UN PASADO (En casa de Pilar.)

The controller detects the current flowing in the power supply wires to the transmitter and converts this into a pressure reading.

The controller can recognise an ‘out of range’

signal if the current is less than 4 or greater than 20mA. This will be displayed as a pressure probe fault.

Refer to the table in chapter 8 para. 6.0

4-20 mA PRESSURE TRANSMITTER

1

2

4 to 20mA +

-X02-1 24V D.C.

0V D.C.

X02-2

CONTROLLER DETECTION

CIRCUITRY

HW 0304

22. SILICON TEMPERATURE SENSOR

22.1 Description

A silicon temperature sensor of the ‘spreading resistance’ type is installed in the air-end adjacent to the delivery port. The sensor protects the compressor unit against excessive discharge temperature by sensing the temperature of the compressed air/oil mixture discharged from the air-end. The resistance of the sensor increases with temperature

22.2 Operation

The resistance of the temperature sensor is

processed within the controller and displayed as an air/oil temperature reading. A high oil temperature warning and/or compressor shut-down is activated if the temperature of the air/oil mixture reaches the trip setting.

FIG. 6.24 SILICON TEMPERATURE SENSOR 1. Probe

2. Body

3. Electrical Connectors

7. Locknut 8. Retainer 9. 'O' Ring 10. Guide Pin 11. Spring

FIG. 6.25 NON-RETURN VALVE (475SR, L75SR)

23. DRIVE AND FAN MOTOR THERMISTORS From June 2002 L45SR, L75SR do not have fan thermistors fitted. All L120SR models do not have fan thermistors.

23.1 Description

The drive and fan motors are each equipped with thermistors of the PTC type which are buried in the windings to protect the compressor against motor over-temperature.

23.2 Operation

If the temperature of the coil windings exceeds a set temperature, the resistance of the thermistor will increase sharply. The sudden increase in resistance will be detected by the controller, causing the compressor to shut down and display a motor fault.

24. DELIVERY NON-RETURN VALVE (475SR, L75SR)

1. Body 2. Cover 3. 'O' Ring 4. Valve Head 5. 'O' Ring

1. Body 2. Inlet Port 3. Valve 4. Spring 5. Solenoid Coil

6. 'O' Ring (not illustrated) FIG. 6.26 BY-PASS VALVE 24.1 Description

The non-return valve is mounted on the discharge outlet of the end. Its function is to isolate the air-end from reclaimer pressure when the compressor is stopped. This prevents oil from being blown back through the air-end after stopping and ensures that the air end always re-starts in the unloaded condition.

The non-return valve consists of a valve body (1) and cover (2) sealed by an 'O' ring (6) and a valve assembly. The valve assembly comprises a guide pin (10) and spring (11), a valve head (4) with 'O' ring seal (9) and retainer (8), secured by a washer (6) and locknut (7). An 'O' ring (5) provides a seal between the valve head and the guide pin. Two studs secure the flange of the discharge pipe.

24.2 Operation

When the compressor is running and the pressure in the reclaimer is below the discharge pressure of the air-end the non-return valve is held open. When the discharge pressure of the air-end falls, a condition is reached where pressure on each side of the non-return valve is the same. The valve spring will then lift the valve head and close it against the seat. Reclaimer pressure will hold the valve closed until air-end pressure rises to overcome the effect of reclaimer pressure and the valve spring.

25. BY-PASS VALVE

25.1 Description (L45SR, L75SR)

The by-pass valve comprises a valve body (1), valve (3), solenoid coil (5), spring (4) and ‘O’ Ring seal (6). The function of the valve is to re-circulate air produced by the air-end when the compressor is running off-load at minimum speed. The by-pass valve is a solenoid operated, normally open, valve mounted on the air-end inlet connector (L75SR) or on the intake NRV (L45SR). The inlet port (2) is linked to the reclaimer cover by a pipe.

25.2 Description (L120SR)

The by-pass valve comprises a valve body (1), valve (3), solenoid coil (5), spring (4) and ‘O’ Ring seal (6). The function of the valve is to re-circulate air produced by the air-end when the compressor is running off-load at minimum speed. The by-pass valve is a solenoid operated, normally open, valve mounted on the reclaimer lid. The outet port is linked to the non-return valve by a flexible hose.

25.3 Operation

During normal running, when the delivery pressure is below the programmed off-load pressure, the solenoid is energised and the by-pass valve is held closed. If delivery pressure rises above the offload pressure the valve solenoid is de-energised and the by-pass valve is opened. Delivered air volume then falls to zero.

If delivery pressure falls below the target pressure the solenoid is energised allowing delivered air volume to rise and reclaimer pressure to build up again towards the target pressure.

26. INLET NON-RETURN VALVE (345SR, L45SR)

FIG. 6.27 INLET NON-RETURN VALVE (345SR, L45SR)

26.1 Description

The non-return valve is mounted on the air-end inlet and secured by four screws. A pipe connected to the air intake filter is secured to the top of the valve by a clip.

The inlet non-return valve consists of a valve body (1) with an integral seat (2) and a valve assembly.

The valve assembly comprises a valve head (3), spring (6) and a valve stem (5) with retaining bar (4). The retaining bar secures the valve assembly to the valve body using two screws.

26.2 Operation

When the compressor starts the depression created by the turning rotors causes a partial vacuum at the intake which lifts the valve head off the seat against the light load of the spring. This allows air to be drawn through the air-end to pressurise the separator vessel.

4. Retaining Bar 5. Valve Stem 6. Spring 1. Body

2. Valve Seat 3. Valve Head

FIG. 6.28 INLET NON-RETURN VALVE (L120SR) 1. Body

2. Air Inlet Valve 3. Stem When the compressor is stopped the valve head returns to its seat and prevents the air/oil mixture from blowing back through the air intake.

27. INLET NON-RETURN VALVE (L120SR) 27.1 Description

The non-return valve is mounted on the air end inlet and secured by 4 screws. A pipe connected to the air intake filter is secured to the inlet of the valve with a jubilee clip.

The inlet non-return valve consists of a body (1) with an integral seat and a valve assembly comprising a valve head (2), valve stem (3) and spring (5). The valve stem is secured to the body by an external domed nut (7).

27.2 Operation See section 26.1.

1

28. BEKO DRAIN (L120SR) 28.1 Description

FIG. 6.29 BEKO DRAIN (L120SR)