Compressor Lubrication

Transcription

1 Compressor Lubrication

2 Lubricants for air compressors There are five types of compressors in common use: Reciprocating Rotary vane Pump or drip lubricated Oil flooded Rotary screw Pump or drip lubricated Oil flooded Roots type Axial flow and centrifugal

3 Reciprocating air Compressors These used to be the most common compressors, but are now only used for small compressors and high pressure units with four or more stages. Rotary vane and screw are now the most common for average pressures and volumes. High volume medium pressures are usually axial or centrifugal compressors. ADVANTAGE For low volume applications, they are normally lower cost. Oil free possible if teflon rings containing carbon are used. Medical, Food and Diving applications High pressures possible with multi-stage intercooled models.

4 Reciprocating air compressor lubrication Requirements Lubricate crankshaft bearings. Lubricate, seal, and cool the pistons Low risk of compressor fires and explosions Crankshaft bearings Journal or rolling element. Oil lubricated. Smooth motion without shock loading or ep requirements.

5 Reciprocating air compressor lubrication Piston in cylinder lubrication, sealing and cooling. (And crosshead) Sliding contact. Good air separation. Good demulse. (Condensed water) Fire and explosion risk High flash point Low tendency to form carbon, especially hard carbon. Low misting tendency

6 Rotary screw compressor

7 Rotary screw air compressors advantages Few moving parts low maintenance costs low manufacturing costs No valves. Smooth pulse free compression with no requirement for a pressure vessel. Oil separation can be included in design In oil flooded types, oil used to seal, lubricate and cool the air as it is compressed. This eliminates water cooling. Single Stage up to 12 bar air pressure

8 Oil flooded rotary vane air compressor 1.Rotor 2. Oil cool 3. Lubricant 4. Air inlet 5. Air outlet 6. Stator

9 Rotary vane compressors description The sliding vanes are carried in slots in a rotor, which is mounted eccentrically in the casing (stator) and rotates between closely fitting end plates The vanes follow the casing contour as the rotor revolves It is apparent that the volume of the pockets formed between the casing and consecutive vanes varies from minimum to maximum and again to minimum in a cyclic manner The ports are located so that air is drawn into pockets of increasing volume, and discharged from pockets of decreasing volume When a vane passes the inlet port, air is trapped between it and the preceding vane, and is simultaneously compressed and carried around to the discharge port

10 Rotary vane and screw compressor lubrication Requirements Lubricate rotor bearings Lubricate, seal, and sometimes cool the vanes or screws. Seal and lubricate the end plates Rotor bearings Journal or rolling element Grease, or oil lubricated Smooth motion without shock loading or ep requirements. Vane and screw lubrication, sealing and cooling Sliding contact requiring ep or anti-wear performance. Good air separation Good demulse (Condensed water) End plate lubrication Sliding contact requiring ep or anti-wear performance. Good air separation Good demulse (Condensed water)

11 Rotary vane and screw compressors Volumetric efficiency is up to 90% Very quiet Few moving parts Low maintenance costs Low manufacturing costs No valves Smooth pulse free compression with no requirement for a pressure vessel Oil separation can be included in design In oil flooded types, oil used to seal, lubricate and cool the air as it is compressed. This eliminates water cooling Suitable for use as compressors and vacuum pumps Single stage up to 7bar air pressure Two stage up to 10bar air pressure

12 Rootes blowers Air Inlet Compressed Air Out

13 Rootes blowers advantages High volume low pressure Capacity up to 1500m³/h Pressure Single stage 1bar Two stage 2bar Run at electric motor speeds 1500Rpm Reasonably priced Oil free operation

14 Rootes blowers description The chamber inside the casing is formed by two parallel cylindrical bores partially intersecting Revolving in each is a two or three lobed rotor The hollows in the sides of each rotor are swept by the rounded heads of the other The rotors are revolved simultaneously by two accurately cut, equal sized gears, positioned outside the casing These rotors, which in every position close all communication between suction and delivery, first uncover the suction port allowing the gap between the rotors to fill with air. This air is then compressed and pushed out the delivery port The roots blower is a positive displacement compressor The Rootes blower is in effect a two or three tooth gear pump

15 Rootes blower lubrication Requirements The rotors revolve without touching each other, and without friction on the casing The gears and bearings are outside the casing There is no need for internal lubrication The gears and bearings are lubricated separately Rotor Bearings Journal or rolling element Grease, or oil lubricated Smooth motion without shock loading or EP requirements Gears Sliding contact requiring EP or anti-wear performance The lubricants used are normally gear oils, hydraulic oils or motor oils

16 Centrifugal compressor Shaft Driven by Electric motor, or Turbine Air In Compressed Air Out

17 Axial and centrifugal compressors advantages High Speed to rpm Noisy Can be driven directly from turbines Electric motor drives require gear drives Few moving parts low maintenance costs Expensive to manufacture No valves Smooth pulse free compression with no requirement for a pressure vessel Medium pressure 10 to 15bar Very high air volumes Ideal for compressing gasses for processes Lubrication system can be combined with turbine or gear drive

18 Compressor Oils Castrol Aircol PD 68 Meets demanding DIN grade VDL Suitable for discharge temperature of up to 220 deg C Excellent Coalescing characteristics satisfactory performance of separators Castrol Aircol SN 68, 100 Synthetic Lubricant Suited to Severe Operating Conditions involving higher temperatures Castrol Hyspin AWS 46,68 & 100

19 Thank You