March/April 1989
Do you know the condition of the oil that is flowing through the engines of your equipment? It could be worse than a system can handle. Here are the hows and whys of analyzing oil regularly to keep engines in excellent shape.
By William Trakas
William Trakas is vehicle maintenance superintendent for Grossman Iron & Steel Co., St. Louis.
Perhaps you haven't experienced this--yet: an expensive--maybe catastrophic--engine breakdown traced to poor oil condition. This condition can be based on either the oil makeup or the contaminants the oil may be carrying. Either situation can seriously affect the performance of your high-cost (not only in purchases but repairs) transportation, handling, and processing equipment.
You can keep a handle on oil condition and prevent potential problems by simply analyzing engine oil regularly. Doing so keeps you informed of the health of your engines and gives you a good idea of how long they can operate without an oil or filter change.
If you're not analyzing oil, you might be changing it too frequently or not changing the oil before it begins breaking down. In the first case, you are spending more money to keep your equipment running than is necessary both in new oil and in labor time. In the second case, the oil is becoming contaminated, losing lubricity and carrying the trapped abrasive particles to major engine components. This increases wear and shortens the engine's life span.
How to Choose an Oil Lab
The first step in establishing an effective oil analysis program is contracting a reputable testing lab. Normally the cost of using one is $7-10 per sample, obviously a small price to pay in comparison to the cost of an engine overhaul.
Your oil jobber can be of great help in locating a lab. Ask the lab for a sample copy of its reports so you can determine if the information is easy to read and understand.
Next find out if the lab will call you immediately if a potential problem shows up in the oil sample.
Also find out whether the lab will help you establish the best drain intervals for your engines based on established trends and the type of service your engines perform. Good labs offer this assistance.
Finally, make sure the testing follows ASTM (American Society for Testing and Materials) standards. These standards have set acceptable levels of metal, water, dirt, and nitration for every type of engine currently in use. For example, the acceptable level of aluminum is less than 40 parts per million in most diesel engines. A higher level indicates excessive wear in such areas as pistons, bearings, or cylinders.
In addition to ASTM tests, most labs perform infrared analysis, which can help you determine if the air-to-fuel ratio is correct depending on the amount of soot found in the oil sample. Make sure the lab you choose offers this test; it can help you determine if glycol (antifreeze) has entered the oil system.
What You Will Find Out
Most oil analysis reports list the types of metal and other impurities found in an oil sample and the quantities in parts per million.
The most common materials and their source in an engine are:
aluminum: pistons, bushings, bearings, and cylinders;
boron: water conditioners and some oil additives;
calcium: dirt;
chromium: cylinder liners, rings, rocker arms, crankshafts, and bearings;
copper: bearings, bushings, air filters, oil coolers, and injectors;
iron: most engine parts;
lead: bearings;
molybdenum: rings, liners, and some additives;
nickel: crankshafts and wrist pins;
phosphorus: oil and gasoline additives;
silicon: sand, dirt, and some oil additives;
sodium: dust, salt water, and some oil additives;
tin: pistons and bearings; and
zinc: galvanized metal.
In addition to listing the contaminants in the oil, the analysis report describes the physical makeup of the oil. Physical aspects include the allowable level of:
oxidation;
nitration;
sulphur; and
soot.
How the Info Helps
Assuming the engine is in good condition, the four physical aspects analyzed can help you determine the length of time between oil changes.
The sample oil analysis report lists not only the physical aspects and the types and quantities of materials found in an oil sample but also interpretation remarks. These remarks are the summarized key to steps necessary for improving oil condition or maintaining its good condition and preventing engine breakdown.
How exactly does all this information help? Here's one example from Grossman Iron & Steel: An "O" ring in the head of a 966 Caterpillar engine had failed, allowing antifreeze to enter the engine oil. Because of regular sampling of the oil, the problem was detected before any significant engine damage could occur. The cost of replacing the "O" ring, approximately $600, was much less than the $5,000 cost of a possible ring or valve job had the problem gone undetected.
On another occasion, a seal had failed on the fuel pump of a Cummins NTC 350 engine, allowing the fuel and oil to mix. This was detected in the oil sample and remedied $200 later with a new seal before the fuel had diluted the oil to the point of damaging the main bearings. The cost to fix the main bearings would have been about $2,500; the cost to replace would have been about $10,000.
In the typical scrap operation, an oil analysis program can be extremely valuable in preventive maintenance of both rolling and stationary equipment. Scrap handling cranes, with their diesel power plant exposed to the severe environment and constant high-speed operation, can be monitored for dirt, water intrusion, and oil breakdown in the engine, hydraulic system, and chain drives.
Modern hydraulic scrap processing equipment can represent an investment of many thousands of dollars. These hydraulic systems normally consist of many complex and expensive components, all subject to wear based on the condition of the hydraulic oil. A regular sampling program can help prevent premature failure of pumps, valves, cylinders, and other components. Whether used for an engine in your truck or a baler piston pump, both of which can cost thousands of dollars to repair or replace, oil sampling and analysis is an inexpensive insurance policy--one your equipment should not be without.
[SIDEBAR]
Using the Results
This oil analysis report for a lugger truck displays measurements in mileage. After reviewing the report and taking into account that it had been over 45,000 miles since a report of elevated copper, we decided we would take the next oil sample at 4,500 miles to determine if the previous reading was false or a symptom of possible wear in the wrist pins or main bearings. (We normally would not take the next sample until 9,000 miles.) If the next sample comes back positive, we will drop the oil pan to physically inspect the main bearings and thrust washers for wear. The physical inspection should take no more than two hours and cost less than $100 to perform. •