REGULATOR SELECTION REGULATOR SELECTION These pages are pinched from
Scuba World
While regulators come in many shapes and sizes, they share a common
set of basic characteristics that will dictate your choice. During
this section I will mention regulators that are particularly good
examples of, or make extensive use, of each specific feature. As
always, define the features your diving demands and demand a
regulator that excels in these areas.
Most regulator 2nd stages have a similar design - a 'hamburger shaped' section flat to your face and a mouthpiece with exhausts just below, to the left and right. While that's majority, the minority come in other shapes and sizes. Side venting models, such as the Apeks Sentinel and 5000 ST, the Poseidon Cyclon and Jetstream plus the diminutive Oceanic Omega II, can operate left or right (ideal for an octopus) and the exhaust bubbles don't obscure your vision if you're upright in the water. The new Poseidon Triton though wins hands down for 2nd stage innovation. Shaped like a chunky mouth organ, this model inside and out is nothing like any other on the market.
Even within the standard shape, both size and weight vary dramatically. Lighter models are less fatiguing and smaller models more suitable to all divers - especially those who are small themselves! It doesn't make a great deal of sense to opt for a small regulator purely for size if the performance is compromised. Don't be afraid to try novel designs or shapes, if they do the job and you find them comfortable, then give them a go.
You don't need to be an expert in the theory of the internal combustion engine to choose a car - but it helps. In your regulator quest, you'll be deluged with TLAs (Three Letter Acronyms!) CEN, DIN, DFC, VAD are just a smattering. First stages, second stages, intermediary pressures and a compatible octopus - all highly tentacle!. With so much 'science' it's useful to ensure you have a basic understanding of the innards and elementary physics to help you assess suppliers claims and separate the facts from fiction. The role of the first stage or reduction value, is to reduce the cylinders varying pressures of between 300 and 20 bar (during the dive) to a constant inter stage pressure of around 10 bar. This figure hasn't been plucked from a hat but is the pressure required to ensure the maximum flow (litres per minute) through a standard sized dive hose - more pressure doesn't equal more flow. There are two basic design principles - piston and diaphragm - the proponents of each naturally stress the strengths of their own designs and the weakness of the opposition. There are so many possible interpretations of each design concept that there isn't a black and white winner and it's impossible to say one approach is better than the other. In reality actual performance is often more to do with a designs practical interpretation, attention to detail and build quality. Listen to both camps, merge the stories and you'll be closer to the truth. However, it's generally true that balanced versions, of both types, is the best design and continues to offer high performance at lower cylinder pressures. This is because the presses are more evenly distributed which means the controlling spring tensions can be very much lower. The object of a first stage is to supply vast amounts of air evenly and consistently, regardless of cylinder pressure (down to 20-30 bar not empty of course!) and second stages demands. It's vital that the air flow rates of the first stage are not a limiting factor to the performance of the second. If the flow can't cope with peak demands the inter stage pressure will fall and breathing resistance rises rapidly. As some of the leading second stages can deliver an average flow of well over 1000 l/m in turn these must be twined with first stages offering even more - at the moment the best are capable of delivering almost 2500 litre per minute. While some suppliers have fixed combinations of first and second stages, others (including Apeks and Scubapro) offer a degree of mix and match, to tailor price and performance. This route also allows partial upgrade rather than scrapping both. Scubapro for example has three 1st stages the Mk2, Mk10 and Mk20, in order of increasing performance and a choice of five second stages. Naturally it makes good sense to pair similar ranges and you wouldn't link the top second with the economy first. Apeks takes an additional tack and has a 'stripped' down first stage, which offers the same high performance as the conventional models but fewer ports - ideal for pony use - see later in the product section.
At present the vast majority of regulators have 'A' clamp fittings and are certified for 200 - 232 bar. However, if you're about to buy, you would be wise opting for one with 300 bar and DIN screw compatibility. Cylinders with DIN or convertible fittings (an 'A' clamp plug which unscrews to reveal a DIN screw) now account for a high proportion of sales. As the table shows, most regulators now come with DIN options. Many can also upgrade existing models to DIN. Apeks (optional) and Poseidon (included) have converters which convert the DIN models back to an 'A' clamp, giving the best of both worlds. Do remember though that there are two versions of the DIN screw fitting - the full 300 bar and low pressure version - make sure you check the labelling and don't assume that a DIN screw = 300 bar - it doesn't. When selecting - 'A' clamp or DIN - pay attention to the clamp itself as many have very slippery handles. Look for models with a good grip but no rough/sharp edges.
