Jokab Safety: safety solutions that fit European Standards. In 2008, the family business Kandern Feuerfest GmbH in Germany has finished retrofitting all presses with the latest safety technology from Sweden, in order to reach all over the highest safety category 4 according to EN 954-1, PL e according to EN ISO 13849-1, and SIL 3 according to EN IEC 62061. In addition to the Pluto safety PLC‘s and BT51 expansion relays, Vital safety modules, Eden electronic safety sensors, Focus light curtains and Smile emergency stops are used. Thanks to the further usability of the existing presses and innumerable moulds (tools) as well as the use of maintenance-free and wear-resistant safety components from Jokab Safety considerable savings could be realised.

Production of Moulded Tiles

After drying, the moulded tiles are stacked on rail-mounted hearth shuttles and pushed into the pottery kiln (Fig. 1), where they are fired at a temperature of 1,000 to 1,400°C. Then follows an approx. 36 hours long cooling-down phase, where programme-controlled fans are blowing cool outside air into the firing kiln. In order to save energy, the hereby generated waste heat is used in the large-capacity drying plant. The finished moulded tiles are finally discharged, palletised and commissioned.

Special Crank and Hydraulic Presses Provide High Quality

The operating processes in the presses are decisive for the quality and dimensional accuracy of the moulded tiles and are based on decades of experience. During the mechanical conception of the presses, the technical manager Frank Szczurek (45) was significantly assisted by the shop mechanic Fritz Renk (52).

One of the crank presses is used to compress the moulded blanks and press out the residual air. Already here, the observance of the narrow tolerance of the end measures requires to take into account the shrinkage which occurs during drying and firing. High productivity is achieved by using a multiple press, which can be operated from both sides and enables either continuous or single-stroke operation. At the hydraulic press, two operators can work at the same time.

Safety Solution from One Supplier

The presses are fully equipped with safety components from Jokab Safety and all of them meet the requirements for the highest safety category 4. Since the presses are also operated by subcontracted workers, the protection of persons was designed to be particularly safe. The safety control of all equipment (Fig. 2) is performed by the Pluto B46-6 safety PLC‘s with 46 inputs and outputs in total, some of which are connected to BT51 expansion relays for increasing the number of output contacts and additional inputs are connected to Pluto B16.

For monitoring the position of hatches, covers and machine parts, dedicated electronic safety sensors Eden with a dynamic output signal (Fig. 3) are used. Their mounting proved to be particularly time-saving thanks to the high tolerance for misalignment and offset. They replace the formerly used electromechanical limit switches which needed to be replaced every eight months.

The Focus safety light curtains in use have a high resolution of 14 mm and protection heights of 300 mm, 450 mm and 600 mm. Some light curtains are directly monitored by 1 RT9 safety relay each, or muted by an Eden safety sensor and a Vital safety module.

For emergency situations, Smile emergency stop pushbuttons with two double NC contacts or a built-in Tina interface have been provided.

Safety PLC System with Additional Functions

The only 90 mm wide Pluto B46-6 safety PLC from Jokab Safety (Fig. 2, left) complies with the highest safety category 4 according to EN 954-1, Performance Level e according to EN ISO 13849- 1, and SIL 3 according to EN IEC 62061.

Thanks to the technology implemented by Jokab Safety, at a single Pluto input 10 switches can be supervised according to the highest safety level. With the conventional technologies of other safety PLC‘s, 20 inputs are required for this. Pluto B46- 6 has a total of 46 I/O‘s, 6 of which are individual safe outputs. Moreover, 16 I/O‘s can be used either as inputs or outputs, and 24 inputs are provided for safety components and other sensors. Since the programming is via the intuitive Pluto Manager software in the ladder diagram, Pluto can be used both for safety monitoring and for controlling smaller machines.

An operator panel (Human-Machine-Interface HMI) can be connected directly to the serial interface or to the safety CAN-bus. Using a gateway, the information can be transferred from one Pluto network to other bus systems, such as Profibus DP, CANopen, DeviceNet or Ethernet, thus creating larger networks.

Slim Safety and Expansion Relays

The 22.5 mm wide safety relays BT51T (Fig. 2, right) are intended for the connection of safety components, such as emergency switches, and for increasing the number of outputs. With 4 NO safety outputs, test input with complete internal supervising, and hardwired selectable delay times from 0 to 1.5 seconds, the BT51T is quite unique. The test input is intended to supervise that contactors or valves have dropped out/returned before a new start can be permitted.

The test input can also be used for starting and the start button can be supervised.

Electronic Safety Module Vital

For simpler tasks, the only 22.5 mm wide electronic safety module Vital is used instead of the Pluto safety PLC. Vital forms the heart of a new concept, which makes it possible to install and dynamically supervise many different types of safety devices connected in the same safety circuit and still achieve safety category 4 according to EN 954-1. It also has automatic or manual supervised reset, dual NO safety outputs, an information output for reset indication, and status information for PLC‘s.

The modules have an LED indication of power ON, presence of dynamic signals and output status. Detachable connector blocks make it easy to change a module. Vital can supervise up to 30 Eden or Tina devices. The 2 outputs have a switching capacity of 6A/250Vac/1500VA/150W.

Positive Experiences

Chief electrician
 (45) has been with the company for 16 years and is responsible of all measurement and control techniques at Kandern Feuerfest. Frank is fully enthusiastic about the safety solution from Jokab Safety, as it ensures the highest safety category 4 on all machines and has in no way reduced the high productivity of the plant. Since all presses and the extensive stock of moulds can continue to be used, it was not necessary to invest in new machines and moulds or in long training courses for the operators.

The easily mounted, userfriendly safety components all come from one single source and work totally free of maintenance and wear despite frequent shocks, formation of dust and oil splashes. In the centre of the safety solution is the Pluto safety PLC with its high functionality and versatility.

Whereas many other suppliers charge high prices for the software and every future update, the Swedish manufacturer offers all this free of charge.

If contrarily to all expectations the replacement of a Pluto should become necessary, the existing programme is simply and automatically transferred from one active device in the network to the new safety PLC.

Frank also praises the good service and the competent advice from the relatively nearby German subsidiary in Spaichingen as well as the European approvals, the reduced occupation of space in the control cabinet and the attractive prices.

Ask for a detailed documentation on the safety components from Jokab Safety with various circuit diagrams.

SPS/IPC/Drives, Hall 8,Stand 202

Andreas Strangfeld
Jokab Safety
Germany, Spaichingen.

Mats Linger 
Jokab Safety AB,
Kungsbacka, Sweden

Contact:

Jokab Safety AB,
Kungsbacka, Sweden
Tel.: +46 300 359 04
Fax: +46 300 730 85
mats.linger@jokabsafety.se
www.jokabsafety.com