Belt driven machines are the Rodney Dangerfield of the maintenance industry – “they don’t get no respect!” For example, look at the image below. Belt driven machines do need a little bit more TLC than they currently get. I want to show you two innovations that will greatly improve your maintenance efforts on these highly efficient drives. I also want to show you why the general way in which we work with belt drives is a good example of what keeps reliability unachievable for many.
First let me say that there are some individuals/organizations who really understand the value of doing this work right. I am reminded of a gentleman called Gary Burger who wrote a very good article on improving the efficiency of belt drives. He says that he “expects to get three to five years from a belt that is running 24/7.” And I believe he gets that, and you can too. Keep in mind that this is not a roof fan that will spin forever, this is a working machine that needs sizable horsepower to turn it over.
The reason I say these drives do not get the respect they need is experience. Like many of you, I have seen belts pried off, then a new set pried on. I have seen large sheaves installed with air guns and never checked for runout, so they vibrate in the axial plane. I have seen string used for alignment or a length of angle iron from the steel rack used as a straightedge for alignment. I have seen air guns used to tension a belt so tight that the belt would not defect, even if you walked on it. And belt dressing, which was used a can at a time to try and stop the belt from squealing. All of these are not acceptable if you had planned on doing the job right. The first time.
What is Belt Misalignment?
The number one reason why belts fail prematurely is heat. Heat dries the belt out which leads to cracking and slippage and the end is not far off after that. The heat is from friction caused by misalignment. To correct misalignment, we must correct the offset and angle errors in both the Horizontal and Vertical planes.
The first belt shows angular misalignment in the horizontal plane (toe-out and toe-in). The second belt shows parallel (offset) misalignment in the horizontal and vertical planes. The third belt shows a combination of angular and parallel (offset) misalignment in both planes. This is what we are normally trying to correct.
One of the reasons why it is difficult to correct this misalignment is because you are constantly correcting the alignment as you tension the belt. If you have ever worked with an adjustable motor base that has one central adjusting bolt allowing the motor to pivot as you tighten it, it is a challenge, to say the least. These bases are lightweight, flexible, and cheap. The inexpensiveness is why they are used but there is a hidden cost. You do a lot more maintenance work with this type of base so there is no saving. The frustration comes from the fact that you are unaware the bases are flexing until it’s too late. This is because it is not something you can see by eye when using a straightedge to align the sheaves. You still must compensate or adjust the alignment as you tension the belt. Download our 5-Step Sheave Pulley Alignment Procedure which provides a simple and effective procedure for sheave pulley alignment of belt-driven equipment.
Thank you John Lambert with Benchmark PDM for sharing this educational article with us!
Alignment by Diana Pereda