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.
KROHNE has been granted several patents for perfecting the technology of containing the stress created in a straight tube due to thermal expansion and are now in a position to make this technology available to highly aggressive and corrosive chemicals.
The Tantalum used by KROHNE is an alloy called Tantalum Ta10W, which is made up of 10% Tungsten and 90% 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.
With the addition of Tantalum, KROHNE can now offer a wide range of wetted materials for most chemicals. This now includes in addition, Hastelloy® C22, Duplex SS 318, Titanium as well as SS316L.
