2200LZJE-HO-C6-N_2013.12.
Chapter 5 Maintenance
Compound 2-stage Screw Compressor 2016**C 5.7 Reassembly
5-64
b) Turn off the control power, and conduct lockout/tagout. After that, remove the indicator glass and
check for looseness of the philips screw for securing the micro-switch 【126】.
c) Check for looseness of the set screw for securing the micro-switch cam 【127】.
d) Check that the wiring of the micro-switch has been removed. After that, turn the switch on and off
and check whether it works properly by using a tester.
e) When the compressor's capacity control oil pressure pipe is opened due to overhaul or the like, pull
the unloader piston to the no-load position/full-load position by using nitrogen gas or compressed air
pressure, in order to check whether the micro-switch senses the 0%/100% position of the
micro-switch cam.
f) In addition, conduct appearance check to find out any traces of water entry inside the indicator,
defects in the switch terminal such as corrosion, wear in the switch roller or micro-switch cam, etc.
Reassembly
To reassemble the unloader indicator, follow the disassembly procedure in reverse.
5.7.14.2 Potentiometer
The potentiometer of the standard-type indicator is of the full rotation type. It senses the continuously
variable position (indicated load of 0% to 100%) of the unloader slide valve, and feeds the sensed
position as electric signals to the control side of the package unit or refrigerating system. Life
expectancy of the potentiometer varies significantly depending on the compressor's installation
environment (with corrosive gas atmosphere or much moisture) or operating state (frequently operated
with partial load, frequently started/stopped, subject to much vibration, etc.). It is a consumable part,
and needs to be replaced periodically depending on the situation.
Disassembly
a) Turn off the control power and conduct lockout/tagout. After that, remove the indicator cover 【146】,
indicator glass 【141】 and indicator glass spacer 【142】.
b) Remove the indicator needle screw 【140】 securing the indicator needle 【139】 to the shaft.
c) Remove the indicator dial screws 【138】 securing the indicator dial 【137】 to the dial supports.
d) Remove the electric wiring of the potentiometer. To avoid future assembly errors, put markings to
indicate positional relationship of wiring by using different colors of tape or the like, and take a note.
e) The potentiometer set-plate 【130】 is fitted between the potentiometer support arms [1] 【134】 and
arms [2] 【135】. Loosen and remove the arms [2] by turning them counterclockwise while holding
the arms [1].
f) When the right and left support arms are removed, the potentiometer 【129】 can be removed
together with the potentiometer set-plate.
g) The potentiometer is secured to the potentiometer set-plate with three philips screws.
Inspection
a) On the terminal block, check whether or not the lead wires of the potentiometer are loose.
b) Check for defects such as cracks in the welded portion of the potentiometer lead wires.
c) Rotate the axis of the potentiometer with hand, and check with a tester whether the resistance value
changes smoothly.
Reassembly
To reassemble, follow the inspection procedure in reverse. Lastly, position the indicator needle correctly
by following the procedure below.
a) When the compressor's capacity control oil pressure pipe is opened due to overhaul or the like, pull
the unloader piston to the no-load position by using nitrogen gas or compressed air pressure. Then,
align the indicator needle to the start point of the semicircular range drawn on the dial face, and fix it.
Next, move the unloader piston to the full-load position, and check that the indicator needle points at
the end point of the range drawn on the dial face.
To Next Page
Loading...
Need help?
General
