Pilz provides the right sensor for every requirement
Where there’s flying metal swarf or hazardous movements on plant and machinery, safety guards or gates ensure the safety of operating personnel.
Their position can now be monitored with a wide range of safety switches, which consider
not just the safety-related aspects, but economic considerations too.
The challenge for the designer is to harmonise safety, productivity and user friendliness on the plant or machine.
The legal position is clear. Before a machine is placed on the market, a hazard analysis
and risk assessment must be carried out and documented. The safety concept for the
respective plant or machine can then be worked out from the risk assessment.
These days, almost all new plant and machinery are safeguarded by means of safety
gates, flaps, fences or enclosures for the purposes of machinery safety and personal
One key reason for using safety gates is to protect operating personnel from injuries
resulting from intervention within the process.
This includes protection from potential emissions as well as flying metal swarf. In the
food industry it is also necessary to satisfy hygienic requirements.
To give operators as much freedom as possible, lift gates and rolling shutter-like constructions have become increasingly popular alongside the classic swing gates or sliding gates.
The fact that plant and machinery has become ever more compact has meant that the sensor technology protecting the safety gates has had to adapt to the environmental conditions. This has resulted in a wide range of version types, which meet high IP protection classes or have ATEX approval as well as having the required resistance to cleaning agents.
It is usually the design engineer who implements the safety-related requirements and selects the components used for safe monitoring.
These days they have access to a wide range of design options and a large selection of safety switches that operate to different principles.
Cost effectiveness and productivity on each machine are the priorities. However, if userfriendliness is not far behind, it is not unusual for safety equipment to be manipulated. For this reason the designer also has the task of identifying potential reasons why devices might be manipulated and to eliminate these in advance at the machine’s development stage.
Despite all the technology, the concept of a totally safe machine is merely an illusion, as it would be practically impossible to operate. So a justifiable residual risk remains.
To keep this residual risk as low as possible the designer should listen carefully to the
machine operator’s requirements and use the appropriate sensor technology.
Today’s safety gates are mainly protected using mechanical safety gate switches or roller switches – in accordance with the risk classification.
One example would be the Pilz mechanical switches PSENmech, which are also available
with guard locking. For many applications they are still state-of-the-art.
Mechanical switches comply with safetyrelated considerations such as positive-opening
and, under certain conditions, can also meet the requirement for manipulation security in accordance with EN 1088.
Robust, non-contact, safe
The signals are evaluated through compatible safe control technology, which also stops the machine and its process in the case of danger.
However, solutions that use mechanical safety gate switches or roller switches do have certain constraints, due in part to the additional work involved in their precision adjustment and their limited service life.
From an ergonomic consideration, many users also feel restricted by a mechanical solution, which can often lead to safety equipment being manipulated.
Non-contact safety switches operating to different principles have been available on the
market for many years. Safety switches such as the PSENmag from Pilz are robust, compact and are based on a magnetic action principle, providing clear benefits. Thanks to the noncontact principle, precision adjustment is unnecessary and high availability is guaranteed over the product’s service life, as there’s almost no wear and tear. The benefits of non-contact switches are clear to see, particularly on gates which are frequently operated, or in areas with increased environmental requirements such as
dust or humidity, for example in the food or woodworking industry.
A recent trend in non-contact safety switches is transponder technology (RFID). It combines all the benefits of non-contact safety switches and also guarantees the highest level of manipulation security through individual coding of the actuator.
So it is possible to achieve a high level of safety with just one switch.
When used with machine tools and machining centres with metal cutting functions, coded safety switches such as Pilz’s PSENcode have the advantage of not attracting metal swarf, unlike non-contact magnetic safety switches.
Safety-related guard locking devices are necessary on an increasing number of applications. Cramped conditions mean that safety guards have to be located close to the hazardous movement.
Not all movements can be stopped quickly enough to prevent a hazard to the user.
That’s why a safety gate has to be fitted with an interlock. The use of process guards in particular is showing an above average increase – they ensure that processes such as “gluing” or “coating” cannot be interrupted at just any position, whether intentionally or by accident, based on quality requirements.
Put plainly, safe sensor technology alone is only half the battle. Safety gate monitoring
is incomplete without a corresponding safety relay on the output side, to evaluate the
signals. With a one-stop solution, users can benefit from maximum compatibility between components.
Safety devices used to be viewed as obstructive, but now the opposite is true: modern safety systems such as the PNOZmulti make handling easier, and plant and machinery more productive.
The PNOZmulti monitors the E-STOP and the enables that control the heaters and valves.
The risk of injury from the packaging machine, therefore, is kept to a minimum, both during operation and in setup mode.
With PNOZmulti the machine has a flexible safety concept, which is really easy to adapt
to the requirements. Now the infeed area has a three-up arrangement, so assembly is
quicker and easier, plus the machine is more productive.
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