12 Bottom Blowdown
Mk8 MM Manual Page | 224
12.3.2 Calculation for Bottom Blowdown Reduction
For timed reduced bottom blowdown with Mk8 MM, the maximum steam production used to base how the
bottom blowdown time is scaled down to is set through expansion option 64. The blowdown time is reduced
according to the ratio of the actual steam production to the maximum steam production for that period. If the
blowdown is calculated above the stored blowdown time set by the user in the bottom blowdown screen,
then the extra time will get carried over to the next timed blowdown. This extra time will remain getting
carried over to the following blowdowns until the steam production has lowered and the blowdown is
therefore lowered.
There can be up to 10 blowdowns over a 24-hour period, with each blowdown:
The configured blowdown time for that period x which has been set by the user is:
= (sec)
The time between the blowdowns which is sent by the user is:
= ()
Therefore over a 24 hour period:
+
+
+
+
+
+
+
+
+
= 24
The blowdown time for that 24-hour period is then:
+
+
+
+
+
+
+
+
+
=
The maximum blowdown period can be calculated as:
() =
24
×
The maximum steam flow which is set in expansion option 64 is:
The average steam flow for that period which is given from steam flow metering is:
The calculated steam flow ratio for that period is then:
=
The adjusted blowdown time according to steam production is then:
=
×
×
24
If the adjusted blowdown time is calculated higher than the maximum blowdown time, the time is carried over
to the next scheduled blowdown operation:
>
Extra time is carried over to next blowdown operation
If the calculated adjusted blowdown time is lower than the minimum blowdown time set in expansion option
63, and expansion option 62 is set for minimum blowdown enforced, then:
<
Minimum blowdown time is enforced
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