Gases and gas handling for the lab environment

BOC Limited
Monday, 19 July, 2010

Over the past decade, manufacturing and process plants across the full spectrum of industry have advanced to meet the growing and evolving demands of the markets they serve. In turn, the design and function of the laboratories which support these plants have had to respond to these changes. Accordingly, the gases and gas technologies used in testing, analysis and measurement, and the associated gas equipment and supply systems have advanced in quantum leaps.

Pure gases come in various purities from ‘industrial’ or ‘technical’ grades to several high-purity ‘specialty gases’ grades. Within the pure specialty grades, purity can vary from the 4.6 grade - being 99.996% pure - to the 7.0 grade at 99.99999% purity. Higher purity means fewer and lower levels of the impurities that cause problems with instrumentation and analytical measurement.

Higher purity gases keep instruments running at optimum levels. These include helium, hydrogen, argon and nitrogen as ‘carrier’ gases and ‘purge’ gases for gas and liquid chromatography and spectrometry. These are required for sample measurement in the gas, liquid or solid phase. Higher purity gases, such as nitrogen, and gas mixtures are also used for instrument span calibration and to set the zero reading: they are especially required for sample measurement in the gas phase.

Quality and reliability are therefore a critical requirement in the supply of pure gas. Pure gas cylinders are provided on the basis of supplier quality assurance, or with a certificate to validate the cylinder contents. Gas mixtures also involve a range of quality levels and require different types of certificate. The most basic mixtures - such as welding gas mixtures - are filled using mass production techniques to keep cost and price low, while specialty gas mixtures are filled in more controlled environments. Mixtures for process applications, such as food packaging or laser gas mixtures, are often supplied based on the manufacturers’ quality systems. However, calibration gas mixtures always require a certificate of analysis so that the reported values can be used by the customer to precisely calibrate their instrument.

Various certificate types exist in the quest to achieve increasing levels of accuracy, traceability and accreditation. The most reliable of these are validated by independent organisations such as NATA, IANZ for the South Pacific region or to international standards such as ISO17025 or ISO Guide 34.

“The most important requirement of any gas used for calibration purposes is that it can accurately and repeatedly report values of the instrument being measured,” said Jenia Mehdizadeh, market manager for Scientific.

Sound analytical protocols are in environmental analysis and testing, a range of sophisticated instruments and next-generation gas chromatography and mass spectrometry techniques play a vital role in the identification and qualification of environmental pollutants. Both techniques and equipment require high-quality specialty gases for instrument operation and/or calibration, in addition to dedicated high-purity gas distribution systems.

Since the reliability of analysis is only as good as the quality of gas being used, distribution systems and equipment for high-purity and specialty gas mixtures must be able to meet increasing demands for high standards of performance and new analysing methods. Impurities occurring in low concentrations as parts per billion can have serious consequences.

To complement the specialty gas range, BOC has introduced HiQ equipment, comprising baseline cylinder regulators and redline supply systems.

The Baseline gas equipment range can provide users with an entry-level range of specialty gases cylinder regulators which are appropriate for more flexible systems or short-term project work where requirements change from time to time - for example, for research projects and R&D labs.

Redline gas supply systems for high-purity gases and specialty gases is a high-tech, patented, precision-designed range of products, modularly designed to slot into central gas supply systems, containing gas panels, valves and points-of-use suitable for purities up to 6.0 (99,9999%). Redline equipment is exclusive to the Linde Group with specialist installation by BOC’s customer engineering service division.

Redline contains many product features. The technology ensures flow and pressure remain constant during use of this equipment. The panels combine face seal connections with welding techniques, mitigating potential for gas leakage compared with more traditional panels which use standard threaded connections. To maintain the quality of gas during cylinder changeover or in supply lines to ensure that samples are not contaminated en route to the lab, a system purge is an essential procedure. Purge assemblies allow the introduction of a purge gas into the system after cylinder changeover. Even with standard carrier gases, a system purge is recommended to remove the potential air and moisture contamination that can occur.

“Good practices such as purging are critical to maintaining the integrity of your gas system. Systems lacking a purge facility increase the risk of introducing contaminants, compromising the quality of gas at the point of use. You wouldn’t drink through a dirty straw and neither should your instruments,” said Mehdizadeh.

It is critical to select the appropriate gas specification along with the supply mode to ensure functionality and quality. Installation of that equipment must be completed by experts with experience in high-purity clean systems such as BOC’s customer engineering services team. Choosing a company that understands the requirements of a specialty gas supply system will ensure that the integrity of the high-purity gas is not jeopardised.

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