Food processing facilities that produce products such as baby food, tomato paste, condiments, cake mixes, etc. employ batch processes in their production facilities. This means, the operator will begin with an empty vessel and make up the final product by adding ingredients.
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The operator must know the amount of a given ingredient to be added. This can be easily achieved with the help of point level measurement switch(es) with control points at the fill point for each ingredient. This usually necessitates installation of multiple sensors — one for each control point.
This kind of application is more challenging than you might think. First, the sensor must be a sanitary design that is easily Cleaned In Place (CIP), owing to the nature of the products being produced. The majority of these products are heavily coating, viscous materials that cause many technologies, including mechanical switches and tuning forks, to fail. The weight of most of these materials can damage technologies that are less robust.
Moreover, a large number of processes are agitated causing the material to splash and coat extensively. In case the switch does not indicate material level correctly, the outcome will be a ruined batch, costly downtime, and possible overfilling requiring clean up.
Level Measurement Technologies
An assessment of the most common point level technologies employed for batch process control is given below.
Floats
Floats should not be used for batch processes. Due to the viscous, coating nature of the material, the float can hang up or jam preventing the switch from indicating a control point. Albeit some floats claim to be of sanitary design, it is practically impossible to clean floats in place. Furthermore, multiple floats are needed (one for each control point) increasing the installation cost.
Tuning Forks and Vibrating Rods
Typically, these food batch processes will begin with a fairly clean liquid such as milk or water, but upon adding more ingredients, a viscous slurry is produced. This viscous material coats heavily, leading to failure of vibration type switches. The sensor can be damaged by heavily agitated slurries, causing failure as with all single point control.
Conductivity Switch
Conductivity switches have been employed for batch process applications, but these are notorious for false level indication because of material bridging between the ground and active electrode. With Conductivity technology, many sensing rods can be installed on one mounting for multiple control points. However, the rods’ close proximity only contributes to the bridging issue.
RF Admittance MultiPoint Switch – The Best Choice!
The best solution for batch process control is Drexelbrook RF Admittance Multipoint II. Only a single sensing element has to be mounted from the top of the vessel on a sanitary Tri-Clamp fitting. The 3A sanitary designed sensor is a steel rod with Kynar or TFE insulation and is developed for Clean In Place processing. It has no moving parts to wear out or hang up.
RF Admittance Cote-Shield driven shield circuitry does not consider even heavy coatings on the sensing element thereby preventing false alarms. The Multipoint II consists of three independent DPDT relays, and control points can be set anywhere along the vertical sensing element. For batch process control applications, the Drexelbrook Multipoint II offers the best solution.
- 3A designed sanitary sensing elements
- No moving parts
- 3 control points on one vertical sensing element
- Cote-Shield circuitry eliminates false alarms due to coatings
- Designed to endure Clean In Place (CIP) demands
Cote-Shield Technology by Drexelbrook
This information has been sourced, reviewed and adapted from materials provided by Ametek STC.
For more information on this source, please visit Ametek STC.