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Purity can be defined as the absence of impurity in a substance, or in our case a pure gas product. With any gas or chemical, there is no such thing as 100%. There is always a potential impurity. It may come from the original source raw material, be naturally produced during production, introduced in the manufacturing supply line, or come from the pre or post production storage container. The amount of allowable contaminate will depend on the specification definition of the final product.
To prevent the potential of accidentally connecting a flammable gas to a oxygen enriched supply line, or a poison gas mixture to an air or oxygen supply line, compressed gas companies follow recommendations for cylinder connections set forth the by various safety groups around the globe.
With any pure product or mixture, the level of impurity can have an effect on the application. With analytical instruments, higher purity gases reduce background interference, minimizes noise and baseline drifting. This may allow for higher sensitivity and lower detectable limits in your readings. In addition, using a higher purity of gas may increase the longevity of the instrument columns, reducing operating cost. Another example would be with the expanding world of laser gases, where impurities such as moisture and hydrocarbons can cause problems in the laser resonator. Moisture destabilizes the beam, absorbs into the coating of some optics, and decreases power output, while hydrocarbons can reduce the gain of the laser, thereby limiting its ability to amplify power.
A pure gas reports impurity levels. The impurities are a result of source material or manufacturing. The levels will vary with each fill, due to potential changes with each source batch. With a gas mixture, a component (impurity) is intentionally introduced to a specific level to meet your specific requirement.
If one refers to pure gases and excludes scarce isotopes, we see currently Xenon as the most precious gas in the world. Xenon is applied in many industry segments. Just as one example, it is filled into light bulbs used as cars headlights. The value of one 50 liter cylinder filled with Xenon gas currently equals a premium high speed car.
The purge block is mounted directly onto the cylinder valve. The three valves to maintain the above mentioned functions are arranged in a compact block which leads to a very small internal volume of only 1. 3 Cm3, this very small volume is all that has to be purged during cylinder change. Another unique feature is the Capillary tube that leads the ultra pure gas deep into the cylinder valve. Here the purge gas will be loaded with contaminants. Through the area surrounding the capillary tube it will be carried to the purge gas out valve. The major advantages is the purging of the inner space of the valve and at the same time the capillary tube avoids the mixing of clean and contaminated gas.
Inlet Tee purge assemblies are connected between the cylinder supply and the supply regulator. Controlled by an isolation valve connected to a regulated purge gas source, this allows you to purge your system to remove potential atmospheric contamination after a cylinder change.
Industrial regulators are designed for use with gas products with no purity or contamination concerns and when accuracy is not required. Specialty gas regulators, while they may look similar in appearance, are manufactured to a totally different specification. The regulator body, diaphragms and springs are cleaned for use with higher purity gases. Many specialty gas products can have reactive properties, and the specialty gas regulator is designed to control these products without any effect to the product, damage to the regulating equipment and offer a certified leak rate to prevent leakage into the working environment.
A single stage regulator reduces supply pressure to a controlled outlet pressure using a single adjusting spring and diaphragm. Single stage regulators require constant adjustment, as the outlet set pressure will tend to rise as the inlet pressure falls. This could cause problems with some applications. A two stage regulator consists of two single stage regulators joined together, with a supply channel from the first to second stage. The first, or inlet stage, reduces supply pressure to a preset intermediate pressure. This pressure is then sent to the second stage, which lowers the preset pressure to an adjustable working pressure. Because the pressure is reduced in two stages, the set pressure is not subject to variation as the supply pressure decreases. But the issue here is the size of the regulator; this is approximately double the size of a single stage regulator. This can be overcome by EXACT type of regulator which is unique in the world which provides a double stage performance with a single stage configuration.
We different types of gas panels: Single Side, Double Side Manual Changeover, Double Side Automatic Changeover. Single Side panels supply gas from single side without any standby. Double Side Manual Changeover panels supply gas from either side with 1 side as primary side & other as secondary side, in this Manual intervention is required during changeover. Double Side Automatic Changeover panels supply gas from either side with 1 side as primary side & other as secondary side, in this No manual intervention is required. When the pressure at the present primary side reaches a pre-set value, the panel switches and makes the secondary side, primary. Often these panels are combined with alarms alerting the personnel that one side is empty. This means that it is possible to change the gas cylinders without interrupting the gas flow.
