18
BlowTime
(H)
This is the length of time of the blowdown used in Intermittent Sampling with Timed Blowdown sampling mode.
This is set in Hours:Minutes and can be set from 1 minute to 8 hours 20 minutes.
At the end of the blowdown time, the controller will check the conductivity of a held sample once again. If the
conductivity is still above the set point, another blowdown cycle will occur.
If the sampling mode is set to
Intermittent with Time Proportional Blowdown
, then the blowdown valve will
open at the programmed Interval, for the programmed sample Duration. At the end of the sample duration time, the
blowdown valve will close, and the sample will be trapped for the Hold Time. If the conductivity of trapped sample
is greater than the set point, then blowdown valve will open for a variable amount of time, depending upon how far
above the set point it is. The controller uses the menus below to determine the blowdown time.
Prop Band
This is the conductivity value above the set point at which the maximum blowdown time will occur. This may be set
for any value between 1 and 10,000
μ
S/cm or ppm.
For example, if your set point will be 2000
μ
S/cm, and the Prop Band is 200
μ
S/cm, then if the conductivity is
above 2200
μ
S/cm the blowdown valve will open for the Max P Time described below. If the conductivity of the
trapped sample is 2100
μ
S/cm, the blowdown valve will open for half the Max P Time.
Max P Time
This is the maximum amount of blowdown time. This is set in Hours:Minutes and can be set from 1 minute to 8
hours 20 minutes. This should be set for the amount of time that it takes for the blowdown to drop the conductivity
of the boiler water by the conductivity value of the Prop Band under normal loading conditions.
At the end of the blowdown time, the controller will check the conductivity of a held sample once again. If the
conductivity is still above the set point, another blowdown cycle will occur, with a new blowdown time calculated.
Figure 8 Conductivity Menu
