is usually known as the scourge of any machine. The eternal battle continues between lubricant technicians
in the wet process industries such as paper and pulp. The competition between outdoor machine applications such as construction and mining and frequent machine washdowns like food processing never seems to come to an end. However, water contamination hazards are not only limited to these industries. They affect all kinds of plants and industries.
Both oil and machines are affected by water. Water promotes the oxidation of lubricants base oil and releases additives that attract water. Later, the water settles towards the bottom of the sump. Water hydrolyzes additives which affect the performance of machines. In some cases, this hydrolysis can produce highly corrosive by-products.
Resultantly, lubricants degraded by water cannot lubricate and protect the machine efficiently. This inefficiency can lead to severe wear and tear.
Read More: What Causes Lubrication Failure?
Water Induced Wear Mechanisms
Common water-induced wear mechanisms include:
Rust And Corrosion
For the production of iron oxides, water attacks steel and iron surfaces. Water binds with the acids in the oil to boost its potential to attack ferrous and non-ferrous metals. As a result, the surfaces deteriorate rapidly in the presence of rust and corrosion, which invite abrasive particles.
Rust is also abrasive. Abrasion exposes fresh nascent metal that deteriorates rapidly in water and acids.
If vapor pressure
reaches low-pressure points of the machine, such as the suction line at the pump, then vapor bubbles expand.
Vapor bubbles need exposure to high pressure suddenly, such as in the load zone of a journal bearing. The water bubbles contract at high pressure and go back to the liquid state.
Consequently, water droplets impact parts of the machine with force in the form of needle-like micro-jets. This damages the machine and causes erosion and localized surface fatigue. Water contamination also gives the oil the ability to entrain air and increase gaseous contamination.
Film Strength Loss
With elastohydrodynamic (EHD) contacts, the pitch line of gear tooth, and rolling bearing, the strength of lubricating film increases. The increase in the film is due to the viscosity of the oil, which increases with pressure. However, water does not possess the same property. The viscosity of water remains constant and drops slightly with the increase in pressure.
Accordingly, the addition of contaminants in water increases contact fatigue and surface-to-surface contact. In high-pressure zones, tribo-chemical reactions cause blisters and embrittlement.
Managing Water Contamination
One of the most effective ways to prevent water contamination is to keep water out from the oil. Water makes its way into reservoirs or sumps where machines interface with the environment.
Tips to keep oil void of water are as follows:
- Mange new oil efficiently
- Use high-quality shaft and wipe seals
- Avoid sprays with high pressure in areas near seals if possible
- Maintain heating/cooling and steam water system seals
Water has a higher specific gravity than hydraulic fluids. Due to its high gravity, it settles down at the bottom of the reservoir. The effectiveness of gravity separation improves by using a cone-shaped tank and increasing the fluid temperature. However, gravity separation is not capable of removing dissolved water completely.
The spinning of fluid can magnify the difference between the specific gravity of water and the fluid. Centrifugal separation removes free water more rapidly than a gravity separator. Moreover, centrifugal separators can remove emulsion water based on the relative strength of centrifugal force and the emulsion of the separator.
However, centrifugal separators cannot remove dissolved water.
This technique can remove emulsified, free and dissolved water. Vacuum distillation units work by effectively boiling water at 150 to 160° and distributing oil over a large surface. Vacuum distillation also removes solvents, fuels, and refrigerants. However, additive vaporization can occur with this technique.
Water contamination can become a severe threat to machines. Machines can become vulnerable to deterioration due to the contamination of water. You should try to keep water away from the oil of your machines. So, technicians should be requested to remove water from the machines.
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