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CHAIN-TYPE WEED SCREEN CLEANING MACHINES:

This type of machines constitutes a major component of our chain-type fixed weed screen cleaning systems installed at open-source water intakes of some irrigation pumping stations in Egypt. The number of machines installed per system differs from site to site as a separate machine is allocated to each water intake. A simple design is adopted to guarantee ease of operation and maintenance. Motion is transmitted to the machine rake through a continuous chain. Rakes are equipped with tines that are positively engaged between screen bars to remove accumulating weeds and debris as rakes move from bottom to top. Other system components complement the machine functions. A greasing system is provided to handle greasing of parts well immersed in water. A control system allows for manual and automatic operation of machines. It is also used to stop machines once rakes are overloaded or the system runs out of grease. Possible emergency stops represent an additional safeguard.

MOVING PARTS:

GEARED MOTOR:

A 3-KW electric motor with brake is combined with a gearbox in one unit providing the torque necessary for the drive shaft at a speed that suits raking requirements. The gearbox is directly coupled to the drive shaft except for the Maryout-2 station where it is geared to it due to space limitations.

DRIVE SHAFT & DRIVE SPROCKETS:

The drive shaft is mounted on two ball bearings fixed to the machine head side plates with tightening bolts. Two stainless steel drive sprockets are keyed to the shaft near its ends. The geared motor providing the driving torque is fixed to one of the shaft ends.

TENSION SPROCKETS:

A 28-mm-thick stainless steel sprocket is fixed to a thick base secured to each machine head side plate. The thick base is provided with a 20-mm tension bolt. Tightening the bolt pushes the sprocket backwards thus increasing the tension in the chain.

BENDING SPROCKETS:

A 28-mm-thick stainless steel sprocket is fixed to a thick base secured to each machine head side plate. This sprocket reverses the chain motion to allow discharge of weeds collected by the rake.

LOWER SPROCKETS:

A 28-mm-thick stainless steel sprocket is fixed to the lower end of each machine side. The sprocket is automatically greased for a few seconds at the beginning of every machine operation cycle. Grease flows through tubes to axial and transverse holes in the sprocket pin. It further flows to helical grooves on the internal surface of a copper sleeve secured to the sprocket.

CHAIN:

A 160-mm-pitch chain transmits motion from the drive shaft to the rake. The chain must be kept appropriately tight. While excessive tension impedes sprocket motion, a loose chain would be easily displaced from its location resulting in possible fracture.

RAKE:

The rake is meant to clear weeds off weed screens. It consists of an I-beam supported by an upper and lower 20-mm strips plus webs distributed along its length. A perforated back strip works as a weed support to avoid collected weed drop in water intakes. The rake front is equipped with 18-mm-thick 62-mm-pitch 50-mm-long tines with longitudinal fastening slots that allow for proper insertion between screen bars during mounting. The rake load carrying capacity amounts to 1000 kg. It travels at a speed of 8.5 m/min. The rake stroke varies according to water intake depth with a minimum of 5.95 m in the Maryout-2 station and a maximum of 10.20 m in Al-Boustan-1 station.

MACHINE FRAME:

The machine frame represents the stationary parts on which moving parts are mounted. The frame comprises a machine head, machine sides and retaining pipes.

MACHINE HEAD:

The machine head comprises two identical 25 mm-thick plates the distance between which is kept by a retaining pipe. Mounted on the machine head are the drive shaft, the two tension sprockets, the two bending sprockets, the geared motor with brake and the torque limiter.

MACHINE SIDES:

Two IPE-270 I-beams supported by retaining pipes form the right and left machine sides. Each side is fixed at its upper end to a machine head plate by six 20-mm-diameter 200-mm-long tightening bolts. The two lower sprockets are fixed to the lower ends. Greasing tubes necessary to grease the lower sprockets extend along the machine sides. A chain pocket is provided to keep the distance between the rake and the screen during weed removal and that between the rake and the slider after leaving the intake.

RETAINING PIPES:

Six-inch-diameter ten-mm-thick retaining pipes are used to keep the distance between the two machine head side plates and that between the two machine sides. A flange is welded to each end of the retaining pipes to allow for fixation. Three retaining pipes are fixed between machine sides except for the Boustan-1 Plant where increased intake depth called for the use of four pipes. A slightly longer pipe is used to support the machine head.