Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23N—REGULATING OR CONTROLLING COMBUSTION
  • F23N5/00—Systems for controlling combustion
  • F23N5/26—Details
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23N—REGULATING OR CONTROLLING COMBUSTION
  • F23N5/00—Systems for controlling combustion
  • F23N5/20—Systems for controlling combustion with a time programme acting through electrical means, e.g. using time-delay relays
  • F23N5/206—Systems for controlling combustion with a time programme acting through electrical means, e.g. using time-delay relays using electrical or electromechanical means

Definitions

• Safety device for industrial boilers comprising relays mounted on a printed circuit board
• the invention relates to a safety device for an industrial boiler comprising electromechanical relays connected to form an electromechanical safety chain.
• the invention applies in particular to industrial boilers comprising for example a gas burner for producing steam or superheated water.
• Such boilers are provided with a safety device which is interposed between one or more sensors and one or more actuators mounted on the boiler to trigger via the actuators a shutdown of the boiler when at least one sensor detects a malfunction of the boiler.
• This fault may be excessive pressure, too low water level or a problem in the burner flame.
• such a safety device is able to open a supply circuit for the actuators on detection of a fault by a sensor.
• the actuators which may for example be solenoid valves, are designed to initiate a shutdown of the boiler as soon as they are no longer supplied with current by the supply circuit.
• Each sensor supplies an alternating electric current at 230 Volts to the safety device in the event of normal operation of the boiler and does not supply this current in the event of a fault being detected.
• Such an arrangement forms a so-called "positive" safety in which a break in the electrical supply triggers the shutdown of the boiler.
• each sensor corresponds to a relay which is kept energized when it is supplied by the current supplied by the corresponding sensor and the relay contacts corresponding to the different sensors are for example connected in series to form a chain of electromechanical safety in the form of wired logic.
• the electrical circuit corresponding to this electromechanical safety chain is closed in the event of normal operation of the boiler and is open in the event of an anomaly in the latter. It is known in such a safety device to add to the electromechanical safety chain a so-called IT safety chain operating in parallel and redundantly to the electromechanical safety chain when the automation and regulation of the boiler become complex and require the use of an industrial programmable controller.
• the IT security chain is generally consisting of a data processing circuit such as a microprocessor which receives as input the electrical signals produced by the sensors and converted into computer signals at 5 volts and which feeds through a transistor controlling a relay the electrical supply circuit of the actuators .
• the output of the data processing circuit is for example wired in series in the electromechanical safety chain which constitutes the main safety chain.
• the standard NF D36504 more specifically specifies (ch 4.2) that the evaluation of the operational safety of an IT security chain must be carried out by a specific test procedure, by injecting directly on the equipping errors in order to simulate an internal fault: a failure of all the memory bits taken one by one is simulated.
• ch 4.2 the evaluation of the operational safety of an IT security chain must be carried out by a specific test procedure, by injecting directly on the equipping errors in order to simulate an internal fault: a failure of all the memory bits taken one by one is simulated.
• Such a test is particularly long to execute, considerably increases the tests which precede the first commissioning of such a boiler and increases its cost accordingly.
• the subject of the invention is a safety device for an industrial boiler comprising electromechanical relays connected to form an electromechanical safety chain, characterized in that the relays are mounted on a support in the form of a printed circuit board.
• the electrical connections between the relays are formed by the tracks of the printed circuit so that it is no longer possible for an operator to modify the operating logic of the electromechanical safety chain.
• these relays are directly soldered to a printed circuit board and the connection to the input / output boards is carried out by means of removable terminal blocks fitted with a coding device.
• These printed circuit boards can be mounted in a compact case, possibly sealed so that it is impossible for an operating operator to access the entire electromechanical safety chain.
• current converters associated respectively with relays of the electromechanical safety chain are provided for converting an electrical signal input from a relay into an electronic signal, the electronic signals supplied by the converters being processed in a logic integrated circuit constituting with the converters an electronic safety chain redundant to the electromechanical safety chain.
• a logic integrated circuit constituting with the converters an electronic safety chain redundant to the electromechanical safety chain.
• the logic integrated circuit is preferably a programmable circuit of the "PAL" type.
• each current converter is an optocoupler so as to isolate from the electrical point of view the two electromechanical and electronic safety chains. In this way, an electrical fault in the electromechanical safety chain does not affect the operation of the electronic safety chain.
• the electronic signals are converted into computer signals by means of microcontrollers to be sent to a computer security chain redundant to the electronic security chain which allows to strengthen the degree of security of the security device without increasing its complexity of implementation since this computer security chain constituting a third security chain, is not subject to the test procedures according to standard NF D36504 described above.
• FIG. 1 is a very schematic representation of the invention
• Figure 2 is a very schematic representation of a printed circuit of the security device according to the invention.
• Figure 3 is a very schematic representation of the arrangement of printed circuits of the device according to the invention.
• the device according to the invention is connected to at least one sensor PT n and to at least one actuator EV m which are generally mounted in the industrial boiler CHA.
• the PT n sensor which is here a pressure switch sends an electric current l n to a safety device DS which is here mounted in an electrical cabinet AE. If this current l n is received , the safety device in turn sends a second electric current Jm towards the actuator EV m which is here a solenoid valve, to maintain this actuator in a normal operating position. If the current l n is not received, the safety device DS commands an opening relay (not shown) of the electrical supply circuit of the actuator EV to cancel the current J m , and thus trigger the stop of the boiler.
• the safety device DS comprises a box containing printed circuit boards hereinafter called printed circuits which form an electromechanical safety chain CH1.
• This box comprises one or more printed circuits on which are mounted the relays forming the first safety chain CH1, so that these relays are not interconnected by wired logic, but by conductive tracks of the printed circuits.
• This type of boiler generally comprises a plurality of sensors associated with a plurality of actuators, and the housing can contain, for example, several printed circuits CI A , CI B , Clc to manage the various sensors of the boiler, as shown in FIG. 3
• these circuits are pinned into connectors of a card called backplane card (not shown) which is also equipped with connectors ensuring the electrical connection with the sensors and with the actuators.
• each printed circuit CI Al CI B , Clc comprises a relay RE n which is kept closed if it receives a current l n from the corresponding sensor PT n to form the conventional electromechanical safety chain CH1.
• the circuits CI A , CI B , Clc have their outputs combined in a main circuit CIP visible in FIG. 3 which includes the connections forming the first safety chain CH1. This main circuit is also mounted on the backplane board.
• the security device sets up the various relays RE n of each printed circuit CI A , CI B , Clc in series, and controls an opening relay for the electrical supply circuit of the actuator or of the actuators of the boiler, from that one of the RE n relays is open.
• the security device could include a second security chain CH2 redundant to the first, this second chain being electronic.
• This electronic chain is also capable of opening the electric supply circuit of the actuator EVm to cut off its electric supply in the event of non reception of an electric current In.
• the advantage of electronic management for this second chain is that validation tests are simpler than in the context of computerized management.
• This CH2 electronic chain can be mounted in a separate box, and connected to the backplane board by specific connectors.
• the current In supplied by a sensor PT n is converted in the printed circuit on which the corresponding relay RE n is mounted by a corresponding converter OC n into an electronic signal.
• This electronic signal is a direct current at 12 Volts intended to be received by a logic integrated circuit CIL to form the second safety chain CH2.
• the logic integrated circuit CIL can be mounted on the main printed circuit CIP of the security device DS, this main circuit itself being connected to the backplane card.
• the main printed circuit CIP receives the electronic signals produced by each printed circuit CIA, CI B , Clc to control an opening relay of the electrical supply circuit of the actuator EV m on the order of the logic integrated circuit CIL.
• Such a logic integrated circuit will advantageously be produced for example with a "PAL” type circuit.
• PAL programmable logic circuits
• These "PAL” circuits operate at 12 Volts and allow logic operators to be made between input channels and output channels at a lower cost. They are permanently configured by electrical breakdown.
• a printed circuit CI A , CI B , Clc also called electronic card receiving the current l n from a single sensor.
• the same card can receive the currents l n supplied by several sensors, so as to manage all the sensors of a member of the boiler such as for example the burner.
• the card includes a relay and an optocoupler for each sensor, the relays being placed in series on the card so as to provide a single output for the electromechanical safety chain CH1.
• the electronic signals from the different optocouplers are then brought together through a local logic integrated circuit which is also mounted on the card CI A , CIB, CI C. This circuit thus provides a single electronic output signal reflecting the state of the member concerned, intended for the electronic safety chain CH2.
• the security device may also include a third security chain CH3 redundant to the other security chains CH1 and CH2, this third chain being computer-based.
• each printed circuit C1 includes a microcontroller which converts the 12 Volt electronic signal into a computer signal clocked by a clock contained in the microcontroller. This computer signal is emitted at approximately 5 Volts.
• the various computer signals are collected by the main printed circuit CIP.
• This CIP circuit is equipped with a microcontroller uniting the various computer signals, and which communicates with an MP microprocessor to form the third safety chain.
• the microprocessor MP also communicates with the microcontroller MCP to trigger a shutdown of the boiler on the order of the computer program for managing the third chain.
• the microprocessor then opens the opening relay of the supply circuit of the actuator (s) EV m through a transistor which is mounted on the main printed circuit.
• the microcontroller MC of this printed circuit can be a parallel-series converter.
• Such a converter receives the electronic signals at 12 Volts as input from each sensor and outputs a serial computer signal clocked at 5 Volts reflecting the state of each of the sensors managed by the circuit CI A , CIB, Clc.
• the microcontroller MCP of the main printed circuit is able to communicate to the microprocessor MP computer data defining the precise state of each sensor of the boiler.
• the security device according to the invention with heterogeneous redundancy gives rise to improved compactness and to an increased degree of security since an operating operator cannot modify its configuration.
• the implementation of a third computer security chain makes it possible to connect the boiler to an information system giving a precise indication of the state of each boiler sensor.

