RWE npower operate a number of coal, oil and gas-fired power stations, and supply gas and electricity to both homes and businesses. Tom Maund, who is a performance engineer in the Performance Development group, kindly wrote the following piece, which highlights the success they've had using the PHD-4 helium leak detector.

"Over the past 18 months, engineers working for RWE npower have carried out a comprehensive series of tests to ascertain the level of condenser air ingress across its portfolio of Coal, Oil, Combined Cycle Gas Turbine (CCGT) and Cogen sites."

"Condenser air ingress has a detrimental effect on the thermal performance of condensers, and can also be attributed to corrosion and other mechanical failures within a condenser. Deviations in condenser backpressure can be very costly, and a typical 500 MW coal fired unit running at 5 mb above target would incur significant additional running costs."

"Fundamental in RWE's approach to identifying source sites for air ingress has been the PHD-4. It has proved both reliable and robust, and several units have been bought to allow greater flexibility for sites to carry out surveys. Helium is sprayed around any areas on a generating unit that may be subject to sub atmospheric or vacuum conditions, and a sample gas is measured at the main air extraction pump exhaust. The helium concentration indicated by the PHD-4 in the sample gas is representative (if not wholly accurate) of the level of air ingress at the spray site."

"Initial issues in the use of the PHD-4 were that it had to be placed near to the air extraction point and watched continuously for any indication of helium being detected."

"As well as this, most units are very noisy, large and spread over several levels - communication between personnel at the spray site and at the sample extraction point was difficult and prolonged the testing period over several days, utilising 3 engineers to carry out a full survey."

"Developments over a period of time have enabled engineers to provide a wireless interface between the PHD-4 and a laptop, which enables operators to get a real-time indication of helium detection at the spray site, which vastly decreases the amount of testing time. Where immediate repairs can be carried out, re-testing can be done to quickly assess their effectiveness."

"In addition to the PHD-4, engineers also make use of the Ultraprobe to carry out vacuum leaks surveys (where access permits) on areas of plant such as Low Pressure Turbine Hood joints that lend themselves to rapid testing. Any suspect areas can then be easily and quickly checked using helium detection."

"As well as this, most units are very noisy, large and spread over several levels - communication between personnel at the spray site and at the sample extraction point was difficult and prolonged the testing period over several days, utilising 3 engineers to carry out a full survey."

"Both instruments form part of a suite of tools and complimentary equipment used by RWE engineers known as COOLAIRS (Condenser On Off Load Air Ingress Reduction System)."