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Wire-free safety system has added fibre

01 March, 2006

Wire-free safety system has added fibre

Turck Banner has launched an easy-to-install safety system based on fibre optics which, it claims, can replace mechanical safety interlocks directly. The Pico-Guard system eliminates the need to run electrical wiring to machinery, and can be used safely in hazardous areas. It is ATEX-approved for use in Zone 1 areas.

The system was developed by Banner Engineering in the US, where it has been available for several years. If a safety door or gate is opened, this breaks a modulated beam transmitted between a sender and receiver mounted on the door and its frame. The break is sensed by a four-channel optical controller.

Each of the four channels can monitor several interlock switches located on a single plastic fibre loop. Extra switches can be inserted into the loop when needed. If required, each channel can monitor a separate zone of a machine, such as its doors, entry gates or guards. The plastic fibres are connected rapidly to the switches and to the controller using snap-lock connectors.

When the system detects a break in the beam -- caused, for example, by a door opening -- or if it receives a safety stop request, it sends a stop signal to the machine controller. There are two solid-state safety outputs to control 24V DC loads or force-guided relays to provide isolated contacts.

The optical switches - which include straight and angled models - allow for some degree of misalignment and vibration, without tripping. There are versions that can be integrated into equipment such as safety gates, and Turck Banner is talking to gate manufacturers about building the system into their products.

Two or more Pico-Guard controllers can be linked via a patent-pending interface. This interface also allows other devices, such as light curtains, e-stop buttons, and rope pulls, to be connected to a controller, thus integrating different safety functions in one controller. Each controller has two of these inputs, as well as a latching output with a manual reset, and a trip output with an automatic reset.

The system is Category 4 approved (to EN 954-1), using a single switch point per door. Turck Banner claims that this is an industry first and is possible because of the system`s patent-pending diverse-redundant, self-checking photoelectric engine, specifically designed for use with plastic fibre optic cables.

A controller and four switches will cost around £600. Turck Banner says that the more doors that are protected, the more economic the system will be. It adds that substantial savings can be made in installing the Pico-Guard system compared to traditional electromechanical safety systems, because no wiring is needed. The company clams that one pilot user, which makes blow moulding machines, found it could fit the new system in half a day, compared to the 2Ĺ days it used to take to install a traditional safety system.

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