Application reports

# 2 : Leak testing of power plants

Condenser problems in large power plant cause considerable loss in plant efficiency and availability...

Application
Condenser problems in large power plant cause considerable loss in plant efficiency and availability. For example optimum working values for the condensor is 30°C and 95,8% vacuum (42 mbar,  absolute pressure), a simple pressure increase of 10mbar in the condensor results a lost of 2,5MW per year for a 525 MW power plant station.

Benefits of adixen tracer gas Methods
Leaks are detected and quantified, making it possible to monitor them over a period of time to determine any deterioration of the joint

• Sensitivity.
• On line identification of air-inleakage.

A major advantage as the overhaul is scheduled one or two times per year, the tracer gas method allows to locate leaks very accuratly during process before these ones impact the efficiency.
During overhaul, as leaks have been identified during inspections, it shorters the maintenance time.

• Fast pinpointing position and identification of leaking part.
• Spraying or sniffing method.

Specification
Condensor must be leak tight under operating conditions, as pressure and temperature are two combined factors to be controlled in order to faster convert water vapor into water.
Air in-leakage is also responsible for corrosion and affect the condensor lifetime.

Current method and reason for Change
• Today helium tracer gas is the most widely used method.
• Smoke test (chemical smoke source) problems because of the presence of air currents (drafts, ventilation, low test sensitivity.
• Ultrasonic leak detection: problems because of surrounding (background) noise, less sensitive as tracer gas method.
• Thermal conductivity: less sensitive as tracer gas method, pressure dependant.
• Halogen test:not allowed any more because of environmental properties

How to use tracer gas method
The helium leak detector is connected on the vacuum line front the liquid ring pumps; helium is released in proximty of
the suspected condenser air-in-leak area
by a spray gun, should a leak be present, the detector measures the flow of gas penetrating the condensor and the leak
can be located.

Equipment used
Helium leak detector ASM 310
The adixen ASM310 is a leak detector that was developed especially for mobile use.
Main focus was laid on compact dimensions and low weight. The ASM310 is the smallest and lightest (21 kg only) Adixen leak detector that is based on a high-end mass spectrometer detector.
The multi functional display allows data and graph storage on an integrated SD card and data transfer according to modern computer standards

Accessories
Wireless solution: Pocket PC and ASM Pocket software to adress large systems;
only one technician is required to perform the complete leak detection.

Tracer gas method: the most sensitive and versatile NDT methods.
An unrivalled sensitivity and wide dynamic range are the key characteristcs for tracer gas leak detection method.
Easy operation, high acceptance and regulation conformity have made tracer gas leak detection methods the optimum solution for maintenance.