Olafur Jonsson (Tovalia)

When producing animal feed, controlling the moisture content is one of the most important control parameters.  Moisture Measurement Sensors in Animal Feed are a very important part of how accurately we can sense and control process moisture.

Moisture content will affect the quality of the finished feed and its shelf life.   Moisture content in the feed will also directly affect the profitability of the feed mill.

It is therefore evident that this parameter should be monitored and controlled to an optimum level at each stage in the process.

Moisture Measuring Techniques

Measuring moisture content can be done by the so-called moisture balance method; this method involves heating a certain amount of material and the weight loss is interpreted as moisture.  This method takes from 25 – 25 minutes and is not very practical if the operator wants to react quickly to changes in the production.

Measuring moisture in animal feed instantly and continuously is however tricky.  The three most common technologies for doing these measurements are:

1. Measuring the response of Near Infrared (NIR) Light as it is reflected off the material
2. Measuring the dielectric properties of the material with Electrical Capacitance
   
3. Measuring the dielectric properties of the material with Microwaves
   

The advantage of NIR is that it can measure more than just the moisture content.   It can measure protein and fat.  However, the NIR requires a separate calibration for each new recipe which is not ideal for compound feed, where recipes constantly change.  For pellets the NIR technology has the disadvantage that it is a surface measurement, it will not measure the moisture inside the pellet.

Electrical capacitance is measured at low frequency.  This is the cheapest method.  However at this frequency, the ionic conduction effects are considerable.  The effects of density as well as temperature are also considerable.

The Microwave method for online moisture measurements of animal feed is becoming the recognised method in the industry.   At microwave frequencies above 2-3GHz, the ionic conduction effects are negligible.  The measurements of dielectric properties resulting from dipolar orientational polarisation of the water molecules inside the material are directly correlated with moisture content.  However, microwaves will be affected by temperature as well as density of the material.

There are several sensor technologies or sensor types that can be used with microwave technology to measure online moisture content in animal feed, but the most common sensor type is the planar sensor, or cavity resonator.  This is a cylindrical cup placed on the outside of a silo or chute.

The installation is fairly easy.  This sensor can be mounted on a hopper or a chute.

The disadvantages of this design is that the measurement area is unknown.  The radiation of microwaves into the material is not defined, but rather depends on the material and the density of it.  Therefore this method had 3 unknowns :

1. the moisture content,
2. the density and
3. the size of the area being measured.

It is often estimated that the measurement area is a few square centimetres.   These sensors need to be cleaned regularly in case there is a dirt settlement on the sensor surface, as the dirt will influence the moisture measurement of the material, because the proportion of the dirt will be significant to the total measurement area.

A New Solution in Moisture Sensing Devices

There is a new design of  microwave moisture sensors on the market now, that use planar antennas.  There are two plates separated by a specific distance.  A Transmitter is in one plate and a receiver in another. This device is mounted on a silo or a hopper and the product passes between these two specifically designed plates as it is sensed for moisture content.  This means the measurement area is known.

The amount of material measured is a cross section of the volume of material between the two plates, which is considerably more than what current planar sensors do.  Effects of dust, dirt or buildup on the sensor are therefore negligible.

As with the planar sensors, this new design is installed in a hopper or a chute.  The requirement for this sensor to work well is that the two sensor plates need to be fully covered with material.

Tested and Proven

This new design has been thoroughly tested in feed mills.  Typical accuracies of 0.4% were achieved during development and evaluation of these sensors.

Graph 1.  Comparison of moisture content by Tovalia sensor and the moisture balance method.  In total 71 samples were analysed from 39 different recipes.  The Tovalia sensor used a single calibration for all measurements.

Fore more information contact Olafur Jonsson or Hennie Pieterse at olafur@tovalia.com or hennie@hpdezign.com

Marcel Benes (Inteqnion) & Hennie Pieterse (hp dezign)

A new breath of Life

Many feed mills have been built before modern-day electronics changed the scene on process control level.  Upgrading your Process Control System might be one of the best investments you can make.  Better control of feed manufacturing operations offers an existing mill a second breath of life resulting in benefits such as:

1. Higher Output as a result of Optimised Production
2. In many cases, Energy Consumption Decrease
3. Reduction in Wear Part Cost
4. Increased Quality
5. Increased Profit
6. Decreased Human Error
7. Feed Safety (Track & Trace Options)
8. Extensive Reporting for Attention Directing purposes

Process Control solutions have been developed for plants ranging from

1. Feed Mills (Mash; Pellet Press and Extrusion Plants)
2. Premix & Micro Dosing Plants
3. Petfood & Aquatic Feed Plants
4. Grain Handling Installations
5. Bulk Handling Installations
6. Flour Mills
7. Oil Processing Plants

How do we do it?

The first step is to understand what the customer has in place.  An analysis of the existing control system will point out the advantages and disadvantages, keeping into account the customer’s management style and market expectations in terms of end product characteristics.  This information is vital in designing a Process Control Solution that will meet the requirements of both customer and the market served.

We would normally do this by visiting the Feed Mill to examine existing MCC’s (Motor Control Centres) and determine how and if we can re-use some of the existing installation and cabling.

