Area: Minning Maintenance Realibility
6.2.1 Filter Plate Repairs
R&B filters: These filters require extensive maintenance on the plates for several reasons.
The plates undergo continuous wear on the seal surfaces due to the lack of a good seal. This is due to the absence of an auto cloth wash after each cycle.
The wear surfaces are repaired by plastic welding and filling. After a while, this ?s no longer possible and the whole plate is taken out and sent away for resurfacing.
The air entry and filtrate discharge ports are not replaceable wear items; they are part of the whole plate. Any wear at these critical points means wear on the plate itself.
Damage occurs on the membrane plates. The rubber membranes are attached to the membrane plates by insertion of the sealing ring into the channel provided on the peripheries of the plates.
These channels are damaged by compression ?n time and membranes cannot be inserted anymore.
In general, plate repair is a continuous process. The plates are collected on site when they cannot be repaired with plastic welding, and are sent to Germany for resurfacing. ÇBI is looking for a local workshop to repair these plates.
MC LASTA filter: There are no membrane plates. Only chamber plates are provided. The air entry and filtrate discharge ports are replaceable units called filtrate rejecters. When worn, they are replaced. Their wear is also an indication of holes in the filter cloth.
To date, no plates have been damaged due to any other factors.

6.2.2 Cloth Change Comparison
R&B filters: The cloth is a single piece. Changing it is a time-consuming and fairly laborious job.
One part of the cloth has to be rolled, squeezed and passed through the feed opening of the plate so that it can be put on the other side of the plate.
Similarly, removing the old cloth is not easy as the cloth becomes harder and very difficult to roll back through the feed opening. It ?s common practice to cut the cloth when removing it from the plates.
MC LASTA filter: The cloth change is very easy. There are two pieces, which are hung on each side of a plate by hanging bars. The filter cloth assembly can be prepared in advance of cloth change. The odd-numbered plate cloth is equipped with a feeding device which is attached to the cloth before it is hung on the bars.

6.2.3 Plate-Moving and Shifting Mechanism
R&B filters: The chains located inside the traverse are equipped with shifter hooks, which glide over the carriages of the plate pack when the press is closed. When the press is opened, one of the shifter hooks engages, due to its own weight, on the last plate and unlocks this plate. The shifter hook now moves the plate suspended from the carriage fitted with offset rollers. This action is repeated until the last plate is opened. The offset roller movement is hindered by dirt accumulating inside the traverse rails, which are difficult to reach and clean. If the locking hooks of the carriages are not caught by the shifter hook of the chain in the proper order, men a group of plates shift together. This overloads the locking hook and the drive motor of the chain mechanism. The locking hook bends or the chain drive motor trips due to overloading. In short, the plate-shifting mechanism is complex.
MC LASTA filter: The plate-moving mechanism is rather simple. The plates are connected to each other by chains at four corners.
When the cylinder retracts, it moves the head plate backwards and the head plate pulls the rest of the plates one by one. The plates move freely on top of two side rails. The greasing of the rails makes it easy.

6.2.4 Washing System Maintenance
RifeB filters: The washing mechanism is a separate unit. It has a trolley with a moving chain and washing device. A geared motor is provided for the longitudinal and the wash travel drives. Both the washing device and the plates have to move to wash the cloth. The problems with plate moving continue during cloth washing. Each washing takes about 45 minutes if there are no problems with plate movements or washing device movements.
The cloth wash is a manual process. The filter has to be stopped and the control unit is changed to cloth wash mode. It is not practical to wash cloth after each cycle since one wash takes 45 minutes.
In addition to these problems, the washing device catches the filter cloth and sometime damages it while the sprays are in upward motion.
MC LASTA filter: The cloth wash is part of the auto cycle; it takes 40 seconds to wash all 41 plates and 40 chambers. Each plate is equipped with three cloth wash sprays as an integrated part of the cloth support bar. Water from the spray water header is connected to the cloth support bars on the even numbered plates by hoses. Wash nozzles direct wash water over the cake side of the filter cloth.

6.3 Safety and Environment
6.3.1 Leaks and Noise from Filter Plates R&B filters: Sealing surfaces deteriorate due to poor cloth washing, especially at the bottom of the plates. Cake remnants deteriorate the sealing surfaces. When the filter comes to the cake blow cycle, the compressed air leaks through these surfaces, creating dust and a shrill whistling noise. The cloth is also damaged by these surfaces.
MC LASTA filter: There is no sealing problem. The effective cloth-washing system after each cycle cleans all the surfaces of the plate. There are no leaks and there is no whistling.

6.3.2 Position and Access to Plates
R&B filters: The working platform is level with the bottom of the plates. This is necessary due to the operator assistance required in cake discharge.
In order that the top of the plates can be reached, a ladder is provided. The operator or maintenance personnel have to put on a safety belt while working on top of the filter.
MC LASTA filter: The working platform ?s located on top of the plates. The support rails, spray nozzles and cloth change bars are all accessible without the need for any safety equipment. One operator can change a filter cloth.