Analysis of common faults of plate and frame filter press

Abstract: The working principle of the plate and frame filter press is briefly described. The common faults of the equipment are listed. The reasons for the failure are analyzed and the corresponding maintenance plan is given.

The plate and frame filter press is a sludge treatment device in the sewage treatment system, and its function is to press-filter the sludge after the sewage treatment to form a large filter cake (mud cake) for elimination. The two plate and frame filter presses of the Handan Iron and Steel Sewage Treatment Plant are Swedish equipment, which is supplied by two screw pumps and two diaphragm pumps with a daily processing capacity of 3,500 tons of sewage. The plate and frame filter press consists of five parts: filter press filter plate, hydraulic system, filter press frame, filter plate transmission system and electrical system. The principle of the working operation of the plate and frame filter press is relatively simple. The hydraulically applied force presses the plate frame group, and the deposited sludge enters from the middle and is distributed between the filter cloths.

Due to the tightness of the plate frame, the sludge cannot overflow. Under the high pressure of the screw pump and the diaphragm pump, the moisture in the sludge leaks out of the filter cloth and flows into the return pipe, while the mud cake remains in the cavity. After the plate frame is relieved, the filter plate is pulled apart, and the mud cake is dropped by gravity and pulled away by the car. Therefore, the pressure filtration process is the last process in the sewage treatment process. The main parameters and data of the plate and frame filter press are: 125 plate frames, which can be expanded to 150 pieces (149 compartments), plate size 1300 × 1300mm, mud cake thickness 30mm, filtration area 297.6m2 filtration pressure 16bar, maximum The closing pressure is 368 bar.

When the plate and frame filter press is pressed, the pressure is 368 bar and the filtration pressure is 16 bar. During operation, the plate frame is continuously pressed, and the middle water oozes out from the sludge medium. Due to the large pressure, the plate itself and the filter cloth are prone to appear. Damaged or blocked. In addition, due to the contamination of the oily sludge, the transportation system is often stuck or unstable.

First, the damage of the plate itself. The reasons for the damage to the plate itself are:

1. When the sludge is too thick or the dry block remains, it will cause the blockage of the feed port. At this time, there is no medium between the filter plates, only the pressure of the hydraulic system itself is left. At this time, the plate itself is easily pressed for a long time. Cause damage.
2. If the supply is insufficient or the feed contains inappropriate solid particles, the plate frame itself will be stressed too much to be damaged.
3. If the outlet is blocked by solids or the supply valve is closed or the valve is closed when starting, the pressure is not leaked, causing damage.

4. When the filter plate is not cleaned, it sometimes causes the medium to leak. Once it leaks out, the edge of the plate frame will be washed out with a small groove. The pressure of the medium will not increase, and the mud cake cannot form. .

Corresponding method for troubleshooting:
1. Use a nylon cleaning blade to remove the mud from the feed port.
2, complete this cycle, reduce the filter plate volume
3. Check the filter cloth, clean the drain, check the outlet, open the corresponding valve, release the pressure
4, carefully clean the filter plate, repair the filter plate

The repair technology of the filter plate is as follows:

After a few years of use, the filter plate washes out some grooves at the corners for some reason. Once the groove marks appear, it will expand rapidly until it affects the formation of the filter cake. At first the filter cake became soft, then became semi-sludge, and finally the filter cake could not be formed. Due to the special material of the filter plate, it is difficult to repair and can only be replaced with new ones, resulting in high spare parts cost. During this period, we tried some repairing agents, but the effect has been bad. Recently, when the oil surface repairing agent was used, the situation finally turned, and the trial effect was very good, achieving the sealing effect. The specific repair method is as follows:

Repair steps:
1. Clean the groove, leak out the fresh surface, and clean it with a small saw blade.
2, black and white two repair agents in a ratio of 1:1
3. Apply the prepared repairing agent to the groove and apply it slightly higher.
4, quickly set the filter cloth, squeeze the filter plate together, make the repair agent and filter cloth stick together, while squeezing the groove
5. After squeezing for a period of time, the viscose is naturally formed and no longer changes. At this time, it can be used normally.

Second, the reasons for water seepage between the plates and frames cause water seepage between the plates:
1, low hydraulic pressure
2, filter cloth pleats and filter cloth with holes
3. The sealing surface has a block.
The method of treating water seepage between the plates and frames is relatively simple, as long as the hydraulic pressure is increased, the filter cloth is replaced, or a nylon scraper is used to remove the block on the sealing surface.

Third, the shape is not a filter cake or the filter cake is uneven

There are many reasons for the failure or unevenness of the filter cake. The supply is insufficient or too thin, or there is a blockage phenomenon. For these failures, it is necessary to carefully investigate the causes, and finally find the exact problem, and then solve the problem by symptomatic treatment. The main solutions are: increasing the feeding, adjusting the process, improving the feeding, cleaning the filter cloth or replacing the filter cloth, cleaning the blockage, cleaning the supply hole, cleaning the drain hole, cleaning or replacing the filter cloth, increasing the pressure or pump power, Low-pressure start, continuous pressurization and other methods.

Fourth, the filter plate is slow or easy to lose. Sometimes, due to oil stains and excessive stains on the guide bar, the filter plate will be slow to walk and even go off. At this time, it is necessary to clean the guide bar in time and apply butter to ensure its lubricity. It should be noted that it is strictly forbidden to apply thin oil on the guide rod, because the thin oil is easy to fall and the lower side is very slippery. The personnel who are here to operate and overhaul can easily fall, causing personal injury accidents.

5. Failure of the hydraulic system.
The hydraulic system of the plate and frame filter press mainly provides pressure. When the oil chamber A increases oil injection, the piston moves to the left, and the filter plate is pressed to seal it. When the oil chamber B is filled with oil, the piston moves to the right and the filter plate is released. Due to the precision of manufacturing, the hydraulic system has fewer failures, so just pay attention to routine maintenance. Despite this, due to the wear and tear, oil leakage-shaped seals appear every one year or so.

Common hydraulic faults are also unsuitable for pressure and hydraulic cylinder propulsion. The main reasons for the inability to maintain pressure are oil leakage, O-ring wear and improper operation of the solenoid valve. The usual treatment methods are to remove and inspect the valve, replace the O-ring, clean the check solenoid valve or replace the solenoid valve. The hydraulic cylinder is not suitable for propulsion. It is obvious that the air is sealed inside. At this time, as long as the system is pumping air, it can be quickly solved.