Patent Application
20100234983
The present invention relates to a control system for a pneumatic transport system for granular materials. More particularly, the present invention relates to a control system for a transport system of granular materials that operates under positive or negative pressures, which cause the granular material to be transferred from one or more central storage points to one or more local storage points situated in different locations, or to one or more points of use such as dehumidification hoppers, mixing systems, processing machines, or other pieces of equipment.
A pneumatic transport system for granular materials essentially includes a unit that generates a positive or negative air flow along one or more pipes connecting one or more granule storage points, sometimes identified as sources in the trade, to one or more destination points, sometimes identified as containers in the trade. A number of other devices may also be included within the transport system, for example, sorting and selection systems, valves for duct cleaning, mixing valves, etc.
Throughout the present description and in the appended claims, reference will be made to “granular materials” or “granules.” A person skilled in the art will appreciate that such terms are meant to include also materials having structures similar to granules, for example, chips, re-milled materials, or powdery materials.
The air flow, whether of positive or negative pressure, moves the granules from the sources to the containers, where the material becomes available for transport to points of use situated downstream, for example another storage unit, a dehumidification hopper, a mixing unit, a processing machine or other types of equipment. An intermediate buffer hopper collecting of the granular material may be provided between the containers and the final point of use, allowing the downstream point of use to be supplied with a desired amount of material for a predetermined period of time even with the upstream container is empty or is undergoing a filling cycle.
The control of the entire system is typically entrusted to a centralized logic control unit, which exchanges information with peripheral units, such as containers, pressure/vacuum units, etc., through a serial or similar connection. The serial connection line must be installed throughout the plant in order to link all components of the system.
The prior art generally teaches two alternative system for starting up and for performing a container filling cycle.
The first system in the prior art may be defined as a “time-limited filling system,” in which the container filling cycle is triggered by a sensor that signals that the container is empty or that a material inside a hopper located below the container has fallen below a predetermined threshold.
The duration of the filling process is typically set by trial and error by an operator that uses a switchboard and that attempts to achieve an optimum filling cycle, such to avoid an excessively long loading cycle and a clogging of the ducts conveying the granules.
Therefore, the evaluation of the duration of the filling process is inherently limited by its essentially manual nature and a series of empirical tests must be performed before a fine tuning of the process may be achieved, with the consequent waste of time and material.
Further, the parameters of this system are not necessarily constant over time, both because of structural aging of the system (particularly due to clogging of the filters of the transport unit or of a filter separating the air from the granules inside the container) and because of possible variations in granule flowability caused, for example, by different lots of material or variations in environmental conditions.
Still further, transport time must be adjusted manually for each change in the type of transported material or when a partial filling is desired, that is, when the containers are not to be filled completely. This may occur, for example, when the amount of material requested downstream of the container is decreased, or when the same container must feed at the same time two users having different processing capacities. If load exceeds consumption, the material may be retained in the container/buffer hopper system, and if the granule had been previously dehumidified or simply heated, too much humidity may be reabsorbed or an excessive cool down may occur.
In the second system in the prior art, a start-up of the filling cycle is performed similarly to the first system, but the filling cycle is terminated when the granules inside the container reach a predetermined threshold, which may be detected by a sensor.
This second system offers the advantages of eliminating or reducing the time and material required for setting up the system and of reducing dependence from the level of maintenance of the system, but does not resolve the inability of the system to change the amount of fill material without resetting the system, because the sensors are typically placed in fixed positions or can only detect a predetermined level of material that has been set manually by the operator.
Another limitation of the systems in the prior art is the low reliability of the level sensors and the high costs of the sensors, especially for heated granules. Sensitivity of the sensors also tends to be highly affected by the type and color of the granule to be detected, and reference values of these sensors often change over time, requiring periodic re-settings.
The logic control of the transport system is generally based on one of two architectures.
A first method of control is sometimes referred to as “centralized logic method.” In this architecture, the central processing unit generally collects all inbound information from the peripheral units, processes such information, and finally broadcasts commands to all system components. As a result, the system components behave as “slaves,” that is, are typically configured only to send information to the central processing unit and to receive commands from it.
A second architecture is sometimes referred to as “distributed logic method.” In this architecture, the central processing unit still collects information, processes it and broadcasts commands to all system components. The system components, however, can execute certain local functions without being managed by the central processing unit, for example, can interrupt an ongoing filling cycle when the local sensor detects that the material has already reached a threshold or when the time elapsed for the filling cycle exceeds a predetermined value.
