Regulators

How is Performance Measured?

How is Performance Measured?

Before you can establish the level of performance required, you must first understand how performance is measured. Many different tests are quoted as a bench-mark level, but the most widely regarded is the US Navy test. It involves both manned and unmanned tests of regulator performance.

The US Navy set 1.4-joules effort as the maximum inhalation effort. In order to qualify for the top level, category A, the regulator needs to meet these criteria at 62m at moderately heavy work rates. In the last test performed by the US Navy only six sport diving regulators qualified as category A.

Two models were from Aqua Lung, the US Divers SE2 and the US Divers Pro Diver. These same two regulators came first and second respectively in the manned tests. These models have since been improved with the advent of the Titan and Legend series from Aqua Lung.

Some divers have performance needs that go beyond the realm of the typical sport diver. The most popular brand for this diving category is Apeks.

The latest regulators from Apeks have recorded less than 1.03-joules inhalation effort at 80 m (Remember, the US Navy class A is 1.4j at 62m). This demonstrates effortless breathing at extreme depths. The Apeks ATX200 is widely regarded as the best performing regulator in the world.

Balanced First Stage

A balanced first stage has a ‘balancing chamber’ which ensures that as tank pressure drops the pressure of air to the second stage is maintained. This allows the regulator to breathe easy even at low tank pressures.

Overbalanced First Stage

As the diver gets deeper the air they breath is compressed and therefore more air is needed to fill the diver’s lungs. This is a basic principal taught in the beginner’s dive course.

Your first stage must be able to sense this outside pressure in order to maintain a steady flow of air to the second stage.

A major difference in the performance of a regulator is its ability to maintain a constant flow at greater depths. All modern regulators sense outside pressure and compensate for the change, however most regulators still have a considerable drop in performance on deep dives as they cannot increase pressure sufficiently to compensate for the high demands at depth.

An innovation only found in the highest performing regulators is called over-balancing. The very same second diaphragm that provides an environmental seal (see previous page) is larger than the internal diaphragm. This means that as you get deeper more pressure is applied to the external diaphragm than would be applied to the smaller internal diaphragm due to the increased surface area. This actually boosts pressure at greater depths significantly improving performance.

Balanced Second Stage

Many companies claim to have a balanced regulator but all they are referring to is the first stage. The world’s best performing regulators also have a balanced second stage. A traditional second stage has a valve spring strong enough to hold back all the pressure from the first stage. This spring pushes against the seating mechanism to stop the air-flow until the diver breathes. When the diver breathes the diaphragm is pulled forward against the lever, which in turn compresses the spring and pulls back the seat to allow the air to flow.

A balanced second stage allows air to pass through the centre of the poppet valve to a counter-balance cylinder, which assists the spring in closing the valve. This reduces the need for a heavier valve spring, which cuts down the effort needed to compress the spring which in turn makes inhalation very easy. A balanced second stage is therefore highly desirable.

Plotting High Performance

Regulator performance is calculated by plotting and recording the breathing cycle. In the diagram below, the inhalation line begins on the right hand and runs across the bottom to the left. The first oscillation (termed the cracking spike) represents the effort required to initially open the valve and begin air delivery. Even at this testing depth the graph shows the low Work of Breathing (WOB), indicating the diver is expending almost no energy in maintaining air flow. The cycle continues and the upper line (left to right) represents the Work Of Breathing whilst exhaling (which is greater due to increased gas density at depth).

The total Work Of Breathing is calculated by measuring the total area within the loop, which in this case is 1.05Joules per Litre. Apeks regulators have been tested with Work Of Breathing figures as low as 0.90J/L at 50metres and 1.03J/L at 80metres, a figure we have yet to see repeated or surpassed by any other regulator in the world. To qualify for the CE (Central European) mark, regulators must be less than 3.0J/L at 50metres, RMV: 62.5 (25L x 25 breaths/min), and for the US Navy Group A (the world’s most severe test standard) the regulators WOB needs to be less than 1.4J/L at 62metres.