DISEÑO DEL SISTEMA DE CONTROL

The air/oil system comprises an air intake filter, inlet non-return valve, air-end, oil separator vessel, oil separator filters, minimum pressure/non-return valve, aftercooler, oil cooler with thermostatic bypass valve and an oil filter. The flow of oil through the circuit is achieved through the pressure

differential existing between the primary oil separator and the oil injection point in the air-end.

5.2 Operation

Air enters the compressor unit through the intake filter (2) and inlet non-return valve (1) to the inlet port of the air-end (7). The air is trapped by the turning rotors and mixes with the oil which enters the casing through the oil injection point.

Continued rotor rotation increases the pressure and temperature of the air/oil mixture which passes from the air-end discharge pipe into the oil separator (4) where primary separation takes place by centrifugal force. Most of the oil is separated at this stage and drops to the bottom of the vessel.

The remaining air/oil mixture then passes through oil separator elements (5) where final separation takes place. The separated oil collects in the bottom of the elements and is scavenged back into the air-end through a small diameter pipe (13).

The filtered air then passes from the oil separator elements by way of the minimum pressure/ non-return valve (3). Provided the air pressure at this stage is above 3.5 to 4·0 bar the air passes through the aftercooler (9) where it is cooled before passing to the delivery outlet (12).

If the air pressure in the primary separator vessel falls below 3.5 to 4·0 bar the minimum pressure valve will close. The valve also incorporates a non-return valve which operates to prevent delivery air passing back into the separator when the

compressor is running off-load.

Oil from the bottom of the primary separator flows under pressure to the oil cooler (10) and during normal running the oil passes through the cooler to maintain the correct temperature. A thermostatic bypass valve (14) is installed in the inlet manifold of the oil cooler.

When the compressor is started, the cold oil in the system bypasses the cooler and flows through the oil filter (8) directly to the air-end. As the oil and air mixture is compressed by the rotors in the air-end, the temperature of the oil increases.

When the oil has reached its normal operating temperature the bypass valve closes and the oil is directed through the oil cooler. The cooled oil then flows to the oil filter where it is cleaned before entering the air-end.

The quantity of oil injected into the air-end is

controlled by a restrictor orifice in the air-end casing.

Oil is injected under pressure through the restrictor orifice into the rotors and a gallery supplies oil to the air-end bearings.

8. Oil Filter 9. Aftercooler 10. Oil Cooler 11. Fan

12. Delivery Air Outlet 13. Scavenge Line

14. Thermostatic Bypass Valve 1. Inlet Non-Return Valve

2. Intake Air Filter

3. Minimum Pressure Valve 4. Primary Oil Separator 5. Separator Filter Element 6. Discharge Pipe

7. Air-end

15. Scavenge NR Valve 16. Blow down solenoid

valve.

FIG. 3.3 AIR/OIL SYSTEM - 345SR, L45SR 2 1

3

5 4

6

7 8

9

10

11

12 13

14

15 16

6. AIR/OIL SYSTEM (475SR, L75SR) 6.1 Description

The air/oil system comprises an air intake filter, air-end, reclaimer, reclaimer filter element, minimum pressure non-return valve, oil cooler and aftercooler, thermostatic bypass valve and oil filter. The flow of oil through the system is achieved by means of the pressure differential existing between the reclaimer and the air-end inlet.

6.2 Operation

Air enters the compressor through the air intake filter (19) to the inlet port of the air-end (18). The air is trapped by the turning rotors and mixes with the oil which enters the casing through a restrictor orifice. Continued rotation increases the pressure and temperature of the air/oil mixture which passes through the discharge port of the air-end and, via the non-return valve (15), into the reclaimer (12) where it is centrifugally separated and the oil drops to the bottom of the reclaimer vessel. The remaining air/oil mixture then passes through the two stages of the reclaimer element (6) where final separation takes place.

The separated oil is collected in the bottom of the element and is scavenged back into the air-end through a strainer (8) and scavenge line (11). A solenoid operated valve (10), fitted in the scavenge line, prevents any oil loss through the air intake filter when the compressor is stopped.

Filtered air then passes out of the reclaimer through the minimum pressure valve (7). Provided the air pressure at this stage is above 4 bar the air will be passed to the air cooler (3) where the warm air is cooled. The cooled, filtered air then passes through a moisture separator to the delivery air outlet (1).

The condensate in the moisture separator (2) is automatically removed by the operation of an electronically controlled solenoid valve (20).

If the air pressure in the reclaimer is at any time less than 4 bar the minimum pressure valve will close.

The valve also incorporates a non-return valve which operates to prevent delivery air passing back into the reclaimer when the compressor is running off-load.

Earlier oil circuit (Fig. 3.4). Oil from the reclaimer flows to the oil cooler. During normal running the oil passes through the cooler to maintain its

temperature at a correct level. A thermostatic bypass valve (5) is installed in the oil cooler. When the compressor is started, the cold oil in the system bypasses the cooler and flows through the oil filters (9) directly to the air-end. As the oil and air mixture is compressed by the rotors in the air-end, the temperature of the oil increases. Once the oil has reached its normal operating temperature the 3-way thermostatic bypass valve directs oil through cooler. The cooled oil then flows to the oil filter where it is cleaned before entering the air-end.

Later oil circuit (Fig. 3.5). Oil flows to the oil cooler (4) via a 3-way thermostatic bypass valve (6) installed in the reclaimer. During normal running the oil passes through the cooler to maintain its temperature at the correct level. When the compressor is started, the cold oil in the system bypasses the cooler and flows through the oil filters (9) directly to the air-end. As the oil and air mixture is compressed by the rotors in the air-end, the temperature of the oil increases. Once the oil has reached its normal operating temperature the 3-way thermostatic bypass valve directs oil through the cooler. The cooled oil then flows to the oil filter where it is cleaned before entering the air-end.

The quantity of oil injected into the air-end rotors is controlled by a restrictor orifice in the rotor casing.

Oil is injected under pressure through the restrictor orifice into the rotors and a separate gallery supplies oil to the air-end bearings.

FIG. 3.4 AIR/OIL SYSTEM - 475SR, L75SR (WITH EARLIER OIL CIRCUIT) 9. Oil Filters

10. Scavenge Solenoid 11. Scavenge line 12. Reclaimer 13. Oil Drain 14. Oil Level Tube 15. Non-return Valve 1. Delivery Air Outlet

2. Moisture Separator 3. Air/Oil Cooler 4. Fan

5. Thermostatic Bypass Valve 6. Reclaimer Element

7. Minimum Pressure Valve 8. Scavenge Strainer

16. Oil Drain 17. Oil Stop Valve 18. Air-end

19. Air Intake Filter 20. Drain Solenoid 21. Strainer 22. Air In 1

2 3 4 5 6 7 8 9

10

11 12

14

13

15 16

17 18

19 20 21

22

Oil flow Air flow Air/oil mixture

1. Delivery Air Outlet 2. Moisture Separator 3. Drain Cock

4. Air/Oil Cooler 5. Fan

6. 3-way Thermostatic Bypass Valve 7. Reclaimer Element

8. Minimum Pressure Valve 9. Scavenge Strainer 10. Oil Filters

11. Scavenge Solenoid 12. Scavenge Line

13. Reclaimer 14. Oil Drain 15. Oil Level Tube 16. Non-return Valve 17. Oil Drain

18. Oil Stop Valve 19. Air-end

20. Air Intake Filter 21. Drain Solenoid 22. Strainer 23. Air In