when to change serpentine belt

{"title":"Flexible Double V Belt , Low Stretch Cogged V Belt For Typical Serpentine Designs","imgUrl":"https:\/\/img.chinax.com\/nimg\/d6\/ad\/c4b2c5f2daef592d1334d79b7456-200x200-1.jpg","attrs":{"Price":"Negotiation","Brand Name":"ROLL, CAMEL","Model Number":"HAA, HBB, HCC","Minimum Order Quantity":"10 pcs","Certification":"ISO9001","Place of Origin":"China","Payment Terms":"T\/T","Supply Ability":"10000 pcs per month","Packaging Details":"Carton","Material":"Rubber","Color":"Black","Cord":"Polyester or Kevlar or Aramid","Size":"AA, BB, CC","Products Name":"Double V Belts","Special Requiry":"According To Customer's Requiry"}}

{"title":"Nitrogen Protection Aluminium Brazing Furnace High Heating Ability CE ISO Approved","imgUrl":"https:\/\/img.chinax.com\/nimg\/49\/d7\/5f723fd3d94f7bd264309b7867bd-200x200-1.jpg","attrs":{"Price":"negotiable","Brand Name":"Aojie","Model Number":"AJLL 1000","Minimum Order Quantity":"1 set","Delivery Time":"15 working weeks - 40 working weeks","Certification":"CE, ISO","Place of Origin":"China","Payment Terms":"T\/T","Supply Ability":"10 sets \/ year","Packaging Details":"It depends on the size and dimension of the equipment.","Mesh-belt width (mm)":"1000","Standard Muffle Length (mm)":"10000","Total Power (kw)":"730","Warranty":"One Year","After-Sale Service":"Yes"}}