Although generally applicable, the crackle test does have some limitations.
1. The method is non- quantitative.
2. Hot plate temperatures above 320°F (160°C) induce rapid scintillation that may be undetectable.
3. The method does not measure the presence of chemically dissolved water.
The crackle test can be performed with a minimum of investment using the following equipment: -
1. A hot plate capable of achieving and maintaining 320°F (160°C) surface temperature.
2. A paint shaker (or equivalent) for oil agitation.
3. An oil dropper tube or laboratory syringe.
WARNINGS
The marine surveyor should know that all oil has to be considered as hazardous and he should avoid oil contact with his skin, eyes and mouth and a sample should never be taken from an engine that is running.
He must exercise extreme caution when performing the crackle test on oils that might contain hazardous gases or low boiling point volatiles which might produce fumes and vapours that present inhalation and/or serious skin or eye injury upon contact. When evaluating these oils, the hot plate should remain under a vent hood that allows the analyst to conduct the test without coming into contact with fumes or vapours.
The analyst must wear protective eye goggles, gloves and a long sleeved overall. The test must be performed in a well ventilated area.
Because different types of mechanical components tend to have various oil related issues, different oil analysis techniques might be applied. For example, reciprocating engines tend to generate fine wear particles. Coolant leak, soot build up and fuel dilution are common problems in lubricants. On the other hand, rotating machinery such as gear boxes tend to generate large wear particles. Acidity increase and moisture contamination are among common parameters monitoring lubricant condition to prevent corrosion.
In almost
all cases, monitoring and maintaining lubricant viscosity within specification is critical to ensure mechanical components are well lubricated. Table 2 shows typical oil analysis parameters and how they relate to problems by equipment types.
Common Oil Analysis Practices
There are several ways to perform in-service oil analysis. The most common ones are outsourcing to an off-site laboratory, using an onsite laboratory or performing route based oil analysis using portable tools.
Outsourcing oil analysis to an off-site oil laboratory is probably the oldest and most common approach in industry. Every year millions of oil samples are analysed by laboratories worldwide. A typical process flow involves a user collecting oil samples from equipment and shipping them to a lab, lab technicians performing requested oil analysis tests and an analyst reviewing the data and providing recommendations. The report is then sent to the management team for review and if needed, maintenance actions are performed.
OIL
Avoid Oil Mix Up
The old sayings that “Oil is oil” and “when in doubt, put engine oil in,” really highlights the under- education on the subject of lubricating oils and the importance of optimized lubrication. Oil mix up is one of the most common lubrication problems contributing to machinery failure. Putting the right lubricating oil in the equipment is one of the simplest tasks to improve equipment reliability. Checking the viscosity, brand and grade of incoming new oil and checking any contamination of alien fluids help reduce the chances of oil mix up and keeps the machine operating.
Contamination Control Solid contamination (sand and dirt) accelerates the generation of abrasive wear.
Liquid
contamination such as moisture in oil accelerates machine corrosion. Fuel or coolant dilution in engine oil will decrease the viscosity therefore generating more adhesive wear (rubbing wear).
It
is critical to keep the lubricating oil clean and dry all the time which requires that cleanliness limits are set and monitoring the contamination continued during the machine’s operation.
OIL CONDITION BASED
MAINTENANCE:
A well balanced oil analysis program can monitor machine wear condition, oil contamination and oil degradation at the same time. Key parameters should be continuously tested and trending of those parameters monitored. If a change of rate is accelerated or if a parameter exceeds an alarm limit, reliability engineers must be alerted and maintenance actions may be required to resolve the potential problems.
O!L The Report • June 2017 • Issue 80 | 43
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