpose in a commercial diving setting is critical since the supply pressure does not automatically adjust with depth — with minor exceptions such as on Oceaneering's Rat Hat. As a result, the diver must manually adjust the spring pressure on the downstream seat. Typically the range is about 250 PSI, the max output pressure of a two-stage low pressure compressor, down to around 80 PSI.

This 170 PSI range allows the diver to adjust for just-above-freeflow from the surface to over 350'. Naturally, this would not be the output of an air compressor at that depth. It is interesting that there are still so many slightly refined clones of that early USD regulator on the market today.

 

[AquaNSun]

I'm looking at the KM plastic adjustable 2nd stage and it's almost identical to the oceanic delta. In the Oceanic design, the adjustment tube, 14, is a chamber and is sealed by an oring, 8, and another oring near piston, 4, which I didn't see in KM diagram. The secondary spring, 5, is working together with the main spring, 26, to acheive the balancing act within the housing (mechanically balanced 2nd). The ambient pressure inside the chamber (inside the adjustment tube) does increase/decrease with depth to maintain a constant force against the seat. It seems like the adjustment shaft, 7, is threaded inside the adjustment tube, 14, so that when you turn the knob, 10, the adjustment shaft moves and compresses the secondary spring, 5, and pushes the piston, 4, against the inlet valve, 25. I may be wrong but that's the best I can think of the design with the attached diagrams.

Halocline: Those are the 2 springs I was talking about in a mechanically balanced 2nd stage. It's a general idea and does not apply to all regulator designs. Im talking in general as in my previous post.

Awap: I believe the KM adjustable you're talking about is a balanced 2nd vs 109 non-balanced?

 

[LeadTurn_SD]

i recently had my mr42 serviced and had the dry CWD kit added and i think it breathes better now than it did without. but it could be the servicing.

That's interesting.

If I had to guess, I'd put my money on the fresh servicing and tune-up rather than the cold water kit (which is essentially a 2nd diaphragm and "transmitter").

The cold water diaphragm should just be "faithfully" transmitting changes in water pressure to the main diaphragm via the transmitter-piston-thingie.

Best wishes.

 

[knowone]

There have been a plethora of generics out there with very similar bodies to Oceanics and some interchangeable parts with the choice of a plug or the basic parts challenged adjustment option pressing against the threaded end of the poppet which consists only of a plastic plunger and body and a spring with the knob only doing one and a half turns.

Some people like knobs.

 

[dougr52]

first off i don't know anything about regulators i am just reading all the post and trying to learn!!
so would this be the BOTTOM LINE ??
a balanced diaphragm 1st stage only makes breathing easier when the tank pressure drops below 400 psi..(true or false)..
most modern day 2nd stages are balanced and if not would still not have much effect on breathing above A depth of about 160 ft. (true or false)...

 

[Akimbo]

…
a balanced diaphragm 1st stage only makes breathing easier when the tank pressure drops below 400 psi..(true or false)...

True, sorta. Ansti breathing machine tests I have seen generally show measurable changes around 500-600 PSI, though too small for people to detect. By 400 PSI the increase becomes pronounced enough that it is hard for a diver not to notice. It is still breathable down to about 250 PSI over bottom pressure. Most modern balanced first stages maintain an awfully constant IP (Intermediate Pressure) down to virtually the IP over bottom. As a result, you may be able to suck 5 breaths out after you notice resistance compared to maybe 60 — mileage varies dramatically based on depth and respiratory volumes.

BTW, the same is true for balanced diaphragm and balanced flow-though piston designs compared to unbalanced pistons.

…most modern day 2nd stages are balanced and if not would still not have much effect on breathing above A depth of about 160 ft. (true or false)...

True. According to Ansti breathing machines, more like 197'/60 meters.