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On-Line Viscometers: How They Can Be Used to End Production Losses

Wed, 01/30/2008 - 10:56am
Loss of production is a thing of the past for a Hong Kong-based company thanks to the XL7 process viscometer from Hydramotion Ltd. The company manufactures FR4, difunctional, multifunctional, and special purpose copper-clad laminates for printed circuit boards, which are used in thousands of electronic applications worldwide. The laminates are made by compressing layers of glass fabric matting pre-impregnated with epoxy resin together with the outer copper layers.

The viscosity of the resin directly reflects its solid content and wetting performance, which in turn determine the quality of the finished product. It is, therefore, very useful to be able to monitor viscosity during production. However, the resin can contain up to 20 percent solid mineral filler. With earlier viscosity measuring equipment, the company found that filler particles, though only a few micrometers in size, significantly affected readings. Moreover, the sticky nature of the resin often caused breakdowns.

There have been no such problems since the Hydramotion XL7 process viscometer was installed on the line. Since volatile solvents are involved, the instrument has to be an intrinsically safe model certified for use in a Zone 0 (Class 1, Division 1, Group A) hazardous area. Unaffected by solid particles in the fluid, the XL7 has given this company a reliable way of monitoring its impregnation process in real time.

It has very stable performance, a good measuring range, and good control of viscosity. That’s how it’s described by the company’s manufacturing engineering manager. He says his resin solution viscosity has been well controlled at the desired value since adopting the Hydramotion instrument. In fact, he now has virtually zero production loss due to viscosity problems.

The unique resonant technology of the XL7 overcomes problems besetting traditional approaches to viscosity measurement and can be adapted to any process environment. The solid stainless steel sensor can be fitted in any orientation with no need for ancillary pipe work. In addition, it has no moving parts to wear out or fail in service.

“The viscometer can handle solids and stickiness without maintenance,” explains the manufacturing engineering manager. “Also, it was easy to install and is very simple to use.”

The XL7 viscometer can be manufactured to suit any process conditions of temperature, pressure, flow rate, viscosity range, and tank or pipe mounting. The instrument is supplied with fittings to match the connection already on the pipe or tank.

Every model of the XL7 viscometer is available as an Intrinsically Safe version, which can operate in Zone 0 hazardous areas (explosive atmosphere continuously present). The standard transducer has all 316 stainless steel construction. However, all wetted parts can be manufactured from alternative materials, e.g. special alloys or Hastelloy, if fluid compatibility is an issue. The sensor can also be provided with a special coating such as fluoropolymer for non-stick applications.

The special probe structure forms a highly efficient filter, which naturally rejects typical plant vibration frequencies, giving very high output stability. This makes it possible to achieve the desired sensitivity and repeatability, even in extremely noisy industrial environments.

Using a patented technique, the XL7 transducer is allowed to run at the fluid temperature. Even at high temperatures, no special cooling is required. The advantage of this is that the transducer does not affect the temperature of the fluid and thereby alter its viscosity. High accuracy and sensitivity are maintained at all temperatures with no need for any special temperature compensation. Also, the viscosity at line temperature conditions can be automatically corrected to viscosity at any other reference temperature.

No on-site calibration is needed. The XL7 undergoes extensive factory calibration to traceable national standards, and this calibration is completely unaffected by installation or environment. The transducer can be positioned anywhere in any size tank or pipe. It can be useful or reassuring to check calibration from time to time, but this is by no means mandatory. In any case, the processor unit software includes a set of diagnostic parameters for this purpose since instruments sometimes have to be checked in order to satisfy quality assurance requirements. In addition, because the instrument is essentially solid-state, maintenance is virtually eliminated.

Hydramotion Ltd. is a leader in the design and manufacture of precision instruments for the measurement of viscosity in industrial processes. The company also offers an inspection and calibration service. More information is available at www.hydramotion.com.

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