When compost systems manufacturer Susteco AB wanted to integrate an effective safety system into Big Hanna, they chose Pluto Programmable Logic Controller (PLC) from ABB, which can accommodate communications from multiple safety sensors, from nearly every safety product available on the market.
“The system ensures that the people who use Big Hanna feel perfectly safe,” says Cecilia Ek, sales director at Susteco AB. “When you work with Big Hanna you can focus entirely on what’s going on inside the machine without having to think about safety.”
Pluto PLC is the “brain” that manages the different types of safety sensors. In the case of Big Hanna, ABB’s Eden concept, a non-contact safety sensor for interlocked doors and safe position sensing, was chosen. The safety sensor is used to ensure that Big Hanna stops when a door or hatch is opened.
“It is absolutely impossible to start the machine until Eden has sent the all clear signal,” says Harald Estving at Elektro Part AB, who was responsible for Big Hanna’s programming.
Eden consists of two complementary parts (Adam and Eve [Eva]), which sense each other’s presence without mechanical contact. Pluto PLC sends a coded signal to Adam. If Adam is in contact with Eve then the hatch is closed and a coded signal is sent back to Pluto stating the system is safe and Hanna can operate. When Eve is absent, however, that means the hatch is open and a stop signal is received by Pluto. Since Adam and Eve do not require physical contact, the Eden system enables greater mounting flexibility compared to traditional mechanical switches.
ABB and Elektro Part AB worked together to find an optimal solution for Big Hanna, which was presented to Susteco. Harald Estving was responsible for the programming and ABB produced a computer-aided design (CAD) sketch showing a modular system where extra hatches could be added if required.
Big Hanna is now at the center of a recycling system at Rosendals Trädgård, an open garden in Stockholm, Sweden, with the main purpose of presenting biodynamic (organic) garden cultivation to the general public. Food waste along with natural dung from the horses, cows and boars is converted by Big Hanna into compost, which means she is great for the environment, but most importantly, because Big Hanna is safe to work with, she is great for her operators.
Words Stefan Johansson Photos Gustav Mårtensson, Patrik Söderman and Anna Rehnberg