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Frequently Asked Questions


What technology is used in Hydramotion viscometers?

We have perfected a technique based on mechanical resonance. This allows a vibrating solid steel or alloy probe to make very sensitive measurements of fluid viscosity. It is extremely robust and unaffected by process conditions.

Learn more about Hydramotion Technology >


If the instrument uses vibration for measurement, won’t it be affected by plant vibration?

Quite the opposite. The XL7’s special probe structure actually forms a highly efficient filter which naturally rejects the typical plant vibration frequencies and, as a result, gives an output stability that few other process instruments can achieve. Electronic filters are also provided in the signal processor unit, although these are not usually needed.

Consequently it is possible to achieve exquisite sensitivity and repeatability, even in industrial environments that might be considered extremely noisy.


Is regular maintenance and calibration checking required?

Because the instrument is essentially solid-state, there are no moving parts, seals or bearings. This virtually eliminates the need for maintenance. It is usual for XL7 viscometers to run on-line continuously for many years and maintain full performance without any intervention whatsoever.

Instruments may sometimes be required to be checked annually as part of a Quality Management procedure, but this is by no means a mandatory requirement for the XL7. However, it can be useful or reassuring to check calibration from time to time, so the processor unit includes diagnostic parameters for this purpose. Hydramotion also offer an inspection and calibration service if this is required.


Can I measure non-Newtonian fluids?

Yes. Actually, most XL7s are used with non-Newtonian fluids. The resonant technique creates a high shear rate and this has the advantage of forcing the viscosity measurement to a relatively flat part of the viscosity/shear rate curve. The result is that high repeatability is maintained even where a fluid shows dramatic non-Newtonian characteristics, such as polymer melts and gels.


Are there any process limitations — temperature, pressure etc?

A viscometer can be manufactured to suit any process conditions of temperature, pressure, flowrate, viscosity range, tank or pipe mounting.

Get in touch with us to learn more or to discuss any specific requirements.


What about sensor materials?

The standard transducer has an all 316 stainless steel construction. All wetted parts can be manufactured from alternative materials where fluid compatibility is an issue, e.g. special alloys or Hastelloy®. The sensor can also be manufactured with a special coating such as fluoropolymer for “non-stick” applications.


Can the XL7 work in explosive gas atmospheres?

Yes. Every model of XL7 viscometer is available as an Intrinsically Safe (IS) version which can operate in Class 1 Div 1 Group A or ATEX Zone 0 environments.


Are there any special skills required to fit an XL7?

Fitting an XL7 is as easy as fitting a thermowell. The instrument is supplied with the process fitting of your choice to match with the connection already on the pipe or tank. All instructions are provided in the User Manual. Complete the simple wiring, bolt on and the viscometer is ready for use.


Is any on-site calibration needed for new viscometers?

Absolutely none. A simple air check will verify there has been no damage in transit. The XL7 undergoes extensive factory calibration to traceable national standards which is completely unaffected by installation. You can position the transducer wherever you wish, in any size tank or pipe, and the factory calibration will be perfectly preserved. The transducer calibration is completely independent of its environment.


Does temperature have an effect?

Using a patented technique, the transducer is allowed to run at the fluid temperature. Even at high temperature no cooling jackets are needed. In this way the transducer does not affect the temperature of the fluid and thereby alter its viscosity. The instrument’s high accuracy and sensitivity is maintained at all temperatures with no need for any special temperature compensation.

Is temperature correction of the fluid possible?

Yes, this is an option. The viscosity at line temperature conditions can be automatically corrected to viscosity at any other reference temperature. All readings of line viscosity, corrected viscosity and temperature are displayed.


How are repairs and servicing handled?

Hydramotion has a world-class service and repair facility. We can arrange courier pickup (if required), service the instrument and arrange courier delivery to any site. Quick response is a key factor in our dealing with servicing issues and we offer a fast-track turnaround where necessary. No matter where you are in the the world, the response is the same.

Contact us for any after sales enquiries or support