FIELD OF THE INVENTION

The present invention relates to a system for filter cloth handling in a filter plant as defined in the preamble of claim 1 , and to a method for filter cloth handling in a filter plant as defined in the preamble of claim 18.

BACKGROUND OF THE INVENTION

Many types of filters, such as membrane filter presses, drum filters and horizontal and vertical pressure filters utilize filter cloths to separate solids from liquids. When in use, the filter cloths clog up and need to be cleaned. The cleaning can be done in the filter, but after a certain time or number of operating cycles, depending on the application, the filter cloths need a more thorough cleaning and need to be removed from the filter. Also, filter cloths wear or may sometimes be damaged and need to be replaced from time to time.

A large filter plant may comprise tens of filters and each of the filters may comprise tens of filter cloths. Since some of the filter cloths are always being cleaned or inspected while others are used in filters, the total number of filter cloths in a single filter plant may be thousands. During their life time, the filter cloths pass through various locations. Conventionally, the monitoring, cleaning and inspection of the filter cloths has required a lot of manual work, since there have not been a system and method for the filter cloth handling that could have been to a large extent automated. Furthermore, it has been difficult to follow the life-cycle of a single filter cloth or to collect data regarding the average lifetime or other properties of the filter cloths in the filter plant.

BRIEF DESCRIPTION OF THE INVENTION

The object of the invention is to solve at least some of the problems described above by providing a system and a method for filter cloth handling in a filter plant. Features that are characteristic to the system according to the present invention are presented in the characterizing part of claim 1 . Features that are characteristic to the method according to the present invention are presented in the characterizing part of claim 18. Features of the embodiments of the present invention are presented in the dependent claims. The system for handling filter cloths in a filter plant according to the present invention comprises at least one filter where the filter cloths being equipped with identifiers or means for data storing are used, at least one rack for dirty filter cloths, at least one rack for clean filter cloths, means for reading the identifiers, a data system and means for storing cloth specific data. The word 'rack' refers to any kind of means that can be used to store and/or move the filter cloths in the filter plant. The invention has several advantages. Since each filter cloth is equipped with an identifier or means for data storing and the system comprises means for storing cloth specific data, it is easy to collect different cloth specific data for various purposes. These data can be used for example to monitor the performance or lifetime of the filter cloths or for spare part management. It is also easier to select suitable filter cloths for each application, forecast cloth demand or prepare automatically a cloth purchase proposal based on the collected data. Effective utilization of data will lead to lower operating costs.

The method for handling filter cloths that are equipped with identifiers or means for data storing in a filter plant according to the present invention comprises at least the steps of moving dirty filter cloths in cloth racks from the filters to a washing station, delivering clean cloths in cloth racks to the filters, cleaning the dirty cloths at the washing station, inspecting the cloths after the cleaning, replacing faulty cloths with new or cleaned and undamaged cloths, and storing the cloth specific data in the memory of the identifiers, means for data storing or a data system. The method for handling filter cloths has the same advantages as the system described above.

Below, there are presented some features of the embodiments of the invention. Although they are presented in connection with the system according to the present invention, many of them can also be applied to the method according to the present invention.

According to an embodiment of the present invention, the system comprises at least one rack for new filter cloths. According to another embodiment of the invention, the system comprises at least one rack for faulty filter cloths. Because of the racks for new and faulty filter cloths, faulty filter cloths can easily be removed from the racks for cleaned filter cloths and replaced by new filter cloths, preferably automatically. According to an embodiment of the invention, the racks for the filter cloths are equipped with identifiers and the system comprises means for storing rack specific data. According to another embodiment of the invention, the identifiers in the cloths and/or the racks can be read contactless and are preferably RFID tags. Identifiers in the cloth racks allow monitoring and storing of data that is specific to a certain set of filter cloths. The use of Radio Frequency Identification (RFID) tags allows reliable reading and writing of data.

According to an embodiment of the invention, the cloth and/or rack specific data is stored in the identifiers. According to another embodiment of the invention, the cloth and/or rack specific data is stored in the memory of the data system. Depending on the application, it is possible to choose either identifiers that can be used to store data or identifiers without this possibility, in which case the data is stored in the memory of the data system.

According to an embodiment of the invention, the system comprises a washing unit for the filter cloths. According to another embodiment of the invention, the system comprises means for inspecting the filter cloths. It is preferable that the system comprises a washing unit and means for inspecting the filter cloths, but is also possible to do the washing outside the filter plant and inspect the filter cloths manually.

According to an embodiment of the invention, the system comprises automated means for moving the racks between different locations in the filter plant. According to another embodiment of the invention, the system comprises means for automatically replacing faulty filter cloths or filter cloths of which planned life time has expired with new or cleaned and undamaged filter cloths. Because of the full automation of the filter plant, the operating costs can be reduced significantly.

According to an embodiment of the invention, each of the filters is equipped with a read/write device that can be used to read and store cloth and/or rack specific data. This allows storing for example data regarding the number of filtration cycles or different process parameters.

According to an embodiment of the invention, the system comprises a storage for filter cloths, which storage is equipped with a read/write device that can be used to read and store cloth and/or rack specific data. According to another embodiment of the invention, one read/write device that can be used to read and store cloth and/or rack specific data is in connection with the inspection unit or in the proximity of said inspection unit. In different locations of the filter plant, different data can be stored and used later on for various purposes, for example for spare part management.

