An experiment - main spring failure

[duckbill]

There are some like that, my R190 has one. But there are others that work internally, either through a spring washer in the orifice (atomic, I think) or a balance chamber (S600?) that separate the 2nd stage seat from the orifice whenever the reg is not pressurized.

Thanks! An automatic seat saver. That's pretty slick. I never knew they existed. Like my Dad used to tell me, "You learn something new every day if you're not careful."

 

[Texfrazer]

Wow - what an awesome thread! Very interesting news about an unbalanced first stage.

Doing this with a Mk 5 or other balanced piston could be a bit dicey due to the inability to get the reg off of the tank. At least I'm not volunteering mine .....

However, I might volunteer one of my Sherwoods, since it would theoretically bleed off any excess pressure through the air bleed.

 

[herman]

Wow - what an awesome thread! Very interesting news about an unbalanced first stage.

Doing this with a Mk 5 or other balanced piston could be a bit dicey due to the inability to get the reg off of the tank. At least I'm not volunteering mine .....

However, I might volunteer one of my Sherwoods, since it would theoretically bleed off any excess pressure through the air bleed.

The Sherwoods (not sure about the SR-1) are flow BY pistons, just like the MK-2 so they would react the same. Getting the regs (MK-5) off may take a while but it will come off sooner or later, some gas is going to leak past the seals or you could speed up the process by loosening the HP gauge hose or any plug in a HP port. You might blow out an Oring but no big deal.

 

[Texfrazer]

My bad about the Sherwood! Thanks for the clarification herman.

On a similar note, I've heard that if the spring washers collapse, then you'll get nothing out of the Sherwoods. I may have to try this out to see if I get some similar results as AquaNSun.

 

[T. Bix]

Just buy a cheap used diaphragm 1st stage and you can ajust any IP you want.

I use my spare Dacor Olympic 400 first stage for running air tools and servicing tires during racing season, I have it set at 140 psi and holds it rock solid no matter what the demand.
BTW: This regulator set still gets regular service at my LDS and still works like a champ. I have tried composite second stages and just don't care for them. Love my old Dacor and will dive with it until the parts run out.

Also this thread is very informative as to the operation of a piston first stage..... If I understand correctly (please correct me if I don't) It seems from the discussion that the LP is considerably lower with the piston type and the pressure drop to unseat the piston can be very low or almost as low as the ambient pressure?? I've never really given too much thought to the workings or differences between the types of regs but I suppose I will need to someday soon.

 

[herman]

My bad about the Sherwood! Thanks for the clarification herman.

On a similar note, I've heard that if the spring washers collapse, then you'll get nothing out of the Sherwoods. I may have to try this out to see if I get some similar results as AquaNSun.

I am hard pressed to believe you would lose all gas flow. The Belleville washers in a Sherwood act as a balancing mechanism for the Sherwoods. The washers allow the HP hard seat to float up and down in relationship to tank pressure which has the effect of adding or reducing load on the piston spring allowing the IP to stay constant as tank pressure changes. The IP would shift a fair amount depending on how many failed- there are 4 or 5 in the regs but I doubt it would cut the air off completely. In addition I would not expect all of them to fail at once, a more likely scenario would be for the tech to leave them out during assembly and that would be caught during testing...or at least one would hope so.

 

[John C. Ratliff]

I use my spare Dacor Olympic 400 first stage for running air tools and servicing tires during racing season, I have it set at 140 psi and holds it rock solid no matter what the demand.
BTW: This regulator set still gets regular service at my LDS and still works like a champ. I have tried composite second stages and just don't care for them. Love my old Dacor and will dive with it until the parts run out.

Also this thread is very informative as to the operation of a piston first stage..... If I understand correctly (please correct me if I don't) It seems from the discussion that the LP is considerably lower with the piston type and the pressure drop to unseat the piston can be very low or almost as low as the ambient pressure?? I've never really given too much thought to the workings or differences between the types of regs but I suppose I will need to someday soon.

T. Bix and others who may want to try this experiment, DON'T DO IT ON A DIAPHRAGM REGULATOR!!! If you do, you will likely have air trapped in the HP side of the regulator, and may not be able to get the regulator off the tank. This regulator is normally open by the spring, and removing it effectively shuts the stage by forcing the seat into the orifice. Putting pressure on it without the spring would put full pressure onto the orifice without a way of removing it. This probably also occurs with the unbalanced piston.

SeaRat

 

[AquaNSun]

For the balanced piston, if the holes in the ambient chamber are big enough and that you can somehow see the piston and push the piston down with a thin L shape stick, this might be able to release the pressure in the 1st stage.

or to block all holes with tape, except one, and then blow a HP air tool inside the hole to push down the piston? I think it only takes a tiny gap to release the pressure and the piston is very light to move.

 

[herman]

John, Aquasun you guys are way overthinking this. Just loosen a HP port hose or plug a little. You might blow an oring or more likely just extrude it but in either case the reg will depressurize in short order.....having the tank valve closed will help however. In either case it's no big deal and the HP orifice in the reg will keep flow to a mimimum.