The point of use is the second stage of a central gas supply system. Together with the gas panel it guarantees a very stable outlet pressure and handles any pressure changes that may be caused in the system, from for instance temperature changes or the pressure changes that are due to the changes from secondary to primary side in a semi-automatic panel.
An impurity is a compound found in the raw material of the product and is generally not reported. A component is a compound that is intentionally introduced into the mixture as a specific level to meet the application requirement. For example, you required helium with 8 ppm of oxygen for a specific calibration of an instrument. The manufacturing plant will use source material with a verified known amount of oxygen, and add additional oxygen to achieve the requested certified level of 8 ppm. If the source Helium is verified to have an oxygen level of 1 ppm, to meet the application requirement an additional amount of oxygen will need to be added.
Because of the need to report low concentrations of impurity in a pure gas, or even a gas mixture, we would take 1 percent of a gas, and divide it by 10,000 and get parts per million. This can be used to report minute levels of impurity material in either gaseous or liquid phase.
LEL refers to Lower Explosive Limit, and is equivalent to LFL, or Lower Flammable Limit. Both refer to the lowest concentration of gas or vapour (% by volume in air) that burns or explodes if an ignition source is present.
A cross purge assembly has the isolation valve connected to a purge gas source, along with additional isolation valves at the supply inlet, as well as an outlet vent valve. The potential for contamination is limited to the purge assembly area itself. Cross Purge Assemblies should be used with toxic and corrosive gases.
Outlet Tee purge assemblies consisting of a supply system isolation valve, and vent valve on the outlet side of the regulator. After connecting to a new gas source, you then purge out the regulator using this captured outlet, rather than your distribution system, venting to open air.
Purging would be critical were there is a need of Toxic/ Flammable/ Corrosive & High purity gases required. In many cases during cylinder changeover/ Maintenance and in shut down operations the need of evacuating the line is the most critical as the gases involved as most hazardous to the working personnel or can contaminate the High purity gas.
Compressed gases are supplied under pressures that range from 3 bar to 300 bar (40 psig to over 4500 psig) depending on the product properties, and supply mode. If released in an uncontrolled manner, the contents could cause damage, and/or interfere with analytical or process applications. In addition, uncontrolled product could result in oxygen deficiency in confined space, or become a toxic or a flammable hazard. Regulators are used to reduce supply pressure to a controlled outlet pressure. The type of regulator used will depend on the physical properties of the gas, as well as purity, flow, and control requirements.
Regulators are supplied with proper connections, as well as materials of construction, for use with the compressed gas as specified by the customer. Because of the risk of cross contamination, or soft goods enrichment, we do not recommend using a regulator on any other product than that to which it was purchased.
The quality of your gas is only as good as your gas supply system. Gas supply panels are recommended with permanent supply installations to reduce the introduction of gas stream impurities during supply change. In some areas, the instrument or process location, overall facilities or economics do not allow for the use of a permanent supply system. In these cases a direct cylinder regulator is used. The choice of regulator will depend on the proximity of the gas supply to the process or instrument, and purity requirements.
The risk of potential accidents is reduced, as there is minimized need to handle gas cylinders inside the work place. A continuous gas supply to each work station means less wasted time and fewer unplanned disruptions for changing gas cylinders. A common gas source also removes systematic errors in, for instance gas chromatography, between work stations. Gas cylinders can be collected in a single area, which facilitates easier gas management and removal of cylinders from labs and work areas. Combined distribution to all users means more effective use of the cylinders which in turn can reduce gas costs and cylinder rentals, as well as transport charges.
It is important to have a right product at right place to get the desired output. In many cases this becomes the key issues to failure. Firstly understand your systems requirements such as the gas and their respective properties, Continuous supply, Remote operation, Alarm/Flow/Auto purging control requirements needed & any other safety options such as emergency shut off etc.,