Overview of Plate and Frame Filter Press

With the deepening of China’s industrialization process, the plate and frame filter press is widely used in mining production. At the same time, mining enterprises pay more and more attention to the application of plate and frame filter press. In the wastewater treatment of sand and gravel system, the filter press is often used as the end mechanical treatment mode of solid-liquid separation, which filters the materials through pressure, especially for the separation of viscous and fine substances. Engineer Fodamon summarized the situation of plate and frame filter press as follows.

Composition of plate and frame filter press

Generally, the structure of plate and frame filter press mainly includes: passive sprocket, thrust plate assembly, filter plate compression plate, support, plate puller, compression plate assembly, oil cylinder seat assembly, driving sprocket, hydraulic station, electric control box, etc.

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Advantages and disadvantages of plate and frame filter press

The plate and frame filter press is mainly applicable to the suspension with high-pressure compressibility or near incompressibility of filter residue. Generally, the suitable concentration of solid particles in suspension is generally less than 10%, and the working pressure is generally 0.3MPa ~ 1.5MPa, which can reach 3Mpa or above in special cases.

Advantages: it has strong adaptability to materials, is suitable for the dehydration of small and medium-sized minerals in various occasions, and has the advantages of simple structure, convenient operation, flexible selection range of filtration area, less land occupation, stable operation and convenient maintenance.

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Disadvantages: the feed inlet of the filter frame is easy to be blocked, the processing capacity is small, the filter cake is difficult to take out, the continuous operation is difficult, the consumption of the filter cloth is large, and the square plate of ordinary materials is not pressure resistant and fragile. Therefore, the condition of the filter frame should be monitored in real time and the filter cloth should be cleaned manually.

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The main process flow of plate and frame filter press is as follows

(1) Press the filter plate: when the compression cylinder (or other compression device) works, move the moving plate to the fixed plate and press the filter plate between them. A closed filter chamber is formed between adjacent filter plates.

(2) Pressure filtration process: the slurry is transported to the filtration chamber by the feed pump. After filling, the pressure filter begins to operate. The solid-liquid separation is carried out by pressurized pump or compressed air pressure.

(3) Loosen the filter plate: use the pulling device of the equipment to separate the filter plate in a corresponding way.

(4) Filter plate unloading: after the filter plates are opened in turn, the filter cake falls off by its own weight and is transported through the lower conveyor.

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Common faults of plate and frame filter press

  1. The filter plate is damaged

Fault analysis: insufficient material supply, blocked feed pipe, no coal slime as buffer in the filter plate, and the filter plate will be damaged under extrusion pressure. The groove of the extruded water flowing through the filter plate is blocked, resulting in the failure of the medium to flow out and the damage of the filter plate. Excessive set extrusion pressure will also cause damage to the filter plate.

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Treatment measures: during operation, the central blowback time shall be sufficient. Check the filter cloth and filter plate regularly and clean up the residue in time. If the feed hole of the filter plate is worn, it shall be repaired with large particle glue or metal repair agent in time.

  1. Water seepage or material leakage between filter plates

Fault analysis: the hydraulic pressure of the hydraulic system is unstable and the feed pressure is high, resulting in excessive filtration speed of the feed liquid, holes and folds on the filter cloth, filter cloth or blockage on the sealing surface, filter cloth not cleaned as required or the cleaning effect does not meet the requirements, which are easy to cause water seepage or material leakage between the filter plates.

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Treatment measures: first, increase the corresponding pressure; If there is a problem with the filter cloth or sealing surface, replace the filter cloth in time and remove the sundries on the sealing surface; Secondly, clean the filter cloth in time; Finally, increase the feed pressure and reduce it to normal value.

  1. Uneven shape or thickness of filter cake

Failure analysis: insufficient or too thin feeding and blockage will lead to uneven cake shape or thickness. For these faults, we should carefully investigate the causes, finally find out the exact problems, and then deal with them according to the symptoms.

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Treatment measures: prepare sufficient materials to ensure the sustainability of materials; Improve construction technology and ensure material quality; Clean the filter cloth or replace it with a new one; Clean the drainage hole, clean or replace the filter cloth; Clean the blocked area of filter cake and clean the feed hole at the same time; Increase the pressure or power of the pump during operation; Start with low pressure and gradually increase the pressure in the process.

