1. PNEUMATICS Chapter 5 Secondary Air Treatment
RBTC

2. Objectives Chapter 5 SECONDARY AIR TREATMENT
Methods of Air Treatment
Contaminant Separation
Contaminant Filtration
Filter Classification
Media Types
Surface Filters
Mesh Particle Size
Depth Filters
Dry Filters
Wetted Filters
Oil bath filters
Adsorption Filters
Absorption Filters
Lubricating the Air
Heavy Lubricators
Fine Lubricators

3. Introduction Chapter 5 Secondary Air Treatment
Definition:
Primary Treatment (Chapter 4) = Cleaning or filtering air as it enters a compressor.
Secondary Air Treatment (Chapter 5) = Removing any contaminants that were carried over through the first part of the system

4. Methods of Air Treatment 5.01
Air is drawn from various surroundings will sometimes remain in the air through the first stages of compressing
These contaminants are in the form of smoke, dust or dirt or lubricating oil picked up from the cylinder walls
Remaining moisture contributes to rust and corrosion
Secondary treatment is accomplished through :
ABSORPTION
ADSORPTION

5. Contaminant Separation 5.03
Separation of contaminants is accomplished by:
GRAVITY SEPARATION
CENTRIFUGAL SEPARATION
INERTIAL SEPARATION

6. GRAVITY SEPARATION 5.03 Accomplished by rapid deceleration
Separators
Scrubbers
Filters
Receivers
This Gravity Separation takes time and only removes the larger particles from air

7. Gravity and Centrifugal Separators

8. Centrifugal Separation 5.04
Cyclone or Centrifugal or Inertial separators use centrifugal force to throw solid and liquid (heavier) particles to the outside.
These units are best fitted for high volume aps
Commonly on intakes for centrifugal compressors
Inertial separators (Impingement Separators) depend on changing direction in a hurry using dispersion plates to allow heavier particles to impinge on the plates or baffles

9. Contaminant Filtration
Particle size – micron = mm or inches
0.01 to 1.0 μ = smoke
0.01 to 0.8 μ = oil particles – aerosols
0.1 to 10 μ = cloud particles
> 10 μ = dust

10. Filter Classification 5.11
Two Basic SOLIDS type filters
SURFACE – regular pattern – narrow range but removes smaller particles as contaminants buildup
DEPTH – irregular pattern – large openings up front scaling to smaller openings at back
Common to use both
Nominal Rating – a filter is classified by the percentage of particles of a given size that it can stop
Absolute Rating - It stops 100% of a given particle size
All are rated by airflow rates

11. Classifying continued
Dirt Capacity = amount, size, type and concentration
Multiple filters should be used to remove specific amounts and sizes of contaminants
MAXIMUM ALLOWABLE PRESSURE DROP

12. Migration – 5.15
Contaminant Migration refers to an excess situation where the filter allows the collected particles to pass through
Abrasion Migration refers to particles passing around the seals of the filter in the housing
Medium Migration refers to the breakdown point of the filter itself – this allows for CONTAMINANT RELEASE

13. Types of Media 5.19 SURFACE FILTERS:
Strainers – metal cloth, disks, screens
Sintered metal powders
Thin, felted fibers
Thin membranes
Woven cloth

14. Media DEPTH FILTER MEDIA: Felted or matted nonmetallic fibers
Packed fibers
Oil bath
Activated carbon and other dessicants
papers

15. SURFACE FILTERS/STRAINERS 5.21
SS - Wire mesh in pneumatic systems
Catch larger particles
SS Wire
Mesh refers to size of opening
Limited by the size of particles they can remove
Two types of weave:
Square Weave – for use where air is clean
Dutch Twill – better for air ‘cuz openings are smaller

16. Wire Mesh – 5.21

17. Strainer Cross Section

18. Strainer and Strainer Baskets

19. Strainer Loop

20. Bag Filter Housing and Bags

21. Cartridge Filter and Cartridges

22. Pleated Cartridges

23. Ribbon Filter
Pet Supplies for clean water

24. Mesh Relation MESH PARTICLE SIZE µ = micron 325 30 µ (0.0012 inches)

25. Depth Filters 5.25 Matted and or packed type filters
Two Types – either Dry or Wetted or Oil Bath
Commonly used for
Compressor intake to stop large particles
To collect moisture, oil and solids
Just prior to end use of air
1) Dry Filters depend on the medium – don’t back wash
2) Wetted Filters depend on a coating of oil – can be cleaned repeatedly

26. Oil Bath 5.28 3) A version of a “wetted” filter Benefits include:
Large volumes
Remove 100% of particles 3 μ and larger
Easy to clean
For intake of lubricated reciprocal compressor

27. Filter Requirements 5.29
Intake for lubricated Reciprocating Compressors
Require 100% of > 10 µ
Un-lubricated Compressors
Require removal 100% of > 5 µ
Dynamic Compressors
Require removal 100% of < 5 µ to protect impellers

28. Other Filters 5.30
Metal Powder – bronze (sometimes SS) for corrosion resistance
Surface Filter
Removal down to 2 µ possible
Remove 90% of free moisture
5.32 Felted Fibers – masses of fibers matted together
5.33 Unfelted Cotton
5.34 Filter papers

29. Adsorption Filters 5.36
Vapor coalesces on the media – the drops settle to bottom
Use carbon or powdered chemicals
Same as desiccant dehydrators
Difficult to regenerate
Use replaceable media

30. Absorption Filters 5.38 Chemical reaction with vapor
Commonly changes color to indicate replacement

31. Lubricating the compressed air 5.39
Common to need lube added to compressed air to reduce wear and corrosion
Some pneumatic components require perfectly dry air
Two types – Heavy or Fine Lubricators

32. Heavy and Fine Lubricators
HEAVY LUBRICATORS 5.41
Supply fine suspended oil mist and heavy droplets
Can use a wick type supplier
Can use a venturi pick-up 5.44
FINE LUBRICATORS 5.45
Add a fine suspended oil mist into air
Used for multiple equipment systems