PilZ - One source for sensor and safe control technology
One source for sensor and safe control technology
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Ostfildern, Oct 15, 2010
In accordance with international law it is the machine manufacturer's responsibility only to place safe machinery on the market. For this it is necessary to carry out and document a hazard analysis and risk assessment in advance. The safety concept for the respective plant or machine can then be worked out from the risk assessment.
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Machine designers are generally responsible for selecting safety components; they can currently choose from a wide range of sensors that operate to different principles, offering a variety of design options when it comes to implementation. The challenge, therefore, is to harmonise productivity with safety and user friendliness.
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For if a machine is not user-friendly, manipulation of safety equipment is bound to occur. When a mistake occurs, as will happen once in every thousand actions, the safety of the operator is put at risk. In critical situations in particular, under time pressure for example, accidents can quickly happen. 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.
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Selection of appropriate safety components
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In order to decide which are the optimum components for safe monitoring of movable guards in accordance with EN 60947-5-3, it is necessary to establish what needs assessing and in what format:
- For example, does it involve a gate, cover or flap which is regularly opened and closed?
- Is the process to be protected as well as the operator?
- What are the environmental conditions on site?
- Are there any airborne metal parts or swarf?
- Are components exposed to heavy soiling, strong vibration, extreme temperatures or even potentially explosive areas?
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Mechanical safety switches – Apparently the cheapest solution
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Even today, mechanical safety gate switches are still widely used for simple safety gate applications where there's no increased requirements for protection against manipulation and defeat. Mechanical safety switches PSENmech use increased extraction force on the actuator to prevent a safety gate, cover or flap from being opened unintentionally. However, two switches are always required, which quickly increases the engineering costs quite significantly. |
Where there is a high pollution degree, swarf is deposited on the sensor within a very short time, and this is difficult to clean. In rugged environmental conditions or when safety gates drop over the course of time, the lifetime of a switch is significantly reduced. In such cases, safety bolts PSENbolt are an ideal supplement to the mechanical safety switches PSENmech: they offer a safe, complete solution comprising safety switch, handle and bolt. |
PSENbolt are particularly suitable for safety gates that are difficult to adjust or in areas where safety gates are often opened and closed, as the actuator is mechanically guided into the switch actuator head. This guarantees that the actuator is inserted correctly into the safety switch when the guard is closed. As a result it provides mechanical protection for the switch.
But that still leaves one problem: Mechanical switches only provide a low level of manipulation protection.
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Alternative for rotatable and hinged gates and flaps: Safe hinge switches
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For rotatable and hinged gates and flaps, safe hinge switches PSENhinge are available as an alternative. The benefit is high plant availability. This is because PSENhinge are manipulation-proof, being concealed within the safeguard - i.e. the hinge. This also saves space. |
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Designed as one functional and installation unit, PSENhinge offer a high level of flexibility in installation, connection and adjustment. They allow systems to be attached to the right or left, for optimum cable feed at a switching point that can be freely set between 0° and 270° and is re-adjustable.
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Non-contact safety switches – Highest level of safety at a low price
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Non-contact safety switches are becoming increasingly established on the market, particularly on machines that are operated frequently and are exposed to heavy vibration. As the response tolerance is generally high, these switches are flexible and easy to install on the machine. Non-contact safety switches are also suitable for applications with increased protection type requirements (IP67 / IP69K).
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Non-contact safety switches distinguish between two operating principles: magnetic safety switches with normal manipulation protection and coded safety switches with high manipulation protection. Pilz supplies both types in the same housing, so it's possible to upgrade quickly and efficiently at a later date.
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Magnetic safety switches – Maximum freedom for installation
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Designers who opt fornon-contact, magnetic safety switches PSENmag have a system at optimum cost. Connector and cable for all mounting and approach directions, plus an assured operating distance of 3 or 8/19 mm, enable flexible assembly and rapid, simple installation.
So sensors on which the angled connectors point in the wrong direction are a thing of the past. The compact design also enables the installation to be concealed, which is an important factor from the start when developing machinery.
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But even with magnetic safety switches there's a catch: They are not suitable in applications with metal swarf, as metal dust is deposited on the switch due to the magnet, invalidating it. So users are better to opt for transponder switches.
