Each factory has its own recommendations for measuring the roll hardness. However the method is very similar in all cases and some general principals can be applied.
1. To prepare the roll hardness tester for use, press the plunger against hard surface and press firmly until the push-button springs out. The hammer is now ready to make an impact.
2. Begin at one end of the roll and not too close to the edge. To carry out an impact, place the roll hardness tester perpendicular to the paper roll. Push the hammer against the surface of the roll at a moderate speed until the impact is triggered. For best results, impact at the same angle and try to apply the same pressure for each reading. Repeat this procedure to obtain a profile across the entire roll in the cross machine direction.
3. The impact angle alters the reading on the scale as the rebound of the hammer mass is affected by gravity. Therefore it is imperative to always use the same impact angle. (TAPPI T 834 om-07 recommends measuring horizontally). Higher values will be obtained on the same roll when impacting horizontally as opposed to impacting vertically.
4. How the results are reviewed depend very much on the working practice of the paper factory. A typical method is this: First, calculate an average from all readings taken; Second, check the variations, i.e. the range between the maximum and the minimum values and third, determine whether or not this exceeds the specified tolerance.
5. It is recommended to check the calibration of the roll hardness tester on a regular basis. The TAPPI Standard T 834 om-07 recommends performing a calibration check each week, or prior to use if you use it less regularly.
6. The impact plunger recoils when it deploys. Always hold the roll hardness tester in both hands.
For More Information About Roll Hardness Testers and other Next Generation Tools, visit the Proceq Website
No comments:
Post a Comment