Viscosity for product quality and process control

Viscosity control for product quality and process control is a crucial aspect of a wide spectrum in manufacturing operation: viscosity directly influences cost efficiency and quality in most processes

Viscosity control for product quality and process control is a crucial aspect of a wide spectrum in manufacturing operation.

As suppliers focus on customer satisfaction and consistency of product, viscosity becomes more important to measure and directly influences cost efficiency and quality in most processes.

In the oil condition monitoring industry (which includes machine, contamination and lubrication condition), viscosity measurement is a form of monitoring machine condition and has challenged process engineers and quality control departments since it can be affected greatly by physical variables.

Viscosity of oil changes because of temperature, load, and also due to the oxidation and contamination of the oil during service.

Additionally in OEM applications, there is a need for the solution provider to deliver a valued-added feature for constant monitoring of viscosity, for example in the dispense control of lube oil blends, or in compressors for monitoring of the oil-refrigerant mixture.

Viscosity management can result in significant savings for equipment that is on a condition monitoring program while at the same time minimizes the downtime in the process.

Hence, maintaining proper viscosity is important because it is an indicator of the status of the equipment and a measure of its operating life cycle.

Whether it is a wrong lubricant being introduced into the equipment, or contamination due to water, or degradation due to issues in rotating parts, real-time and online viscosity monitoring can provide a "heads-up" view before a failure mode occurs.

Proactive maintenance is prudent strategy in extending the equipment life and reducing downtime.

Having access to real-time and on-line viscosity data allows monitoring changes as a function of the condition of the equipment and duty cycles eliminating the need to make decisions based on intermittent, "snapshot" data acquired from periodic sampling.

Historically, for real-time viscosity data, costly and inflexible mechanical products have been used.

Up until now there has been no viable "electronic way" to measure viscosity and processors have been forced to measure infrequently or utilize a wide range of methodologies with repeated cost/benefit trade-off.

For process engineers, there is a need for minimizing equipment failures and reducing the cost of analysis using a oil viscosity sensor that operates in real time.

BiODE ViSmart acoustic wave, resonance based electronic viscosity sensor and measurement systems changes all this and provide a solution oriented product to the oil condition monitoring industry.

The BiODE ViSmart sensor system can measure viscosity from 0 to 100,000 cP ranges (can measure higher ranges and is material dependent) with +/-1% repeatability, in operating temperature environments of -20deg C to 135deg C.

The ViSmart sensor has no moving parts, uses semiconductor technology and is housed in a hermetically sealed four-ounce package.

The ViSmart sensor measures temperature at the same time, hence relieving the customer of providing a separate temperature measurement device.

PRINCIPLE OF OPERATION.

The industry is familiar with kinematic viscosity (centistokes) and dynamic or absolute viscosity (centipoise), which are related as centistokes = centipoise/specific gravity.

The BiODE instrument introduces a third class of viscosity, called acoustic viscosity.

Acoustic viscosity has units of centipoise x specific gravity.

Knowledge of the specific gravity allows conversion between these three units at a fixed shear rate and temperature.

This method of measuring viscosity employs a shear acoustic wave resonator in contact with the liquid.

The viscosity of the liquid determines how thick a layer of fluid is hydro-dynamically coupled to the surface.

The loading of the acoustic resonator caused by this viscously-entrained liquid is determined by the thickness and density of the entrained film.

The response of an acoustic viscometer is thus proportional to the product of the viscosity, the density and the radian frequency of the vibration in the limit of low frequencies.

The acoustic wave resonator supports a standing wave through its thickness.

The wave pattern interacts with electrodes on the lower surface (hermetically sealed from the liquid) and interacts with the fluid on the upper surface.

The bulk of the liquid is unaffected by the acoustic signal and a thin layer (on the order of microns or micro-inches) is moved by the vibrating surface (the vibration amplitudes are on the order of a single atomic spacing).

BiODE ViSmart can be immersed in a fluid and can also accept a droplet sample as little as 100 micro-liters.

The overall dimensions of the BiODE sensor are approximately 1.3 in x 1.1 in x 0.3 in (smaller than a matchbook).

The BiODE system is inherently network-enabled (including provisions for wireless data transfer) and allows data analysis on a system other than the computer physically connected to the sensor.

The system is readily extensible to distributed process control or to field-portable measurements.

The display of measurement information is immediate and continuous and is a marked improvement over current technology.

