Noncontact system balances safety with efficiency

The Sipha safety interlock system offers a unique mix of noncontact reliability, unmatched protection against defeat by tampering and fail-safe operation.

Competitive pressures in the global market mean that machine safety is often competing with factors such as machine efficiency, compactness and cost as a manufacturer's primary concern.

Under these circumstances the best choice of protective measures is a device or system that combines high levels of safety provision with simplicity of design, optimised size and ease of fitment.

One system of protection that meets all of these requirements is coded noncontact safety interlocking.

Smaller and easier to fit to machines than mechanical interlocks, noncontact sensing devices are ideal for use where mechanical interlocks will not fit or where damage to mechanical actuators or switches is possible.

Noncontact devices also have considerable operating tolerances, which means that they can accept some guard wear or misalignment and still function properly, something that cannot be relied on with mechanical interlocks.

In addition, the fact that noncontact devices are fully sealed and have no dirt traps makes them ideal for use in hygiene-sensitive environments, and also applications where dust ingress would otherwise cause problems.

Before a noncontact system can be adopted on a machine a risk assessment must be undertaken.

This should be based on a clear understanding of the machine limits and functions.

These must then be analysed to identify which ones pose a potential hazard.

In this process it is important to consider all the limits and stages of the life of a machine including installation, commissioning, maintenance, decommissioning, correct use and operation as well as the consequences of reasonably foreseeable misuse or malfunction.

If the results of a risk assessment indicate that a noncontact sensing system provides adequate safety provision, then the machine designer must consider factors such as the integrity of the control unit and the sensors to be used.

In this appraisal the designer must ensure that any noncontact safety devices considered must not fail to danger and should not be easy to defeat with magnets other than those supplied by the safety supplier.

Both these essential requirements are designed into Guardmaster's latest noncontact safety interlock system, the Sipha.

The Sipha system offers a unique mix of noncontact reliability, unmatched protection against defeat by tampering and fail-safe operation.

Advanced monitoring facilities and dual channel operation (for higher levels of safety) mean that its performance is equivalent to, or better than, most mechanical safety interlocks.

The Sipha system comprises a Sipha 6 control unit, coded sensors and an actuator.

Each sensor contains multiple switching devices connected in a dual-channel system.

For the sensor to be operated the internal switching devices have to be actuated in the correct sequence within a specific time period.

In this way only the supplied actuator can be used to operate the sensor.

The heart of the Sipha system is the Sipha 6 control unit.

This provides the facility for individual monitoring of up to six Sipha noncontact safety interlocks, each with its own status indication, from a single controller.

For the OEM machine builder, this facility is extremely convenient; it simplifies installation and is extremely cost effective.

More importantly, it enables the Sipha system to maintain a Category 3 rating (ie a single fault in any of its parts does not lead to the loss of safety function) under the harmonised European Standard EN945-1 "Safety of machinery - safety related parts of control systems".

As well as providing added functionality, the Sipha 6 control unit also offers the customer considerable flexibility in machine safety circuit design.

In addition to the normal Sipha sensors, the control unit allows mechanical interlock switches and emergency-stop pushbuttons to be connected.

This high level of functionality is further complemented by the provision of the six inputs.

These enable the Sipha to function in true dual-channel safety systems, providing added levels of operator safeguarding, and the ability to replace a safety relay if the customer requires.

The control unit also optimises the ability of the Sipha system to accept misalignment of its actuator and sensor, a feature that allows for guards that become out of line as a result of wear.

Among its facilities is a time-delay function, manually adjustable between 0 and15s, which expands the capabilities of the Sipha system by providing an additional output signal that can be used for emergency stopping under control, and for interfacing with PLCs and industrial PC controllers.

Both the standard Sipha, and its more robust sister product for arduous environments, the Sipha GD2, are the ideal safety switches for use in hygienic orientated industries (food, pharmaceuticals, semiconductors) and harsh environments where electromechanical switches can give problems.

Sipha's encapsulated, IP67 and IP68 (GD2) sensors and actuators are designed to cope with the high-pressure hosedowns which are common in the food industry, and with operating environments which are extremely dusty.

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