Corrosion-restant Coriolis mass flowmeter

Paul Boughton
Krohne has launched a new Tantalum version of its OPTIMASS 7300 Coriolis mass flowmeter, to handle the highly aggressive and corrosive fluids found in the chemical industry.

The past decade has seen Coriolis flowmeter technology become the accepted standard in many chemical industries.

However, one area where the technology was challenged was the measurement of highly aggressive and corrosive fluids. This was due to the commercial availability of a suitable measuring tube material to handle these chemicals.

Generally, the wall thickness of Coriolis measuring tubes are significantly less than the associated process piping, which will tolerate a higher rate of corrosion before failing. This is an area where wetted material selection for a Coriolis meter is critical.

Tantalum has been used by some Coriolis manufacturers in the past, but the twin bent tube designs made these expensive. This was due to the flange, flow splitter as well as the measuring tubes all being made from Tantalum.

It was not until the advent of the single straight tube design, that the material looked more attractive, due to the design now only needing the measuring tube and the raised face of the process flange to be made from Tantalum. This brought major cost advantages over the equivalent bent tube designs, but was not easy to achieve as Tantalum does not have the same tensile strength as Titanium which is traditionally employed..

The Tantalum used by Krohne is an alloy called Tantalum Ta10W, which is made up of 10 per cent Tungsten and 90 per cent Tantalum. Krohne have found that it is the ideal material for use in its OPTIMASS 7300 mass flowmeter as Tungsten provides the additional tensile strength required to handle the stresses associated with straight tube technology.


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