According to an embodiment of the invention, at least some of the following cloth specific data is saved in the memory of the filter cloth identifiers or in the data system: arrival time of the filter cloth to the filter plant, date of the first usage of the filter cloth, type of the filter cloth, number of overall operating cycles of the filter cloth, number of operating cycles in different filters, number of operating cycles after last cleaning or date of the last usage.

According to an embodiment of the invention, at least some of the following rack specific data is saved in the memory of the rack identifiers or in the data system: number of the cloths in the rack, types of the filter cloths in the rack, average life time of the cloths in the rack or last position of the rack.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

A preferred embodiment of the invention is now described with reference to the drawing. Fig. 1 shows a schematic view of an embodiment of a system according to the present invention. Filter cloths arrive from the cloth manufacturer to the filter plant and are stored in racks for new filter cloths in a cloth storage. Each filter cloth is equipped with an identifier that can be used to identify the cloth and possibly also for storing data. Although it is preferred that each cloth can be identified, the system can work even without identification, if the cloth specific data is stored in data storing means that is attached to the cloth. Although the word 'identifier' is used in this description, it will be appreciated by a person skilled in the art that in many embodiments of the invention also other means that can store cloth or rack specific data could be used. The identifiers can be for instance Radio Frequency Identification (RFID) tags, which can be read and written contactless from a distance. Many types of RFID tags are commercially available from different suppliers and could be used in the filter cloths, providing that they resist the pressure, temperature and possible bending in the filters. The identifiers can be attached either directly to the filter cloths, or alternatively to some other part that is fixed to the filter cloth and follows the same cloth through the whole cycle in the filter plant. For instance, if the filter cloths are attached to a hanging bar and are removed from the filters together with the bar, the identifiers can be located in the bar. Another option for the placement of an identifier could be a filling shoe that is attached to a filter cloth.

Also the racks for the new filter cloths are equipped with identifiers. When the filter cloths arrive to the filter plant, information regarding for example the properties and the supplier of the cloths and the arrival date is stored in the memory of the identifiers or the data system. The number and type of the filter cloths in each filter cloth rack is also stored in the memory of the data system or the identifier in the rack. The storage for filter cloths is equipped with a read/write device that can be used to store data in the memories of the identifiers in the filter cloths and the racks. The same device also detects when a filter cloth rack leaves the storage. The racks with new filter cloths work as repair racks, from which new filter cloths can be taken to replace faulty filter cloths or cloths with expired lifetime. In the system presented in Fig. 1 , the filter plant comprises three filters. The filters can be either continuously operating filters, such as drum filters, or filters with discontinuous operation, such as vertical or horizontal pressure filters or membrane filter presses. Preferably the filters are equipped with washing devices that can be used to clean the filter cloths after a certain number of operating cycles or after some predefined operating time, or alternatively when it is noticed that the performance of the filter has worsened. The filters are equipped with read/write devices that can be used to store different data regarding the operation. The read function is used to identify the filter cloth and the write function is used to store data. For instance, when a new filter cloth is put into the filter, the read/write device identifies the cloth and stores into the memory of the identifier or the data system the date of the first usage. The filter also counts the number of operating cycles, and when the cloth is removed from the filter for cleaning, the number of operating cycles in that particular filter is stored in the memory of the identifier or the data system. Also the number of operating cycles after the last cleaning and the total number of operating cycles are counted and stored in the memory. When the filter cloths become so badly clogged up that they cannot be cleaned effectively enough using the washing devices in connection with the filters, the cloths are removed from the filters and moved to the racks for dirty filter cloths. An automated crane or a similar means can be used for the purpose of removing the cloths from the filters. At this point of the process, the cloths with expired life time can be separated from the other cloths. Alternatively, all the cloths can be put into the cloth racks for dirty filter cloths and the cloths with expired life time can be removed from the racks at another location. The rack with dirty filter cloths is moved to the washing unit, where the dirty filter cloths are thoroughly cleaned. Preferably the washing unit and the racks are so designed that it is not necessary to remove the filter cloths from the racks but the cloths can enter the washing unit in the racks. After the washing, the cloths are inspected and faulty cloths are removed from the rack and put to the rack for faulty filter cloths. Another option is to inspect the cloths before the washing, but at least in case of visual inspection the inspection is easier to make for cleaned filter cloths. Inspection can be done manually or using suitable technical means, for instance optical devices. After the removal of faulty cloths, a corresponding number of new cloths are moved to the rack with cleaned cloths from a repair rack. Preferably, the type of the failure in a faulty filter cloth is defined and stored in the memory of the data system. This data can later be used for product development purposes or for selecting suitable filter cloths for different filters and applications. When the rack for faulty filter cloths is filled up, it can be moved to a location where the faulty cloths are disposed. After removing the faulty filter cloths from the rack, the empty rack is returned to the filter cloth storage to be used again for new filter cloths. Alternatively, the rack can be returned to the location where the cleaned cloths are inspected and faulty cloths are removed from the cycle. When the repair rack is empty, it can be returned to the cloth storage or serve as a rack for faulty filter cloths.

When the cleaned filter cloths have been inspected and faulty filter cloths have been removed from the rack and replaced by new filter cloths, the rack is ready to be moved to the filters, where the dirty filter cloths are again replaced with cleaned cloths.