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A helium release valve, helium escape valve or gas escape valve is a feature found on some diving watches intended for saturation diving using helium based breathing gas.
| | This article needs additional citations for verification .(March 2008) |
A helium release valve, helium escape valve or gas escape valve is a feature found on some diving watches intended for saturation diving using helium based breathing gas.
When saturation divers operate at great depths, they live under pressure in a saturation habitat with an atmosphere containing helium or hydrogen. Since helium atoms are the smallest natural gas particles—the atomic radius of a helium atom is 0.49 angstrom and that of a water molecule is about 2.75 angstrom—, they are able to diffuse over about five days into the watch, past the seals which are able to prevent ingress of larger molecules such as water. This is not a problem as long as the watch remains under external pressure, but when decompressing, a pressure difference builds up between the trapped gas inside the watch case and the environment. Depending on the construction of the watch case, seals and crystal, this effect can cause damage to the watch, such as the crystal popping off, as diving watches are designed primarily to withstand external pressure.
Some watch manufacturers manage the internal overpressure effect by simply making the case and sealed connected parts adequately sealed or strong enough to avoid or withstand the internal pressure, [1] but Rolex and Doxa S.A. approached the problem by creating the helium escape valve in the 1960s (first introduced in the Rolex Submariner/Sea-Dweller and the Doxa Conquistador): A small, spring-loaded one-way valve is fitted in the watch case that opens when the differential between internal and external pressure is sufficient to overcome the spring force. As a result, the valve releases the gases trapped inside the watch case during decompression, preventing damage to the watch. [2] The original idea for using a one-way valve came from Robert A. Barth, a US Navy diver who pioneered saturation diving during the US Navy Genesis and SEALAB missions led by Dr. George F. Bond. The patent for the helium escape valve was filed by Rolex on 6 November 1967 and granted on 15 June 1970. [3]
Automatic helium release valves usually don't need any manual operation, but some are backed up by a screw-down crown in the side of the watch, which is unscrewed at the start of decompression to allow the valve to operate. As decompressing saturation divers is a slow working conditions requirements regulated process to prevent sickness and any other harmful medical effects, [4] [5] the helium release valve does not have to be able to cope with extremely rapid decompression scenarios, that can occur in a material/medical pass-through system lock.
Helium release valves can primarily be found on diving watches featuring a water resistance rating greater than 300 m (1000 ft). ISO 6425 defines a diver's watch for mixed-gas diving as: A watch required to be resistant during diving in water to a depth of at least 100 m and to be unaffected by the overpressure of the breathing gas. Models that feature a helium release valve include most of the Omega Seamaster series, Rolex Sea Dweller, Tudor watches Pelagos, some dive watches from the Citizen Watch Co., Ltd, Breitling, Girard-Perregaux, Anonimo, Panerai, Mühle Rasmus by Nautische Instrumente Mühle Glashütte, Deep Blue, Scurfa Watches, all watches produced by Enzo Mechana, Aegir Watches and selected Doxa, selected Victorinox models, Oris models, TAG Heuer Aquaracer models, and the DEL MAR Professional Dive 1000 watch.
Other watch manufacturers such as Seiko and Citizen Watch Co., Ltd still offer high-level dive watches that are guaranteed safe against the effects of mixed-gas diving without needing an additional opening in the case in the form of a release valve. This is normally achieved through the use of special gaskets and monocoque case construction instead of using the more common screw down case-backs.
To enable changing the time or date during their dive, saturation divers have to act somewhat counterintuitive regarding the water resistance management of their diving watches. On the initial and any later blowdown or compression, most saturation divers consciously open the water-resistant crown of their watches to allow the breathing gas inside to equalize the internal pressure to their storage/living environment. [6] This pressure differential mitigation strategy allows them to later open the water-resistant crown at their storage pressure, to be able to adjust their watch if required during their (often weeks long [7] ) saturation period under regularly varying pressure levels between worksites. The storage pressure is generally kept equal or only slightly lower than the pressure at the intended divers' working depth. Opening a watch case (by unscrewing a crown) means expanding its internal volume. In a significantly higher external pressure environment, any expansion will be impeded by this environment. Every opening and closing action of a release valve or crown seal involves a risk of dirt, lint or other non-gaseous matter ingress, that can compromise the proper functioning of the seal and watch.
