Sample Selection and Identification
The best in-depth analyses are usually performed on full-width samples submitted to the fabric manufacturer's lab. A full-width sample of the forming fabric, about one foot (.305 m) wide, should be supplied along with small samples of other areas of particular interest such as areas having holes, damage, soil, etc. All samples should be clearly labeled with the fabric identification number. It is also essential to mark the front/back side, sheet side, direction of run and dates on/off. Include comments regarding the actual performance of the fabric (ie: retention, drainage, power, load, cleanliness in running, etc.). Comments should be as specific and accurate as possible. Submit sheet samples made on the fabric. These are helpful in defining the performance of the fabric in regard to formation, wire mark, holes or other operating conditions.

Analysis Procedures
Wear measurements are made in the lab on both the top and bottom wear surfaces of the fabric sample and these are generally expressed as a percent wear. The wear measurements tell how much relative wear has taken place in a particular area of the fabric. Caliper profiles are an important part of any full-width sample analysis. Because both top and bottom wear occurs in varying degrees across the fabric width they can have separate or combined effects on the total caliper loss of the fabric. A continuous caliper profile (see Fig. 1) tells where high wear areas are occurring across the fabric width and thus helps identify suspect wear-causing locations across the width of the paper machine. Air permeability is measured across the fabric width before and after cleaning the sample and is then compared to the original value for the fabric. This tells if there is any loss or drainage and how much of that loss is attributed to wear and/or mill residues.

	Photos taken of both the top and bottom wear surfaces help to clearly communicate the type of wear, the degree of burring and fibrillation and their effect on the overall wear conditions of the sample.

Using the Analysis
The most obvious use of a returned sample analysis is to locate the cause(s) of excessive fabric wear. By carrying the caliper profile to the machine and looking at all the bearing components within a high wear area, one can usually find which components are wearing the fabric. Knowing the type and degree of wear can lead to the offending components more quickly because they tell whether the wear is top or bottom side and from a roll or stationary element. Wear analysis performed on several fabrics in succession permits the generation of wear curves that define average wear in relation to cycles or revolutions on the machine. These wear curves can show sudden changes in potential life brought about by machine alterations before they can be detected by the average life of fabrics run. Like any other tool the return sample analysis is only as good as the use to which it is put. The analysis should be part of a consistently applied program of paper machine maintenance and care.