Landscapes

• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Safety Devices In Control Systems (AREA)
• Burglar Alarm Systems (AREA)
• Protection Of Static Devices (AREA)
• Cookers (AREA)
• Selective Calling Equipment (AREA)
• Fire Alarms (AREA)
• Electric Stoves And Ranges (AREA)
• Constitution Of High-Frequency Heating (AREA)

Applications Claiming Priority (3)

Publications (2)

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• 2001
  • 2001-06-20 FR FR0108095A patent/FR2826433B1/fr not_active Expired - Fee Related
• 2002
  • 2002-05-17 CN CN02812455.3A patent/CN1278072C/zh not_active Expired - Fee Related
  • 2002-05-17 EP EP02738266A patent/EP1402216B1/de not_active Expired - Lifetime
  • 2002-05-17 WO PCT/FR2002/001675 patent/WO2003001116A1/fr active IP Right Grant
  • 2002-05-17 US US10/480,920 patent/US7385316B2/en not_active Expired - Fee Related
  • 2002-05-17 CA CA2451033A patent/CA2451033C/fr not_active Expired - Fee Related
  • 2002-05-17 AT AT02738266T patent/ATE354767T1/de not_active IP Right Cessation
  • 2002-05-17 DE DE60218310T patent/DE60218310T2/de not_active Expired - Lifetime

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