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3.6 Typical applications -
condensate contamination detection system (CCD)
System description
Note: Most countries have regulations that limit temperature and contamination levels for
fluids being dumped to drain. It is also essential to follow guidelines issued by bodies such
as the UK Health and Safety Executive.
The Spirax Sarco CCD system monitors and displays the conductivity of condensate return,
and will redirect the flow to drain if the conductivity increases above a pre-set level to avoid
contaminated water being returned to the boiler feedtank. It will not detect contaminants that
do not change the conductivity, such as oils, fats, or sugars.
A conductivity sensor and a temperature sensor are mounted in a bypass line as
shown in Figure 9. A check valve in the main line ensures a flow past the sensor under
low flow conditions. The 500 mm head prevents flash steam flow in the bypass line.
We recommend a 3-port diverter valve such as the Spirax Sarco QL. A spring retract
pneumatic actuator is normally fitted to cause the valve to divert on failure of the air supply.
Alternatively, two 2-port valves (M20, for example) may be used as shown in Figure 10,
one as a spring-to-close isolating valve in the condensate return line, and one as
a spring-to-open dump valve, in the drain line. On detection of high conductivity, the
isolating valve closes and the dump valve opens, both under spring pressure.
Suitable 3-port solenoid valves may be selected from the Spirax Sarco range, and are
described in separate literature.
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