In both cases, every system component connected to the serial communication network requires a unique physical address, which is set up manually by the operator during installation, for example, using dip-switches.
A limitation common to all the systems in the prior art is the complexity of the required wiring. In fact, in both the centralized logic and in the distributed logic solutions, installation of the required communication wiring causes significant hardware and labor costs.
Further, installation time, allocation of addresses and debugging of the system, as well as the time needed to fix possible connection and/or addressing errors cause additional costs that affect the profitability of the system.
Still further, wiring and installation require spaces that significantly affect machine layout and the position of the granule containers feeding downstream machines.
It is an object of the present invention to provide a control system for a pneumatic transport system of granular material that includes a plurality of containers.
It is another object of the invention to provide an automated management system for filling containers disposed within a transport system of granular materials, thereby reducing to a minimum or eliminating the manual operations involved in setting up and configuring the system before start-up and also the manual processing required to modify operating parameters according to local conditions or to the type of transported material when the system is already operating.
A transport system constructed according to the principles of the present invention may include a wireless communication network instead of or together with a traditional wired network for interconnecting the individual components of the system.
The high degree of automation of the control system according to the invention is achieved by continuously monitoring the weight of a container during the filling cycle, such to determine when the filling must start and when it must be interrupted once a pre-established amount has been reached.
More particularly, a system according to the invention provides for monitoring a container through a series of statistical parameters related to effective filling time, weight of the transported material and, consequently, flow rate of the incoming material. In the event that a filling cycle in progress has one or more parameters, such as time and/or other parameters, that fall outside of the values contained in saved historical data, the system can warn a supervision system, the centralized control system, and/or an operator connected to a communication network (wired or wireless) through portable terminals. If, for example, the time required for the filling cycle and measured by timers is significantly longer than a statistical value processed by the system, an alarm can be generated to warn of possible problems along a transport duct or of lack of material in one of the sources.
In addition, the system is self-teaching with regard to the consumption of material per unit of time, or the flow rate of the outgoing material released by each granule container.
Measurements can be executed locally with weighing instruments connected to a control card coupled to each container, or remotely with the centralized control unit and/or with a supervision system, which can obtain data regarding weights at pre-established intervals for each node or container interconnected within the network. In the event that a simultaneous filling of two or more containers is required, instead of following, for example, a FIFO-type logic (First In First Out) to manage the first emptied container, filling priority may be given to the container with a higher historical flow rate.
This configuration makes it possible to determine whether a request for material from a user (the outbound material flow rate) is slowing down and thus intervene by reducing container load amounts, so to maintain a proper temperature and degree of humidity in the granules.
Likewise, filling amounts may be managed if, by gathering data about the state of the granule (such as temperature and humidity) through suitable sensors properly installed in the container, a possible degradation of the material (such as excessive cooling, humidity reabsorption, etc.) is detected.
By using a system according to the invention, material consumption may be determined with precision, allowing the storage of work data, the forecasting of consumption and the installation of alarms to monitor the material remaining in the sources, for example when the source is an external silo, the refilling of which requires reserving a tank truck well in advance.
The amount of the transported material may be managed by equipping the containers with one or more weighing instruments, and additionally with a set of sensors to detect or measure humidity, temperature or other parameters. All these instruments provide the management system with sufficient information to generate system archives, alarms, forecasts and information on the state of the system.
The new control system for managing a plurality of granule containers may use wireless technology for communicating between the central processing unit and the peripheral units or containers based on a protocol that can automatically recognize each unit upon connecting with the communication network. Moreover, the wireless protocol allows the automatic allocation of a unique address for each device connected with the communication network.
A wireless network technology according to the invention may include “self-healing” functions in the event of temporary or permanent failures of local control cards coupled to the containers.
The use of a wireless network further allows access to the network with portable or similar devices having wireless network interfaces which, once connected to the control network, enable an operator not only to collect and configure the containers or nodes of the network in the immediate vicinity but also to perform such operations for any remote container or node included in the network.
A wireless network generates a significant reduction in system costs with respect to a granule transport system that is based on a wired communication network and provides a number of advantages that include:
speed of installation of the system because there is no longer the need to physically lay network cables;
lower system costs because there are no network cables;
lower installation costs because the positioning of network cables imposes a significant limitation in the layout of machines and granule container systems feeding those machines; and
elimination of incorrect configurations caused by typical connection errors of cabled networks, such as network cables incorrectly coupled to the connectors, a mistaken positioning of electrical conductors in the network cables, possible disconnections and accidental cut-offs of cables.
