Vacuum system, maintenance cleaning

Are there changes in the product (film) that might be due to changes in the vacuum environment The operator s evaluation of film color, reflectance, and uniformity over the fixture can be noted on the process traveler s first check (Sec. 11.4.2). A log of work (work log) performed on the processing system, such as maintenance, cleaning, modification, replacement, etc., including the date and personnel involved, should be kept. These records should be reviewed frequently and discussed with the maintenance/operator persoimel. 

Vacuum engineering The design and construction of a vacuum system to meet processing requirements. This includes the design trade-offs that make the system more amenable to operation, cleaning, and maintenance. See also Vacuum technology. 

Vacuum technology (vacuum technology) The operation, cleaning, maintenance, and repair of a vacuum system so that it continues to meet processing requirements. See also Vacuum engineering. 

This chapter covers examples of system modifications made to prepare for maintenance. Each unwise modification created equipment damage. These incidents were simple changes intended to isolate, protect, clean, or clear equipment, and the methods chosen created problems. In some cases equipment was subjected to partial vacuum or positive pressure beyond the tolerable design limits. 

Balzers TPU 170 and the Welch 3134 are good-quality turbomolecular pumps. They have an ultimate vacuum limit of 10 Torr and pumping speeds of 300 L s from 10 to 10 Torr. Other pumps with speeds up to 10,000 L s are available, although these rates are reduced somewhat for light gases such as H2 and He, which have high molecular velocities. The turbomolecular pump is a very clean pump, requires no trap between itself and the system, and is not sensitive to contamination (although in some cases the forepump should be protected by a cold trap). It is not widely used in routine laboratory applications however, as it is quite expensive and demands careful maintenance. 

Filter cloth changing and replacement of product—contacted O-rings—are required when cleaning between products. Wear parts are the O-rings and filter cloths. These should be changed on a preventive maintenance basis approximately every two to three (2-3) months. The membrane has a lifetime of approximately one (1) year and, of course, must be chemically compatible with the solvents as is the filter cloth medium. Preventative maintenance is required for the vacuum and hydraulic (water) system. 

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