Setting intermediate pressure

[Bryan]

I have been getting a lot of E-mails lately about setting the intermediate pressure on double hose regulators. This particular item sparks about as much debate as asking which motor oil is best!!!
I am going to state my OPINION and what I would call my OWN best practice on setting IP and then leave it up to discussion.
Once again, this is my OPINION and should not be taken as fact. I am not telling you to follow anything I say. U.S. Divers has the adjustment procedures outlined very carefully in the service and repair manual for their regulators and it is my recommendation that you follow their guidelines.

Broxtons, DA Navy, DA Navy Approved Only…
I back out the horseshoe support screws 2 ½ turns from the stops. Some sources suggest 1 1/2 turns. You will have to experiment to find what is best for your regulator. Then I insert the wire pin through the holes in the wire support pins. This is a very important step as the pin is part of the fulcrum and adds greatly to the downward pressure put on the 2nd stage seat.
Then place the regulator on a cylinder with 500 psi of air pressure in it and slowly turn it on. I gradually increase the IP by turning in the center adjustment screw until a slight leak in the 2nd stage is heard. Then back off a little on the adjustment till the leak stops. Operate the horseshoe lever a few times to let air flow through and to allow the 1st and 2nd stage pressures to cycle and equalize a few times. Once more turn the adjustment screw in until the 2nd stage starts to leak and then back it off ¼ turn from the point it started leaking. Cycle the horseshoe lever again a few times and your IP should be as good as it gets for this regulator type. I usually let it set for 10-15 minutes under pressure and come back and check it again just to make sure.

More info

http://www.vintagedoublehose.com/downlo ... erhaul.pdf


MORE TO COME

[Bryan]

I'm surprised that no SAM missiles have been sent this way.....Normally this subject causes all kinds of opinions.....

Anyhow, On to the DA Aqua-Master....Once again, my opinion on this and I'm certainly open to new ideas on this subject.

The 2nd stage LP spring tension is the # 1 factor you are contending with when setting the IP on this regulator. My belief is that USD intentionally set the IP rating low on the DA because the factory setting of 110 +/- psi will work almost 100% of the time and be a decent performer at that pressure.
Using a cylinder at 500 psi, assemble the2nd stage LP assembly; let the spring put pressure on the seat. Slowly increase the IP pressure until a slight leak is heard and then back off 1/4 turn further you will notice that the LP is quite a bit higher than the factory rated pressure and the cracking effort will have been reduced by a measurable amount!.....ONCE AGAIN THIS IS JUST MY OPINION AND I AM NOT SUGGESTING THAT YOU DO ANYTHING OTHER THAN FOLLOW THE FACTOR MANUAL TO A T.

[1stab]

Bryan, your talking about the HP spring adjustment in the 1st stage, right? Above, you mention LP instead of IP.

That's pretty much my method and it seems to work. With the 2nd stage assembled but not adjusted, I increase the spring pressure in 1st stage until there's a slight leak. I back off a 1/4 turn. I then adjust the 2nd stage the same way. I tighten the little nut until there's a leak and back off a 1/4 turn. I then place the diaphragm on top and then the box cover and squeeze. I listen for any leaks. If it leaks, I'll back off a bit by bit until it stops.

Finally I conduct a leak/freeflow test in the tub when its all together.

And that's my opinion.

[Bryan]

Last but certainly not least is the balanced 1st stage as is found in the Royal Master and Royal Aqua-Master. There are several other double hose regulators with balanced 1st stages but I’m confining my comments to the USD line for now.
The beauty of a balanced 1st stage is that it could care less if there is 200psi or 2000 psi in the cylinder as it performs just as well at either pressure.
Basic Scuba by Fred Roberts, The USD Service Manual and Vance Harlows Scuba Maintenance and Repair manual all have great descriptions and some drawings of balanced and unbalanced 1st stages in action. Great material if you want to know more details…..Back to the subject….
Always follow the USD Factory Service Manual recommendations for setting IP pressure on any USD regulator. In my OPINION the RAM is a much better performer when you use a higher than recommend IP pressure. There are many other Vintage Divers out there that have done a lot of experimenting on this subject and have had some very impressive results. I will give them the opportunity to chime in and give their opinions.
Once you have the regulator back on a cylinder (pressure makes no difference) adjust the IP till you hear a slight 2nd stage leak, back off a ¼ turn and its set. I follow this procedure ½ dozen times just to make sure I’m on the money with the adjustment. Follow the procedure for adjusting your 2nd stage lever and you should be set.

For those of you who like to experiment, Try the IP at the factory setting. Put your diaphragm and hose back on the box. BIG WORDS OF CAUTION HERE…Never…Ever breathe directly out of the box. It is VERY likely that direct suction on the box will result in the main diaphragm collapsing downward slamming the regulator into free flow. Good and easy way to POP YOUR LUNGS….BE SAFE, Put your hose on the box and breathe normally. You can measure your cracking effort with a magnehelic gauge if you are so inclined or just by your own feel. Then set the IP in alternate fashion and check your breathing effort then….I think you will notice quite a difference in effort and IP pressure.
Just to clarify….This is my OPINION. I am not suggesting you should try any of this. The USD manual is the ultimate source for direct information on service and service procedures…

Magnehelic Gauge in McMaster-Carr Part # 4021K11 Use a 0-3" WC gauge as a general rule of thumb. Regulators that pull much over 2" are unuseable IMO.....

[ebj]

Bryan,
I really appreciate your wisdom in setting the ip for the RAM. I had set mine using a guage and following the Conshelf XIV specs to bring it to 145psi at 500psi tank pressure and again checking it at 3000psi. Your method is so much easier! Thanks again!

[treasureman]

I have folowed the instruction as indicated in the previous posts.

In order to increase the IP and get a free flow or leak, the ip is around 190 using one of VDH guages. I back off a quarter turn, retest IP is now 120. I adjust to take to 145, it seems to sit there no leaks.

I adjust the 2nd stage until it leaks, then back off, and seat the diaphragm, put it all back together then try a few breaths. It seems to suck, and when i draw a hard breath it will go into free flow mode. Is my horshoe too high?

[treasureman]

Now the latest news.

The Ip was set at 140, put the cans back together, diaphragm back in, tried a few breaths.. Now IP is 125 steady, drops about 6 psi during a regular breath, and when you draw a hard breath, i get a whoosh of air at the mouthpice almopst like autop inflate. I have noticed that when i draw a large breath, i feel air at the exhaust holes in the front can . Is tghius some sort of blow by. I thought the back can covered by the diapragm would be air tight, and no air would pass through to the front can and the exhaust holes (ports)

I am at a loss, I am fed up, been tinkering with this for three days now.

On regular steady breathing seems fine, but in hard breath mode, it does the whoosh and seems to dump air into the front can.

Better minds would be appreciated

[captain]

The air from the front can is probably being caused by the diaphragam springing back after being sucked in so hard.

[treasureman]

How is this possible if the edges are held in place netwen the front and back cans?

[treasureman]

I am going to send the whole thing over to Bryan, and have him work his magic.

[captain]

How is this possible if the edges are held in place netwen the front and back cans?

When the diaphragm is sucked in during inhalation ambient air is sucked into the front of the box through the exhalation holes, when the diaphragm springs back to normal relaxed position it blows the air back out. The diaghpram is acting as a pump pumping air in and out of the box top just as water is pumped in and out .

[treasureman]

right... i forgot basic physics. either way, the darn thing is going off to bryan to be tuned to perfection

[JES]

right... i forgot basic physics. either way, the darn thing is going off to bryan to be tuned to perfection

A wise decision that will save much frustration.