Filling machine upgrade delivers 30 per cent speed increase

Unilever was recently faced with a familiar production issue whereby under-performing obsolete equipment presented a risk to continuity of supply. The question in this case was whether to replace a filler with a brand new one or to refurbish the existing line and remove problematic areas. Unilever investigated by calling in Farasons (the original machine builder) and its technology provider Capley Marker Systems.

At its Port Sunlight plant, Unilever manufactures many home hygiene products. In particular, the hyper chlorite (household beach) production line was showing signs of low performance when Unilever's standard metric of OEE (overall equipment efficiency) was applied; monitoring the number of shifts required to adhere to production schedules also indicated there were problems. Complete replacement would have been capital-intensive and it was known that the performance of the bottle filling was limited by particular issues rather than overall wear and deterioration.

In discussion with Farasons it was agreed that new-technology intelligent load cells and a new automation controller would bring the machine back into efficient production. Particular productivity problems were associated with all three attributes of OEE. These were: performance, as the bottle handling and filling was slow; availability, as the weighing and control system was unreliable and parts were hard to obtain; and quality, as the bottles had to be overfilled by weight to be sure that commercial requirements were satisfied.

40 intelligent load cells

Key to the upgrade programme was the use of 40 HBM intelligent load cells and their integration with a new Siemens S7 logic controller (PLC). The logic controller was mounted on the machine carousel to simplify load cell connection, with external connections made through a slip ring assembly. HBM intelligent load cells are used for bottle filling valve control, bottle presence detection (through tare) and leak detection (by measuring rate of weight change during filling).

The load cells are connected by multi-drop RS485 to the S7 communications port. All values are available in engineering units directly from the intelligent load cells. Additionally, the load cells communicate via digital I/O with the controller for valve control during filling. Indeed, filling is performed in two stages, course and fine, to ensure the finla weight is accurate.

Mounted on the carousel, the PLC communicates through a slip ring assembly that carries RS485 to a calibration and programming port and also Profibus to a Siemens touchscreen HMI for machine operation. 24V power to the controller is also fed via the slip rings.

Fortunately the new intelligent load cells have a similar physical size and mounting to the old sensors, which made the mechanical upgrade relatively straightforward.

Major improvements recorded

Capley Marker discussed the functional design requirements with Unilever personnel and developed a system that proved - via OEE monitoring - to be a vast improvement on the previous system.

Thanks to continuous OEE monitoring by Unilever, the rebuilt filling machine's performance can be accurately compared. Filler speed is up by 30 per cent, weighing accuracy is significantly improved and 'giveaway' is now said to be negligible. There is also less spillage by overfilling and less maintenance required. The machine runs 24 hours and either four or five days a week, depending upon schedule, so there is therefore spare capacity to respond to market demand changes. Unilever utilises SQC and production improvements were instantly confirmed. The site was therefore measurably more efficient and in step with group KPIs.

The critical filler refurbishment was part of a comprehensive upgrade of other machinery in the bottling line and, as such, was part of a larger time-critical plan. During the project all work had to be done on-time as bleach manufacture at Port Sunlight is central to Unilever's bleach capacity. Capley Marker, working with Farasons and Unilever's engineers, brought the project in on time and on budget – thereby avoiding any possible delivery issues with Unilever's many retailers.

Mark Stuffin, Unilever Engineer, says on behalf of the project team: "The refurbishment has proved to be very effective and it was the right decision, being far more cost-effective than wholesale machine replacement."

The automation, control and sensor know-how exhibited by Capley Marker systems was central to this comprehensive machine rebuild and should ensure another 20 years of service.