Condenser Tube Leak.

The first indication of a tube leak will come from the change in conductivity or chemical analysis of the condensate out of the hot-well.

The sampling connection can be brought into service to draw off samples of condensate from particular sections of the condenser to locate and isolated the section with the offending tube bundle.

When sections and tube bundles with the leak have been located, the decision to go into one side operation or to come down and off-the-line can be made.


Unit OFF-THE-LINE with turbine gland seals on and holding vacuum.
This mode of operation can be set up on the one side condition and for short periods of time with both side shutdown and open, provided that gland seal leak-off the condenser does not build up and overheat the turbine. When either of these two operational mode conditions are in effect, the leak detection procedure will be the same as for when the unit remains on-the line at reduce load, but without the added problem of the heat buildup.


Unit OFF-THE-LINE with vacuum broken and in cold condition.
This mode will probably be reserved for outages and major repair. In this situation recommends the performance of a full hydro-test although there are detection systems utilizing devices such as high frequency sound generator on the steam side and detectors on the water side, experience to date has not shown this or any other system to be as conclusive and precise as the hydro test.

Usually the fill for the hydro-test will sufficient to make the tube leak or leaks visible or known. Sometimes the leak is small and would take a long time to become apparent. This is where the previous calculation of the leak quantity would be of help in making a determination if ultra-violet light sensitive dye should be introduced along with the hydro fill water to make the leak more apparent in a shorter period of time. The two dyes in general use for hydro-test leak detection are Rhodamine-B and Fluorescein.

This ideal preparation for this hydro-test would be to blow all the tubes clear of debris pluggage and dry of residual water deposit and wet areas on the tube sheets before the fill water reaches the tubes.


Unit ON-THE-LINE at reduced load and one bank out of service.
This is the mode in which heat buildup becomes a major factor in reducing the proficiency of the craftsmen and the component materials of the systems device to locate the leaks.

In order to keep the intensity of this heat sink effect as low as possible, all hot drain and dumps should be shutdown and tagged out on the out of services side for as long as this condition or mode of operation is in effect.
To permit workmen to enter and function within these water boxes, cool outside air will have to be force in and pulled out by fans and/or air horn educators mounted in the man-way openings.

This forces circulation should be through the individual water box alone with no pressure differential between the inlet and outlet box so as to preclude an air flow through for two reason, More hot air will be brought into the work area and some of detection processes or procedures will be neglected by this false flow.


Leak Detection.
There are a number of procedures used to locate condenser tube leaks. Proper procedure selection should begin with the leakage location as a calculation of it size by the degree of contamination in condensate. Then establish if the total quantity of leak is from one source in one tube or from a number of small sources in a number of tubes.

The methods for locating a leak are:
1. For ruptured or broken tubes producing large leaks, the in-rush of air may be sufficiently audible to the unaided ear or sensitive to touch, to be immediately evident and produce an unmistakable determination of its precise location.

2. For cracked or split tubes producing medium to small leak. The use of a foam generator to coat the tube sheets with a layer of foam. With a layer of foam sealing both end of the tubes, a leak will be indicate by sucking a hole in the foam layer. Or use a thin plastic sheet to cover the tube sheets. If the plastic is drawn down into the tube, the leak is somewhere in the tube wall down the length of the tube.

3. For pits, minute leaks in the wall and roll joint use of ultrasonic detector. The passage of air through small orifice like breaks in the tube wall or roll joint sets up or produces vibrations in the 35kHz have be found extremely useful in finding tube leaks. Or use of tracer gas injection.

A homemade variation on the Freon gas and halogen detector and professional type system based on helium gas and a mass spectrometer as a detector are two readily available methods. When using Freon gas set the halogen detector probe in the vacuum pump air discharge vent. Set the cool air recirculation flow to enter the water box side. This aids the injected gas to flow through tubes.

The helium gas method is conducted in a similar manner. This method uses a mass spectrometer as a detector.