Having performed many conveyor chain pull calculations over the years I can tell you that any change to the configuration of the conveyor layout will affect the chain pull and the tension. The location of a drive in relationship to vertical curves, changes in elevation either up or down and near ovens has a great deal to do with chain tension. M. H. in the letter requesting help should have a full chain pull calculation done on the system as it is now. He should also evaluate the condition of bearings in the trolleys and the turns. Four years of use could have increased the chain pull due to lack of PM and/or application. M.F.
As a point of reference, in the April 2004 issue (www.pfonline.com/articles/clinics/0404cl_paint4.html), M. H. discussed his modified paint line. Part of the change involved moving the drive and take-up units. For about four years, the drive unit was located approximately 25 ft after the take-up unit and at the same elevation, and sheared no drive pins. Currently, the take-up unit is located 25 ft after the drive unit and on a plane eight feet lower. The overall length of the line has increased from 810-835 ft. Since the move three months ago, he has sheared six 3/8-inch drive pins. He had two different contractors tell him the new configuration is correct and two others tell him it’s wrong. (I can just see the engineering, production and plant maintenance people in finger pointing sessions trying to place the blame.)
I told him, in my usual business-like manner, that he should be happy to know that, by shearing, the pins are doing their job. Otherwise, he may have had to replace a drive motor or the gear train in the drive unit. The pins are shearing because the resistance to movement of the conveyor has increased, and the change in resistance could be due to increased friction caused by the change in elevation. Fortunately, M. F. was kind enough to write and offer a solution to the problem. He must know that I am always willing to listen and eager to learn. Thanks again for your help M. F.