Top Editors ... Watch your wasteline

Title: Watch your wasteline
Date: 07/01/2009
Autor: Lynda Searby

With energy and raw material prices rising steeply, it’s never been more important for food and beverage
manufacturers to watch their ‘wastelines’

Wasting product and energy through excesses such as overheating and overfilling is something manufacturers can ill afford in the current climate. Fortunately, advances in areas like flow metering and vision technology are increasing the scope for monitoring and eliminating such inefficiencies.
Flow metering and control can be used for varied tasks such as injecting CO2 into cheese packs, adding prover yeast liquid to baking products, dispensing cream and dressings into pouches and introducing air into fondants and ice cream. The idea is that a more controlled measurement of the process can help to reduce potential losses.
According to Bronkhorst High-Tech, a specialist in mass flow metering and control, mass flow metering of gas and liquids is increasingly specified in the food and beverage industry as producers seek greater control over ingredient dosing and process parameters.
“Flow meters that measure the mass, rather than the volumetric flow of fluids, are recognised as more accurate and less susceptible to variations in temperature, pressure and viscosity,” said UK MD, Andrew Mangell. “This translates into more precise measurement, consistent product quality, greater control over production costs and elimination of process losses.”
Bronkhorst has just launched a range of mass flow meters, called the Mini CORI-FLOW, which uses the coriolis effect. Coriolis devices exactly measure fluid throughput, regardless of changes in fluid temperature, pressure, viscosity and density. However, they are typically applied to medium-to-high flow rates, as measurement of low rates is complicated and costly. The Mini CORI-FLOW has been developed to address the needs of the low flow
market. Siemens, meanwhile, has been focusing on the other end of the spectrum – on optimising dosage accuracy at high speeds using coriolis systems.
Its Siflow FC070 mass flow transmitter is said to achieve measurement accuracy as high as +/- 0.1% of the rated flow, and incorporates features to enhance performance when operating at high speeds.
The Siflow FC070 is in operation at Danish manufacturer KiMs, where it is helping the snack producer monitor oil consumption more closely.
At KiMs, a combination of palm oils and sunflower oils are used for frying potato chips (crisps). 60 tonnes of these oils are consumed every week, amounting to 2,850 tonnes annually.
KiMs wanted to improve its method of recording how much oil was ending up in the potato chips, and how much was being wasted through spillages, leaks or quality control checks. It had been relying on manual calculations to do this, which was time-consuming and not really accurate enough.
As KiMs’ process is fully automated using Siemens’ Simatic systems, Siemens was the logical choice for flow metering instrumentation.
Siemens specified a solution based on coriolis mass flow metering, comprising three Sitrans Mass 2100 D125 flow meter transducers, each coupled to a Siflow FC070 flow transmitter. The three flow meters are placed in a battery with a valve matrix set up that allows them to measure the supply to three production lines. This makes it possible to perform in-line and continuous measurement of the oil volumes consumed by each of the three production lines. Oil going to product and to waste can be calculated immediately and automatically, with high precision.
While KiMs originally set out just to measure flow rate, the coriolis flow meter also presented the opportunity
to measure other parameters. KiMs has used this versatility to implement measurement of flowing medium temperature and density, without having to invest in additional instrumentation. The density value shows whether the flowing medium being dosed is palm oil or sunflower oil.
More accurate dosing is not the only area in which food and beverage processors can tighten up on losses arising from product wastage.
Machine Vision Technology (MVT) has supplied a European biscuit manufacturer with a 3D laser camera scanning system that is expected to pay for itself within 12 months by minimising product waste.
The product being monitored comprises biscuit, coating and filling and is sold and packaged by weight.
MVT’s system checks the dimensions of the biscuits as they exit the oven. If any are underweight, extra fillings and coatings have to be added later in the process to make up the weight, and these are more expensive than the biscuits. If biscuits are very under- or overweight, they have to be discarded.
Thirty rows of cooked biscuits travelling at 100 columns per minute pass underneath the scanner and any that fall outside the set tolerances for length, height and width trigger an alarm so the operator can isolate the rogue
product and take corrective action to eliminate the problem, whether that be slowing the conveyor or adjusting
the oven temperature.
Previously, dimension checking was carried out manually, which resulted in slower and less reliable detection of problems. This meant a significant amount of product could end up out of specification before the defect in production was corrected.
2D vision systems, although more limited in their scope, also have a role to play in reducing product losses.
One such system is the Inspector, which was launched at last year’s PPMA by SICK. Its advantage over 3D systems, according to SICK vision systems specialist David Hannaby, is cost.
“The Inspector is low cost enough that manufacturers are able to install it at various points within the production process, rather than just at the end of the line, so they stop adding value to a product that is already faulty.”
The example he gives is that of compartmentalised ready meals. The Inspector can check each compartment is full before the meal is lidded, wrapped, sleeved and coded, and can send a signal to the filler to increase or reduce the dose.
Another technology that may help biscuit and baked good manufacturers reduce waste and cut energy costs is the Total Heat Sensor from McQueen Cairns.
The sensor, which has been used by the likes of United Biscuits, measures how much heat is available to products as they pass through the oven in terms of ‘heat flux’ rather than air temperature. This enables the total heat and humidity levels for all zones within an oven to be monitored, so variations that don’t show up on air temperature
gauges can be detected.
The sensor has been used in practice to provide product waste savings of £200,000 (€260,000) a year for a biscuit manufacturer, according to McQueen Cairns.
The problem the manufacturer was having was that a complex secondary process involving robotic packaging kept causing line stoppages. During the stoppages, the upstream oven was overheating and producing over-baked product on re-start, resulting in £3,000 (€3,900) per day in waste product.
McQueen Cairns monitored the oven heat flux profile during production and stoppages and identified new, more suitable settings for no-product operation. This reduced the waste resulting from an overheated oven by two thirds.
While heat flux might be complex for production personnel to understand, one device that most people will be familiar with, and that is often overlooked when considering process control, is the variable speed drive.
ABB says the biggest consumer of electricity in industry is the electric motor. Most motors are run at full speed, continuously, although this is not always necessary. Yet only 5% of the motor population is fitted with a variable speed drive, despite the potential savings that can be made.
For example, if a 100kW fan is throttled by 50% and running 24 hours a day, the savings on energy will pay for the variable speed drive in less than six months.
In dough mixing, variable speed drives rated from 2.2 to 7.5kW can be applied to various mixer types; drives rated from 0.37 to 15kW can be applied to the dosing pumps used to add ingredients like water, milk, sugar, salt, fat and flavourings to the flour; and the belt or screw conveyor used to transfer mixed dough to the forming stations can also use a variable speed drive, typically in the range from 0.37 to 15kW.
Such are the savings to be made by monitoring and controlling the processes in today’s high throughput plants that it is key to a company’s success to do so effectively and continue to reduce its production losses.