Lubrication reliability for electrical equipment
Modern lubrication technology and practices can help improve the reliability of outdoor electric utility equipment such as high-voltage switchgear and circuit breakers. Different types of synthetic lubricants have demonstrated an ability to outperform conventional lubricants and excel at extreme temperatures, resist drying out, and help prevent wear and corrosion that can lead to equipment seizure and failure. Reliable lubrication is especially important on system protection devices.
Highly engineered specialty lubricants provide proven, effective performance for long-term lubrication of outdoor electrical equipment. The lubricant types include:
- Greases – These typically are made up of oil, thickeners and special-purpose additives. Greases with fluorosilicone base oils resist chemical attack and drying out in high temperatures; these and other specialty greases also withstand stiffening in extreme cold. Applications include trip-latch-and-close bearings, flange gaskets, and various seals and O-rings.
- Anti-Seize Pastes – These resemble greases but usually have close to equal amounts of oil and lubricating solids, some additives, and no thickeners. The oil serves as a carrier for the solid lubricants, which bond to surfaces and provide long-term wear and corrosion protection. Pastes are especially suitable for switchgear where parts are static for long periods, loads are high, speeds are slow and friction is sliding rather than rolling.
- Oils and Dispersions – Oils might have only a few percent additives, while dispersions may have some solid lubricants. Oils are typically used with equipment such as turbines in continuous motion under various speed and load conditions. Dispersions are usually used as penetrating oils or aerosol sprays, which can free up seized parts but not provide long-term lubrication.
- Anti-Friction Coatings (AFCs) – AFCs have a solvent carrier, resin binder and solid lubricants plus other additives. These paintlike materials dry to a bonded lubricating film that is unaffected by dust, dirt or moisture. Normally applied to equipment parts during assembly, AFCs work best on machine components with slow speeds and high loads, providing long-term lubrication.
- Silicone Compounds – Greaselike silicone compounds contain silicone fluids and inert silica fibers. They can be used for light-load lubricating and moisture sealing applications. Typical uses include sealing connections, lubricating switches, coating insulators to retard flashovers, and sealing/preserving rubber equipment gaskets.
Choosing the best lubricant for the job is critical for performance and reliability – not to mention total cost of ownership for your equipment. Identify key objectives such as extended lubrication intervals, elimination of corrosion, reduced seizures or quicker trip times. “L.E.T.S.” can guide selection:
- Load – Heavy, moderate or low? Shock, vibration and frequent stop-start cycles indicate extreme operating conditions.
- Environment – Temperature extremes, contamination such as fly ash or salt spray, and humidity are important considerations.
- Temperature – Heat and cold affect lubricant viscosity, and synthetic lubricants can meet exact application requirements.
- Speed – Slow speeds can require higher-viscosity oils or solid-lubricant pastes or coatings; high speeds need greases or oils; and static loads must have lubricating solids.
Two common causes of electrical equipment failure are component seizure and degraded lubricant.
- Component Seizure – Pastes and coatings with solid lubricant can help prevent rust and galvanic corrosion from causing seizure on equipment exposed to the elements and static operating conditions for long periods. These lubricate without drying out or washing out.
- Lubricant Degradation – Mineral-oil greases are more prone to evaporation than synthetic greases, and they tend to separate from thickeners over time. Specialty greases and pastes are formulated to resist drying out, solvent washout and loss of lubricating ability.
Choosing the right application-matched specialty lubricant can help design, operating and maintenance engineers enhance the performance and reliability of electrical equipment while extending relubrication intervals and protecting against service outages and costly unplanned maintenance.
This is an edited article provided by Dow Corning Corp. For more information, visit www.dowcorning.com.