hugedodge2000
Guest
What is a balanced regulator?? Or over balanced for that matter??
balanced reg??
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The long answer:
The term "balanced" regulator refers to a valve design that uses balancing air pressure to negate any effect the downstream force of the incoming air may have on the effort needed to open the valve.
In a first stage this means that the air pressure coming in from the tank has no effect on the ease at which the valve opens and consequently that changes in tank pressure have no effect on the intermediate pressure (IP) developed in the first stage.
This means the pressure of the air sent to the second stage is constant regardless of tank pressure. It also means that in general the regulator designer can use a larger orifice than would be possible with an unbalanced design which equates to higher air flow, a more stable IP during inhalation and generally much better performance.
In a balanced second stage, the poppet is again balanced so that the air pressure on one side is equal to the air pressure on the other side. This means that theoretically any drop in IP will not affect the effort needed to open the valve when the diver inhales. In practice, balanced poppets are not perfectly balanced but instead have a slight downstream bias (the area that the air pressure acts on is larger on the side where the air enters the second stage than it is on the "balance" side of the poppet). This ensures that if the high pressure seat in the first stage fails that the second stage will vent the excess pressure by freeflowing before the low pressure hose bursts.
The balanced poppet in the second stage also allows the use of a much larger orfice and with a much lighter spring acting on the poppet. The larger orifice allows much more airflow and higher performance, while the lighter spring makes the poppet more responsive, and increases the life of the seat. In general balanced second stages are offer much higher flow rates and usually lower inhalation effort than unbalanced second stages.
The short answer:
A balanced reg is a good thing and worth the money if you plan to get into deep diving or want a reg with maximum performance and minimum inhalation effort throughout the dive.
An exception to this are circumstances where you want a very simple and bullet proof regulator or where it is desireable to have a design where the internal spaces of the reg (at least downstream of the high pressure seat) and the dynamic o-rings are always at no more than intermediate pressure. Deco regulators fall into this category and for that application an unbalanced "flow by" regulator is hard to beat.
"Overbalanced" is a confusing term with different definitions depending on the manufacturer.
Scubapro for example refers to the term to means that the piston stem in the first stage is made slightly undersize where it ocntaxcts the HP o-ring compared to the seating edge on the end of the piston that sits agaisn tthe orifice so that the area of the seating edge itself is not an unbalanced factor in the design. Otherwise with a piston stem of constant diameter, the area of the seating edge itself, although fairly small, is not balanced and asa result the intermediate pressure drops 4-6 psi as tank pressure falls from 3300 psi to 300psi.
Apeks however refers to "overbalancing" as a situation where the difference beween intermediate pressure and ambient pressure becomes greater as depth increases. This proportionate increase in the realtive IP with increased depth supposedly offsets the lower flow rate that occurs as the viscosity of the air increases at the higher absolute intermediate pressures needed at depth. It however also means that the pressure of the air sent to the second stage increases relative to ambient pressure as the diver goes deeper which means a lightly adjusted regulator would tend to freeflow as you went deeper. The regulator consequently has to operate in a detuned condition at depth, or the diver has to increase the spring tension acting on the poppet via an adjustment knob to prevent the freeflow at depth.
In my opinion, the trade off is not worth it as, assuming the first stage has adequate gas flow, the increased viscosity effects will not be a factor at any depth remotely reachable on open circuit scuba.
The term "balanced" regulator refers to a valve design that uses balancing air pressure to negate any effect the downstream force of the incoming air may have on the effort needed to open the valve.
In a first stage this means that the air pressure coming in from the tank has no effect on the ease at which the valve opens and consequently that changes in tank pressure have no effect on the intermediate pressure (IP) developed in the first stage.
This means the pressure of the air sent to the second stage is constant regardless of tank pressure. It also means that in general the regulator designer can use a larger orifice than would be possible with an unbalanced design which equates to higher air flow, a more stable IP during inhalation and generally much better performance.
In a balanced second stage, the poppet is again balanced so that the air pressure on one side is equal to the air pressure on the other side. This means that theoretically any drop in IP will not affect the effort needed to open the valve when the diver inhales. In practice, balanced poppets are not perfectly balanced but instead have a slight downstream bias (the area that the air pressure acts on is larger on the side where the air enters the second stage than it is on the "balance" side of the poppet). This ensures that if the high pressure seat in the first stage fails that the second stage will vent the excess pressure by freeflowing before the low pressure hose bursts.
The balanced poppet in the second stage also allows the use of a much larger orfice and with a much lighter spring acting on the poppet. The larger orifice allows much more airflow and higher performance, while the lighter spring makes the poppet more responsive, and increases the life of the seat. In general balanced second stages are offer much higher flow rates and usually lower inhalation effort than unbalanced second stages.
The short answer:
A balanced reg is a good thing and worth the money if you plan to get into deep diving or want a reg with maximum performance and minimum inhalation effort throughout the dive.
An exception to this are circumstances where you want a very simple and bullet proof regulator or where it is desireable to have a design where the internal spaces of the reg (at least downstream of the high pressure seat) and the dynamic o-rings are always at no more than intermediate pressure. Deco regulators fall into this category and for that application an unbalanced "flow by" regulator is hard to beat.
"Overbalanced" is a confusing term with different definitions depending on the manufacturer.
Scubapro for example refers to the term to means that the piston stem in the first stage is made slightly undersize where it ocntaxcts the HP o-ring compared to the seating edge on the end of the piston that sits agaisn tthe orifice so that the area of the seating edge itself is not an unbalanced factor in the design. Otherwise with a piston stem of constant diameter, the area of the seating edge itself, although fairly small, is not balanced and asa result the intermediate pressure drops 4-6 psi as tank pressure falls from 3300 psi to 300psi.
Apeks however refers to "overbalancing" as a situation where the difference beween intermediate pressure and ambient pressure becomes greater as depth increases. This proportionate increase in the realtive IP with increased depth supposedly offsets the lower flow rate that occurs as the viscosity of the air increases at the higher absolute intermediate pressures needed at depth. It however also means that the pressure of the air sent to the second stage increases relative to ambient pressure as the diver goes deeper which means a lightly adjusted regulator would tend to freeflow as you went deeper. The regulator consequently has to operate in a detuned condition at depth, or the diver has to increase the spring tension acting on the poppet via an adjustment knob to prevent the freeflow at depth.
In my opinion, the trade off is not worth it as, assuming the first stage has adequate gas flow, the increased viscosity effects will not be a factor at any depth remotely reachable on open circuit scuba.
SparticleBrane
Contributor
^ Best explanation yet!
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