IN-PROCESS MEASUREMENTS.

Most existing in-line viscometers are large and bulky and response is slow and inaccurate while many units have difficulty measuring fluids with high or variable shear rates.

They also present challenges in cleaning, operating and most only provide analog outputs and are therefore difficult to interface to modern process control equipment which accept more flexible digital inputs.

The benefit of the BiODE digital design is that it is inherently much smaller, much faster, much more durable and reliable, much lower cost, and much more scaleable than existing products.

Its design is much more flexible than existing systems, and much easier to connect to a wide selection of process control devices because it outputs digital rather than analog signals For in-process measurements, the ViSmart can be mounted directly in the reactor tank for batch applications, or in the pipe for in-stream applications in multiple customer specific custom options.

The ViSmart is unaffected by static, laminar or turbulent flow since the operating shear rate of the ViSmart is several orders of magnitude higher than fluid flow characteristics.

Also it is immune to vibration and orientation effects.

As long as the fluid is in contact with the sensor surface, viscosity will be measured.

Additionally, no customer calibration is required (it is factory calibrated to NIST traceable mineral oils).

The ViSmart has the ability to integrate other off-the-shelf products for pH, pressure, conductivity and RTD measurements and can be deployed for full integration for Intranet viewing or host plant control software.

Finally, since the ViSmart is a high shear rate viscometer a 1:1 correlation with current low-shear viscometer methods is material dependent and can be generated as a library database for customers.

For plant-wide scalability, up to eight ViSmart units can be connected to the industrial plant control hub product, ViscNet which can deliver outputs (4-20 mA, TCP/IP, etc) for integration and control of solenoid valves and pumps.

APPLICATIONS.

Recently, a customer in the oil condition monitoring industry evaluated the ViSmart as part of its product quality procedures.

Clearly, one can observe exactly at the point where the contamination mixing took place.

Though the test methodology is simple and straight-forward, the data acquired clearly indicated the following to the customer: The ViSmart can conduct condition monitoring at low levels of contamination.

The response of the ViSmart to the contamination is instantaneous.

Given the robust nature of the ViSmart, its suitability for OEM applications for oil condition monitoring is very viable.

The ViSmart on-board electronics and communication protocols provide the necessary interface for integration to OEM product platforms such as compressors, gearboxes, turbines and etc, allowing the equipment manufacturers to provide value-added features of viscosity monitoring and control.

And since the ViSmart is a semiconductor product, its cost-affectivity to performance ratio is very high, carrying the ability to be deliverable in large scaleable volumes with a very high degree of reliability.

For an OEM customer providing gear-boxes to multiple industries, the ViSmart is able to continuously show the behavior of the synthetic oil in real-time.

It is clearly observed that the each of the samples has a different viscosity value.

The data can also be explained further: The value for the "New" oil is the lowest because it experiences the most amount of shear-thinning.

The value for the "Contaminated" sample is lower than the "Used" sample, because there was more water inclusion into the gearbox over the course time it was installed in a challenging environment.

It is important to note that the water contaminated viscosity value is lower because of the high shear rate of measurement by the ViSmart sensor.

Depending on the rheological curve and the behavior of the non-Newtonian mixture, high shear rate viscosity values will be of a different nature than those obtained by traditional mechanical devices.

Next generation of the BiODE ViSmart includes a low shear rate version and the ability to vary the applied shear rate electronically allowing the oil condition monitoring industry to be able to determine the viscosity "signature" of the oil.

This patent-pending capability within the same size form factor as seen above extends the "tool-kit" of the maintenance engineer.

Such a capability which at the current time resides at analysis labs, allows the process and/or maintenance engineer to gain a complete understanding of the performance of the oil across the entire spectrum of conditions that are indicative of actual process conditions.

This also brings the analytical and process teams together, enabling them to work from a common set of data points for better, more accurate and faster decision making.

BiODE ViSmart, eCup and ViscNet products offer viable in-line measurement techniques for process control in manufacturing environments, especially in tandem with end-point analysis for a variety of different viscosity and measurement needs.

They are designed to provide instantaneous, real-time in-process viscosity measurements, providing customers with a continuous digital audit trail.

The ViSmart small size and lack of any moving parts using state of the art semiconductor sensor technology, coupled with the eCup and/or ViscNet provides the process operator with a cost-effective and flexible tool to reduce operating costs, minimize process errors, improve final product quality while increasing productivity and enabling increased control of process parameters.

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