Development and design a of a proper Process Control System could generally be outlined as follows:

1. Analysing the Process and understanding the Operational Parameters (Process Control Variables) that effect
   • how the Plant is operated (from Drawings and Process Flow & Instrumentation Diagrams)
   • the Quantity of Output from the Plant
   • the Quality of Output from the Plant
   • a visit to the feed mill is vital
2. Analyse and quantify all Instrumentation & Sensing Devices (field components) sensing the process operational parameters (these output signals become the input signals for the automation system) such as:
   • Temperature
   • Pressure
   • Moisture Content
   • Flow Rates
   • Motor Loads
   • Motor Speed
   • Weight readings from Load Cells
   • Other Signals
3. Analyse and quantify the Current Electrical Control System
   • especially the MCC’s including all it motor groups, frequency converters and all connected cabling
   • Look which MCC / motor groups can be reused (or leave in place)
   • View if there is enough space to place Remote I/O for connecting signals to the automation
   • Consider if some motors should be more effective when RPM is controlled by a frequency converter
   • Survey the cabling system
   • Position Touch Panels near important machines like pellet presses and extruders
   • Signals from Instrumentation and Sensing Devices are sent to Process Control Hardware 
     • Signal Conversion and Automation via PLC’s
     • MCC’s (Motor Control Centres), Distribution Panels and Touch Panels
     • Cabling & Cable Trays
     • Feed Mill Computer(s)
4. Design the Process Control System & Software
   • The automation system is built up of the following:
     • PLC’s (Programmable Logic Controllers) PLC’s are used for the direct control of Electric Motors, Slides, valves, etc.  Main operational tasks are given to the PLC which makes PLC’s responsible for the actual of the process and its parameters.
     • SCADA (Supervisory Control and Data Acquisition).  the SCADA system full fills two main functions:
       1. It gives a Visual Overview of the Feed Mill; all the processing equipment; equipment status (running or not) as well as the actual and required parameters to alarms.
       2. It forms the link between the PLC and the Feed mill Server / PC
     • Process Control Software (Batch Explorer) for overall control of the Plant and includes functions such as:
       1. Administration such as raw material & bin management and inventory control
       2. Formulation management of all products produced
       3. Product orders for fully automated production
       4. Reports covering inventory, production, out loading
       5. Tracking & Tracing from raw material / supplier to finished product / customer (and vice versa)
       6. ‘Batch Explorer’ is a Manufacturing Execution Software (MES) by Inteqnion especially developed for feed mills. More than 50 installations are successfully used by Feed Mills around the world.
       7. Optional interfaces to ERP or formulation software such as Bestmix is possible.
       8. ‘Batch Explorer’ sends its orders through SCADA to the PLC, which will do the actual control of the processing equipment.
5. Implementation of the Automation Steps above
   • It is our goal to switch from a manual or existing control system to a fully automated system with minimum disruption of operational activities and production output from the plant.

Online Support

The internet changed the world!  It also makes it possible to remotely assist and support an automated Process Control System 24 hours per day and 7 days per week.

Need an improved Process Control System?  Contact us today to learn how Inteqnion can help getting a new breath of life into your existing Plant.

Investing in a new feed mill or upgrading an existing one may ask for a substantial investment.  It is therefore understandable that feed mill owners and operators take care minimising investment cost.  However, Costs over the Lifetime of a Feed Mill should be the total concern, and not the cost of the initial investment only.

Engineering & design : is it worth it?

Few feed mills find it cost effective employing full-time staff of Mechanical, Electrical and Structural Engineers looking after their need for plant expansion or building a new feed mill.  It is therefore not uncommon outsourcing these services when time comes to expand or build a new feed mill.

Naturally it seems difficult for new or existing feed millers to accept that allocating part of their investment to the initial engineering & design of their new feed plant or existing feed plant expansion, is worth it. Engineering & design services could be classified as an intangible product.   However, the effect of engineering & design results in a very tangible outcome.  An outcome that may result in acceptable operational costs after installation, or an outcome where excessive operational & maintenance costs constraints the main purpose of the feed mill.

Costs factors

The chart “Costs over the Lifetime of a Feed Mill” was produced by the American Feed Industry Association and applies in many countries around the world.  Engineering & design contribute for only around 1% of the investment over a feed mill’s lifetime.  Even Equipment & Installation cost of the processing equipment and plant totals around 15% of the total cost over the lifetime of the feed mill.  Operational and Maintenance cost on the other hand, could be as high as 50% or more, depending on Engineering, Design and Equipment quality.

A direct relationship exists between operational & maintenance cost and the initial engineering & design (and associated costs) of the new feed mill or feed mill expansion.  We may appear to save money by investing in low cost equipment or a poorly designed feed plant, but sadly the savings turn into costs when unnecessary maintenance and operational costs start occupying daily feed mill life.

Proper Engineering & design

Engineering & design affects a feed processing plant in at least the following ways:

1. Functionality : the plant must be and should be designed to fulfil a very specific function – meeting and exceeding the expectations of the feed mill’s customers in terms of physical and nutritional product quality.  Failure to create a design that meets functional requirements may make it useless.  Even if the cost of such a design is low.  And let’s face it, even a relatively “cheap” design could turn out to be “expensive” if it fails to do the job!
2. Downtime : Inferior plant design and inferior equipment may result in unnecessary operational constraints, failures and downtime.  It negatively effects operational and maintenance cost and has the potential to disappoint feed mill customers and even drive them to competition.
3. Cost : The above chart confirms that initial investment cost is only one cost factor, and that ongoing operational and maintenance costs not only exceed the initial investment cost but continues into the future.

An industry colleague used the expression : “The bitterness of poor quality (includes Engineering & Design of Plant & Equipment) remains long after the sweetness of low price is forgotten”.  Investing into a new feed mill or a feed mill upgrade is a fine balance between saving on the one end but investing on the right end.

We can help you making sure you get this balance just right – Contact us today!