Machine safety with sensors

This article discusses what safety light lists, also known as safety light curtains or safety light curtains, are and how they are used to maintain and promote machine safety.

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What is machine safety?

Machine safety is the elimination and management of risks that can be caused by a machine. The risks associated with these machines can be present in all phases of the production process. Machine safety therefore relates to risks before, during and after production. These risks are not limited to physical injury, but also less immediate hazards with major consequences such as damage to workplaces.

How is machine safety determined and pursued? With safety norms it is possible for companies to comply with the necessary safety for personnel and production processes. Machine safety includes, burt is not limited to the following safety norms:

  • EN 61496-1: Machine safety - Non-contact electrical protection devices
  • EN 13849: Safety of machinery - Safety related parts of control systems
  • EN 61508: Functional safety of electrical/electronic/programmable electronic systems related to safety

ATTENTION! Machine safety and all related matters must be supervised by an authorized person. All information in this article is for educational purposes only.

Safety light grids for zone safety

Safety light curtains or safety light grids are safety components that help prevent personal injury caused by machines. Such a light grid always consists of a transmitter and a receiver. These are housed in an elongated profile.

The transmitter and receiver are installed facing each other in an application. This allows the diodes in the transmitter to emit a direct beam to the receiving photodiodes in the receiver. This creates a wall of light formed by parallel rays between the transmitter and the receiver. When a person passes it, it sends a signal to the machines to switch them off immediately. Due to this functionality, the safety light curtains are often used in locations where people and machines work side by side.

Muting, blanking and cascade

With the aid of a controller or safety relay muting and blanking can be used. Mutingis the temporary switching off of some of the diodes in a safety light curtain. This prevents the machine from stopping unnecessarily due to the detection of objects that are allowed to pass. This is useful for regularly passing fixed-height autonomous vehicles.

Blanking is the permanent switching off of some of the diodes in a safety light curtain. This is useful when passing safe objects must be permanently ignored. Think of boxes on a conveyor belt with a fixed height.

Finally, it is possible to arrange several safety light curtains horizontally in a series. The result is a long wall of parallel vertical beams of light to protect a wider area. The name of this application of safety light curtains is cascade-arrangement.

Door interlocks for safe entry

Safety light curtains can be used in production processes and areas where man and machine work together. Where this is not possible, door interlockscan be used. Another name is trapped key interlocks. These are safety components that make it impossible to enter a hazardous area while the machine is operating.

The locks can be mounted on room doors, on machines themselves and valves. The locks are equipped with personalized locks and keys. The locks can only be unlocked or locked when all keys are present in the locking mechanism.

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This way unsafe access to machines, rooms and pipes can be prevented. Authorized persons such as mechanics can only enter when the keys have been removed and the machines have been completely stopped. These can therefore only be restarted with the return of all keys.

Safety mats, safety edges and safety bumpers: prevent impact

An accident can occur out of your sight or approach without your awareness. In that case, there are several machine safety components to make a difference here. This includes safety mats, safety edges and safety bumpers. These components differ from the aforementioned safety light curtains and door locks. Safety mats, safety edges and safety bumpers prevent direct contact and an impact with a dangerous machine.

Safety mats

Machine safety using switching mats

Safety mats can be custom designed, because every application is different. These mats are placed near and around a dangerous machine. This makes the immediate vicinity of the machine safer for employees who consciously or unconsciously enter this area.

The safety mats are fitted with interlocking magnetic links on the inside. When someone steps on this mat, this pressure causes the links to release each other. Disengagement breaks the circuit, bringing the machine to a standstill.

Safety Edges

Switch lists for machine safety

Safety Edges are also available with customization. These are long rubber profiles with magnetic links on the inside. A stainless steel mounting plate is attached to the underside of the rubber profile, through which the connection cable is also routed. 

The safety edges are applied at locations and points within the production process where pinching can occur. Think of industrial doors that close vertically or machine parts where, for example, hands can get caught. Upon impact, the magnetic link is opened and with it the circuit, which shuts down the machine or door.

Safety bumpers

Machine safety with switch bumpers

Safety bumpers are blocks of foam that, just like the safety mats and edges, are provided with a magnetic link. The safety bumpers are often used on heavy hangar doors, theater stages and AGVs

The safety bumpers extend the braking distance and thus prevent a dangerous impact. Upon contact with the bumper, the internal link chain opens. This interrupts the power supply to the machinery in time and thus shuts down everything.   

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