These drawings constitute a part of this specification and include exemplary embodiments of the invention, which may be embodied in various forms. It is to be understood that in some instances various aspects of the invention may be shown exaggerated or enlarged to facilitate an understanding of the invention.
Detailed descriptions of embodiments of the invention are provided herein. It should be understood, however, that the present invention may be embodied in various forms. Therefore, the specific details disclosed herein are not to be interpreted as limiting, but rather as a representative basis for teaching one skilled in the art how to employ the present invention in virtually any detailed system, structure, or manner.
The present invention relates to a control system for equipment that transports granular material pneumatically and that stores the granular material. A system configured according to the principles of the present invention includes a highly automated management system for loading a plurality of containers and reduces to a minimum or entirely eliminates manual settings and configurations during start-up, as well as the steps required to modify operating parameters when conditions or types of materials to be transported change.
A control system according to the present invention may employ a wireless communication network instead of a traditional wired network for interconnecting the individual containers or nodes.
For the sake of simplicity, the following description relates to pneumatic transport equipment based on negative pressure, which is illustrated in
Moreover, transport equipment will be described herein, which is controlled by a “distributed logic” system (
A person skilled in the art will recognize that the control system described herein is applicable also to pneumatic conveying systems and plants that are controlled through a “completely centralized logic” system. Hybrid solutions are possible, in which control is centralized for certain aspects, governed mostly by a central control unit, and decentralized for other aspects, in which a part of the control is delegated to local controller 5, which may be a microprocessor card.
The high degree of automation of the transport system of the present invention is achieved by continuously monitoring the weight of every granule container, which, once the tare weight is recorded, determines material weight inside each container and, consequently, an evaluation of the amount of granular material that has been transported.
Thus, load measurement may be performed either locally through a control card which is coupled to granule container 5 and to which one or more weighing units are connected, or remotely through centralized controller 6, which is configured to acquire weight data at predetermined time intervals by interrogating local controllers 5 coupled to individual nodes or containers 2 and interconnected within a network.
Every granule container 2 or the respective buffer hopper 3 may additionally be equipped with a plurality of sensors 9 for detecting or measuring temperature, humidity or other parameters, as described in greater detail below.
Real time information on the weight of the granular material inside container 2 may be processed by the control system, in its local 5 or central 6 unit, firstly to determine when container 2 is empty (
In general, the amount of granular material provided during a refilling cycle may be determined by one or more control algorithms.
The filling and control situations illustrated in
Once the filling process of container 2 has begun, weight information is provided in real time and is used to determine the moment when the filling cycle must be interrupted because a maximum level has been reached. Related data may be employed in several ways, two of which are described hereinafter.
In a first method of determining duration of a fill cycle, the filling is “time-limited,” but, differently from the prior art, filling duration is not set manually by the operator but instead is calculated by the control system on the basis of a statistical processing of weights and durations of the previous filling cycles.
In a second method of determining duration of a fill cycle, the filling is interrupted as soon as the weight of the material inside the container reaches a predetermined value (
Statistically processed historical data on the weight of every filling of container 2 and on the time required to complete such filling is used by the control system, whether local 5 or central 6, to determine an average time limit, within which the filling cycle must be completed and, consequently, an average rate of material inflow rate to receiving container 2. In the event, for example, that the filling cycle in progress lasts longer that the statistically processed average time limit value, and by a percentage larger than a predetermined tolerance value, an alarm alerts of possible problems in the transport duct, of an irregular fill due to the defective closure of the discharge flap 11, and/or of lack of material in one of the sources.
If receiving container 2 is not filled within the time that has been predetermined based on average reloading time, local controller 5 coupled to receiving container 2 can independently decide to extend the filling time to add the missing amount of material. This extension of the filling time, identified also herein as extra time, is a supplemental period of time added to the predetermined time.
The statistical processing of historical data on the weight of every fill, the time necessary to complete the fill and the interval of time between fills may be used by the control system, either local 5 or central 6, to estimate with sufficient precision the consumption of material per the unit of time or flow rate of outbound material from each granule container 2.
In the event that the simultaneous filling of two or more containers 2 is required, instead of following a FIFO-type logic (First In First Out) to manage the first emptied container, filling priority may be given to the container with a statistically higher outbound flow rate.
Moreover, a system according to the present invention is configured to determine whether demand of material from the point of use is slowing down, if, for example, the time elapsed between fills is increasing with respect to the values between preceding fills. In an embodiment of the invention, the system may decrease the weight limit set point, thereby reducing the refill amount, in order to preserve its desired temperature and dew point values.
