1. Lube tip: foaming is affected by oil level
In a circulating system, it is crucial to check the oil level before introducing
antifoam agents to address a foaming problem. Foaming issues can be caused
by oil levels that are both too high and too low. Insufficient oil could lead to the
formation of a vortex inside the reservoir at the circulating pump’s inlet, drawing
in air. If there is too much oil in the circulating system, it could result in oil coming
into contact with a surface of the machine that it should not, which could result in
slinging the oil, or churning it.
Sometimes, the amount of foam may prevent an oil-level reading being taken.
While it is never advisable to insert any solid object into an oil reservoir without
knowing its internal shape and size, you may be able to insert plastic tubing
(clear) straight down to the bottom of the reservoir. Create a seal by covering the
top of the tubing tightly, and extracting it – this should show the real oil level.
2. Lube tip: how particles create more particles
Abrasive wear can cause a chain reaction in lubricated machinery. The typical
chain reaction is: abrasive particles become work hardened, the work-hardened
particles produce more particles, and then the new particles become work
hardened. This chain reaction continues until the particles are removed by
filtration or the machine fails.
3. Lube tip: thermal failure in lubricants
Lubricants can thermally degrade for a variety of reasons and causes. Unlike
oxidation, thermal failure can occur in new lubricants with healthy additive
packages. However, many of the symptoms of oxidation are also symptoms of
thermal degradation.
One of the most common causes of thermal failure in hydraulic fluids and some
lubricating oils relates to aeration, i.e. entrained air bubbles. These bubbles can
become rapidly compressed in hydraulic pumps and in the squeeze zones of
bearings. This results in high localized temperatures. Hot surface carbonization
is another form of thermal failure. When an oil thermally degrades, problems
associated with sludge, varnish, deposits, viscosity change and additive
decomposition will often occur.
4. Lube tip: gearbox sump
Overfilling a gearbox sump can be just as damaging as underfilling it. Overfilling
may cause air entrainment and foam, overheated oil and leakage due to
overflow. Over time, oxidation may occur due to increased temperatures and
exposure to air.
5. Lube tip: kinematic viscosity
Kinematic viscosity is a measure of a fluid's internal resistance to flow under
gravitational forces. It is determined by measuring the time in seconds, required
for a fixed volume of fluid to flow a known distance by gravity through a capillary
within a calibrated viscometer at a closely controlled temperature.
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