Jokab Safety Case Study: Filling Machines Reach Highest Safety Category
16 February 2010
The Pure-Pak filling machines installed in the Skåne Dairy in Malmö, Sweden were equipped with non-contact safety sensors for monitoring the hatches. If one of the twelve hatches is opened, the sensor gives a signal for an immediate machine stop. The non-contact sensors increase the reliability of the machine to 100% over the previously installed mechanical sensors, which helps to avoid costly downtimes.
Figure 1. The Pure-Pak PR90 filling machine can fill up to 9,000 milk cartons of 1.5 litres per hour. The machine is equipped with twelve Eden E sensors for harsh environments.
The Pure-Pak PR90 machine (Figure 1) with a capacity of 9,000 cartons per hour can be used for filling milk, fruit juice, wine, soup or sauce into 1.5 litre rectangular cartons.
Non-contact safety sensors
Eden E is a non-contact safety sensor designed for use in harsh environments (Figure 2). It consists of two complementary parts, called Adam E and Eva E, which are 12mm thick, 30mm wide and 60mm long.
The detecting distance is 12±2 mm which makes it easy to install them on a door, gate or hatch.
Eden has dynamic input and output signals. In contrast with mechanical or magnetic switches, Eden is active all the time, and a door requires only one sensor pair to achieve the highest safety level category 4.
Eden’s signal is monitored by a Vital safety module which can control up to 30 interlocked doors at safety category 4 according to EN 954-1. Vital can also monitor other safety devices at the same time.
Figure 2. The pair of Eden E sensors for monitoring doors and hatches according to safety category 4 consists of Adam and Eva. Only Adam is connected to a cable.
Filling the cartons
The Pure-Pak cartons are delivered to the dairy in the shape of blanks. The machine automatically forms the blanks into cartons and the cartons are then bottom sealed.
A few stations later, the cartons are filled by a servo-driven filler and lifter. The last station takes care of the top sealing of the cartons.
Depending on the type of filling machine, up to 27 Eden safety sensors are used. The E-version for harsh environment is ideally suited for high-pressure wash-down with cleaning and disinfecting foam (Figure 3). The automatic cleaning is carried out up to four times a day.
Another advantage of the electronic solution over the mechanical one is that no keys are needed, which means no mechanical deterioration. Recent tests have proven that Eden E can operate in a temperature range from -70 to +90°C.
Each machine is equipped with two Vital electronic safety modules (Figure 4) for reaching category 4 hatches supervision.
Figure 3. The safety sensors for harsh environment are ideally suited for high-pressure wash-down with cleaning and disinfecting foam.
Vital dynamically supervises the Eden E non-contact safety devices. It has automatic or manual supervised reset, dual NO safety outputs, and an information output for reset indication and status information for programmable controllers (PLCs).
Up to 30 safety devices can be connected to each Vital. The result of the hatches supervision can be seen on a touch screen (Figure 4), where an open hatch appears as a red area.
The central emergency stop cabinet contains five safety relays with dual and monitored internal safety functions.
Lars Bengtsson, Project Engineer at Elopak, says he still remembers the time before Eden when the machine operation was interrupted at least once a week due to the failure of one of the mechanical switches. The downtimes had caused tremendous costs over months and years.
(This article adapted from a report by Anders Dieterle, Jokab Safety, and Lars Bengtsson, Elopak.)
Click here for UPDATE: ABB acquires Jokab Safety
Figure 4. Lars Bengtsson demonstrates the use of the touch screen for starting and monitoring the filling machine.
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