Exchanger Leak Testing
Benefits of a TRACERCO Diagnostics™ Leak study
- Real-time measurements
- Identifies the leaking exchanger reducing downtime and production
loss
- Eliminates the need for traditional methods of shutting down the
unit or bypassing the equipment
- Significantly reduces the costs associated with confirming and
locating a leaking exchanger
Detection Technique – Detects leaks of 0.5 % or greater
Tracerco’s heat exchanger leak testing can be performed using 2
different methods. The standard on-line technique is to mount detectors
on the high and low pressure lines of each exchanger and inject a radioisotope
tracer that is compatible with the streams. As the tracer flows through
the exchangers along with the higher pressure stream, the detectors on
the piping will respond to the passage of the tracer, if one of the exchangers
has a leak, the leak into the low-pressure side will be at the same concentration
of tracer as its percentage in the feed. Though diluted by the effluent,
the detectors on the low-pressure exit lines will show a response. Comparison
of the area under the leak detector response curve to the area under the
injection detector response curve, allows the percentage leak to be approximated
if present. The limitation of this technique is in its sensitivity. This
technique is the easiest and quickest way to perform an on-line leak test
only if it is expected that 0.5 percent or more of the feed is leaking
into the effluent. Sometimes, the sensitivity can be improved to 0.2 or
even 0.1, but the more typical limit is 0.5 percent.
Sampling Technique – Detects leaks as low as 100 ppm
 The
external detection technique is only one method employed to determine
leakage. A second method uses a sampling technique where a sample point
on the low-pressure exit line is used to draw material over a short time
period. The tracer material and injection procedures are exactly the same
as the external detection method, but instead of mounting detectors on
the high and low pressure lines, sample points on the low-pressure lines
are set-up that usually use a sample cooler where the hot process liquid
is condensed/cooled and collected in sample containers. Alternatively,
samples can be collected in sample cylinders. The collected samples are
counted sequentially with a very sensitive radiation detector over several
minutes. Compared to the on-line tracer technique where the tracer material
flows past the detector in a few seconds, much smaller amounts of radiotracer
can be measured in the samples through accumulation of counts over time.
This technique has been used to find leaks as low as 100 ppm.
Chemical Tracer Technique – Detects leaks as low as 1 ppm
To address the need to find leaks smaller than 100 ppm, Tracerco carried
out an extensive research and development program looking at the application
of specialist chemical tracers. A number of tracers were identified and
tested, some of which are compatible with organic liquid or vapor streams
and others with aqueous materials that are chemically and thermally stable,
and can be readily detected in samples by specialized gas chromatography.
Samples are delivered to a local Tracerco laboratory where they are analyzed
for tracer content. These chemicals can be found in hydrocarbon samples
at concentrations as low as 1 part per billion (ppb).
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