6 - Sensors and devices for machinery protection

Abstract

This chapter focuses on the operating principles of a wide range of sensors and protection devices used in machinery protection. Most sensors used in machinery protection have been developed specifically to work with mechanical guarding systems or to provide direct electronic guarding systems such as light curtains. The major subdivision of safeguards is between guards and safety devices. Both of these are to protect persons from the hazards that cannot reasonably be removed or be sufficiently limited by design. A safety device should be provided such that it automatically prevents the operator from coming into contact with the dangerous part of the machinery. A safety device has to ensure that while the dangerous part is exposed, it does not move, and the motion of a dangerous part stops before any person can reach it. The use of locked gates and guards has traditionally been the most reliable method of guarding. The method relies on a responsible person having possession of the key to the guard at all times. Locking systems can be divided into two basic types: mechanical trapped key interlocking and electrical control interlocking.