by Jim Parker,
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 size.
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
- 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
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
These filters also absorb
moisture so this, plus the additive package, prevents any acid build up.