Gases and gas supply systems used in testing, analysis and measurement have advanced in quantum leaps. Credit: Linde Gases
As the design and function of industrial laboratories have changed to meet new research and manufacturing demands, the gases and gas technologies used in testing, analysis, and measurement, and the associated gas equipment and supply systems have advanced.
Pure gases today come in various purities from industrial or technical grades to high purity specialty gas grades that can vary from 4.6 grade (99.996% pure) to 7.0 grade (99.99999% pure). Higher purity gases should reduce problems with instruments and analytical measurement.
High purity gases help keep instruments running at optimum levels. Helium, hydrogen, argon, and nitrogen are used 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. High purity gases and gas mixtures are also used for instrument span calibration and to set the zero reading.
Quality is 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. Increasingly, quality-conscious customers and stringent industrial quality systems are demanding an individual certification of analysis for each cylinder supplied.
Gas mixtures also involve a range of quality levels and require different certificates. The most basic mixtures are filled using mass production techniques to keep cost and price low; specialty gas mixtures are filled in more controlled environments. Mixtures for process applications, such as laser gas mixtures, are often supplied based on the manufacturer’s 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 instruments.
Various certificate types exist in the quest to achieve increasing levels of accuracy, traceability, and accreditation. The most sophisticated of these are validated by independent organizations such as China’s National Institute of Metrology (NIM), the National Association of Testing Authorities (NATA), Australia, the United Kingdom Accreditation Service (UKAS), or the Office of DAP German Accreditation System for Testing (DAP) to international standards such as ISO17025 or ISO Guide 34.
The characteristics of gases used to calibrate instruments have also made huge strides including the shelf life of gases. HiQ 60 calibration gases from Linde Gases, Munich, Germany, have a five-year shelf life, exceeding the three-year term from other suppliers.
Equipment and distribution
Sound analytical protocols are at the heart of work taking place at laboratories every day and in environmental analysis and testing. 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 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 analyzing methods. Impurities occurring in as low concentrations as parts per billion (ppb) can have serious consequences.
A system purge is an essential procedure 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. 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 any potential air and moisture contamination that can occur.
Over a period of time, standard threaded connection panels are subject to minor vibration, which can result in potential hazardous gas leak. The use of welded connections creates a permanent connection, while the use of face seal fittings ensure a leak-tight service from vacuum to positive pressure at the gas supply and distribution connection.
Gas detection systems are critical in a lab setting to protect personnel from the consequences of a gas leak. This can be achieved by installing a fixed detection system in the form of sensors, which are suitable for production laboratories where the types of gas being used are predictable from year to year. An alternative is to use a detection instrument, carried by each worker in the lab, which sound an alert when gas is detected in the laboratory environment. This option is flexible and suitable for use in R&D laboratories where the gases being handled can change from month to month.
Gas handling safety and international
Legislation in the European Union to boost the safety of gas handling and usage to entirely new levels impacts product registration, classification and labeling, packaging and transportation, storage, product information, and product disposal.
High purity gases keep instruments running at optimum levels so quality is a critical requirement. Credit: Linde Gases
REACH, (Registration, Evaluation, Authorization and Restriction of Chemical) substances is a European Union regulation on chemicals and their safe use. Now in the implementation phase, REACH was developed to ensure a high level of protection for human health and the environment. This includes the promotion of alternative methods for assessment of hazards of chemicals, as well as the free movement of substances on the market in the European Union. REACH makes industry responsible for assessing and managing the risks posed by chemicals and providing appropriate safety information to their users. Substances in volumes over one ton per year that are either manufactured or imported into the European Union (even in preparations/mixtures and articles), now have to be registered.
The Globally Harmonised System of Classification and Labelling of Chemicals (GHS), addresses the classification of chemicals by types of hazard and proposes harmonized hazard communication elements, including labels and safety data sheets. It aims at ensuring that information on physical hazards and toxicity from chemicals be made available to enhance the protection of human health and the environment during the handling, transport, and use of these chemicals. The GHS also provides a basis for harmonization of rules and regulations on chemicals at national, regional, and worldwide levels, an important factor also for trade facilitation.
The global implementation of GHS affects over 60 countries and came into force on December 1, 2010, directly impacting all pure gases in the E.U. countries. The reclassification of gas mixtures will be implemented in 2015.
Another critical piece of gas safety is the quality standard ISO 10156, which impacts how flammable and oxidizing gases are defined, labeled, and stored.
While most countries have systems for the classification of hazardous chemicals—including gases—to ensure safe transportation, storage, use, and disposal, to date, various national or regional systems have not always been compatible. This incompatibility has meant the re-labeling, or the use of multiple labels on a product, increasing the risks involved in handling gases. For organizations operating at an international level, the need to comply with multiple regulations on hazard classification and labeling has meant that end users may perceive inconsistent label warnings, therefore increasing the risks involved in handling a particular gas, in addition to the added time or barriers companies may face to align their classification and labeling with local requirements.