Oxygen gas is used in a large number of applications throughout the world. The aviation, medical and diving recreation industries use oxygen to enhance breathing while other industries use oxygen in applications such as welding.
The gas is contained and transported in compressed gas cylinders and pressure gauges are used to monitor the pressures within those cylinders. The pressure gauges are typically mounted on regulators that control the output of the oxygen gas in the cylinder.
The use of oxygen poses many dangers and special care and handling need to be taken when using the pressure gauges, regulators and other equipment to keep them free from contaminants.
Oxygen is not a flammable gas and cannot ignite or burn by itself, but it easily supports combustion and makes all materials or contaminants more flammable and easier to ignite than when exposed to ordinary air. The intense concentration and pressure of the oxygen within a compressed gas cylinder can cause violent reactions with contaminants, resulting in explosions, fires, significant damage to equipment and personal injuries.
The major contaminants that can cause the most damage in the presence of oxygen are various types of hydrocarbon-based oils and greases and small metal particles or other debris.
Hydrocarbon-based contaminants are easily combustible and although they are harmless in normal air, they are extremely dangerous in the presence of oxygen. Particle contaminants such as metal shavings provide the necessary fuel for combustion and can easily ignite when exposed to high concentrations of oxygen. Even small amounts of contaminants can have violent reactions in the presence of oxygen.
Due to these dangers, standardized requirements and classifications have been developed for the cleanliness of all gauges and equipment used for oxygen. The main emphasis for all of these standards is to diminish the risk of catastrophic incidents by reducing the potential fuel sources that are present on the equipment used in the oxygen environment.
Calibration of pressure gauges used for oxygen requires special cleaning, labeling and packaging procedures that qualified calibration laboratories are required to perform before returning the gauges to their customers.
The cleaning operation for oxygen pressure gauges is essential to the safety of the use of the gauges. The cleaning process usually involves flushing the internal chamber of the pressure gauge with special solvents to remove any residual contaminants that may be present. The solvent from the pressure gage is then inspected, in both ambient and blacklight, to observe the number and size of the contaminants within the solvent.
This process is repeated until the inspection meets the required cleanliness classification for the gauge. The surfaces of the pressure gage are also inspected with a backlight to ensure their cleanliness.
Any accessories are also cleaned and inspected, usually through an ultrasonic method immersed in the solvent. Some alternative cleaning methods have been developed recently due to restrictions in the use of hazardous solvents or solvents containing chlorofluorocarbons (CFCs).
Proper notifications must be placed on all pressure gauges that have been cleaned for oxygen use. A label or sticker with wording such as ‘For Oxygen Use Only’ or ‘Use No Oil’ must be prominently displayed on the gauge face.
The gauge must be packaged individually and placed in a sealable, plastic bag. Many standards require double bagging to further protect the gauge and keep it clean for safe use. The pressure gage opening is protected with plugs or caps that have also been cleaned for oxygen use.
Any accessories that have been oxygen cleaned, such as fittings, hoses or valves are also packaged individually after cleaning.
Hydrocarbon contaminants should never come into contact with oxygen gauges that have been properly cleaned. Oxygen gauges should never be handled with bare hands or leather or contaminated gloves. New cotton or latex gloves should only be used and the gloves should be discarded after each use.
When preparing the gauges or accessories for use, the protective bags should always be opened in a clean environment. All tools used for connecting the gauges to the regulator or other accessories, such as wrenches, should also be properly cleaned prior to use.
When stored, oxygen gauges must be kept separated from other pressure gauges or tools that may have had contact with oils and they should always be stored in their protective packaging.
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