Process control calibration mixtures
Process control analysers monitor the composition of gas and liquid streams. This instrumentation requires calibration with specialty gases mixtures, also known as span gas or test gas.
The number and diversity of specialty gases calibration mixtures used for process control is infinite. At Coregas we generally make these products to order for you according to your specifications. This means that you get precisely what you need and we always go the extra mile to make sure you get it exactly when you need it.
The most common quality level for process control gas mixtures is to use ISO 17025-accredited gas mixtures. Certified reference materials with ISO 17034 accreditation are also suitable for process control applications but the extra precision, traceability and cost are not always required.
Process control gas instrument calibration span gas mixtures are used for short term calibration events. If the operator is in attendance for the calibration, they may make any required adjustments to the regulator outlet pressure; so these applications are suitable for single stage cylinder pressure regulators. If the calibration is automatic or remote, a two-stage automatic changeover panel, which allows continuous supply of gases as a depleted gas cylinder switches over to a reserve cylinder, is recommended.
Whether you specify chrome-plated brass or stainless steel depends on the components in the calibration gas mixture. For fully inert components, chrome-plated brass is suitable. If the mixture contains any traces of corrosive gases such as mercaptans, ammonia, or oxides of sulphur or nitrogen, then upgrading to a stainless steel regulator is essential to preserve the precise certified composition of the calibration gas mixture.
In addition to a span gas, most instrumentation will also require a zero gas such as Nitrogen 5.0 grade or Zero Air. Single-stage chrome-plated brass specialty gases regulators will be suitable for these gases if they are used in clean environments. If they are used offshore where salty sea spray exists, or in refineries, natural gas processing facilities, biogas production plants or water treatment facilities where traces of H2S are generally present in the air, then a stainless steel regulator is recommended. The biotechnology and pharmaceutical industry also often chooses to specify stainless steel for cleanliness.
Instrumentation pure gases and gas mixtures, such as helium for gas chromatography or hydrogen and air for FID flames are continuous flow applications. In these situations, the use of a two-stage regulator is essential to ensure a stable gas supply pressure as the content of the cylinder is depleted. Better still would be the use of a two stage automatic changeover panel which allows continuous supply of gases as a depleted gas cylinder switches over to a reserve cylinder.
Our experienced specialty gases customer service and sales teams can discuss your process control zero and span gas mixture requirements and recommend for the most appropriate gas pressure regulator. Coregas is Australia's only supplier of the Spetrolab range of gas control equipment, which is the ideal gas control equipment range to accompany our high precision calibration gas mixtures.
Here are a few examples of typical process control calibration gas and liquid mixtures from various chemical processing applications:
Nitrocarburising heat treatment furnace CO2 addition, eg NDIR analyser calibration
Nitrocarburising heat treatment furnace ammonia addition, eg TCD analyser calibration
Natural gas amine treatment for sweetening (H2S removal), eg Lead Acetate tape analyser calibration
Natural gas dehydration (water removal in adsorber or glycol scrubber)
Total sulphur measurement in crude oil refining (crude assay or product control), eg PUVF analyser calibration
Continuous catalyst regeneration (CCR) unit nitrogen purge process control, eg TCD analyser calibration
Catalytic steam methane reformer for hydrogen production final product purity control, eg TCD analyser calibration
SCR NOx reduction DeNOx process control, eg Chemiluminescence analyser calibration
Combustion control flue gas oxygen measurement, eg Zirconia oxygen sensor calibration
Crude natural gas analysis for process control (many different synthetic natural gas hydrocarbon mixtures will be used, one example is given here)