Compressive strength tester with integrated moisture sensor and strip feeder

L&W Compressive Strength Tester STFI has several functions to make measurement easier, such as the automatic strip feeder that moves the test strip forward after each measurement. This makes measurement easy and quick as test strips can be measured without requiring any action from the operator. The instrument either makes a predefined number of measurements or takes measurements until the sample is exhausted. The test cycle is rapid; it takes only one-and-a-half minutes to measure a series of 20 measurements. This makes the instrument the fastest compressive strength tester on the market. A further benefit of automatic strip feeders is that the sample is unaffected, as the test strip does not need to be physically moved forward by an operator. Moisture from fingers has a negative affect on measurement results. L&W Compressive Strength Tester STFI therefore gives better and more accurate measurements.

Used directly at the paper machine

L&W Compressive Strength Tester STFI comes with an integrated moisture sensor. The ability to make quick and ongoing checks of the compressive strength is decisive in determining product quality. For traditional paper testing the test material must be conditioned before measurement in order to give correct measurement values, which is time consuming. The result is false measurement values, which in the long run can cause increased and unnecessary production costs. A change in moisture content of one percent in the test sample leads to a change in compression strength of approximately 7 percent. The integrated moisture sensor is used to correct the measured compressive strength to the equivalent compressive strength for a correctly conditioned sample. The integrated moisture sensor means that the instrument can be used directly at the paper machine, thereby simplifying handling. Moisture content correction with L&W Compressive Strength Tester STFI requires information about the moisture content and calibration data. Ten calibration curves are measured and loaded before delivery.

Proven measurement technology

The instrument employs the short-span compression test (SCT) method, which has been well established for 30 years. The SCT method is the best one for estimating and optimizing the compressive strength of liner or fluting. Methods such as ring crush test (RCT) underestimate the strength of low grammage material (see figure) because the sample ‘buckles’. The SCT method was originally developed by the Swedish research institute the STFI. In fact, in many markets the SCT method is referred to as the  ‘STFI’. Lorentzen & Wettre developed the first instrument to utilize the SCT method.

L&W Compressive Strength Master Kit

The L&W Compressive Strength Master Kit makes it possible to compare your instrument with three reference instruments from Lorentzen & Wettres. Read more on page 26. New instruments are accompanied by a one year free subscription to the L&W Compressive Strength Master Kit, which includes four sets of reference paper samples.