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Coding for excellent manipulation protection – Transponder switch with integrated evaluation
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Coded safety switches fit the bill when specifications call for the highest level of safety as well as manipulation protection. With non-contact, coded safety switches PSENcode you have the smallest, coded safety switch with integrated evaluation, in other words excellent diagnostics, as well as built-in protection against manipulation and defeat. The highest level of manipulation is achieved by transmitting a unique code from the actuator to the switch (key lock principle). |
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Different manipulation levels can be achieved thanks to the various coding types: from coded (PSENcode switch accepts any PSENcode actuator) – to fully-coded (PSENcode switch accepts only one PSENcode actuator, which can be taught in 8 times) – to a unique fully-coded actuator (PSENcode switch accepts only one PSENcode actuator, no teach-in facility).
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So one safety switch PSENcode is sufficient for applications up to PL e of EN ISO 13849-1, SIL 3 of EN/IEC 62061 and Cat. 4 of EN 954-1. The integrated evaluation in PSENcode also saves an additional evaluation device.
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Process protection via non-contact, coded safety gate systems
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If gates, covers or flaps, for example, have to be repeatedly opened for operational or assembly purposes, enabling operators to access the protected area, it is necessary to check how the plant or machine in the process can be stopped immediately.
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Safety-related guard locking devices are used where cramped conditions mean that safety equipment has to be positioned in close proximity to a hazardous movement. In this case, the safeguards must not only be safely monitored but safely locked as well.
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Only then is the operator safely protected in the event of a dangerous overrun movement. For safety reasons it may also be necessary to disable the guard locking device only in conjunction with safe standstill detection or a safe delay time.
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Another field for safe guard locking devices can be found in protecting the process cycle. Plant and machinery that protect hazardous movements with overrun, cooling or curing phases etc. are found particularly in woodworking, car production and the packaging industry. For example, a "gluing process” should not be interrupted at just any time, whether intentionally or by accident, as this would adversely affect quality.
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Non-contact safety gate systems - Safe position monitoring with process guarding in one system
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The disadvantage with mechanical guard locking devices, however, is that they are difficult to adjust and only have a short service life. That's why new types of safety gate concepts combine the principle of non-contact safety switches with the function of a safe guard locking device. Here Pilz can offer safety gate systems PSENslock, a non-contact, coded safety switch with a safe magnetic interlock of 500 N or 1000 N (BG GS-ET 19) in one system. |
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With this combination of safe position monitoring and process guard locking, PSENslock provide a safe alternative to existing mechanical technology. Highest possible protection against manipulation and defeat, combined with low wear and tear, ensure a long service life and protect investment.
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Save time and costs with integrated systems for safety gate monitoring
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The new Pilz safety gate systems PSENsgate also rely on a combination of electronics and mechanics. The highest category can be achieved using a single system. The safety gate system combines safety gate monitoring, safe guard locking and control elements in a confined space – and that includes additional functions such as E-STOP and escape/auxiliary release. |
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As shearing and breakage of the bolt and pin are also reliably detected, the system offers enhanced safety for machinery with a particularly high hazard potential. Complete systems such as these are mostly used on larger safety gates, which enable operators to access plant or machinery.
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With PSENsgate you have a combination of devices which, in the past, users have had to assemble separately: All safety functions and control elements are now available in a single turnkey system. Taken together, this saves time and costs when it comes to project configuration, design, documentation, purchasing and installation.
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Coding guarantees the highest possible protection against manipulation and defeat. A closing lock can also be implemented by using up to five padlocks on the bolt.
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The benefits of complete solutions
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With safety-related equipment on machinery it's not just the individual components that matter but the way in which they interact: complete solutions with fully compatible components, composed of safe sensor technology and safe control technology, offer high potential savings in project configuration, design, documentation, purchasing and installation.
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When sensor(s) and evaluation device are purchased from a single manufacturer it means that the interfaces between the components are already compatible. One benefit that is certainly worth considering: the user has no need to pore over data sheets and observe complex tests in order to ensure that the selected components actually interact smoothly.
With Pilz products you can save time and costs in the implementation of all components, including certified safety.
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Individual Pilz components can be packaged together to suit any automation requirement. The comprehensive product range covers the whole spectrum of safety requirements for optimum safety gate monitoring.
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With corresponding evaluation devices and pre-assembled cables – especially for series connection and decentralised periphery – users no longer need to worry about connection cables or the necessary installation materials.
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However, a product can only ever be as good as the expertise with which it has been selected and used within an application. That's why Pilz provides individual consultation and comprehensive support, plus services. Users can assemble the services they need to suit their requirements:
from an individual device to a system of co-ordinated components and beyond to consultation, support with the control cabinet design or complete commissioning of a machine. A totally optimum combination – and safe.
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