What is an interlock?

In order for us to live and work safely, it is crucial that “machines do not operate when there is a hazard.” One mechanism that realizes this concept is “interlock.”

An interlock is a safety “key” that prevents a machine from operating unless certain conditions are met. It is used to prevent accidents caused by incorrect operation or carelessness.

Everyday Interlocks

For example, think of a microwave oven. It will never start heating if the door is open. It only begins to heat when the door is securely closed. This is the very concept of an interlock: the machine operates only when the condition “the door is closed” is met. This prevents potentially hazardous actions through a “system” rather than relying solely on human attention.
We are protected by such interlocks in our daily lives, even without being aware of it.

And this concept and mechanism become more important in places where many machines are operating, such as manufacturing plants.

International Standards Related to Interlocks

Interlock is defined in international standards such as ISO 14119. These standards define how to select and design devices to ensure that a machine stops operating if safety covers and doors are opened, and that it never starts operating unless they are closed.

For example, the differences between the devices (Types 1 to 5), measures to prevent misuse or tampering (disabling the mechanism), and other considerations for creating safer interlocks are outlined.

Interlocks in Manufacturing Facilities

As machines in factories are large and powerful, they can cause serious accidents if operators’ hands or bodies get too close due to carelessness or by mistake.

An interlock device called a “safety switch” is therefore required. This device is installed on the doors around a hazardous part of a machine and prevents the machine from operating when the doors are open. It is not until the doors are closed that the machine starts operating. If a door is opened during operation, a signal is sent automatically to stop the machine.

This system is designed on the premise that human error, such as “accidental touches” or “instinctive reaching out,” cannot be completely prevented, no matter how careful the worker is. In other words, it is based on the idea of ​​“protecting safety through systems, not solely relying on human attention.”

Interlock is an essential concept to avoid accidents both in everyday life and in factories. In manufacturing facilities, in particular, the proper use of interlock devices such as safety switches can prevent near misses and create a safe working environment for everyone.

Related Products