The standards and features for diving watches are regulated by the ISO 6425 – Divers' watches international standard. ISO 6425 testing of the water resistance or water-tightness and resistance at a water overpressure as it is officially defined is fundamentally different from non-dive watches, because every single watch has to be tested. ISO 6425 provides specific additional requirements for testing of diver's watches for mixed-gas diving. [8]
Some specific additional requirements for testing of diver's watches for mixed-gas diving provided by ISO 6425 are: [9]
A diving cylinder or diving gas cylinder is a gas cylinder used to store and transport high pressure gas used in diving operations. This may be breathing gas used with a scuba set, in which case the cylinder may also be referred to as a scuba cylinder, scuba tank or diving tank. When used for an emergency gas supply for surface supplied diving or scuba, it may be referred to as a bailout cylinder or bailout bottle. It may also be used for surface-supplied diving or as decompression gas. A diving cylinder may also be used to supply inflation gas for a dry suit or buoyancy compensator. Cylinders provide gas to the diver through the demand valve of a diving regulator or the breathing loop of a diving rebreather.
Surface-supplied diving is a mode of underwater diving using equipment supplied with breathing gas through a diver's umbilical from the surface, either from the shore or from a diving support vessel, sometimes indirectly via a diving bell. This is different from scuba diving, where the diver's breathing equipment is completely self-contained and there is no essential link to the surface. The primary advantages of conventional surface supplied diving are lower risk of drowning and considerably larger breathing gas supply than scuba, allowing longer working periods and safer decompression. Disadvantages are the absolute limitation on diver mobility imposed by the length of the umbilical, encumbrance by the umbilical, and high logistical and equipment costs compared with scuba. The disadvantages restrict use of this mode of diving to applications where the diver operates within a small area, which is common in commercial diving work.
Saturation diving is diving for periods long enough to bring all tissues into equilibrium with the partial pressures of the inert components of the breathing gas used. It is a diving mode that reduces the number of decompressions divers working at great depths must undergo by only decompressing divers once at the end of the diving operation, which may last days to weeks, having them remain under pressure for the whole period. A diver breathing pressurized gas accumulates dissolved inert gas used in the breathing mixture to dilute the oxygen to a non-toxic level in the tissues, which can cause decompression sickness if permitted to come out of solution within the body tissues; hence, returning to the surface safely requires lengthy decompression so that the inert gases can be eliminated via the lungs. Once the dissolved gases in a diver's tissues reach the saturation point, however, decompression time does not increase with further exposure, as no more inert gas is accumulated.
A diving bell is a rigid chamber used to transport divers from the surface to depth and back in open water, usually for the purpose of performing underwater work. The most common types are the open-bottomed wet bell and the closed bell, which can maintain an internal pressure greater than the external ambient. Diving bells are usually suspended by a cable, and lifted and lowered by a winch from a surface support platform. Unlike a submersible, the diving bell is not designed to move under the control of its occupants, or to operate independently of its launch and recovery system.
A diving chamber is a vessel for human occupation, which may have an entrance that can be sealed to hold an internal pressure significantly higher than ambient pressure, a pressurised gas system to control the internal pressure, and a supply of breathing gas for the occupants.
Water Resistant is a common mark stamped on the back of wrist watches to indicate how well a watch is sealed against the ingress of water. It is usually accompanied by an indication of the static test pressure that a sample of newly manufactured watches were exposed to in a leakage test. The test pressure can be indicated either directly in units of pressure such as bar, atmospheres, or as an equivalent water depth in metres.
The Rolex Oyster Perpetual Submariner is a line of sports watches designed for diving and manufactured by Rolex, resistant to water and corrosion. The first Submariner was introduced to the public in 1954 at the Basel Watch Fair. It was the first watch to be waterproof up to 100 metres (330 ft). The Rolex Submariner is considered "a classic among wristwatches", manufactured by one of the most widely recognized luxury brands in the world. Due to its huge popularity, there are many homage watches by well-established watchmakers, as well as illegal counterfeits. The Rolex Submariner is part of Rolex's Professional line.
A diving watch, also commonly referred to as a diver's or dive watch, is a watch designed for underwater diving that features, as a minimum, a water resistance greater than 1.1 MPa (11 atm), the equivalent of 100 m (330 ft). The typical diver's watch will have a water resistance of around 200 to 300 m, though modern technology allows the creation of diving watches that can go much deeper. A true contemporary diver's watch is in accordance with the ISO 6425 standard, which defines test standards and features for watches suitable for diving with underwater breathing apparatus in depths of 100 m (330 ft) or more. Watches conforming to ISO 6425 are marked with the word DIVER'S to distinguish ISO 6425 conformant diving watches from watches that might not be suitable for actual scuba diving.
