Pistons over diaphragm regulator

[shockere85]

Can someone explain what are the major differences between the two types of regs?

[DevilDiver]

Originally Posted by shockere85

Can someone explain what are the major differences between the two types of regs?

Here you go......

I can't believe I beat Larry to this! I dive a balanced piston Atomic B2 and have been very happt with it.



Understanding SCUBA regulators

Breathing underwater is like a dream come true. SCUBA regulators come in hundreds of designs and features. As we cover the different types of regulators, remember that the most important feature of a regulator is “ease of breathing”.
At the highest level of scuba regulator design is Open-circuit or Closed-circuit regulator systems. Closed-circuit is what is commonly called re-breather regulators. A SCUBA diver’s exhalation is directed back into the scrubber to be re-cycled back into breathing the breathing air mixture.
Open circuit scuba regulators allow the diver’s exhalation to be directed back into the water. Open-circuit or SCUBA regulators can be further defined into four main types: Diaphragm and Piston regulators and each can be balanced or unbalanced.
Look at this diagram of an unbalanced piston regulator. Tank pressure influences the demand valve mechanism. This will make the regulator harder to breathe at lower tank pressures and/or difficult to breathe at deeper depths. Because of the piston regulator’s design, water pressure will enter the inside chamber, this can lead to extra cleaning during your annual maintenance.




1. HP spring
2. Ambient water pressure
3. Intermediate chamber
4. Valve and HP seat assembly
5. HP air
6. Air to second stage


The balanced piston regulator isolates tank pressure from the demand valve. It is this isolation that allows the regulator to breathe easier through out the tank pressure ranges during the dive. Once the tank gets as low as 500 – 700 psi, even this regulator will begin to breathe with more difficultly.





1. Air to second stage
2. Intermediate chamber
3. HP spring
4. Ambient water pressure
5. HP air chamber
6. Valve and HP seat assembly
7. HP air
8. Balanced piston assembly

One last note of piston regulators, they are simpler to maintain and use fewer parts than a comparable diaphragm regulator.


The unbalanced diaphragm regulator has been called the regulator that never was. It was built at one time, but today you will not see it on your local SCUBA stores shelves. This type of regulator uses an upstream valve design. Today’s regulators use a down stream valve technology. If an upstream valve regulator fails, it will stop delivering air to the diver. If a downstream valve regulator fails, you will still get air. Downstream valves have also been called a “fail safe” regulator design.




1. HP air
2. HP air chamber
3. Intermediate chamber
4. Diaphragm
5. Diaphragm balance spring
6. Ambient water pressure
7. Air to second stage
8. Valve & HP seat assembly
9. HP spring

The balanced diaphragm regulators also have more arts and are more complex than their piston counterparts. Since the diagram design also acts as an environmental seal, cold water divers prefer this design. This environmental seal is also preferred by divers working in contaminated and silty water.





1. Air to second stage
2. Valve balance spring
3. Intermediate chamber
4. Diaphragm
5. Balance spring
6. Ambient water pressure
7. Valve & HP seat assembly
8. HP air
9. HP air chamber



Second stages (common to all regulators). When the diver inhales, the pressure drops and the diaphragm moves towards the low pressure of the second stage regulator, this in turn will move a valve which restores the pressure. When the diver exhales the diaphragm flexes outward and stops against the housing of the second stage regulator. Any excess air is shunted outward through one way valve positioned at the exhaust port.

[BouzoukiJoe A.K.A. wrecker130 AKA Chuck Norris AKA joeforbroke (banned)]

Good job, Devil, nice to see all the info in one place.

[Splitlip]

The pistons cannot be environmentally sealed. The Diaphagms can.

I dive pistons

[DevilDiver]

Originally Posted by Splitlip

The pistons cannot be environmentally sealed. The Diaphagms can.

I dive pistons

Atomic Regs (piston) can be environmently sealed.

[Splitlip]

Agreed.

But as I understand it, they are sealed by packing them with "grease". Other Mfg's do the same. A bear to service.

Looking at the graphics, how else could a piston be "sealed".

Zeagle Environmentally Sealed First Stage

[lund0485]

Thanks you devil diver, I haven't seen this explained with diagrams, this makes sense now.

[DevilDiver]

Originally Posted by Splitlip

Agreed.

But as I understand it, they are sealed by packing them with "grease". Other Mfg's do the same. A bear to service.

Looking at the graphics, how else could a piston be "sealed".

Zeagle Environmentally Sealed First Stage

From Atomic manual:

For diving in extreme cold waters below 50°F (10°C), we recommend
having the first stage sealed with the installation of the optional antifreeze
kit (standard in T2 & M1). This is a rubber sleeve that fits over
the ambient chamber ports of the first stage to prevent icing of the
first stage. This is a factory or dealer installed item, as it requires some
special tools and disassembly of the first stage for filling of the chamber with a special low temperature lubricant.

[Splitlip]

I probably should have stated pistons are not sealed while diaphragms are (by virtue of design).

"sealing" a piston requires packing it with the lubricant to act as the ambiant water normaly would. I am guessing the rubber sleeves covering the ports would act like mini diaphragms?

Maybe somebody else can provide better info on that.

I think if one were to anticipate cold or dirty diving, he would be better off buy a diaphragm. See below.


"Piston regulators by engineering design are simple and reliable (less moving parts to fail). They offer extremely high flow (ranging in the neighborhood of 300 cfm and can supply 20 divers with air at once). As such, piston regulators can meet the demands of deep diving very well.

However, because of the water pressure balancing chamber's design, exterior water is in direct contact with the piston head and shaft which is the coldest part of the regulator (expanding gas from the tank comes out at about -4 degrees Celsius) and there is a risk of freeze up of this section of the regulator. Furthermore, extremely contaminated water (ie. heavy sediment or organic chemicals) can also damage the 2 orings in this region that keep water out and air inside the regulator). Various manufacturers attempt to compensate for these weakness by one of three ways (or a combination of the three).

• The piston spring may be coated with an anti-icing compound and the piston head and shaft may have thermal isolating bushings.
• The balancing chamber may be sealed with a silicone gel or christolube.
• The balancing chamber may be sealed and filled with air from the regulator thus relying on a dry air bleed type of water pressure balancing.

Of the three mentioned methods, the later two are the best for dealing with bone-chilling cold waters and contaminated waters. With regards to the christolube versus silicone gel pressure transmission media, christolube tends to be the better compound as it offers high insolubility to water and it's higher fluidity does not markedly impede the movement of the regulators components."

[captain]

Diaphragms are not all sealed by design. The diaphragm on the Aqua Master and Royal Aqua Master two hose regulators are sealed by design because the 1st stage spring is not exposed to water. Most all single hose diaphragms are not sealed by design and still must have some type of additional protection just as pistons do.