Sanitary Batching Systems- Weight Addition/Loss in Weight Systems

March 13, 2017

At Holland, we’re no strangers to sanitary batching systems. One of the most common customer challenges we’re asked to solve is a simple batching application. Our customers turn to Holland for a one stop, robust solution that is cost effective and quick to implement. Previous posts have focused on batching systems that are volume based solutions- systems that incorporate a flow meter to control a process. This post will instead focus on weight addition systems and the different system solutions available.

So let’s say you have a recipe for a product you make all the time. A recipe is, by definition, a set of instructions for obtaining a desired outcome. Every recipe has a several ingredients. How we choose to add those ingredients to a receiving vessel is a critical question that must be addressed early in the process design. One way to do it is with a flow meter used to volumetrically measure each ingredient introduced. While this may work well if you only have one ingredient or may be just metering off from a bulk tank, a volumetric system does have its drawbacks. For one, accuracy is limited to accuracy of the flow meter used. In some cases, the meter used is a turbine meter. These can have accuracies that deviate as much as 5%.

Even if the accuracy of your flow meter is sufficient for your application, many recipes call for a mass of product to be added- pounds, kilograms, etc, NOT a volume. To do this, best practice would indicate that we take a direct weight NOT volumetric measurement. When using a volume to add mass, you depend on a density based conversion and depending on processing conditions, fluid density can vary. The only way to do take a direct mass measurement is with a Coriolis meter, which often run well into the tens of thousands of dollars, depending on line size. Can you imagine if you have multiple ingredients, necessitating multiple coriolis meters? You also can’t pass solids or dry products through a flowmeter.

As an alternative to volume based batching systems, let’s consider a weight based alternative. With a weight based system, we use either a floor scale or load cells to measure the weight of either the receiving or dispensing container (a future post will take a closer look at weight by addition vs. weight by loss systems).
For this post, we’ll assume that the receiving vessel is on load cells. With the receiving vessel on load cells, we can add multiple ingredients, liquid or dry, while only measuring one process. This greatly reduces the instrumentation cost of a system. Using a controller, either a PLC or something even simpler, like a Mettler Toledo IND690, valves can be opened and closed, pumps start and stopped once volumes are added. Controllers like the IND690 allow for recipe programming and storage and also have a digital display with tare functions to allow for manual addition if need be.

At Holland, we’re able to take you all the way through system development. We usually start by working with a client to either design and fabricate a batching vessel, or retrofit an existing vessel to accommodate load cells. We then help identify and install auxiliary equipment that is very important AFTER ingredients are batched in- components like mixers, RTDs, and tank outlet valves. Once we identify what you want to measure and how you want to measure it, we can start working on HOW we’re going to add ingredients. This can be by Waukesha PD pump, Masterflex peristaltic pump, or Quattroflow Quaternary diaphragm pump. We can also supply the proper ITT diaphragm or Waukesha seat valve to control flow in. Once that is done, we can work with you to size and select an appropriate floor scale or load cells. Coupled with the right control system, we have a fully functioning batching system, capable of adding a variety of different ingredients and storing several different recipes. So if you have any questions about your next sanitary batching application, contact a Holland Sales Engineer today.