Roller parts shall meet the following requirements

a. roller parts and welds should not produce damage and cracks, not loose at mating;
b. roller axial displacement shall not exceed 1.5mm.
6. Idler rollers to 550 r / min rotation, with its waterproof and dustproof performance should meet the vertical conveyor following requirements:
a. dust roller (refer to non-contact type seal) in a container with coal dust, continuous operation 200h, the dust must not enter the bearing grease, the working conditions in

the water spray, continuous 90 degree turn conveyor operation 72h, when the water shall not exceed 150g;
b. waterproof roller (finger contact type seal) in the flooded working conditions, continuous operation shall not exceed the amount of water 24h backward 5g.
7. Roller (not including buffer roller) in the design of a reasonable choice, speed is lower than 550r/min case, life is not less than 20000h, the failure rate is less than 12%.