The main function of a sand washing machine is to wash sand. Currently, there are three common types on the market: wheel bucket sand washing machines, spiral sand washing machines, and drum sand washing machines. Which type of sand washing machine is the * economical?

　　Wheel bucket sand washing machines are mainly small to medium-sized, with hourly outputs ranging from 30 to 280 tons. They primarily use rotating impellers to wash the sand. After the sand is put into the washing tank, the rotating impellers knead, wash, and lift the sand. The washed sand is then transported to the stockpile by a conveyor.

　　Spiral sand washing machines are generally suitable for large-scale sand washing plants. They are large in size, require a large floor space, and are more expensive. Furthermore, spiral sand washing machines consume more water during the washing process, but correspondingly, the sand washing cleanliness is higher than that of wheel bucket sand washing machines and drum sand washing machines.

　　Rotary drum sand washing machines primarily rely on the rotation of the drum and high-pressure water jet spraying to wash sand. They consume a large amount of water and produce a large volume of washed sand, and are generally used in construction sites, cement plants, and sand and gravel pits. Relatively speaking, rotary drum sand washing machines have a high output and are suitable for large-scale projects.

　　In summary, the * economical sand washing machine is the bucket wheel sand washing machine. Bucket wheel sand washing machines are small in size, inexpensive, and use less water during the washing process, making them more economical in terms of both initial investment and subsequent operating costs.