I manage a car wash that uses a STI Conveyor Systems Flowline 30 flat belt system. For about a month and a half now we have been having issues with our drivers' side belt has been slipping under the weight of multiple vehicles. We are at a point where we can only load one vehicle onto the belt at a time. The drive-sprockets were recently replaced as well as the drive bearing. We have the recommended 12in-16in (14in in our case) of catenary sag on the underside of the conveyor, and all return rollers are properly placed underneath. We are at the point where we are not sure what else the problem could be. I was hoping someone in here has had the same/a similar issue and could offer some guidance.
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STI Conveyor Flowline 30 slipping under weight
- Thread starter Sam.g427
- Start date
Our tech is also at a loss. He just ordered new flights to replace the ones that have exploded (The belt shifted over one tooth causing the flights to hit the prongs on the plate at the end) as well as more new sprockets to replace the ones that have been worn down because of the belt slipping. I could see the sprockets being the issue if a majority of the teeth had been worn down, but they're mostly still in tact. I would agree that it should be an emergency repair, however that is not my call to make.
Is this an internal tech or a trained STI tech? Sounds like you need an expert.
Wash Dragon
New member
You might want to check the shaft coupling that connects the driver-side belt.
If the coupling is damaged or slipping, torque may not be transferred properly, even if the sprockets and bearings are new.
Also, ensure the belt tension is balanced on both sides and check for any oil or detergent buildup on the underside of the belt that could cause slipping.
If the coupling is damaged or slipping, torque may not be transferred properly, even if the sprockets and bearings are new.
Also, ensure the belt tension is balanced on both sides and check for any oil or detergent buildup on the underside of the belt that could cause slipping.
Last edited:
Wash Dragon
New member
In the worst-case scenario, there could be a partial mechanical failure somewhere in the drive line — such as a cracked shaft or a sheared key — that still allows the system to operate under light load, but slips or loses synchronization under heavier vehicle weight.
This would explain why the belt appears to function with one car but fails when multiple cars are loaded.
This would explain why the belt appears to function with one car but fails when multiple cars are loaded.