2004-12-14 - ABB has supplied an AK100 thermal conductivity gas analyser to Oldbury power station near Bristol.
The new meter is a direct descendant of the one it’s replacing - an old Cambridge DDI Katharometer that has been in service since the power station was constructed 45 years ago. The DDI is still in good working order and is only being replaced to comply with ATEX, the latest European directive on equipment used in hazardous areas.
The new ABB AK100 Hydrogen Purity and Purge Gas Monitor and the old Cambridge DDI Katharometer both analyse gases by measuring their ability to conduct heat. They are used in power generation to monitor the purity of hydrogen, which acts as a coolant around the generators. Thermal conductivity analyser technology traces its roots back over 80 years and continuous development has today made the ABB AK100 the most accurate and stable Katharometer yet. ABB designed the AK100 system specifically for this application.
During normal operation it monitors the purity of hydrogen, which must be maintained because hydrogen forms an explosive cocktail if mixed with air. As well as plant safety, maintaining the purity of the hydrogen is vital in order to optimise plant performance.
Hydrogen’s low viscosity and density helps to significantly reduce windage losses caused by drag in the generator, which operates at its optimum efficiency only when hydrogen purity is at a maximum. As the purity of the hydrogen drops, the operational efficiency of the generator falls, so that an eight per cent drop in purity can lead to losses of £2,500 per day for an 800MW unit.
During maintenance shut downs, the AK100 also helps ensure that the hydrogen is purged from the generator using carbon dioxide and then that the carbon dioxide is purged using air. Only then is the generator safe for any maintenance work.
Two thermal conductivity analysers are used to monitor hydrogen, carbon dioxide and air concentrations. The analysers can be installed in Zone 0 hazardous areas. The associated intrinsically safe power supply units must be installed along with the monitor in a safe area.
The ATEX 137 Directive came into force in June 2003 and requires operators to carry out a risk assessment of potentially explosive risk areas and to install ATEX-certified equipment where necessary. ABB's AK100 system is certified to meet ATEX Ex II (1)G and CENELEC EExia IIC standards for intrinsic safety.