RGU REGULATOR DETAIL

Meet Ken Swain (the tall good looking one)

Our Guest Advisor on RGU Regulators

Ken and I have been conversing by e-mail for quite some time now. While I have explored many aspects of the RGU, Ken has gone way past me on the regulator side. Strangely we both own 5 of these units. We met at DEMA 2002 and had a great time together exchanging war stories and information on the units. I learned a lot in those couple of days. I asked and he agreed to take some pictures and write the text for this page to fill in some of the gaps that I have have left.

As a small boy Ken grew up watching Sea Hunt (first run!) and became certified as a diver as soon as he turned 16 in the late 60s. Like many of us who learned to dive back then know, he found you often had to "build yer own". A mechanical engineering degree formalized his compulsive tinkering with all manner of dive gear. Piloting aircraft, first for the USAF and now for a major airline, supports his addiction. His passion to build his own equipment led him to build his own airplane 25 years ago. He still flies it. These days he frequently haunts the deep, cold, historic wrecks of the Great Lakes. His dive boat "M.A.C. Animal" has taken him to sites from the southern tip of Lake Michigan to Isle Royale in northwest Lake Superior. Ken is also a regular contributor to the rebreather list.

I only get the credit or blame for the html. As I do a number of pages,I know how much work Ken has put in to this in providing us an invaluable resource.

My thanks to Ken from all of us.

I am now going to turn it over to Ken.

1. This is where I use my RGUFM regulator and bottle. It is my version of Dave Sutton’s Franken Rig. While many divers purchase the RGU to use as a pure oxygen rebreather limited to 20 feet, a number of us are using it as a "kiss" oxygen supply for closed circuit or mixed gas rebreathers.
2. And here I am diving it inside the new wreck off of Key Largo, the Spiegel Grove. The O2 addition button is visible on the outside of the rebreather on its lower left side.
3. One each regulation RGUFM constant mass flow O2 regulator. This is the heart of the RGU rebreather. It produces .9 liters a minute of Oxygen to depths exceeding 110 feet. The black rubber button is an injection button bypassing the constant flow system.
4. Here are the two versions of capture rings for the rubber O2 addition button covers. They are interchangeable.
5. The ring simply screws off. Like all bits on this regulator, it may take a bit of “gentle persuasion” to get it off the first time. Be mindful what you put the tools to. The parts are brass and can be easily buggered or broken.
6. Here we see, in order, the capture ring, the back up ring, the heavy rubber button cover, and the O2 bypass button itself. Note- if you block the output of the regulator without adequately supporting this rubber cover, as when adjusting output pressure, the button cover can blow out. It is a simple matter to screw off the capture ring, put all parts back into place, and replace the ring.
7. This is the cavity left once the button assembly is removed.
8. The parts constituting the O2 bypass button assembly.
9. This little gem is a relief valve assembly to allow interstage pressure to bleed off in the event of a blown high pressure seat. It can and does sometimes leak. If you increase your interstage pressure you will need to adjust it tighter by first loosening the middle lock nut, screwing the top nut in a turn or two, and retightening the lock nut. In any event it would be wise to disassemble it, clean it, and coat the soft seat with a hint of O2 safe lube.
10. Left to right, the adjustment nut, lock nut, spring, soft seat & carrier, and hard seat/ base.
11. WARNING: Don’t use this valve as a lever point when tightening the reg onto the O2 bottle. They are relatively soft brass. They can and do break.
12. The cap removed from diaphragm end of the regulator. The white ring is a rubber gasket that seals the backside of the diaphragm at atmospheric pressure, enabling its CMF ability. The screw at the left adjusts interstage pressure and, consequently, flow rate. I’ve worked with 7 of these regs now and all came adjusted dead on at 0.9 liters per minute flow rate. Individual interstage pressures varied from 58 to 65 psi to achieve that rate. Highest adjustment- before bottoming adjustment screw- is in the 85 psi range, which yields a flow in the 1.2 to 1.3 lpm range. I dive mine adjusted to about 80 psi for a flow rate of about 1 lpm. At that interstage pressure it stops flowing O2 at about 140 to 145 ft depth.
12B. Getting the cap off is a bit tricky, here is how to remove it.
13. Diaphragm cover removed from reg and adjustment screw removed from cover.
14. Parts in order as found below diaphragm cover. Left to right: reg, diaphragm w/ back up plates, back up ring, spring, spring locator, cover, adjustment screw, cap.
15. Close up of diaphragm and back up plates. On left is inner plate that contacts high pressure seat pin. On right is outer plate that mounts the adjustment spring.
16. High pressure seat pin and its brass carrier still mounted in the regulator body.
16B. Here is how you can get that part out. Man is a tool making and using animal.
17. Right to left: HP seat pin, brass pin carrier/ hp hard seat, hp soft seat, spring locator, spring, reg body.
18. On the other end of the regulator, the inlet filter cone as removed by first screwing out the threaded capture sleeve.
19. At the outflow end we find the ultra fine filter screen, a gasket, and the metering orifice.
20. Close up of the screen, gasket, and orifice.
21. One last note: This reg broke while on a dive trip. The threaded output piece was sweat soldered into the reg body with not all that much metal to metal contact. Avoid severe side loads to this part and keep in mind that the nut that attaches to it is a FINGER TIGHT knurled nut! Leave the vise grips in the toolbox when attaching whatever you use for an output fitting.
Here is all the tool set you need to strip the regulator down. Note the vise available from Harbor Freight.

All the internal parts, exploded on the bench. As far as I can tell, the piece that captures the nut that attaches reg to bottle is sweat soldered in place and is not removable.





Fantastic job Ken....

Tom

After Thoughts

While some folks such as Ken and Dave Sutton have good luck when they utilize the RGU tank and regulator as an oxygen injection system, I have encountered an operational problem unless I am diving close to home. The tank is a .8 liter tank that when filled to 200 bar gives about 160 liters of oxygen. That is plenty for a two hour dive. The 200 bar requires a booster pump and all three of us have one as do many other rebreather divers. That is fine if you are taking the tank in a car but I fly to many of my dive sites and it is frowned upon to take a tank filled to 200 bar in your luggage. I get around that by arranging oxygen on site. It is often only 2200 or less psi or about 145 BAR. This means only about 115 liters of oxygen. This is only enough for a little over a one hour dive with a good safety factor. I just don't usually want to come out of the water in that short of a time.

My solution is to use the little RGU for shallow dives on the last day of a trip but use a larger tank during the week on my nitrox rig (The Hippocampus). Even with the lower pressure, I can have dives up to three hours or even just reload the rebreather twice a day...enjoying all the diving I want to. I use a tank that has 245 liters of oxygen at 2200 psi. To do this I adapted the RGU regulator to a medical oxygen tank. I found that a CGA 660 brass male fitting mated perfectly to the regulator as you can see in the picture above.

Ken has also sent me some information on how he fills his tanks and the gauge system he built to monitor the oxygen pressure while diving. This will be presented on another page. I'm going diving on Roatan for a week leaving this Friday so I gotta pack and do a couple of honey doos.... Tom



Here are some pictures of Ken and some of his diving buddies in action....

	And that my friends is the fruit of the labor. Tinkering, good diving, good friends, good fun, and not one damned bubble. What else is there?