Se instruye a la UACI, dar seguimiento y cumplimiento a la presente resolución

The specifications of the unloader indicator for SCV-series has been changed from December 2014 Moriya factory production.

For details of the new indicator specifications indicator after change, refer to the separately dedicated manual. In this manual, previous standard type indicator is the described.

The unloader indicator is implemented with micro switches, micro switch cam, and potentiometer.

These parts are used to detect the change in the rotation angle of the indicator cam shaft, which converts the axial position change of the unloader slide valve into rotational position change, convert the change into an electric signal, and send the signal to the package unit and/or the controller of the refrigeration system.

To check the unloader indicator after inspection, adjustment, or parts replacement, coordination with the controller side will be required. Even in a case where the compressor is carried out of the installation site for overhaul, the indicator assembly is often removed from the compressor (to be kept at the site) and the inspection/adjustment and parts replacement are performed at the site. Thus, this section provides a detailed procedure, which may be helpful after the reassembly work.

 When removing the indicator block or performing inspection/adjustment or parts replacement, be sure to shut down the control power and use lock-out and tag-out procedures. If the power is not shut down, there is a risk of electric shock.

5.5.12.1 Potentiometer

The potentiometer of the indicator is a full-turn potentiometer, and it is used to feedback the unloader slide valve position, in the form of electric signal, to the control system of the package unit or refrigerator system to complete the feedback control system to enable non-incremental, indicated load 0 to 100% continuous control of the load. While the expected service life of the potentiometer will significantly vary depending on the installation environment of the compressor (e.g. corrosive gas atmosphere, moisture, etc.) and operational conditions (e.g. frequent partial load operations, frequent start/stop operation, vibration, etc.), the potentiometer is a consumable part that requires regular replacement according to the situation.

■ Inspection

a) Check at the terminal block that the lead wires of the potentiometer are not loosened.

b) Check for any crack or other defects in the soldering of the lead wires of the potentiometer.

c) Manually rotate the shaft of the potentiometer and measure the resistance value using a circuit tester to check that the resistance value changes smoothly.

5.5.12.2 Micro-switches and Micro-switch Cam

The traditional standard unloader indicator uses two micro-switches and one micro-switch cam to detect the indicated 0% and 100% capacity control positions of the unloader slide valve.

If the micro-switch fails or any of these connections becomes loose for some reason, correct position detection cannot be made, and it causes a problem in the operation control of the compressor.

■ Inspection

a) In the normal condition where the hydraulic line for the capacity control of the compressor is not opened, set the unloader piston to the no load and full load positions from the manual capacity control circuit and check the operation of the control circuit to see if the micro-switch can detect the 0% and 100% positions of the micro-switch cam (i.e., by checking the operation of the relevant relays and contacts).

b) After shutting down the control power and carrying out the lock-out and tag-out procedures, remove the indicator glass and check that the micro-switch mounting screws [126] are not loosened.

c) Check that the hexagon socket head cap screw (set screw) securing the micro-switch cam [127] are not loosened.

d) After checking that the wiring for the micro-switch has been removed, turn on and off the switch to check the normal switching operation of the micro switch using a circuit tester.

e) If the hydraulic line for the capacity control of the compressor is opened for overhaul or other work, use nitrogen gas or compressed air to set the unloader piston to the no-load and full load positions and check if the micro-switch can detect the 0% and 100% positions of the micro-switch cam.

f) Carry out other visual inspection including any indication of water intrusion in the indicator, any rust on switch terminals, any wear of the switch roller or micro-switch cam, and so on.

5.5.12.3 Reassembly

To carry out the reassembly, follow the disassembly procedure in reverse. Lastly, correctly adjust the indicator needle position according to the following procedure:

a) If the hydraulic line for the capacity control of the compressor is opened for the purpose of overhaul or other work, use nitrogen gas or compressed air to set the unloader piston to the no-load position.

Then, set and fix the indicator needle to the origin of the figure to show the rotation on the dial.

Next, set the piston to the full load position. Make sure the indicator needle points to the end point of the figure on the dial.

b) In the normal condition where the hydraulic line for the capacity control is not opened, use the manual capacity control circuit to move the piston.

While the control power is turned on, the indicator cover must be mounted to prevent possible electric shock.

Then, after the piston position is fixed, control power is turned off, and the lock-out and tag-out procedures are completed, remove the indicator cover and secure the indicator needle in position.

SCV-series Screw Compressor 5.5 Reassembly 5-55

Figure 5-20 Development View of the Unloader Indicator (Traditional standard type)

Table 5-13 Component Parts of the Unloader Indicator (Traditional standard type)

P/N Part Name Q'ty P/N Part Name Q'ty

121 Micro-switch base plate 1 136 Hexagon socket set screw, M3×14 3 122 Hexagon socket head cap screw, M6×20 3 137 Dial, SCV 1 123 Micro-switch base plate 1 138 Phillips Screw, M3×5 2 124 Phillips Screw, M3×10 2 139 Indicator needle 1

125 Micro-switch 2 140 Phillips Screw, M3×10 1

126 Phillips Screw, M3×25 4 141 Indicator glass 1

127 Micro-switch cam, 0 to 100% 1 142 Indicator glass spacer 1 128 Hexagon socket set screw, M4×8 1 143 Electric cable gland 1

129 Potentiometer 1 144 Bracket 1

130 Potentiometer mounting plate 1 145 Hexagon socket head cap screw, M6×15 2 131 Phillips Screw, M3×5 3 146 Unloader indicator cover 1 132 Terminal block 1 147 Hexagon socket head cap screw, M6×15 3

133 Phillips Screw, M3×20 2 148 Plug 1

134 Dial plate support [2] 2 214 Spring pin 2 dia. ×8 1 135 Dial plate support [1] 2 265-2 Spring washer, M3 7

Figure 5-21 Sectional Views of SCV-series Unloader Indicator (Traditional standard type)

SCV-series Screw Compressors

6-1

Chapter 6 Troubleshooting

Table 6-1 describes typical trouble symptoms of compressors, their causes and actions to be taken.

The explanations of this Chapter are assumed that the compressor is used in the general refrigeration cycle.

Table 6-1 Troubleshooting 01: Compressor does not start up

Direct cause Root cause Action

Power source is off. Mostly caused by forgetting to

turn on after inspection. Use a check sheet for post-inspection actions and implement finger pointing and call check to prevent forgetting.

Main motor failure Mostly caused by activation of

overload protection circuit. Refer to the instruction manual of the motor for details including other causes and actions.

Adjust the position of the cam and switch, and tighten them.

Use thread locking agent when necessary.

When compressor's vibration is unusually high, see Item No. 11

"Compressor generates abnormal vibration and/or sound".

Failure of oil supply line for capacity control

Improper adjustment of oil flow control valve (throttled

excessively).

Readjust.

Leak/clogging in piping or

solenoid valve Remove cause

Check oil for contamination Replace oil if necessary Oil pressure not detected Failure of oil pressure

protection device, pressure sensor, relay, etc.

Identify defective devices, investigate causes of failure and take necessary actions.

Then, replace failed device(s).

Pressure pipe is clogged. Remove clogging, and check oil for contamination/replace oil.

Cooling water circulation is not confirmed.

Failure of devices such as cooling water pump and related circuits

Identify defective devices, investigate causes of failure and take necessary actions.

Then, replace failed device(s).

Circulation route is clogged. Remove the clogging.

Failure of electromagnetic contactor, relay, etc. in compressor startup circuit

Aging degradation Replace with new one.

Poor installation environment Replace ventilation fans, etc. if defective.

Improve temperature, humidity and ventilation at the installation site.