The purpose of the first stage is to drive a set of low pressure (LP) ports, which feed your BC, suit, octopus and primary 2nd stage. As the latter makes the main demand for air, some models have a specific port optimised for high throughput. A typical regulator will also have a least one high pressure (HP) port, to feed a submersible pressure gauge. Increasing numbers are providing an additional HP port, which offers a choice of location for the gauge and also provides the option to, say, interface an additional air integrated computer. Hose fittings / swivel A fully equipped regulator may have up to six hoses waving about like the tentacles of an octopus, all with the possibility of tangling. The better these hoses can be directed, the less likely they are to get in the way and worse still snag on sharp objects. A number of suppliers are attempting to optimise hose ergonomics using techniques such as rotating hose turrets (Apeks, Oceanic Scubapro, Spiro), hose swivels (Dacor) or optimised port positioning (Dacor, Mares, Poseidon, Spiro, US Divers). You can help yourself here too by having excessively long hoses shortened. When buying/fitting your BC and dry-suit etc. have a competent shop to ensure a closer fit. Sealed to keep in touch with the ambient pressure, a 'standard' first stage allows water to enter part of its 'innards'. In heavily contaminated or cold waters this design can be bad news. To simultaneously prevent freezing and the ingress of sand etc. the whole stage can be sealed from the surrounding water. The seal can be an integral design feature, as with models such as Apeks, an upgrade as with Scubapro or a simple add-on cap system such as with the Poseidon. The Sherwood dry bleed system achieves the same objective but in a very different way. See the product section later.
The higher the performance at the demand valve end, the greater are the demands on the hose. Heavy breathing at depth requires the delivery of vast amounts of air. Basic physics though imposes its own restrictions and for any specific orifice diameter and temperature there's a maximum flow rate - no matter how glossy the advert! An increasing number of designs are therefore opting for wider bore hoses and other increased flow tactics.
The second stage or well-named demand valve, is the 'action end' and supplies air - on demand. Once most divers have fitted the first stage, that's the last they think of it and their mind is concentrated on the second stage's performance and physical characteristics.
Most second stages are quite bulky, as unfortunately they have to obey the basic laws of physics. Peak performance demands large diaphragms, large exhausts and wide bore hoses. There's scope though for 'bending' these laws by novel design. The new Poseidon Triton, for example, has two smaller exhausts in place of the single larger version. However, this is not to decry a small second stage. If you're not a cold water, hard working, deep diving sort but a warm water leisurely diver, then a diminutive first stage could be the ideal comfort solution.
A comfortable and secure mouthpiece inevitably plays a major part
in your dive satisfaction. Of all the suppliers Spiro and US Divers
in particular extol the virtues of their design, the 'comfo-bite'
mouthpiece. This looks somewhat strange but it does live up to its
name and is very comfortable. A number also cater for differing mouth
sizes and offer two or three versions. Most soft silicon models with
an appropriately sized shield are fine. However, you shouldn't place
too much emphasis on this element and reject an otherwise fine
regulator on the basis of the mouthpiece - remember they are
removable - if you don't like it swap it!
The conventionally designed regulator sits on your chin with the exhausts exiting each side. It's quite surprising then how few have a comfortable soft rest. The best, which include models from Apeks, Spiro and Scubapro, perch gently on the chin and front impacts are cushioned and not transferred to the teeth. Ones that sit a little proud with a hard surface are the worst they are easily knocked by objects etc and impact against your chin. In contrast most side diaphragm models are clear of the chin and stand proud. This is comfortable provided that its light in air and preferably close to neutral in water.
Increasing numbers of second stages now incorporate controls and whether you like them or not is a personal opinion. Whatever your view you can rest assured, with quality models they're not just decoration, they really do work!
