Application

Modern power station installations often use Hydrogen gas, with its excellent thermal conductivity properties, as the coolant medium for high capacity turbo generators or alternators; with the efficient performance and safe operation of the plant being critically linked to the gas quality used. During the commissioning and decommissioning of the alternator it is essential that the hydrogen is safely introduced and purged. Therefore, air must first be purged from the system by an inert gas such as carbon dioxide (CO₂). The hydrogen coolant is then introduced and replaces the purge gas. To decommission the turbogenerator the purge sequence is reversed. During daily operation, the hydrogen purity must also be monitored to ensure that the H₂ has not become contaminated by air leakages. Not only will air ingress produce a potentially explosive atmosphere but it will also affect the viscosity of the H₂ coolant gas, increasing drag and hence, windage losses. The Alternator Purge Gas Monitor series measures all stages of the fill-purge cycle as well as measuring hydrogen purity during normal operation.

Principle of Operation

The Alternator Purge Gas Monitor uses the proven katharometer technology from the K1550 analyser range. The katharometer comprises two chambers, each with an identical thermal conductivity sensor. One chamber is sealed and is filled with a reference gas whilst the other receives the sample gas. The difference in thermal conductivity of the reference and sample gases is translated into a concentration via an internal algorithm. The inherent stability of this system and integral temperature compensation, make the instrument one of the most accurate available.

System Description

The K1650 fixed analyser consists of display /controller unit, pre-mounted in a panel for easy retrofitting and a remote sensor assembly. The remote sensor assembly consists of a katharometer supplied in a wall mounting, IP65 enclosure complete with flowmeter and sample flow control valve. The sensor is certified to European standards for use in Group IIB + H₂ gases, and the zener barrier interface, incorporated in the display/controller unit, allows ‘live-working’ on the sensor unit.

The K1650 analyser has three pre-configured ranges to enable measurement of hydrogen purity plus all stages of the purge cycle: 0 to 100% CO₂ in Air; 0 to 100% H₂ in CO₂ and 80 to 100% H₂ in Air. For sites using nitrogen or other purge gases, please contact us for an alternative solution.

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