Pony bottle

A pony canteen is a baby apart abounding diving cylinder, generally of alone a few litres capacity, which forms an continued scuba set and which is adapted with its own absolute regulator. In an emergency, such as burnout of the diver's capital air supply, it can be acclimated as an alternating air antecedent or bailout canteen to acquiesce a accustomed ascendance in abode of a controlled emergency pond ascent. The key aspect of a pony canteen is that it provides a absolutely absolute and bombastic antecedent of breath gas for the diver.

Configuration

In a pony canteen arrangement the aback regulator is a complete diving regulator (first and additional stages, and generally a submersible burden gauge) on a abstracted butt which is not advised for use as primary breath gas during the dive. It provides a absolutely bombastic emergency air supply. The admeasurement of the pony canteen butt is usually abate than that of the primary scuba cylinder. It should about accommodate abundant breath gas to accomplish a absolutely controlled acknowledgment to the surface, including any appropriate decompression stop or assurance stop appropriate forth the way. The appropriate pony butt accommodation will depend on the contour for safe ascendance to the apparent appropriate for a accurate dive plan. A pony canteen acclimated for action diving may be 6, 13 or 19 cu ft in the USA, while 2 litre and 3 litre are accepted sizes in Europe. For abysmal or abysmal abstruse diving or bones diving 30 and 40 cu ft (5 litre and 7 litre) cylinders are generally used. The pony canteen is a minimum claim for anyone accomplishing abandoned diving, who has no another antecedent of air in the anatomy of a buddy's accessible catchbasin and octopus regulator1 if the dive is to a abyss area the diver is not able to do a safe chargeless ascent. In accurate diving operations, pony bottles can a accepted allotment of tethered scuba diving operations area the diver is generally abandoned but affiliated to the apparent by communications equipment.2 Several scuba manufacturers aswell accept produced a minimalist haversack accouter that accurately supports a aback army pony canteen alone for use by a able scuba diver in bank baptize diving or for baiter aliment purposes

Options in Carrying

There are several options for the ascent of a pony bottle. The a lot of accepted way pony canteen is agitated is by acclimation it to the ancillary of the primary (back gas) scuba butt by straps or clamps, which may cover a quick-release arrangement (as in the aloft picture). The a lot of accepted another is "slinging" it amid two D-rings on the diver's scuba accouter or airiness compensator.4 Another achievability is to arise the canteen in a baby accustomed bag, from which the pony canteen may be calmly removed. This affords the befalling of "handing off" the absolute arrangement to a associate diver if that associate needs to allotment air. This is a abundant safer action than the buddies accepting to accept to be affiliated through use of bashed regulators. The accession of a pony canteen to the defined accessories will add an off-balanced weight to the ancillary on which it is mounted. To atone for this an according acclimation weight is generally added to the catchbasin bandage on the adverse ancillary of the pony, or in an off-side weight pocket. Attention have to aswell be paid to area the pony canteen additional date regulator is placed during the pre-dive associate check.

Alternative solutions

The pony canteen is a antecedent of back-up by accouterment an another antecedent of breath gas for the diver as an able advancement to his/her primary gas accumulation in the accident of abortion of the primary system. The pony canteen is advised for use in "bail out" situations – situations in which the dive have to be aborted and safe acknowledgment to the apparent have to be facilitated. There are several another solutions to accouterment such a bombastic gas accumulation for bond out purposes which are in accepted use in diving. These alternatives are listed in the afterward table forth with a appraisal on how these solutions analyze with pony canteen acceptance as a advancement system:

Alternative air source Comparative functionality

Octopus The octopus is an added bombastic additional date regulator taken off the absolute aboriginal date regulator and absolute primary air supply. Because of this, a abortion of the aboriginal date regulator or the burnout of the gas accumulation from the primary catchbasin makes this band-aid inferior to a absolutely bombastic breath gas arrangement such as a pony bottle.

H and Y colonnade valves The primary catchbasin can be adapted with a valve with two abstracted controllable outlets, both of which can arise its own aboriginal date regulator. One aperture is affiliated to the primary additional date regulator, the added to the octopus. This eliminates the crisis of abortion in a individual first-stage system. It does not abate the accident of accident of breath gas from the individual primary gas supply.

Doubles Using a accompanying catchbasin arrangement with isolating assorted provides abounding back-up in gas accumulation as able-bodied as the adeptness to abstract any adulterated apparatus which ability be aperture abroad breath gas. Doubles aswell accommodate abundant greater accommodation than pony bottles. However, because the gas in the arrangement is aswell for use during the dive itself it requires that the diver pays added absorption to gas administration to ensure that an able aggregate of assets is accessible for any bailout claim at any appearance of the dive. However, if the additional catchbasin alone serves the purpose of bailout, the diver is abounding with ample added aggregate and weight which is not appropriate in a abate pony canteen system.

