Figure 2-12.—Tape cleaner/certifier

process to clean a tape is to use a magnetic tape cleaner/certifier similar to the one shown in figure 2-12. Knives are used to remove any protrusions from the oxide surface. It is estimated that a maximum of 90% of all tape errors are removed in this manner. Most tape cleaners clean tape by wiping the oxide and back surface of the tape. Loosened dirt, oxide particles, and other debris are removed from the tape by wiping assemblies. When the EOT marker is sensed by a photoelectric cell, the tape is automatically reversed, and the wiping assemblies clean the entire length of tape in the opposite direction. The wiping tissue used is made of a special textured fabric and is wound on a spool. It is important to change the wiping material frequently at the point of contact with the tape. This is done to avoid entrapment and retention of abrasive dirt particles at the tape surface being wiped. Some tape cleaners, like the one shown in figure 2-12, move the wiping material along automatically. In addition, most tape cleaners repack the tape as it rewinds, using a built-in machine programmed tension arm. This feature helps to relieve irregular tape pack tension, thereby reducing the possibility of tape deformation inside the tape reel. The repack tension arm is shown in figure 2-12. Tape cleaning equipment that combines tape cleaning and recertification (figure 2-12) operates in the following manner. Any protrusions are removed by a knife edge during the first tape cleaning pass. At the same time, the location of every error that was not removed on the tape pass is indicated on a recording chart (figure 2-12, upper left-hand corner). The location of each error is identified by its distance from the beginning-of-tape (BOT) reflector. On the second pass, that is the return pass, the certifier stops at every unremoved error area and the operator, using a microscope, endeavors to remove the error with a sharp knife or scalpel. Upon completion, a recertification operation will usually restore the tape to a near error- free condition. On a 2,400-foot tape reel, each recertification operation averages 15 minutes. All tapes—scratch tapes, work tapes, save tapes, and data tapes—should be cleaned after every 10 uses or every 90 days, whichever is more frequent. All tapes should have a cleaning label attached to the back surface of the tape reel. Each time a tape is cleaned, you should log the Julian date and initial the cleaning label. Some helpful measurement criteria, used by several of the AIS installations for determining retention or disposal of magnetic tape, areas follows: ABSOLUTE-END-OF-LIFE— The tape contains so many flaws (errors) that it can not function at all. PRACTICAL-END-OF-LIFE— The tape can produce usable results, but because of cost and annoyance of failures, it is impractical to use it any longer. LEVEL-OF-REJECTION— This is a judgment call and must be based on your past experience or expertise, you might say. Some librarians and management personnel feel that after a tape is cleaned, if 15 write errors occur throughout the tape, then the tape has reached the threshold of rejection. Figure 2-12.—Tape cleaner/certifier. 2-18