Alfa Laval PureBallast 135 Compact USCG, System Manual

Page: 98 / 412

1. Perform a backflush.
2. Open page 3.1 Trend and analyze the trend curve for V201-8.
Before the backflush, the valve shall move as fast as possible to a steady
position where it creates required pressure. If not, parameter p166 shall be
adjusted.
3. Adjust parameters, and perform a new backflush.
4. See if the curve has improved. Repeat until satisfactory result has been
achieved.
5. See if the time between backflush initiation and backflush can be
shortened . If possible, adjust parameter p310. See parameter p310 in the
example below.
Example
In this example, five backflushes are performed. After the first four
backflushes, the PID parameters where changed for pressure regulation to
adjust the movement of the control valve V201-8 before the backflush.
The illustration is taken from page 3.1 Trend . Backflush is indicated by the
movement of the backflush valve V309–1 (pink line) and the movement of
control valve V201-8 is indicated by the blue line.
1
st
backflush
Parameter p166 is set to 0.30. But it takes too long time for
V201-8 to get into position to create desired pressure (1). The
curve slops downwards in a long bend, which means that it
takes time for V201-8 to find correct position.
2
nd
backflush
Parameter p166 was adjusted to 0.6. This made the valve
movement much faster in the beginning, shown by the steep
curve at the beginning. But then a more slow regulation starts,
shown by the soft slope (2). This was a change for the better,
but not enough.
3
rd
backflush
Parameter p166 was increased to 1.2 which resulted in a
satisfactory valve movement (3): A fast movement, followed by
a minor adjustment. A small overcompensation can be noted
(curve goes too low), that might be adjusted by decreasing the
value to 1.1.
4
th
backflush
During the first backflushes, parameter p310 was set to 60
seconds. The parameter defines time between a backflush is
triggered and it actually starts. But now, when V201-8 is
calibrated, this time can be shortened. Before the fourth
backflush parameter p310 is set to 15 seconds. The shortened
time span is indicated by the braces in the illustration.
5
th
backflush
No parameter was changed. This backflush is only showed to
confirm that the parameter setting is OK and that the curve (5)
for V201-8 is basically the same as for backflush three and four
(3 and 4).
200000695-1-EN-GB 93
Operating instructions and control system description 3 EN