The control system may also intervene on the fill amount if, by gathering data on the state of the granule, e.g. temperature and humidity, through suitable sensors, e.g. temperature and dew point, installed in suitable positions 9, a degradation of the granules such as excessive cooling, humidity reabsorption, etc, is detected.
As shown in
The statistical processing of information related to weight, duration of each fill cycle and time intervals between fill cycles provides for a precise determination of consumption of material through the transport system over time, the creation of historical work archives, the generation of consumption forecasts, and the positioning of alarms for restoring material in the initial sources. In accordance with the configuration illustrated in
As shown, a plurality of granule containers 2 that are provided as components of a transport system may be controlled through a centralized or decentralized control architecture. Either architecture is implemented through a communication network that transmits commands and coordinates container refilling operations, the interchange of information within the network, and/or the collection of data detected by the plurality of local controllers 5. As an alternative to a traditional wired network, the present invention provides for a wireless communication network interconnecting the granule receivers, each of which constitutes a node of the network.
The advantages of a wireless communication network with respect to a wired communication network include:
lower system costs because there are no network cables;
lower installation costs because there is no positioning of network cables;
speed of installation of the system, because network cables no longer need to be physically installed; and
elimination of incorrect configurations due to typical connection errors of cabled networks, such as network cables incorrectly coupled to the connectors, a mistaken positioning of the electrical conductors in the network cables, possible disconnections, and/or accidental cut-offs of cables.
A feature of the wireless communication network employed in the present invention is that the interconnection topology of the nodes may be configured dynamically. As a persons skilled in telecommunications networks will appreciate, there are many possible connection topologies between nodes (e.g. Mesh Network, Cluster Tree Network, etc., an exemplary topology being shown in
In an embodiment of the present invention, the nodes of the wireless communication network are configured automatically, that is, the operator does not have to provide a unique address for each electronic card in the system (e.g. set up the dip-switches on the local controllers of the granule containers). In this embodiment, the wireless protocol has typical functionalities, for example, uses a DHCP (Dynamic Host Configuration Protocol), which provides for the automatic allocation of a unique address for every device in the communication network.
Local controller 5 coupled to granule container 2 is equipped with hardware and related interface software that implements a suitable communication protocol for the wireless network. Such interface enables the local controller to exchange data, commands and information with any other node of the network (whether a receiver, a central controller, and/or one or more control/programming and/or supervision systems) without burdening the local controller coupled the container with the control and management of the wireless network.
Access to the wireless network is controlled and managed by interface hardware, which generally includes a network processor that manages all the parameters and processes related to the reception and transmission of information, for example, address allocation of the network node, routing of messages between different network nodes, verification whether the data received is correct and whether data have been received and transmitted in case of error, implementation of network “self-healing” strategies in the event of failure of one or more nodes, etc.
Such self-healing function is provided in the wireless communication network protocol and provides for a continuing operation of the system when one or more nodes are not functioning due to temporary or permanent failures or due to maintenance of the granule containers, without requiring a manual intervention to define a new network configuration that excludes the missing nodes.
In addition, the wireless network enables an operator to use portable, palm-sized, mobile or similar devices equipped with wireless network interfaces for supervising, programming and/or collecting data without implementing procedures and connections typical of wired systems.
In general, a pneumatic transport system for granular materials may extend across large areas as is typical in industrial installations. Operators may need to know the status or modify the settings of a particular granule container 2, which is included in the network, or conduct a diagnosis of local controller 5 coupled to container 2. With a hard wired system, this is achieved by connecting an interface or control device, such as a palm-sized device, directly to local controller 5 of granule container 2 or with a user interface of central controller 6. In both situations, this operation is not easy because, in the first case, the operator must access the granule container physically, sometimes in an elevated position, for the wired connection of the palm device to local controller 5 to take place, while, in the second case, the operator must physically access remote central controller 6.
Instead, by using a wireless network configured according to the principles of the present invention, diagnosis, configuration and data collection are made possible by equipping the operator with a palm-sized or similar device that has a wireless network interface. Such device becomes part of the wireless control network of the granule container system and allows the operator not only to collect and configure the network containers or nodes in his immediate vicinity but also to perform those operations for any remote receiver or node pertaining to the network.
While the invention has been described in connection with a number of embodiments, it is not intended to limit the scope of the invention to the particular forms set forth, but on the contrary, it is intended to cover such alternatives, modifications, variations and equivalents as may be included within the scope of the invention.
Therefore, with reference to the preceding description and the attached drawings, the following claims are set forth.