The Rolex Oyster Perpetual Date Sea-Dweller is a line of diver's watches manufactured by Rolex, with an underwater diving depth rating of 1,220 meters and up to 3,900 metres (12,800 ft) for the Sea-Dweller Deepsea variant. In 2022 the dimensionally large Deepsea Challenge Sea-Dweller variant with an official depth rating of 11,000 metres (36,090 ft) was added to the line. The Rolex Sea-Dweller is part of Rolex's Professional line.
L'impermeable is the name of the first waterproof watch invented at the end of the 19th century and manufactured by the West End Watch Company, one of the oldest Swiss brands still active.
To prevent or minimize decompression sickness, divers must properly plan and monitor decompression. Divers follow a decompression model to safely allow the release of excess inert gases dissolved in their body tissues, which accommodated as a result of breathing at ambient pressures greater than surface atmospheric pressure. Decompression models take into account variables such as depth and time of dive, breathing gasses, altitude, and equipment to develop appropriate procedures for safe ascent.
Scuba skills are skills required to dive safely using self-contained underwater breathing apparatus, known as a scuba set. Most of these skills are relevant to both open-circuit scuba and rebreather scuba, and many also apply to surface-supplied diving. Some scuba skills, which are critical to divers' safety, may require more practice than standard recreational training provides to achieve reliable competence.
Surface supplied diving skills are the skills and procedures required for the safe operation and use of surface-supplied diving equipment. Besides these skills, which may be categorised as standard operating procedures, emergency procedures and rescue procedures, there are the actual working skills required to do the job, and the procedures for safe operation of the work equipment other than diving equipment that may be needed.
Surface-supplied diving equipment (SSDE) is the equipment required for surface-supplied diving. The essential aspect of surface-supplied diving is that breathing gas is supplied from the surface, either from a specialised diving compressor, high-pressure gas storage cylinders, or both. In commercial and military surface-supplied diving, a backup source of surface-supplied breathing gas should always be present in case the primary supply fails. The diver may also wear a bailout cylinder which can provide self-contained breathing gas in an emergency. Thus, the surface-supplied diver is less likely to have an "out-of-air" emergency than a scuba diver using a single gas supply, as there are normally two alternative breathing gas sources available. Surface-supplied diving equipment usually includes communication capability with the surface, which improves the safety and efficiency of the working diver.
Diving hazards are the agents or situations that pose a threat to the underwater diver or their equipment. Divers operate in an environment for which the human body is not well suited. They face special physical and health risks when they go underwater or use high pressure breathing gas. The consequences of diving incidents range from merely annoying to rapidly fatal, and the result often depends on the equipment, skill, response and fitness of the diver and diving team. The classes of hazards include the aquatic environment, the use of breathing equipment in an underwater environment, exposure to a pressurised environment and pressure changes, particularly pressure changes during descent and ascent, and breathing gases at high ambient pressure. Diving equipment other than breathing apparatus is usually reliable, but has been known to fail, and loss of buoyancy control or thermal protection can be a major burden which may lead to more serious problems. There are also hazards of the specific diving environment, and hazards related to access to and egress from the water, which vary from place to place, and may also vary with time. Hazards inherent in the diver include pre-existing physiological and psychological conditions and the personal behaviour and competence of the individual. For those pursuing other activities while diving, there are additional hazards of task loading, of the dive task and of special equipment associated with the task.
The following outline is provided as an overview of and topical guide to underwater diving:
Diving procedures are standardised methods of doing things that are commonly useful while diving that are known to work effectively and acceptably safely. Due to the inherent risks of the environment and the necessity to operate the equipment correctly, both under normal conditions and during incidents where failure to respond appropriately and quickly can have fatal consequences, a set of standard procedures are used in preparation of the equipment, preparation to dive, during the dive if all goes according to plan, after the dive, and in the event of a reasonably foreseeable contingency. Standard procedures are not necessarily the only courses of action that produce a satisfactory outcome, but they are generally those procedures that experiment and experience show to work well and reliably in response to given circumstances. All formal diver training is based on the learning of standard skills and procedures, and in many cases the over-learning of the skills until the procedures can be performed without hesitation even when distracting circumstances exist. Where reasonably practicable, checklists may be used to ensure that preparatory and maintenance procedures are carried out in the correct sequence and that no steps are inadvertently omitted.
Robert August Barth was a United States Navy Chief Quartermaster, pioneering aquanaut and professional diver. He was the only diver to participate in all U.S. Navy SEALAB missions led by George F. Bond. Barth is considered to be the father of the Rolex Sea Dweller. In 1967, he developed the idea for the helium release valve which was patented by Rolex on November 6, 1967.
