Belt Press System Breakdown
A. Main Frame
D. Steering Assemblies
E. Tensioning Assemblies
F. Hydraulic Power Unit
G. Feed System
H. Gravity Drain Section
I. Wash Stations
K. Drive Train
L. Dewatering Belts
M. In-Line Mixer
Main Frame: A rigid, self-contained, steel structure consisting of side frames and cross members. The frame resolves the dewatering pressures into vertical loads that are transferred to the foundation. While the frame maintains the structural integrity of the machine, it relies on the foundation to hold the machine level and preserve the alignment.
Rollers: Fabricated assemblies that provide a bearing surface for the belts. The roller shafts (journals) are machined on both ends to accept the roller bearings. The rollers may be any of the following types:
(1)Perforated Roller: roller with a perforated shell with open ends to allow the water to be drained away quickly.
(2) Plain Roller: any non-perforated roller of varying diameter with the job specified covering. Used as steering rollers, tensioning rollers, pressure rollers, nip rollers, or as idler rollers.
(3) Drive Roller: Rubber coated rollers used to pull the dewatering belts through the press.
Bearings: Bearings support the rollers on both ends and maintain parallel roller alignment. The cast iron bearing housing is split horizontally to allow access to the bearing without disturbing the bearing alignment. All bearing housings incorporate button-head grease fittings for maintenance purposes. The steering bearings are direct mount, straight bore, cylindrical roller bearings. All other bearings are direct mount, double row spherical roller bearings. The bearing shaft seal is a triple seal comprised of the labyrinth, an electrometric face seal and quad ring. For additional moisture protection, the seal is covered by a shaft-mounted splashguard.
Steering Assemblies: The Belt press has two hydraulic steering assemblies each comprised of a steering roller and a hydraulic or positioning unit. The steering assemblies monitor the positions of the two dewatering belts that go through the pressure zone of the press and make adjustments to maintain belt alignment in the center of the machine. The steering assemblies work by moving one end of the steering roller so that the steering roller is turned to a small angle relative to the belt direction. The belt responds to this change in angle by moving toward the end of the roller it touches first. The components of the steering assemblies are:
(1) Hydraulic Positioning Unit: The unit has a belt position-sensing paddle that is constantly in contact with the belt. This paddle turns a hydraulic valve that adjusts the flow of hydraulic fluid to a hydraulic steering cylinder. As the cylinder responds, the steering roller position is altered. The stainless steel sensing paddle has a ceramic wear plate to protect the belt edge.
(2) Steering Roller: The steering roller is a smooth faced roller with cylindrical roller bearings. The bearing housings are attached to swivel plates to accommodate the roller movement. This arrangement avoids seal misalignment when the steering roller moves.
Tensioning Assemblies: The two belts that do the pressing each have a hydraulic tensioning assembly that consists of two hydraulic cylinders, a tensioning yoke and a two-position, four-way control valve.
In a three-belt press option the independent gravity section belt has tension applied by compressed springs. There are adjusting screws on each end of the gravity deck tension roller. The belts may be tensioned or retracted at the control valve on the belt press. The amount of belt tension is regulated at the pressure regulator on the pump head. An optional dual control manifold regulates the upper and lower belt tensions independently. The regulator knob on the head of the hydraulic pump controls the upper belt tension. The regulator in the end of the hydraulic control manifold controls the lower belt tension. Tension indicating pressure gauges are provided for each belt. The individual tensioning components are as follows:
(1) Hydraulic Cylinders: Respond to changes in pressure from the hydraulic pump and pushes or pulls on the tensioning yoke to increase or decrease belt tension. There is one hydraulic cylinder on each end of both tensioning yokes.
(2) Tensioning Yoke: A fabricated steel assembly supporting the tensioning roller. The tensioning yoke has a hydraulic cylinder on each end of the yoke that transfers the force from the cylinders to the belt by moving the tensioning roller closer to or further away from the frame. The tension yoke maintains absolute equal belt tension across the entire width of the machine.
(3) Control Valve: A two-position, four-way valve, which regulates the flow of hydraulic fluid to the hydraulic cylinders in the tensioning and steering assemblies. The hydraulic lines connecting the valve to the tensioning cylinders have independent shutoffs to isolate the individual belts.