Controls fall into two types - inhalation and Venturi. Inhalation resistance, as its name suggests, controls the 'cracking' effort required to start the air flowing and to continue the flow. This is usually a little less due to internal design features that optimise the flow. With the inhalation control turned back to its lowest setting, you have to suck quite 'hard' to start the air flow - this is represented in the diagram by the solid green line. With inhalation resistance set to low (represented by the solid red line) you hardly have to suck at all! With many of the models, if you set the resistance to its lowest possible levels in the shallows you don't have to suck - take it out of your mouth and it free flows. The inhalation control is used to set the breathing resistance to suit your own personal tastes and to cater for more extreme conditions. When the resistance is set to its lowest possible level the regulator gives its best performance but is very susceptible to free flows and instability. This can include anything that causes an increased pressure on the diaphragm such a swimming head down or into a strong current. Indeed even a face down posture alone cause a pressure differential of a few mbars, enough to set of the highest tuned models. In any of these instances the controls can be turned back to reduce sensitivity.
There's much confusion surrounding the Venturi effect and many divers assume it influences the inhalation effort. When it's employed in actual regulator designs, the Venturi effect doesn't change the cracking resistance but improves the flow once it's flowing! With high levels of Venturi effect, the regulator actively 'blows air' into your lungs - see later in 'breathing characteristics'. This is shown on the diagram by the dashed lines going below the '0' mark as there is no need to continue sucking - air is being blown. The top two lines (red and green vertical dashes) are with low Venturi and lower two lines (red and green vertical dashes) with high Venturi settings.
Of course it's possible to incorporate a fixed amount of Venturi effect but with a Venturi control you can influence the amount of effect according to the depth and your own tastes. Greater depths require more assistance for the same results, as the air is more dense and 'sluggish'. To help separate facts from fiction, bear with me while I briefly digress into basic physics to provide the background. The Venturi effect is named after the Italian scientist that discovered it back in the 17th century when regulators were not even a glimmer in Cousteau's eye! In essence the fast flowing air exerts a drag on the slower air and in this case causes a pressure reduction. In diving terms the Scubapro analogy was widely praised and felt, even by the competition, to be a fine representation of the concept - so who am I not to plagiarise! They use an air gun inside a sealed box - the front is cut away otherwise you wouldn't be able to see the effect. When the gun is switched on the Venturi effect reduces the air pressure inside and pulls the flexible membrane inwards, operating the switch continuing to keep the air flowing and upping the flow.
While second stages have always been affected by cold, the more their performance improves, the greater the risk of freezing. This is because expanding air cools and the greater amounts being delivered obviously the greater the cooling effect. Modern models tend to be designed to freeze open, working on the principal that a 'free flow' is better than a 'no flow'! This itself though can be disastrous as a high performance regulator free flowing can empty a full cylinder in a few minutes. Most suppliers have cold water features as standard or a model specifically optimised for cold water diving. These include using metal parts, as these conduct breath heat to the chilled sections. Using non stick parts, often made from Teflon, is another option and one employed by Mares and Seac. In addition to simply using warmth conducting metals, a specific heat sink can be fitted. This route is taken by Sherwood and US Divers. The sink soaks up the warmth from your exhaled breath and stores it to help keep the internal workings above freezing point. In the normal course of events, the warmth is simply lost through the exhausts. Irrespective of design, keeping the second stage dry internally is one of the best ways of ensuring that it doesn't freeze open. Necessary practices like buddy breathing compromise even the best models.
The cylinder air is kept as dry as possible to prevent corroding the innards. While dry air is good for them, it's not for you and causes the standard divers dry mouth, which of course has to be quenched at the end of the day with numerous pints! A more scientific but less social solution has been developed. We all know that breathing on a cold mirror mists it with a film of tiny water droplets. The Sherwood Oasis 2 and others have employed this phenomenon to recycling your breath's natural moisture. Inside this second stage is a metal plate which captures the moisture from the exhalation before it leaves the exhaust. The incoming dry air circulates over the now damp plate, absorbing moisture and keeping your mouth and throat comfortably moist.
Quite a number of suppliers seem keen on change for change's sake. It's almost like the spring fashions - the innards remain the same but they launch a new and obviously different 2nd stage shape and colour scheme. Sadly many of these are purely sales gimmicks, to tell the world you've got this year's model. While like most divers I enjoy experimenting with the new, I must admit to recommending regulators that have had time to prove themselves - we have all seen a few too many recalls. I will leave it up to you to make up your mind.
