Protecting workers, machine operators and even unauthorized persons is a priority for those designing and building installations in machinery sources – regardless of the industry. What is more, with the right safeguards in place, a production process, warehouse or even an individual machine benefits from higher productivity, shorter downtimes and (crucially in the food or pharmaceutical industry, for example) high hygiene standards. Preventing the presence of unauthorized persons and protecting operators is possible, among others, thanks to safety switches – elements dedicated to supervising automated processes. Due to the important function they perform, they must be proven and reliable. This is why we recommend to our customers solutions from Schmersal, a German brand specializing in industrial protection. These are high-quality switches and sensors with a long service life that are designed for use in modern automation systems (e.g., supervised by industrial networks using the AS-Interface standard). Below is an overview of these products, including compatible safety relays and a number of associated accessories.
Safety switches
First and foremost, one should pay attention to the wide range of Schmersal switches. TME offers both standard (magnetic) switches and precision digital switches utilizing RFID technology. The supplier’s portfolio is divided into series with different electrical and mechanical characteristics.
Interlocking switches
Interlocking switches prevent access to dangerous areas: parts of the production process, transmission lines, as well as rooms and chambers where environmental hazards (increased temperature, presence of fumes, etc.) may exist. The switches can detect if an actuator key breaks or becomes separated from its door mounted position, transmit a signal to the control unit and lock the door/cover. The locking force for Schmersal products in the TME offer is from 500 N to 10 kN. Most of the switches have a high ingress protectioin rating (IP67 or IP69), dzięki so they can be successfullyused in mechanical processing plants, paint shops, CNC machines etc.
They are also characterised by high thermal tolerance; many models operate in temperatures from -25°C to 60°C. The switches operate from 24 V AC/DC to 230 V AC and have 1 to 4 outputs with NO, NC, or NO-NC contact configuration. Schmersal products meet the requirements of the ISO 14119 international standard defining optimal characteristics for industrial interlocking elements.
It should be noted here that the extensive Schmersal range includes switches with additional functionalities: they enable the construction of a complex protection system for machine operators, speed up inspection (e.g. by signalling the device status with easy-to-read LEDs), and provide additional safety features. For example, some products (including the AZM300 series) utilize RFID technology, which practically prevents them from being accidentally started. Complex installations will benefit from the use of series-connected switches – the MZM100 series, for example, not only enables the max. length of the sensor chain of 200 m, but also intelligent diagnostics of the whole series. Selected Schmersal products are fitted with AS-Interfacecommunication modules and can therefore be used as an actuator in industrial networks of this popular standard. The manufacturer’s product range also includes (depending on the model) three-way switches with protection against incorrect locking, electromagnetic locking, and compact design.
Key-operated switches
These switches have a similar function to locking switches, but differ in the method of actuation: detection, closing and locking is carried out by inserting a key into the key slot thereof. This solution is mostly used for sliding doors and covers. These articles are characterized by compact size (even 30x60x30mm), wider thermal tolerance (for selected models even -30…90°C) and lower energy consumption. Schmersal articles can be installed in any position and have a high ingress protection rating (IP67). They have up to 3 contacts. Furthermore, the products of the manufacturer are characterized by an exceptionally long service life of one million cycles, resulting in reduced maintenance costs. TME also offers keys dedicated to Schmersal products.
Magnetic switches
Safety sensors of this type detect a magnetic field (usually generated by a permanent magnet), informing the system of a change in the position of a protective element (enclosure). Although these elements do not themselves contain a mechanical lock, their design has the advantages desired in many industries. Primarily, they are resistant to mechanical wear. In addition, they can be installed in an invisible place and remain completely insensitive to dirt (as well as shocks, so that their ingress protection rating is IP69K). These features mean that they are often used in food or cosmetics industries; the BNS 40S and BNS 120 series from Schmersal are dedicated for these applications.
As with interlock switches, many of the supplier’s magnetic sensors can be connected to AS-Interface and thus make your production line safe. The maximum switching voltage depends on the selected model and ranges from 24 V DC to 100 V AC/DC. Schmersal magnetic switches are fitted with M8 and M20 connectors and pre-installed cables with lengths from 1 m to 10 m. Depending on the model selected, the maximum sensor range is 5 mm to 10 mm.
RFID safety switches
RFID safety switches are triggered when the actuator is near the limit of the sensor’s switching distance – which means that, from a practical point of view, they cannot be triggered accidentally (or even deliberately, to ‘bypass’ security features). Unlike the models described above, they only have digital outputs (transistor, PNP) and are designed to work with control modules. They are characterized by relatively long range (up to 12mm), low supply voltage (24V DC) and very high resistance to vibrations, shocks and dirt.
Hinge safety switches
Hinge safety switches are a perfect solution for panel elements and aluminium profiles. They have three pairs of contacts (two normally closed and one normally open) with maximum current parameters: 1 A for voltages up to 24 V DC and 2 A for 230 V AC. They are made of glass fibre reinforced plastics and aluminium (hinge only), thanks to which they are distinguished by resistance to oil and petroleum spirit. The contacts are made of silver, which ensures their high durability (one million cycles). The positive break angle is 14°.
Safety relays and expansion modules
Schmersal safety relays are designed for emergency stop systems in accordance with EN 60947-5-1 and IEC 61508 standards the most important safety regulations for process industries and machinery sector. These elements can cooperate with safety curtains, related active optoelectronic protective devices (AOPD), as well as sensors with potential-free outputs (closing the circuit). The devices have 3 or 4 safety contacts (stop category 0) for wire-break and earth fault detection; they are also equipped with status LEDs and a separate (auxiliary) signalling output. The installation is carried out using terminal blocks (clearly labelled on the front of the body). The relays are designed for mounting on a DIN rail, in a control cabinet (IP20 ingress protection rating). Their supply voltage is 24 V AC/DC.
Accessories
In addition to the switches and relays themselves, Schmersal also supplies a full range of complementary articles – from simple mechanical components to actuators that work with the switches described. When ordering selected products from the manufacturer, it is worth checking the accessories offered by TME, the use of which will facilitate the installation of security devices, while ensuring their full effectiveness.
Actuators
All safety switches requiring actuators (key-operated, RFID, magnetic) have dedicated actuators manufactured by Schmersal. The TME offer includes articles cooperating with the above-described sensors. The advantage of their use is the guarantee of the correct operation of the set and the ease of installation (compatible spacing of mounting holes, etc.). Our catalogue also includes external actuators for AZM 201 interlock switches, i.e. emergency exit handles.
Interlocks
are optional elements that prevent inadvertent closing of the door/cover (e.g. during repair or maintenance). Schmersal interlocks are compatible with AZ 16, AZ 201, AZM 201, and AZM 400 series products.
Cables
Schmersal cables dedicated to the AZ 15, AZ 201, AZM 201, AZM 400 series can also be purchased at TME. These are cables with a round connector at one end and contacts at the other. Products are available in lengths from 2 m to 10 m.
Magnets and mounting elements
Finally, it should be mentioned that TME offers a wide range of mounting elements to facilitate the installation of Schmersal switches. These are mechanical items supplied by the manufacturer, such as replacement screws or door handles (for performing emergency exits), as well as plugs and centering devices (which allow the door or cover to be closed evenly). Our online catalogue includes mounting kits allowing non-standard mounting of selected switches (e.g., installation of a key switch at right angles to the cover surface). This product group also includes magnets for reed switches.
Text prepared by Transfer Multisort Elektronik Sp. z o.o.
