Laboratory gases will always play a significant role in the everyday life of anyone working in any lab. A gas chromatograph (GC) or a mass spectrometer (MS) is just a sizable paperweight without gases.
But with the myriad of gases and gas grades to choose from and gas company representatives who are not always up to speed on the upper end of the specialty gas spectrum, how does one make the best choice?
INDUSTRIAL GASES VERSUS SPECIALTY GASES
Standard gases that are used in tasks such as welding or metal cutting are called “industrial gases.” Tanks are filled with the gas of choice for the application and shipped out to the customer. When the tank comes back empty it is simply re-filled, and out the door it goes again.
This is not the case with specialty gases. A specialty gas must meet or exceed a particular set of specifications and should never be allowed to leave the gas company’s gas lab until the cylinder in question has proven its worth under great scrutiny. Using ultra-highpurity (UHP) helium as an example, let’s walk through the process involved in earning the coveted “ultra-high-purity” status. First, the cylinder is fitted with a positive open/closed valve that ensures a high level of leak integrity. Second, the cylinder must be treated to a baking process to remove any contaminants from the inside of the cylinder walls. The tank is placed in an oven and baked for eight hours at 140ºF. During the baking process, the tank is purged with an inert ultra-high-purity gas and then quickly placed under a vacuum. This purge/vacuum sequence is repeated seven times during the eight-hour baking period.
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