Machinery's Handbook, 31st Edition
2520 Lubricant Filtration Filtration Systems.— Although contamination cannot be completely eliminated, with diligence and the use of effective filtration techniques and methods the effects of contami nation can be seriously mitigated. Working on the understanding that fluid cleanliness is the basis for contamination con trol, primary filtration commences on the virgin stock oils prior to the lubricant being placed in the working reservoir or lubrication / hydraulic system. Once the lubricant is in a working system it will immediately begin to attract contami nants already in the system, from the air, outside sources, manufacturing materials, and wear materials that must be filtered out as the lubricant moves through the system. Table 20 shows a typical pressure flow lubrication delivery, hydraulic system complete with a minimum filter media package. The function of these filters is to reduce operating costs and increase component life; therefore they must be properly sized for the system and be of the highest quality. There are two basic types of filter design, surface filters and depth filters. Surface filters are the most common and use a screening material to trap debris. Depth filters are deep cleaning filtering devices that use multiple layers of dense materials to “polish” the lubri cant. Depth filters are usually set up in parallel with the basic filter system and allow a small percentage of the lubricant flow to bypass the pump and be depth cleaned. Table 20. Typical Minimum Filtration Requirements for a Closed Loop Lubrication Hydraulic System Delivery Section Pressured B Return Section Gravity
Lubrication Delivery System
H
Pump
D
E
C
Reservoir
A
G
F
B
A
Portable Filter Cart
Location
Type
Degree Medium
Material
Purpose
A Pump Suction B Pump Delivery Header C Return Line D Reservoir Vent E Reservoir Fill Port
Surface Surface Surface Surface Surface Surface
Gauze, Paper
Pump Protection
Felt, Paper, Cellulose, Sintered Metal
Fine
Primary System Protection Wear Products Protection Remove Airborne Contaminant and Condensation Prevent Course Solids Ingress
Medium Felt, Paper, Cellulose
Course / Medium Course
Wire, Wool, Paper, Oil Bath Desiccant
Gauze, Paper
Capture Ferrite Wear Metals And Debris
F
Drain Plug
Fine
Magnet
G Drain Valve H Delivery Bypass Filter
n/a
n/a
n/a
Water Removal
Carbon, Cellulose, Diamataceous Earth, Felt
Lubricant Deep Cleaning And Polishing
Depth Very Fine
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