| DESCRIPTION
The Crane Safety Monitor electronic unit is made for use in hoists as
an overload guard and monitor for working conditions.
The unit is powered by a primary switched power supply (AC or DC), which
will operate at all standard mains voltages without reconnecting. The
supply as well as all relays and sockets are placed on the DIN-standard
connecting bar. The Crane Safety Monitor is built into a protective steel
box which meets the requirements for the international protection specification
class IP65.
The signal from the load transducer is processed in the microprocessor
after analog/digital conversion, and compared to the limit and time parameters.
The result is the alarm outputs which drives the switch relays. Both a
strain gauge as well as a current signal of 4-20mA can be used as an input
signal.
The unit is self-checking and a malfunction of the transducer amplifier
or the cable will indicate overload.
The microprocessor together with the push buttons and the 2 lines by
16 characters LCD display, makes the readout of values and parameters
very easy. The working values can be the actual load, the Theoretical
Duration of Service, the total service time, total number of lift starts,
the peak value, etc. The parameters can be the limit levels, delays, hystereses
and also the calibration data. The LCD display includes a back light which
will be turned on when any push button is pressed and go off automatically
after approximately 4 minutes.
The users manual describes how the limits are set up regarding levels
and delay times and how the working values are read from the display.
The calibration manual describes how the unit is set up regarding the
full load, type of inputs, how the input signal is calibrated, etc. Changing
the calibration parameters requires a coded entry to avoid unauthorized
mistakes.
The Crane Safety Monitor has three switch functions (Lim 1; Lim 2A and
Lim 2B), each controlling a relay. Lim1 can be used for slack rope protection
limit switch or warning. Lim2A is used as a delayed overload limit switch
while Lim 2B can be used as an instantaneous overload limit switch. All
limit switches have functions for delays, hysteresis and switch on/off
polarity.
The system provides a time alarm which will affect the same relay as
Lim2B. This can be used for alarm at a preset time of the Theoretical
Duration of Service.
The recording of the Theoretical Duration of Service, TDS, is a time/load
function calculated during the lifting and/or the lowering movements.
The computation of the time/load function are following the European Standard
FEM9511 and REM9755. An idle hoist with load in hook does not record any
Duration of Service. The input for the recording of the TDS is by means
of two relays; one for the low speed movements and one for high speed
movements. The time is recorded as soon as either relay is activated by
a hoisting movement.
Since crane maneuvering circuits operating voltage are different from
manufacturer to manufacturer the hoisting movement inputs must be individually
adopted to the various cranes.
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