1.0 Introduction
The LeakHunter Plus, Model 8066, is a hand held instrument typically used for detecting
leaks in gas plumbing joints, and for testing the integrity of sealed units using a tracer
gas. The magnitude of the leak is indicated by a bargraph display and an audible tick.
Operation can be one, or two handed. The audible tick and a peak hold mode allows
operation in awkward situations where the display is not visible. The peak hold mode
causes the display to retain the highest reading detected. A nozzle is available for
measuring large leaks by allowing the sample to be thirty times greater than with it off.
An extended probe is supplied to facilitate access in difficult applications.
An internal pump draws leakage gas and surrounding air in through the nozzle, then
over the sensor that measures the thermal conductivity of the gas/air mixture. Thermal
conductivity is defined as the rate of flow of heat through a medium. The gas/air mixture
escapes from the instrument via four holes in its base.
The LeakHunter Plus will indicate when a gas is present that has a thermal conductivity
that differs from that of the ambient air on which it was zeroed. The instrument is
normally zeroed in ambient air comprising a mixture of approximately 78% nitrogen and
21% oxygen. Hence, the instrument is not very sensitive to nitrogen or oxygen, but has
a high sensitivity to helium and hydrogen since these have very different thermal
conductivities from air. (See Section 8.) A gas may have a higher or lower thermal
conductivity than air, and thus produce a positive or negative reading on the display.
The instrument has four gas group ranges to target the gases having thermal
conductivities that differ from air by different degrees.
The instrument can indicate a leak in terms of concentration (ppm), or flow rate (cfm,
ml/sec or ml/min). Readings are approximateand relative; the instrument is intended to
aid in the precise location of a leak, and to give an indication of its severity. Flow rate
readings assume that all the leaking gas passes through the probe: If some of the
leaking gas escapes to the surrounding air, without passing through the instrument, the
flow reading will be inaccurate to that extent.
The unit is battery operated using standard or rechargeable battery cells. A power
transformer is supplied for operating the unit from a 120VAC source.
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