Aug 2014
Gas Transmission
Gas Generator Preservation Assessment
Aug 2014
Apr 2017
National Grid Gas Transmission
Charles Crossley, Mike Marcinko, Roy Hughes ,
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Network Innovation Allowance
Gas Transmission Networks
Gas turbine engines (gas generators) are used by National Grid to provide power for natural gas compressors which are used in turn to maintain pressures on the transmission network. Gas generators use atmospheric air as part of the internal combustion process during operation. When the units are not operating moist atmospheric air accelerates corrosion of internal engine components.

Gas generators can spend prolonged periods out of operation, leading to equipment degradation requiring early overhaul. The current preservation techniques can be difficult to fully implement and a major element of ensuring ongoing engine reliability is an engine ‘test run’ performed every 28 days. This test run increases environmental impact through direct engine emissions and gas venting.

Gas generator preservation techniques involve a combination of solutions. Most short term measures involve injection of substances into the engine in order to reduce the impact of moisture upon metal alloys.

While this can provide adequate results it requires significant resources to implement and reverse. As such these standard techniques are not usually implemented on our gas generators.

The aim therefore is to improve on these techniques by providing a solution which is effective, quickly reversible, environmentally responsible and safe. This will focus on the reduction of air humidity below an advised 40% threshold. This will be achieved by integration of an instrument air flow into the engine wash system. Instrument air is produced at a relative humidity of around 1% and when mixed with atmospheric air within the engine will reduce humidity to the desired levels. In order that sufficiently low humidity levels are reached, sealing of the gas generator air intake may be required. This solution should also remove our requirement for a full 28 day compressor ‘test run’.

This solution is an innovative method of using existing site equipment in a different way in order to improve our asset longevity and reliability.

Knowledge from this project will allow National Grid to update the gas generator preservation strategy which will effect a reduction of natural gas venting associated with preservation techniques.

Identify fit for purpose preservation technique to effect the reduction in humidity of gas generators and carry out a trial of the solution(s) to determine long term engine preservation.