Coriolis transmitter enhances process visibility at Manchester chemicals plant

Manchester, UK  - Operators at the Chemtura (formely Great Lakes Chemicals) facility in Manchester, UK, were having problems with a batch line for manufacturing various water treatment chemicals for heating systems and desalination. The application involves combining three feeds into a tank, blending and pH balancing the batch, and pumping it into a storage tank using a traditional Coriolis meter to measure flow.

With some batches the product needs to be filtered when it is pumped from the tank, which reduces the flow and increases metering problems, according to Roger Marsden, director of Westmeade Services Ltd, which provides technical support for the Manchester operation.

"We had huge discrepancies between the metered inputs and the output, and it was clear that the Coriolis meters were not ‘seeing’ all the product passing through,” said Marsden. "Depending on the flowrate, up to 200 kg of product was missing. And in situations where the product had to be filtered, as much as a 1000 kg went unmetered."

Westmeade engineers turned to Invensys' Foxboro CFT50 digital Coriolis transmitter to resolve the problem based on its ability to meter accurately during the difficult start and end stages of the batch. The instrument was installed in series with the existing meter on the outlet to properly compare performance.

The engineering team added a chart recorder to capture data, with a two second update time. Data collected included the start and end of a typical batch, the two mass flow readings, and the transmitter density reading to indicate the percentage of air in the fluid.

Prior to the onset of flow, both meters showed a zero reading, while the density reading indicated that the meters were “wet and empty.” Once the flow began, at 18 seconds, the new unit started up immediately, whereas the other meter required some 16 seconds to register the flow, allowing approximately 4 kg of material to pass through unmetered.

Once the batch was in full flow the two meters matched each other. At the end of the batch, some two hours later, both meters registered the drop in flow at 130 minutes, but as the flowtubes drained the other meter stalled. It failed to register the final blow-though of product.