GESTRA LRR 1-52, Original Installation & Operating Manual

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8 LRR 1-52, LRR 1-53, URB 55 - USA - Installation & Operating Manual -
850703-00
Specialist terms, abbreviations
Here, we explain some abbreviations, specialist terms, etc., which are used in this Manual.
Blowdown controller
A blowdown controller is a conductivity controller with special features for actuating continuous
blowdown valves on steam boilers. It can also be used as a conductivity controller in other types of
system.
Continuous blowdown
Continuous and/or periodic removal of a certain (defined) quantity of boiler water via a continuous
blowdown valve, e.g., BAE46 or BAE47.
To determine the total dissolved solids in the boiler water, its electrical conductivity is measured in
μS/cm, although some countries also use ppm (parts per million) as the unit of measurement.
Conversion: 1 μS/cm = 0.5 ppm.
Intermittent boiler blowdown
Intermittent blowdown is achieved by the abrupt opening of the intermittent blowdown valve for a
period of around 3 seconds.
Time-based pulse/interval actuation of the intermittent blowdown valve optimizes the removal of
sludge from the boiler. The interval between the intermittent blowdown pulses can be set between
1 and 200 h (intermittent blowdown interval). The actual duration of intermittent blowdown can be
set between 1 and 10 seconds. For large boilers, repeated intermittent blowdown pulses may be
required. Repetition can be set between 1 and 10 with an interval from 1 – 10 seconds
(pulse interval).
External intermittent blowdown
If more than one steam boiler is connected to a single blowdown receiver, simultaneous blowdown
is not permitted. In this case,an external interlock control can monitor and control the individual
blowdown operations.
Temperature compensation
The conductivity of water changes as the temperature falls or rises. To obtain meaningful readings,
it is therefore necessary to base the measurements on the reference temperature of 77 °F (25 °C)
and to correct the measured conductivity using the temperature coefficient tC.
Cell constant
The cell constant is a geometric variable of the conductivity electrode and is taken into account
when the conductivity is calculated. However, this constant may change during operation, e.g., due
to dirt deposits on the measuring electrode.
If the result of a reference measurement differs from the indicated conductivity reading, first check
the temperature compensation.
Modify the cell constant only if the temperature coefficient setting is no longer adequate for correct
compensation. Change it until the reading and the indicated conductivity match.