Effective Belt Cleaning with Water-Based Systems
Belt-washing systems operate on principles similar to traditional belt-cleaning methods but with the crucial addition of water. However, they are more technically advanced and significantly more effective than traditional mechanical belt-cleaning methods alone. Introducing water into the process has three primary benefits for cleaning conveyor belts:
- Water helps to "soften" and loosen material, making it easier to remove using a scraper.
- It prevents material from accumulating on the belt-cleaning blade, thereby enhancing cleaning efficiency.
- Water reduces friction between the belt and cleaning blades, which reduces wear on both components. This extends the lifespan of both the blade and the belt and increases maintenance intervals.
The typical belt washing system contains water-spray bars or nozzles, belt cleaning devices, and possibly a belt-drying system. It also includes arrangements for handling discharge of the effluent and for separation, recycling, and/or disposal of the water and removed material, along with and enclosure, sealing components, controls, and access.
Methods for Washing the Belt
Conveyor belts can be washed effectively using several methods, three of which were described by Dick Stahura in his 1987 paper titled "Conveyor Belt Washing: Is this the Ultimate Solution?" These methods are known as flood, bath, and wash-box techniques.
A. Flood Method
The flood method employs high-pressure water jets to act as a substitute for a traditional belt scraper. It forcefully removes carryback from the conveyor belt using water alone, with a following squeegee-type blade used to remove any remaining water.
These jets typically spray water at 400 to 700 kilopascals (60 to 100 pounds per square inch) and may also be supplemented with compressed air. This method requires specialized nozzles and clean water to work effectively, and it consumes more water compared to other washing systems.
The adhesiveness of conveyed materials and belt speed can limit this method. To ensure thorough cleaning, belt speeds generally should not exceed 5 meters per second (1000 feet per minute).
B. Bath Method
The bath method involves pulling the belt through an enclosure filled with water. It does not use spray jets, nozzles, or active components but relies on maintaining water levels and exchanging water as needed to prevent sediment buildup.
This enclosure can be positioned along the belt return or at the gravity take-up, where the weight of the water "bath tub" can be part of the conveyor's counterweight tensioning system. The effectiveness of this method depends on ensuring the belt remains submerged long enough to loosen carryback.
C. Wash-Box Method
The wash-box method is considered the current best practice in belt washing. These systems combine water spraying (similar to the flood method) with a traditional belt cleaner in an enclosed box. The specifications of the wash box can vary based on belt speed, conveyed materials, belt width, composition, and required levels of cleaning and drying.
Certain conveyor systems may have specific site constraints, such as water usage limits or environmental standards, which can influence the choice of washing method.