An indication device indicates an undesired operation condition of a
centrifugal separator and comprises an inlet valve situated in a supply
conduit to the separator, and an outlet valve situated in an outlet
conduit from the separator. During normal operation of the separator the
valves are adjusted in open normal valve positions for passing normal
flows through the supply and outlet conduits. A control unit is adapted to
activate a signal generator to generate an error signal in response to a
pressure sensor if the pressure sensor during a predetermined period of
time during operation of the separator senses a course of pressure change
in the outlet conduit different from an expected normal course of pressure
change, when the inlet and outlet valves during predetermined period of
time are adjusted in valve positions which at least substantially
decreases the flows in the supply and outlet conduits from the normal
flows.
