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the two heat exchangers. The first chilled heat exchanger takes enough of the water vapor from the sample to protect
the pump. The second heat exchanger is under a slight pressure and the dew point is at its minimum because it is on the
discharge side of the pump. The sample pump location within the sample system is a matter of choice and
good engineering.
The condensate must be removed from the heat exchanger(s) using one of the following methods:
1. A continuously running peristaltic tubing pump can be used with the heat exchanger either under pressure or vacuum.
This is an easy solution which lends itself to leak testing because of the positive displacement nature of the peristaltic
pump. It is, however, a device which requires periodic maintenance to replace the tubing.
2. Condensate can be removed from the heat exchanger using an eductor with a flow limiter to draw some of the hot,
wet sample through the heat exchanger along with the condensate. This method utilizes the heat exchanger as a bypass
condenser and serves the purpose of reducing the time lag in the sample line without loading the chiller with the water
vapor in the bypassed sample.
3. A float drain trap can be used to collect the condensate running out of the bottom of the heat exchanger(s) if the heat
exchangers are at a slight positive pressure with respect to the atmosphere. The float drain trap functions like a steam
trap. The float rises to discharge the condensate when there is enough to lift the float.
4. A small drain tank can be provided with a dual level, conductivity type level control to collect the condensate. When
the tank is full, the level controller will start a pump to remove the condensate until it reaches to the lower electrode.
When contact is lost, the pump stops and the condensate continues to fill the tank. Typically, a peristaltic pump is used
to remove the condensate. The advantage is that the pump only runs occasionally and bypasses no gas sample. The
peristaltic pump requires less maintenance because it does not run continuously.
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MAN.600.REVE.06302015
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