Volume vs Weight Batching
By: Kelly Buck
Engineers design many different types of batching systems but the first question they ask is whether to use weight batching or volume based batching. Each system has advantages and disadvantages.
Volume Based Batching – When we look at a system that is built using a volume based solution, we usually see flow meters attached inside of the feed or exit piping of the system. These operate by measuring how fast or slow the liquid product is moving through the piping of the system. These are tied to an indicator of some sort to measure how much of the ingredient has flowed into the tank. These solutions are often times less accurate due to a number of different factors. For starters, flow meter readings vary based on the physical properties of the ingredient. Viscosity, pressure, temperature, and consistency all have an effect on the flow meter reading. There is also inaccuracies due to the consistency changes of the flow.
Often times the flow of the product is not measure correctly when the system is ramping up or down. Spill loss is also a consideration with flow meters, due to where they often sit inside of the piping of a system. Flow meters are also more difficult to maintain, due to their location inside of a production system. However, flow meters do have less of an upfront cost when installing into a system. They also require basically no operator interfacing, which means that there is no training needed on the part of your operators.
Weight Based Batching - Weight batching is a highly accurate, more consistent means of controlling a batching process. Weigh modules are often placed under a tank or from suspension points to measure the gain and loss of mass to the vessel. With a weigh module system, the physical properties and state of the batching solution doesn’t matter since the weigh modules are outside of the process itself. These systems have been used to measure applications ranging from concrete mixtures to full liquid processes. Weigh modules are also easier to maintain than volume based batching solutions, due to their location in the process and how easy they are to get to.
The only concerns with accuracy on a weight batching system would be regular calibration of the equipment by a local provider. Weigh module systems have a higher upfront cost, but with a higher ROI due to longer life of the equipment. There is more training for operators on terminals, but batching systems with a dedicated batching controller have many more options for automation. Batching controllers also give you advanced weighing options, such as preemptive flow control to avoid overfilling or over batching.