Safety interlock switches are devices that protect a machine and its operator. Sometimes installed at the machine's access points, the safety switch cuts off power to the machine when the switch is engaged. Many times, a machine guard or an access gate activates the safety interlock switch when it's opened.

Safety switch suppliers offer mechanical safety interlock switches and non-contact safety interlock switches. Mechanical safety switches directly monitor an access gate and shut off the source of power to either the entire machine or a component of the machine. Non-contact safety switches use an actuator, at least one read head and a control unit that is connected to multiple power contactors. When purchasing safety interlock switches, consider the following:

1. Order safety interlock switches that are designed specifically for your application.

2. Evaluate the environment in which the safety switch needs to operate.

3. Add an additional level of safety with a key-lock operated safety interlock switch.

Action Steps
The best contacts and resources to help you get it done

Buy a safety interlock switch that fits the application

Many safety interlock switches are designed to function with an access gate. When the machine guard or access gate is opened, the machine won't operate. Most applications use access gates that slide, lift up or are hinged. When ordering a safety interlock switch, purchase one designed specifically for your type of access gate.

I recommend: Buy safety interlock switches designed specifically for use with movable machine guards or access gates that need to be closed for operator safety at Schmersal. Find safety switches designed for hinged, sliding or lift-off guards and barriers at Omron Scientific Technologies. The switches cut off the power supply to the machine when the guard or barrier is open. IDEM Safety Switches manufactures safety switches for machine and conveyor applications.

Purchase durable safety switches

Safety switches are often subjected to abuse. If your machinery operates in corrosive environments or in areas with poor air quality, make sure the safety interlock switch has reinforced housing that is corrosion resistant. A sturdy metal housing in preferable around moving components.

I recommend: Euchner-USA offers reinforced thermoplastic and die cast aluminum versions of its safety switches. The company's safety interlock switches have integrated actuators that monitor the position of movable components. Order mechanical and non-contact safety interlock switches made from glass-reinforced polymer or baked epoxy-coated material at Norstat. Find reinforced plastic and die cast aluminum safety interlock and safety limit switches at ISE Controls. The safety switch supplier serves a wide range of industries, including food processing, automotive and textile.

Increase safety with key lock operated safety switches

Key-lock operated safety switches add an additional element of safety by requiring a key to operate the machine. A key ensures the safety switch won't be accidentally engaged if it's bumped. With a key-lock operated safety switch, you control who has access to the machine.

I recommend: Find key-lock operated safety interlocks at Steven Engineering. The company offers safety switches in a variety of sizes, styles and configurations. Honeywell Sensing and Control manufactures key operated safety interlock switches for a variety of applications. The switches are encased in a zinc die cast housing.

Tips & Tactics

Helpful advice for making the most of this Guide

• •  Many safety switches offer additional safety features, such as emergency overrides and visual indicators. Safety interlock switches with manual time delays continue to function even when the machine's controls are off.