A solid lubricant is used in situations such as-
- Heavy machinery working at very loads and slow speeds.
- Where parts to be lubricated are not easily accessible.
- Where a liquid or a semi-solid lubricant film cannot be maintained (e.g. Commentator blades of electric motors Machinery or)
- Machinery working at high temperature and pressure where liquid lubricants will easily catch fire.
- In machinery working in zero gravity (e.g. Spacecraft) or nuclear radiation fields (e.g. nuclear reactor).