As always choose for purpose - calm shallow Caribbean diving is far less demanding than a deep, no clear surface UK wreck in November. All quality regulators on the UK market will cope with the first but I would only be happy with a handful (or two at pinch) with the latter. If you're looking for leading edge performance, check the specifications (CEN and the suppliers own graphs) and wherever possible get to try an example under actual conditions. A general warning - a test breath in the shop is like taking a sports car for a drive around the dealers' showroom - meaningless! In actual fact the better the model often the poorer its 'in air' performance - after all they're meant to work with water against the diaphragm.
There's not space for an in depth section on care and servicing issues but I decided to mention this vital necessity to prick the consciences of the guilty! Once you've found your ideal regulator treat it well - a caring relationship ensures you and it, have a long and fruitful partnership. Irrespective of your level of experience read the manual - I say that even as an IT consultant! There are so many new models and designs that you cannot guarantee that the operations and post dive washing routines of your old models still apply. Take particular care of the first stage filter. This sintered disc is the entry to your prized regulator but is often badly neglected and many are heavily corroded/clogged. If the disc is partially blocked it will limit the whole units performance. To improve performance Scubapro others are using conical (better flow) and corrosion resistant filters.
With any test process the tests should attempt to match and measure the likely usage. If you're buying a motor bike for commuting, a city run is the ideal test dive - rather than a five man motor cycle display team in a sports field! The same is true for regulators, unfortunately few shops are equipped with a 50m test tank and those that have one outside not surprisingly prefer you to hire the gear. This means that part of your selection tests such as ergonomics are shop practical and others, like sheer performance, are best assessed by more objective tests. It's good to know though that these machine based objective tests do seem to tally with your own subjective assessments in the real world. In my experience those regulators with top flight joules per litre ratings (see later) also deliver the goods underwater.
We humans have our own personal preferences and one diver's dream can be another's nightmare. We are also swayed by our eyes and unconscious prejudices. It's very dangerous therefore to rely on an individual judgement for regulator testing. You wouldn't give any credence to a 0-60 mph test based on the driver's own estimates of speed and the passage of time. The same is true when it comes to SCUBA gear - machine based performance tests are the only possible impartial and objective technique.
The tests are carried out in a pressure chamber, with the regulator attached to a breathing machine. The standard test simulates a diver working at 50 metres, breathing 25 breaths per minute and with a ventilation rate of 62.5 litre per minute.
The chart above is the standard output - don't panic it does become meaningful with a little explanation. The calibration is in Kilo pascals (kPa) which means more when converted - 1 kPa equals a 10 cm column of water - in other words the higher the figure the harder you have to suck or blow. The maximum allowed in the CEN test (see later) is 2.5 kPa with a recommended limit of 1.75 kPa. The black line surrounding the green shaded area is the amount of effort, at intervals, throughout a single breathing cycle. The inhalation starts at the right on the blue zero line and moves to the left.
The exhalation effort graph is show directly above. The maximum 'heights' for each curve are the maximum inhalation and exhalation efforts respectively. These maximums are just peaks at specific moments - the test also shows how much effort a whole breath takes. This is the total work cycle and is the area enclosed by these curves. The work measurement is in Joules per litre (J/l) with a maximum allowable under the CEN standards of 3 J/l. For optimum performance you want low maximums and a low work load - in other words the closer the lines are to the zero the better. The inhale line on some models test charts looks a little different, as it rises above the '0' line. This is due to the previously described Venturi effect, coming into play after the start of inhalation and dramatically reducing breathing effort. Set to its maximum this positively blows air into you, therefore the effort itself is 'negative' and the line above the '0'
It won't come as any surprise that the cold water certification repeats the same test technique but simply in cold water - chilled to 5C for five minutes.
To be sold in the European community, all of the vital life support gear must, from the 1st of July, be tested and certified to CEN standards. This is a Europe wide equivalent of our national BSI 'Kite mark'. Regulators themselves must reach the EN250 standard, which involves a variety of tests, including a machine breathing test and oachine breathing test and optional cold water certification detailed earlier. Other gear that must comply includes; BCs, gauges, computers etc.
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