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What is a safety device? | APAC

Safety components are used to provide safe control of machinery based on the concepts of machine safety for ensuring the safe operation and maintenance of machinery and equipment in factories, chemical plants, and other work sites. Sometimes safety components are built into machinery and equipment beforehand, and sometimes they are attached to the machinery and equipment as needed.

Safety components are useful for reducing the risks when using a machine.
If a safety component fails or is controlled differently than intended, the risk immediately increases and the possibility of harm to human is higher. For this reason, safety components are required to have specific safety functions (machine functions that could lead to increased risk if they fail).

Safety components used in machinery and equipment are used for the following purposes.

Limiting the work envelope of machines
Mechanical stoppers, wedges
Limiting the pressure of steam and air
Release vents (safety valves)
Detecting the opening and closing of doors

Interlock switches (Figure 1), safety limit switches

Preventing touching of machine moving parts
Covers, lids

Detecting the approaching of a person to the machine or
the presence of a person within the work envelope of the machine

Safety Light curtains, safety laser scanners (Figure 2), safety mats

Quickly detecting contact by a person with the machine
Bumper switches
Activating immediately when an operator senses danger
Emergency stop switches (Figure 3)
Checking the safety status and allowing the machine to output
Safety controllers (Figure 4), safety relay modules (Figure 5)
Ensuring safety during robot teaching and other operations
Three-position enabling switches (Figure 6)

Safety Column

Safety-related Parts and Non-safety-related Parts


In the field of machine safety, which deals with safety components, we distinguish the safety components in an entire control system by referring to the safety-related electrical control systems as “safety-related parts” and the other systems as “non-safety-related parts.” Safety components refer to devices used in “safety-related parts.” A signal indicating the safety status is sent using (electrical) energy from the input section to the logic unit only when safety has been confirmed.
The machine is started up by receiving a start command from a non-safety-related part only while a safety signal is recognized by the logic unit. On the other hand, if the safety status cannot be confirmed or the safety-related part itself has failed, the machine shall not start.

Interlock is the main function for this purpose. An interlock is a function that maintains stoppage of operation of a hazardous machine when a door (cover) of the hazardous part of the machine is not closed or when a person is working in the hazardous area.

The non-safety-related parts of the control system allow the machinery and equipment to fully demonstrate its performance. Specifically, these are the parts that control the functions that are the selling features of the machine, such as its motor speed control and precise positioning control of the movement range.

The typical relationship between the entire control system of a machine and its safety-related parts and non-safety-related parts is shown in Figure 7.