On the Belt press with the optional independent belt tension control manifold, two control valves are provided in the manifold, one for each belt and the isolation valves are deleted.
Hydraulic Power Unit: an assembly of press mounted components that provide all hydraulic power for operation of the steering and tensioning assemblies. The unit consists of a 1-gallon reservoir suction strainer, pump-motor assembly and control valves. The pressure gauge is dual scaled for hydraulic pressure in pounds per square inch (psi) and dewatering pressure in pounds per linear inch (pli). The normal operating limits shall not be exceeded any time during the operation. The operation shall be in the green area of the gauge.
A constant speed motor powers the variable displacement hydraulic pump. The hydraulic pressure is adjusted by regulating the pressure regulator on the pump. Hydraulic oil is filtered through the externally mounted suction filter.
Depending upon the specific site installation, an optional manifold may be installed after the hydraulic pump. This contains the valves and pressure regulators to provide independent belt tension control.
Feed Assembly: Stainless steel assembly that distributes the incoming sludge across the belt to begin gravity dewatering. The feed distribution assembly has a standard ANSI flange for connecting to the sludge feed line. The three-belt option uses a flooded bottom feed box with an overflow weir. The feed box has drains on the lower corners.
Gravity Drain Section: Consists of the horizontal drainage grids, sludge plows, the drainage trays and piping, and the sludge restrainers.
(1) Drainage Grids: Series of polyethylene strips arranged in a chevron pattern that support the dewatering belts. The strips are installed on a steel grid above the drainage trays. The polyethylene provides low friction wiper bars for removing excess water from belts.
(2) Chicanes plows: angular wedge plows that turn the sludge and provide clear openings for the free water to drain into the drain pans. They pivot independently on the support bar that allows them to float directly on the belt and ride smoothly over the belt seam. This minimizes belt wear and prevents obstructions from blocking the sludge flow.
(3) Drainage Trays: Assortment
of stainless steel pans that collect the filtrate for piping to the machine
sump. The piping is designed to be self-venting to provide maximum
(4) Sludge Restrainers: Stainless
steel guides that prevent sludge from running off the sides of the
dewatering belts. The sludge restrainers are fitted with a neoprene
strip seal at the bottom to maintain the seal between the belt and the
Wash Stations: There is a slotted stainless steel box containing the wash spray tube for each belt. The wash spray tube generates an overlapping spray pattern from the jet nozzles to blast embedded and surface particles from the belt. The wash tube has an internal brush for cleaning the nozzles while the machine is running. The wash station entry and exit slots are covered with seals to protect the belt and to prevent over spray escaping from the wash box.
Scraper (Doctor) Blades: Each belt has a scraper assembly fitted with polyethylene blades mounted in pivoted steel blade holders. The scraper blades remove the dewatered sludge cake from the dewatering belts. The scrapers are held against the belt by patented over-center spring-loaded levers. The spring preload is set at the factory at the time of assembly and does not require any field adjustment.
Drive Train: The base model Belt press has a single drive roller with a shaft mounted gear motor. This is a self-contained helical gearbox with its own splash lubrication system. There are options for dual drives and a three-belt arrangement with its own drive assembly. The shaft mounted belt drive gear motor(s) pull the belts through the dewatering press by rotating the drive roller(s). See the Drive Train details in section 10 for more information on the motors and gear reducers. The drive train receives its initial input from a variable speed drive unit. This allows the speed of the belts to be varied from approximately one to 5 1/2 meters per minute. With the Aquabelt conversion the belt drive(s) use higher horsepower motor(s) for the necessary increased speed. The drive on the independent gravity belt in the three-belt option provides belt speeds up to 40 meters per minute. The operating belt speeds will be set by the operator depending on the dewatering conditions. All the above drives use an electronic variable frequency drive for speed control. A mechanical variable drive is also available, but can only be used on presses with a single drive since it would not be possible to correctly match the speeds between two mechanical drives.
Dewatering Belts: Polyester woven mesh joined by a stainless steel clip to form an endless band.
In-Line Mixer: Self-cleaning variable orifice venturi mixer used to condition the sludge prior to dewatering. The mixing energy may be varied independently of the flocculation by moving the mixer arm and counterweight.