Choice of Pony Bottle Size

Given that the individual action of the pony canteen is to accommodate a antecedent of breath gas for a controlled and advisable ascendance to the apparent in an emergency situation, it is a lot of important that the pony canteen admeasurement is called to be acceptable for that purpose. Even if accomplishing no decompression diving, the absolute affluence of breath gas have to still be acceptable to accumulation three phases of the ascent:

enough gas to acquiesce for a abbreviate aeon at abyss to bound array out any problems, if necessary, afore abiding to the surface

enough gas to accomplish a safe bit-by-bit ascendance to assurance stop abyss and

enough gas to do a complete assurance stop.

At the end of this time the pony canteen should still authority abundant gas to accommodate acceptable burden for bland breeze from the regulator aboriginal stage.

Pony canteen gas burning against assorted dive depths

Stage of ascent Max abyss 15 metres (49 ft) Max abyss 20 metres (66 ft) Max abyss 30 metres (98 ft) Max abyss 40 metres (130 ft)

Sort out problem: 2 account at max depth 150 litres (5.3 cu ft) 180 litres (6.4 cu ft) 240 litres (8.5 cu ft) 300 litres (11 cu ft)

Ascent from max abyss to 5 metres (16 ft): ascendance at 9 accent per minute (30 ft/min) 67 litres (2.4 cu ft) 113 litres (4.0 cu ft) 229 litres (8.1 cu ft) 379 litres (13.4 cu ft)

Safety stop: 3 account at 5 metres (16 ft) 135 litres (4.8 cu ft) 135 litres (4.8 cu ft) 135 litres (4.8 cu ft) 135 litres (4.8 cu ft)

Total 352 litres (12.4 cu ft) 428 litres (15.1 cu ft) 604 litres (21.3 cu ft) 814 litres (28.7 cu ft)

Air accessible at 150 confined (2,200 psi)

Pony canteen 3 litre 450 litres (16 cu ft) 450 litres (16 cu ft) 450 litres (16 cu ft) 450 litres (16 cu ft)

Pony canteen 6 litre 900 litres (32 cu ft) 900 litres (32 cu ft) 900 litres (32 cu ft) 900 litres (32 cu ft)

The table aloft is complete to appearance gas captivated in just such a scenario: 2 account at abyss for "sort-out"; a safe amount of ascendance to 5 meters; followed by a 3 minute assurance stop. Calculations are based on a abundant breath amount of 30 L/min and an antecedent catchbasin burden of 150 bar (2,200 psi). In this accurate book the 3 litre pony is just acceptable for diving at 20 meters but not 30 meters. It is important that anyone selecting a pony canteen should do such an assay for his/her own breath rates, butt burden to be used, and appropriate ascendance profile, or yield admonition in the selection. Aswell it is important to agenda that back ecology of actual air is a key affair in ascentcitation needed, a submersible burden barometer clear at all times aswell needs to be absorbed to any pony canteen system.

Breathing gas

As apparent in the archetype calculations above, the accommodation of accepted pony bottles accomplish them able as acting as bombastic bail-out accessories for accepted recreational diving purposes – i.e. non decompression dives at base not to beat 30 metres (98 ft) (for nitrox)5 or 35 metres (115 ft) (for air). A accepted aphorism of gas acceptance in this ambit is that the "bailout gas should bout absolute breath gas".6 In these terms, this agency that air based diving should accept air in the pony, nitrox diving should be backed up by nitrox in the pony. This leads to the altitude that with account to dive tables or dive computer, that the about-face fabricated amid cylinders does not access calculations for present or approaching decompression allowances. To maximise assurance margins, it is absolutely important that pony bottles should be abounding to their best acceptable butt burden to accommodate a best assets for bailout purposes. Often in boats gas refills to these college banned are not possible, so it is important that pony be abounding above-mentioned to the dive cruise excursion. Pony bottles are accessible with either A-clamp or DIN applicable valves so the adapted applicable have to be accessible should the pony charge to be refilled.

Safety Considerations

It is actual important that the diver includes testing of pony canteen activity as allotment of the pre-dive tests to assure that it is absolutely accessible for use. (Some defined yield pony bottles army in a way that the butt valve is calmly accessed, and advisedly dive after aboriginal aperture up this butt valve -a awful arguable and alarming approach, abnormally in recreational diving). Because of the alterity amid pony canteen accommodation and capital yield capacity, it is basic that the regulators and the associated SPG for these altered units be calmly and acutely different, as bond up these regulators or gauges can bound advance to a apocryphal ”out of air” emergency. It is aswell important to never use the pony canteen as allotment of the accustomed air accumulation for a dive or to extend an agreeable dive by agency of pony canteen gas – even if it is aural decompression limits. The pony is an emergency device, and needs to be advised as such.