Conveyor Line Problems

Question:

We recently modified our paint line to include more take off areas in our assembly department. Part of the change involved moving the drive unit and take-up unit. Previously, the drive unit was located approximately 25 ft after the take-up unit and at the same elevation. It was in this location for about four years. In this length of time, we had no problems with shearing drive pins. Currently, the take-up unit is located 25 ft after the drive unit and on a plane eight ft lower. Since the move three months ago, we have sheared six 3/8-inch drive pins. This creates a safety hazard as well as damages some of the parts on the line. The overall length of the line has increased from 810-835 ft. Line tension, lubrication and line density have remained the same. We have had two different contractors tell us the new configuration is correct and two tell us it’s wrong. I am hoping you can share some light on this subject. Thank you. M.H.

Answer:

You should be happy to know that, by shearing, the pins are doing their job. Otherwise, you may have had to replace a drive motor or the gear train in the drive unit. I am neither a mechanical engineer nor a tribologist. However, I tend to agree with the latter contractors who say the configuration is wrong. Although line tension, lubrication and line density have remained the same, the pins are shearing because the resistance to movement of the conveyor has increased. The change in resistance could be due to increased friction caused by the change in elevation.