The effect of internal surface finish of aluminium alloy cylinders on the stability of sensitive gas mixtures

Adam Lomax,  EffecTech (GB)

The measurement of reactive species is important within industry for process control, environmental monitoring and the calibration of safety critical equipment. Nearly all the field equipment used for these measurements are comparators; this makes the stability of the reference gas used to calibrate field equipment highly critical.

However, reactive species have inherent issues with stability. Even if a gas mixture has been manufactured and calibrated to a high standard, if the species begins to decay within the cylinder it may not allow for the correct calibration of field equipment.

Gas companies often cite internal surface roughness as a critical factor for gas stability. It’s true that a rougher surface can provide recesses for accumulation of contaminants (e.g., lubricant residue, wash chemicals, etc.) and in some instances potential reaction sites. However, roughness is often of secondary importance compared to the inherent chemical nature of the internal surface, especially when locally active sites are present (e.g., exposed intermetallics and other surface features that can promote catalytic activity and affect gas stability).

Over many years Luxfer Gas Cylinders have developed their process technology to provide an excellent product to meet the needs of these markets e.g. electronics, environmental, etc.. The SGS™ interior is achieved at Luxfer Gas Cylinders Ltd., in Nottingham, through proprietary, time-sensitive manufacturing operations.

This poster reports a comparison of the stability of reactive gas mixtures when stored in aluminium cylinders with three different internal surfaces. The internal surfaces are: acid washed, standard (no acid wash) and SGS™. It will outline several novel methods used to assess the cylinder stability, devised and tested by EffecTech, and discuss the conclusions drawn from these methods.

Pen Profile

EffecTech is a global leader in the production of high quality calibration gas mixtures accredited to ISO 17025. EffecTech’s ISO 17025 scope covers sulphur mixtures and other reactive gases as part of its core business, and so the company has invested in extensive trials in order to improve cylinder stability. The research team at EffecTech has drawn on over 20 years of in-house knowledge and experience of instrumentation, gas chromatography and data processing as well as utilising the company’s gas mixture production facilities and extensive analysis capabilities to collect the high quality analytical data required for these trials.

Adam Lomax graduated from Loughborough University in 2008 with a B.Sc. in Chemistry, and is currently studying Mathematics and Statistics at the Open University. From 2008 to 2013 he was employed at the EffecTech Group’s headquarters in Staffordshire, UK as a Senior Gas Quality Engineer, carrying out the calibration of gas quality instrumentation at sites across the world. From 2013-2015 was employed by Petrofac and was responsible for calibration and maintenance of oil and gas metering equipment in the Ninian oil field. In 2015, he returned to EffecTech and is now the Operations Support Engineer, responsible for maintenance and development of EffecTech’s measurement infrastructure.

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