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Product category: Flowmeters and Flow Sensors
News Release from: Krohne | Subject: Optimass 7000 Coriolis Mass flowmeters
Edited by the Engineeringtalk Editorial Team on 05 March 2007

Chemical manufacturer makes flowmeter
choice

The chemical manufacturing company has chosen Krohne's Optimass 7000 Coriolis Mass flowmeters for its laboratories and production plants.

A leading international supplier of coatings and plastics additives has chosen to use Krohne's Optimass 7000 Coriolis Mass flowmeters in its laboratories and production plants after comparative tests against a competitor demonstrated significantly better results from the Optimass meter The chemical manufacturing company undertook the tests as a result of problems encountered at its plant where it was using straight-tube mass flowmeters to control the dosing of various chemicals with differing viscosities

Up to eight chemicals needed to be added sequentially to a container during the production process for coating additives, often in minute quantities, in order to improve the properties of finished products.

The production of faulty batches was driving up costs to an unacceptable level because of the level of wastage coupled with the high price of the chemicals.

The company began an investigation to determine what was causing the problems.

During the investigation, measurements taken using precision scales revealed deviations of various magnitudes for different substances when compared with the results from the flowmeters.

It became clear that the flow measuring problems were related to the different viscosities of the materials being used.

A number of possible solutions were investigated, including changing the type of meter used or adjusting the meters every time the product being measured was changed.

All these options would add substantially to production times and costs.

The chemical company therefore looked for a manufacturer able to provide replacement straight-tube flowmeters with acceptable levels of accuracy despite changing product viscosities.

It decided to directly compare Krohne's Optimass with the original meter.

An Optimass was installed vertically in series and flange-to-flange with the competitor's unit during the tests.

The company then measured the mass flow rate for three products with different viscosities on both units.

The company did several test runs for each product.

During the test, the initial flow rate of up to 25,000kg/h was reduced to a maximum of 1,000kg/h for fine dosing.

Both units met the customer's accuracy specifications and had a stable zero point when comparative measurements were made on Xylene, a low-viscosity product.

When the product was changed to Bupol, which has a higher viscosity of 200mPas, major shifts in the zero-point occurred with the first meter.

Even after stopping the flow, the counter readings continued to change.

Every measurement taken during fine dosing with the original meter had over 10% error.

When tested at a low flow rate with Polyglycol, which has a high viscosity of 400 mPas, the measurement error on the original meter reached almost 15%.

With all three products tested, however, the Krohne Optimass readings remained reliable and accurate.

By employing adaptive sensor technology in the design, Krohne has succeeded in making its Optimass Coriolis straight tube meter independent of process conditions.

In addition, compared to conventional mass flowmeters, the electronics used in the Optimass significantly improve measuring behaviour at the low end of the metering range.

This enables users to very precisely measure even the low flow rates that occur with highly viscous media, without having to reduce the pipe diameter, which in turn would lead to a higher pressure loss.

Since the units are able to measure low flow rates over a wide range of nominal diameters, overdosing does not occur and meter readings remain accurate.

The Krohne Optimass was able to fully demonstrate these benefits at the chemical manufacturing plant.

Exact and reliable measurement is essential to the chemical manufacturing process, particularly for mass flow metering at the end of the distribution heads from which various products are delivered to the mixing vessel.

The results of the mass measurement are fed to a process control system (DCS) that controls the dosing valves for about 35 production units.

Up to 20 different substances can be dosed from each distribution head.

After completing the comparison test, the company decided in favour of Krohne's Optimass and has since tested Optimass T08, T10, T25 and T40 units in various applications.

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