... distortion, no broken, attractive and durable.( adopting aluminum fan blade in the past, which had some problems caused ... (27”),830mm*830mm*400mm(30”),900mm*900mm*400mm(31”),1000mm*1000*400mm(39”),1100mm*1100mm*400mm(40”), ... , extend service life.Adopt automatic belt tensioner,make fan work smoothly:Adopt the Aluminum Magnesium Alloy pulley and ... safety net firstly,no rusting forever: poultry exhaust fan