Control System Project for UK Malt Producer

In March 2016, leading UK malt producer Bairds Malt asked Gibbons Engineering Group to modernise an agitator system at its Witham plant. The project was so successful that Bairds soon commissioned Gibbons to repeat the trick at its facility in Pencaitland, Scotland.

Overview
The project concerns an agitator system consisting of a trolley weighing approximately two tonnes mounted with 13 screws which moves along a germination tank containing bulk malted barley.

As the trolley progresses along the tank, the malted barley is continuously turned by the screws in order to allow the germination process to occur at the optimum rate. An elevator and conveyor system then removes the product ready for the kilning process.

Our client recognised that the existing equipment was outdated, unreliable and inefficient, awarding Gibbons a full turnkey package of design and manufacture of the control system along with installation, programming and commissioning.

Design

The system consists of:

• One 1.1 kW progression motor to move the trolley controlled by one of two ABB ACS580 variable-speed drives depending on duty or standby mode.
• Toothed wheels enable a sensor to register the position of the trolley at any given moment, stopping the system immediately if an irregularity is flagged.
• 13 screws driven by 0.75 kW Gibbons stainless steel motors and connected to individual DOL starters. Gibbons’ stainless steel motors were specified due to their dust-tight IP69K casing which enables safe exposure to washdowns with high-pressure water jets.
• One 7.5 kW elevator motor controlled by an ABB ACS880 drive.
• One 11 kW overhead conveyor motor controlled by an ABB ACS880 drive.
• Three touchscreens – one each on the machine, control panel and in the control room.
• A new conveyor containing 15 slides complete with open or closed feedback signals.

During the normal (turning) process, the load on the progression motor is monitored. Above a pre-set level, the speed is reduced to lessen the load for a set period at which time normal speed is resumed. If the load does not reduce during the reduced speed mode, the machine is reversed for a pre-set time and then resumes normal operation.

Similarly, during the emptying (stripping) mode, the load on both the progression and discharge elevators is monitored utilising the same control philosophy.

In addition, the system includes:

• Stainless steel enclosures throughout for extended longevity
• Stainless steel cable support structure
• OLFLEX ROBUST FD cables with halogen-free TPE sheath for superior flexibility, with a power chain to allow movement alongside the conveyor
• Ethernet communications for touch screen and PLC interconnection
• Switchable LAN connection to enable programming changes and fault diagnosis to be made remotely from our Essex base

Gibbons had a two-week window while the plant was closed in which to complete the project and despite this tight timeframe, the project was delivered to schedule.

The system continues to perform as designed, helping Bairds Malt to increase the productivity, reliability and energy efficiency of the process.