by Jim Parker, Environmental Dept.
North Carolina Department of transportation
Raleigh, North Carolina
Types Of Filters
- Full Flow
1. Full flow filters are the ones everyone is familiar with since they are on everyone's cars. All the fluid goes through them before it goes back to the
crankcase or reservoir depending on the application. These are also know as surface filters and rating is generally from 10 to 40 microns, however, this is a nominal rating and 30 microns is
about the smallest particle they remove. There is a by-pass valve in the system to protect the equipment in the event of a clogged filter and during cold starts.
2. By-pass or side stream filters have been around since the 30's but it has been in the last 10-15 years that they have seen wide spread use. They are
known as depth type filters and the better ones depend on absorption of the contaminations. This is possible since only 10% of the oil flowing is going through these filters. The slower the flow
through the filter and the larger the filter the better the removal. These filters remove particles in the 1-10 micron range and smaller. A by-pass valve is not required since they are installed
in a side stream or parallel stream. There has been some concern about additive removal but the depth type absorbent filters do not remove additives unless it's a solid such as graphite. The
absorbent type filters which consist of chemically active materials such as fullers earth, active clays, charcoal and chemically treated paper may remove additives.
- Nominal filter Rating
- Absolute Filtration Rating
- Filtration Ratio (Beta)
1. A nominal rating is an arbitrary micrometer value indicated by the filter manufacturer and due to its lack of reproducibility this rating is of little or no value. Tests have shown
that particles as large as 200 microns will pass through a nominally rated 10 micron filter.
2. An absolute rating gives the size of the largest particle that will pass through the filter or screen. This is the size of the largest opening in the filter.
3. A Filtration ratio is the ratio of the number of particles greater than a given size up stream from the filter to the number greater than the same size down stream from the filter.
We all have heard of microns and most of you know they are pretty small. This chart will give you a better indication of what a micron is and why it's important. One of the main ways it's
used is to establish standards for evaluating and rating filters. This is done by using international standards organization (ISO codes). It's important for you to know two things about a filter
and this data should be based on a test by an independent laboratory. You want to know how much sediment the filter will hold during its useful life and what sizes particles it removes.
Comparative Sizes Minimum engine Size Reference Microns Inches Clearances Human hair 100 .0039 Visible to eye 40 .00156 20 .00078 Rod bearings Main bearings Fine sand 12 .00046 Valve stem
Piston 10 .00039 5 .000195 1 .000039
Silicon, soot, other, water, fuel, wear metals
Silicon and soot are the two main contaminants in our equipment. Others are water, fuel, glycol and wear metals such as copper, lead, nickel, tin, chromium and others.
The most important steps in reducing silicon contamination is to make sure air filters fit properly, air is not by-passing, air ducts are tight and properly maintained. The
largest soot particles is only one (1) micron but soot is very abrasive and also thickens the oil.
The major contributing factors to soot build-up is lugging the engine, idling, worn rings, worn injectors, incorrect fuel/air ratio and poor spray patterns. Soot forms as a
result of a mixture that is too lean or too rich but the rich mixture is the major culprit causing the oil to thicken.
Water contamination may come from several causes with liner pitting being the major one.
The main causes of fuel contamination is rich mixture and poor spray pattern.
All the above causes contribute to wear metal contamination. When soot thickens the oil the tight clearances may not receive proper lubrication and the abrasive soot contributes to the
problem. Glycol also reduces the quality of the lubricant resulting in further wear of the metal surfaces.
Major Causes of Wear and What Can Be Done About It
The causes of wear and what we can do about them. The simple answer of course is friction but our interest is to focus on contaminants that increase friction to unacceptable limits.
Particle size is our major concern in controlling wear. Particles ranging from 10 to 20 microns are the major causes of wear. Larger particles as a rule are too large to get between
the tight clearances of modern day equipment. The other particle sizes to be concerned about are what are described as ultra-fine which are in the 4 micron size and down. These can act as a
lapping compound when they come in contact with surfaces. These ultra-fine particles can be monitored with wear metal analysis and they are removed by a good by-pass filter. They will not be
removed by a typical 5 or 10 micron filter.
Blood Test For Equipment Components
- Metals Concentration
- Physical Data
- Particle Count
Types of Equipment for Lube Analysis
- Inductive Coupled Plasma
- Atomic Absorption
- Atomic Emission
1. Inductive Coupled Plasma: Analysis uses a flame to burn the sample and it will identify metals up to two (2) microns in
2. Atomic Absorption: is basically the same as inductive coupled plasma.
3. Atomic Emission: Uses an electrical charge to burn samples and it identifies: Hard Metals up to 4-5 micron - iron,
chromium, nickel and others. Soft Metals such as aluminum, copper, tin and others up to 10-15 microns.
Lube Analysis Cost
- A. We receive the percent concentration of 20 elements such as copper, iron, aluminum, nickel and others.
- B. The physical data includes viscosity, soot, fuel, water, glycol and solids.
- C. The chemical analysis includes total base number (TBN) or total acid number (TAN). This tells you if your additive package is still good. Only one is necessary and we prefer the TBN.
- D. The particle count tells you the number of particles above a certain micron size in the oil.
You can develop a pro active maintenance program so you are not continually responding to things you have no control over. You can anticipate problems and develop a maintenance schedule which
ensures a better utilization of your work force, reduces cost and reduces down time. We have discussed the value of such a program with various industry officials throughout the country and the
bottom line is it extends equipment life and saves money.
We are presently using Gulf Coast filters on our ferries, motor graders, tandem dump trucks and parts washers. We are also using them to filter hydraulic fluid and reclaim or recycle
We found out about these filters in discussions with the Air Force test and evaluation unit at Eglin Air Force Base Florida. We discussed their use with Army and Air Force personnel at
various locations throughout the United States. We also discussed their use with a variety of industry officials, including oil companies, throughout the United States. Every report we received
was very positive. The most impressive of all was an Air Force report of the tear down and inspection of a series 60 (425HP) Detroit engine with 500,000 miles on it and only one oil change at
250,649 miles. The oil was inadvertently changed when a leaky oil pan gasket was replaced. At 500,000 miles the bearings measured the same as new bearings. No adjustments were required and the
drained oil was put back in the engine. The truck now has over 700,000 miles and still no oil change. The filter is changed at 10,000 and the make-up oil keeps the additive package up.
These filters also absorb moisture so this, plus the additive package, prevents any acid build up.