HSO 2024 to HSO 2035 Installation, Operation and Maintenance Manual
Issue 1.2 : 03/10
Publication 2-119
Page 29 of 94
(c)
Unscrew and remove the cap covering the calibration button and
LEDs.
(d)
Select ‘hand capacity control’. Move the capacity control slides to
the minimum load position. The slides must remain at minimum
load for the duration of step (e).
(e)
Press the calibration button once. The red LED will illuminate for
30 seconds, then ‘flash’ to indicate that the HBLVDT is ready for
maximum load calibration.
(f)
Check ‘hand capacity control’ is selected. Move the capacity
control slides to the maximum load position. The slides must
remain at maximum load for the duration of step (g).
(g)
Press the calibration button once. The red LED will illuminate for
30 seconds then extinguish to indicate that calibration is complete.
(h)
If the compressor was not already running and at operating
temperature, wait until steady operating temperature is achieved
before repeating the calibration procedure from (d) to (g).
(i)
Refit the screw cap over the calibration button and LEDs.
To calibrate the HBLVDT using the procedure described in 4.7.2 it is
necessary to run the compressor. If the compressor does not start the
calibration may be so far out that the plant controller will flag an analogue
input error on the HBLVDT channel, or the signal may be so far away
from 4 mA that the controller does not consider that the compressor is at
minimum load. The compressor is interlocked to prevent starting unless
the slide valves are at minimum load, refer to 4.1.1, therefore, either of
the above conditions will result in the controller refusing to allow the
compressor to start.
To enable the compressor to start under these circumstances and to
allow the compressor to continue running during the HBLVDT calibration
procedure, the plant controller must provide a way to temporarily disable
the ‘minimum load interlock’ and the ‘HBLVDT analogue out-of-range
error trip’.
CAUTION
It is essential for safe compressor operation that the
minimum load interlock and the HBLVDT analogue out-
of-range error trip are both re-enabled as soon as the
calibration of the HBLVDT is completed.
4.7.3.
Fitting a New HBLVDT Electronics Module
In the event of malfunction, the HBLVDT electronics module can be
replaced without disturbing the compressor pressure envelope.
NOTE: the electronics inside the module can be
damaged by static discharges so take all relevant
precautions, including earthing yourself before touching
the module. Also, it is important that the 24 V dc power
supply to the HBLVDT is turned off before removing the
old module or fitting the new one.
(a)
Switch off the 24 V dc power supply to the HBLVDT. Disconnect
the DIN plug.
(b)
Loosen the 2 hex head socket grubscrews which secure the
module to the stainless steel pressure containment body. Carefully
withdraw the module.
(c)
Fitting the new module is the reverse of the dismantling sequence.
Tighten the 2 grubscrews evenly and alternately.
(d)
Reconnect the DIN plug and switch on the 24 V dc power supply to
the HBLVDT. Check the calibration as described in 4.7.1 or 4.7.2.
