Mechanical seals have proven to be the most widely accepted means of positive sealing of rotating shafts. Proper consideration and evaluation of operating parameters in the seal design, materials selection, and the administration of environmental controls can lead to long, trouble-free economic operation.

Extensive use of mechanical seals first took place in the automotive industry. With the use of engine coolants, other than water, it became necessary to positively seal the coolant pump. The successes of mechanical seals in automotive coolant pumps were soon extended to refrigerator compressors and other applicances. Although seal development continues in these areas, mostly in the area of materials, the sealing services imposed by this type of equipment are relatively simple and are not subject to constant change. The advantages of mechanical shaft seals are: no need for adjustment, infrequent replacement, lower overall costs, and no leakage. These were soon recognized by most industries utilizing rotating equipment. Today, over 80% of all new pumping equipment is furnished with mechanical seals.

The operating conditions encountered in water pumps used in large circulating hot and chilled water systems are not severe. However, the mechanical seals used on these pumps frequently give short seal life, and avoidable failures require repeated maintenance and/or replacement.

Long, trouble-free life can be achieved through a better understanding of mechanical shaft seals by all parties involved. More consideration in the selection and application of mechanical seals and their environmental controls by system design engineers, careful installation and startup procedures by contractors, and proper operation by system owners cannot help but lead to this goal.