What Is Excessive Belt Stretching and How Can I Prevent It?

Excessive belt stretching is a rather common problem among furnace users around the world . When a brand new belt is heated repeatedly inside the furnace, the intensive heat combined with the pulling force stretches the belt over time. Although it is normal for a belt to stretch over time, excessive belt stretch can create several problems.

After the belt stretches, the extra belt length under the furnace may get caught by other mechanical parts under the furnace. The extra length may also touch the floor and pick up dirt, oil or water on the ground. The belt length should be checked during regular maintenance so that the excess length can be removed if necessary. In some cases, the belt stretches so much that the width of the belt decreases. That means the usable surface on the belt is decreased and ultimately reduces the rate of production.

When a furnace belt stretches, the only solution is to replace the belt and it is a rather costly repair so here are a few tips to avoid excessive belt stretching:
1. Get the right material. Different processes with varying temperature ranges require specific materials. Consult with the engineers and let them know your process and operating temperature range so they can get the material that is right for you.
2. Know how much your product weighs and how many will you will be putting in the furnace at one time. Calculate how much weight is being loaded onto the furnace before you order a belt. Get a heavier gauge wire if the products are heavy. However, a thicker wire also mean more heat is absorbed during heating and released during cooling, and therefore, results in a lower efficiency.
3. Make sure the friction pulleys are parallel to each other and the belt is not slipping on the pulley. A belt that is not tracking correctly will deform unevenly and it will shorten the life span of the belt. A belt that is slipping on the friction pulley will creating groves on the plastic friction pulley over time and eventually creates pressure points on the belt. This problem also occurs if the cross wire going across the width of the belt is also deformed.
4. Do not stop the belt during cooling down of the furnace. If the belt is stopped during the cooling down process, one section of the belt ends up being heated for an extended period of time. This also shortens the life span of the belt. During the shut down process, keep the belt running until the temperature drops down to 300-400°C. After the furnace cools to 300-400°C, you can shut down the belt and the furnace together.