Archimedes screw pump
The Archimedes screw pump is used to raise the fluid constant pressure to a given geodetic height by means of a rotating screw (a real screw). The screw works according to the principle of the irrigation device invented by Archimedes.
All sides of the screw are open, can be several meters long, are usually made of sheet metal, and can have up to three threads or drivers. It rotates in an open semicircular groove inclined about 30°. Each time it rotates, the screw will suck a limited amount of water from the lower water storage tank (determined by the inclination angle, diameter and lead or pitch of the screw), and raise it to the top speed of the tank with a relatively low amount of rotation ( Below 100 rpm).
According to the immersion depth of the bottom end of the screw, the volume flow of the Archimedes screw pump will be automatically adjusted within a certain range as the amount of liquid in a single scraper changes. The operating principle assumes that the screw is always immersed in liquid, at least half the diameter of the lead channel of the screw, and the width of the gap between the screw and the steel plate or concrete tank should not be too large (to minimize leakage).
The lower bearing is submerged in water (see Plain Bearing) and must be lubricated with fresh water or grease. The upper bearing is usually a rolling bearing and also absorbs axial forces. The gear box is connected to the upper end of the screw.
If Archimedes screw pumps are specifically designed for this purpose, they can pump heavily polluted surface water or sewage, and even pump sand. The nozzle is purely geodetic, with a maximum range of 6 m and an efficiency between 60% and 80%. Depending on the flow rate, the screw diameter can reach several meters. Archimedes screw pump is simple and easy to operate, can easily adapt to various working conditions and operate economically. However, they often have to compete with submersible pumps.
