1. Lubrication of Circuit Breaker Mechanisms

2. What is different about circuit breaker lubrication?
Many of the same components as other industries, but they do not operate in the same way
Long periods of inactivity
Large temperature swings
Outdoor exposure
Much longer service intervals
Wear is not usually an issue

3. Lubrication issues for MV circuit breakers
Greases harden - do not have adequate life for typical CB maintenance intervals
No zerk fittings – lubrication is difficult
Oils deteriorate – chemical reaction with moisture, oxygen and heat
Labor intensive – requires major disassembly to maintain
Result – slow trips and no recloses; burned coils and motors
This oxidized and hardened grease no longer has lubricant in the thickener

4. What is grease
Grease is a fluid lubricant (oil) mixed with a thickener. It often contains additives to give it special performance characteristics

5. Types of oils and greases
Petroleum Oils (Mineral Oils)
Made from paraffinic or naphthenic oils
Complex mixture of different crude oils
Little control over molecular structure means variation of lubricating properties
Synthetic Oils – many unique names
Manufactured from few raw material components
Desired lubricant properties can be controlled
PAO is acronym for polyalphaolifin: very good lubricating properties; suitable for many bearing, bushing and moving contact applications
Ester oils have polarity that attracts them to steel bearing surfaces: very good lubricating properties; moisture can be absorbed over time, which degrades them

6. Types of oils and greases
Silicone oils
Usually have very good oxidation and evaporation properties: good choice for low temperature, moderate load, long life applications
Applications include moving switch contacts
Compatible with many plastic materials. .
Fluorosilicone oils
Excellent resistance to oxidation, evaporation and wash-out from water or chemicals such as degreasers and penetrants
Types of oils and greases

7. The components of grease
Grease Thickeners
Thickeners are classified as soap or non-soap
Soap thickeners include aluminum, calcium, sodium and lithium
Non-soap thickeners include silica gel, clay, urea and PTFE
Soap thickener can be combined with other materials to raise the temperature at which the grease liquefies. The greases made with these enhanced thickeners are called complex greases. Thickeners are used to make the lubricating fluid semi-solid so it does not flow out of tight spaces.
Additives
Mostly used to enhance properties of the base oils
Antioxidants
Corrosion inhibitors
Anti-wear
Viscosity stabilizers
The components of grease

8. Selection of grease
Remove old grease or be aware of thickener compatibility
Consider low temperature performance and other environmental factors
Choose a synthetic grease. There is no advantage of petroleum base grease for circuit breaker applications. What life do you want?
Select a grease with base oil that resists oxidation. This is key to long, satisfactory performance.
Synthetic oils have much better oxidation characteristics than petroleum oils because of the control of properties during manufacturing. PAO and ester oils, except for the low molecular weight oils, have both good oxidation and good evaporation characteristics.
Silicone and fluorosilicone oils used in greases have even better oxidation and evaporation properties, resulting in longer life.

9. New methods: Materials
Fluorosilicone oil. It is thin enough to penetrate tight clearances, evaporates very slowly and does not oxidize. It is a good lubricant and has long life.
Fluorosilicone grease (eg. Dow 3451 grease) is used where parts can be reached.

10. Basics
Yearly Exercise During preventative maintenance Rejuvenate grease with a compatible oil. Lubricate all pivot points with oil , in various positions during maintenance charged / discharged / open / closed. Clean old grease off and apply new grease lightly. Never use aerosol penetrating solvents they are temporary and dry out any remaining oil in the grease. Upgrade to longer lasting grease during overhaul activities.