10 Application Considerations for Limit Switches
When specifying a limit switch to best suit the needs of your application you should consider:
1. Electrical - To apply a control device, the type of rating for the inductive load must be known.
2. Mounting - The mount location should depend on the environment and prevent false operations by normal movements of operator or machine components.
3. Actuation - Proper actuation selection and cam design will greatly increase the life of your limit switches.
4. Moisture and Corrosion - Materials used in a limit switch greatly depend on factors such as temperature and harsh application conditions.
There are different environmental considerations that match the applicable NEMA ratings.See chart below.The factors you would need to look at is if the switch would have to be submerged & watertight, if yes, what is the duration of submersion? Let’s say if it is prolonged submersion, then you would offer NEMA 6P certification. If there would be just splashes of water, then a NEMA 4 or 4X would work.
5. Temperature Requirements - High temperature conditions in your facility may affect the lubricant type and contact material, and housing type of a limit switch.
6. Hazardous Locations - Presence of flammable fluid (liquid, gases, or vapors) and combustible dust may affect the housing material.
7. Housing Materials - Heavy duty limit switches that are used near furnaces, ovens or in a steam plant next to steam lines, they need to be specified for high temperature.Based on the temperature either a bronze or an aluminum housing would work. Typically, bronze housings are used for temperatures up to 150°C (300°F) and aluminum is used for temperatures up to 180°C (356°F).
8. Lever/Actuator Materials - Plastics will potentially melt, use steel, brass or bronze depending on other requirements such as moisture and corrosion.
9. Internal Lubrication - High temperature applications require higher grade lubricant which will be reflected in the temperature rating. Otherwise, high temperatures can cause the lever to become stiff and unable to maneuver correctly.
10. Hazardous Location Considerations –
- The switch should be rated based on specific requirements of the application.
- Explosion proof design is where the contacts are contained within the explosion proof housing to help eliminate risk of fire or explosion.EA800 and EA880 series are designed to meet NEMA and CSA standards.