  1. The plate frame of the plate frame filter press is damaged

Fault analysis: firstly, when the material supply is insufficient or contains solid particles, the plate and frame will be damaged by excessive force. Secondly, when the filter plate of the filter press is not cleaned well, the medium will leak out and the edge of the plate frame will be washed into the small ditch.

A large amount of medium leakage leads to the failure of pressure rise and mud cake formation. Finally, if the flow outlet is blocked by solids or the feed valve or outlet valve is closed during start-up, there is no pressure leakage, resulting in damage.

Treatment measures: use nylon cleaning scraper to remove the mud at the inlet and outlet; Carefully clean the filter plate of the filter press and repair the filter plate of the filter press; Reduce the volume of filter plate of filter press; Check the filter cloth of the filter press, clean the water outlet, check the outlet, open the corresponding valve and release the pressure.

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  1. Slow movement

Fault analysis: because the guide rod is easily polluted by oil stains, the movement speed of the filter plate is reduced, and even the filter plate can not run along the track, which deviates and falls off.

Treatment measures: when the movement is slow, the guide rod shall be cleaned in time and coated with grease to enhance the lubricity of the guide rod. At the same time, be careful not to apply thin oil on the guide rod. Because the thin oil is not sticky and will not be well attached to the guide rod, the thin oil is easy to fall down and the lower part is very slippery, causing certain hidden dangers to the safety of operators.

  1. Hydraulic system failure

1) The oil pipe joint leaks oil. Limited by the working environment and service time, the oil pipe and joint will be aged after use for a period of time, and then oil leakage will occur. Replace the corresponding oil pipe.

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2) Low pressure and high pressure pumps do not work. The filter press cannot realize the closing and opening functions. Check the oil pump motor and its corresponding circuit module and replace the damaged parts.

3) The plate and frame filter press does not maintain pressure and cannot be closed. The failure of hydraulic system to maintain pressure is often caused by the failure of one-way valve, and the plate and frame filter press is no exception. At this time, check the check valve on the head main cylinder and replace the damaged check valve.

4) The solenoid valve does not act, the directional valve is blocked or worn and does not work, so it is impossible to operate according to the procedure. Replace the corresponding valve block.

5) The hydraulic cylinder crawls, there is noise, and the piston is worn. It may be caused by the air in the hydraulic pipeline, or it may be caused by the tight fit between the new oil cylinder and the sealing ring and excessive friction. For the phenomenon of air inlet, if there is no bleeding device, the air can be forcibly discharged. For excessive friction, apply lubricant to the master cylinder. The plunger surface is modified by chromium coating. Due to the long-term bare leakage of the plunger of the main oil cylinder, the surface is easy to rust due to the erosion of flushing water, the sealing surface is uneven, the sealing effect is poor, and it is easy to leak oil. Chromium coating treatment can resist water corrosion.

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6) The hydraulic motor does not work. The internal gear of the hydraulic motor is worn or the gear teeth are broken, causing the motor to not work. Replace the hydraulic motor.

7) There is oil leakage at the valve block joint. Replace the corresponding O-ring and the corresponding oil pump. Replace the corresponding solenoid valve and clean the oil flow hole of the directional valve. If the cylinder is worn, replace the master cylinder. Check the planetary gear in the hydraulic motor and replace the worn gear or hydraulic motor. Replace the sealing ring.

  1. High solid content of filtrate

Fault analysis: high feed pressure, damaged filter cloth or different types of filter cloth, short black water reflux time will lead to high solid content of filtrate.

Treatment measures: if the filter cloth is damaged or the model is inconsistent, the damaged filter cloth shall be replaced in time. High feed pressure leads to high filtration speed of feed liquid, which can reduce the feed pressure to normal value. Finally, extend the setting time of black water reflux time.

In daily production, the maintenance of plate and frame filter press should be strengthened to ensure its service life and improve production efficiency, so as to better serve the production of mining enterprises and create more value.

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