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Manual RS8FM602 © Danfoss 02-2016
EKC
326A
Guideline for setting automatic safety control
The following ratio between pressure and temperature can be used
to set the automatic safety control.
Regulation limitations of the receiver pressure
Safety functions
There are two safety functions for the receiver. They are only avail-
able for gas-cooled regulation.
A P-belt must be installed to be able to regulate the function, but
both are standard set to zero, which makes the function inactive.
Receiver pressure's max. limit
Set a max. receiver pressure. If the controller register receiver
pressure beyond the set value, the ICMTS valve will be closed.
The opening degree will be linear through the p-band so that the
ICMTS valve will be closed by pressing 'set max. receiver pressure'
plus 'set-p-band'.
If the valve's opening degree is set to a limited value and cannot
be fully closed, the set opening degree value will be at the pres-
sure 'set max. receiver pressure' plus 'set p-band'.
As such, gas can still be sent through the valve.
Receiver pressure's min. limit:
A minimum receiver pressure limit can be set. If the controller
register receiver pressure below the set value, the ICMTS valve will
be opened. The opening degree will be linear through the p-band,
and the maximum permitted opening degree of the ICMTS will be
present by pressing 'set min. receiver pressure' minus 'set-p-band'.
If the setting of the valve's opening degree is limited and it cannot
be fully opened, the set opening degree value will be at the pres-
sure 'set min. receiver pressure' minus 'set p-band'.
Note
The PI regulation of the receiver pressure must have space to
regulate without restrictions.
This means that there should be sufficient space for the PI regula-
tion to move around the reference, i.e. at least 2-3 bars – both over
and below the reference.
The value is very dependent on the tuning of the PI regulation
and the system dynamics.
An example may be a 40-bar plant in which the receiver's refer-
ence pressure is set to 35 bars. Here the system can interfere
with normal regulation because the high pressure limit is very
stringent.
Appendix