tailieunhanh - Mechanical Engineers Reference Book 12 Part 14

Tham khảo tài liệu 'mechanical engineers reference book 12 part 14', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Seals and sealing 15 67 starting a pump against a closed valve can be avoided or made less damaging - again the seal manufacturer may be able to help. Seal selection Selecting the most appropriate sealing system for a specified duty can be a difficult exercise which is best left in the hands of a reputable seal manufacturer unless particular company expertise and experience is available. In addition to the primary seal secondary containment and ancillary equipment may be required and the manufacturer may also be able to make other suggestions for improving the reliability of the final design. The basic steps involved in seal selection are worth knowing and will aid the liaison betwen manufacturer and user. The manufacturer will require the following data to make a primary seal selection Precise and complete seal housing dimensions Running pressure including the seal chamber pressure if known Running temperature Physical and chemical properties of the sealed fluid Expected life Required leakage Specification of any secondary containment and ancillary systems will require further information regarding the sealed fluid . auto-ignition point toxicity flammability tendency to decompose tendency to crystallize percentage of solids . Company or other regulations regarding permitted leakage levels should also be consulted. For a more extensive guide to seal selection the reader is referred to reference 24. Seal installation Training The fitting of mechanical seals is a skilled job and should be carried out by trained personnel. Site surveys indicate that between 25 and 40 of all seal failures may be attributable to incorrect fitting. Cartridge seals reduce the risk of fitting errors significantly and their use is to be encouraged. All reputable mechanical seal manufacturers offer training courses on seal installation and the investment of time and money for making use of these services will inevitably return dividends in reduced premature seal failures