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T–61 SECTION 15    HANDLING AND STORAGE The  following  has  been  condensed  from  RMA  Bulletin  No.  IP-3-4:    "Storage  of  Power Transmission Belts": Recommendations for proper belt storage is of interest to designers as well as to users. Under favorable storage conditions, high-quality belts maintain their performance capabilities and manufactured dimensions.  Good storage conditions and practices will result in the best value from belt products. Power  transmission  belts  should  ideally  be  stored  in  a  cool  and  dry  environment.    Excess weight against belts resulting in distortion should be avoided.  Avoid storing belts in environments that may allow exposure to sunlight, moisture, excessive heat, ozone, or where evaporating solvents or  other  chemicals  are  present.    Belts  have  been  found  to  be  capable  of  withstanding  storage, without changing significantly, for as long as 8 years at temperatures less than 85 F (30 C) and relative humidity below 70 percent without direct contact with sunlight. Proper  handling  of  synchronous  belts  is  also  important  in  preventing  damage  that  could reduce their performance capabilities.  Synchronous belts should never be crimped or tightly bent. Belts should not be bent tighter than the minimum recommended pulley size specified for each belt section, or pitch.  Belt backside bending should be limited to the values specified in Table 21 for a minimum diameter backside idler. SECTION 16    STANDARDS APPLICABLE TO BELTS Different belt tooth configurations are shown in Figure 19 and their characteristics are described in Table 3, both on page T-15.  Since synchronous belts are manufactured by several manufacturers, each  has  established  individual  standards.    Subsequently,  the  following  general  standards  have been published: 1.   Specifications  by  the  Rubber  Manufacturers  Association  for  Drives  using  Synchronous Belts. 2.   Synchronous Belt Drives – specification by the International Organization for Standardization. Based on these, as well as standards developed by belt manufacturers, the following information is presented in this handbook: Recommended Tension for Length Measurement ........................................ Table 22 Belt Width Tolerances ....................................................................................Table 23 Pitch Length Tolerances ................................................................................ Table 24 Center Distance Tolerances  .......................................................................... Table 25 Overall Belt Thickness dimensions ................................................................ Table 26 Overall Belt Thickness Tolerances ................................................................ Table 27 Length Measurement The pitch length of a synchronous belt is determined by  placing  the  belt  on  a  measuring  fixture  comprising two  pulleys  of  equal  diameter,  applying  tension  and measuring the center distance between the two pulleys. One of the pulleys is fixed in position, while the other is movable along a graduated scale. The  fixture  is  shown  schematically  in  Figure  33. Any  pair  of  equal-diameter  pulleys  of  the  proper  pitch and  manufactured  to  specifications  may  be  used  for measuring.  The measuring tension is given in Table 22. Fig. 33    Length Measuring Fixture NB = Number of Teeth of Belt Np = Number of Grooves of Pulley Center Distance Total Measuring Force