초록 ▼

A device intended to meet flameproof approval requirements is configured to have two compartments separated by an energy-limiting barrier. The first compartment of the device houses the wiring terminations that bear ignition-capable energy and, therefore, must be flameproof. The energy-limiting barr

A device intended to meet flameproof approval requirements is configured to have two compartments separated by an energy-limiting barrier. The first compartment of the device houses the wiring terminations that bear ignition-capable energy and, therefore, must be flameproof. The energy-limiting barrier is configured to limit the energy that can reach the second compartment to a level that is not ignition capable. This allows the second compartment to be safe without meeting the flameproof requirements, and allows user-interface elements such as switches and indicators to be designed in a more cost-effective manner.

대표청구항 ▼

What is claimed is: 1. A flameproof apparatus comprising: a flameproof housing; a flameproof compliant input connection disposed through the flameproof housing to receive a wire to connect the flameproof apparatus to an external power source; a flameproof compliant output connection disposed throug

What is claimed is: 1. A flameproof apparatus comprising: a flameproof housing; a flameproof compliant input connection disposed through the flameproof housing to receive a wire to connect the flameproof apparatus to an external power source; a flameproof compliant output connection disposed through the flameproof housing and having a voltage source line; a voltage converter disposed within the flameproof housing and having a converter input connected to the flameproof compliant input connection and having a converter output, wherein the voltage converter converts the voltage from the external power source to a converter output voltage that is less than or equal to a predetermined maximum output voltage; and an energy limiting barrier disposed within the flameproof housing and having a barrier input operatively connected to the converter output and a barrier output operatively connected to the voltage source line, the energy limiting barrier comprising a limit circuit to limit the output voltage at the voltage source line to be less than or equal to the maximum output voltage. 2. A flameproof apparatus in accordance with claim 1, wherein the limit circuit includes a voltage limiting device disposed between the converter output and a common line such that the voltage limiting device connects the converter output to the common line when the converter output voltage exceeds the maximum output voltage. 3. A flameproof apparatus in accordance with claim 2, wherein the voltage limiting device includes a diode. 4. A flameproof apparatus in accordance with claim 2, wherein the voltage limiting device includes redundant diodes. 5. A flameproof apparatus in accordance with claim 2, wherein the voltage limiting device includes a Zener diode. 6. A flameproof apparatus in accordance with claim 2, wherein the voltage limiting device includes redundant Zener diodes. 7. A flameproof apparatus in accordance with claim 1, wherein the limit circuit includes a current limiting device connected with the converter output, wherein the current limiting device operates as to form an open circuit when current from the converter output exceeds a predetermined maximum output current. 8. A flameproof apparatus in accordance with claim 7, wherein the current limiting device includes a fuse. 9. A flameproof apparatus in accordance with claim 1, comprising: a further flameproof compliant input connection disposed through the flameproof housing; a further flameproof compliant output connection disposed through the flameproof housing; and a connection line extending between the further flameproof compliant input connection and the further flameproof compliant output connection, wherein the energy limiting barrier comprises a further limit circuit operatively connected to the connection line and configured to limit the connection line voltage to be less than or equal to the maximum output voltage. 10. A flameproof apparatus in accordance with claim 9, wherein the further limit circuit connects the connection line to the barrier output such that the connection line voltage does not exceed the output voltage at the barrier output. 11. A flameproof apparatus in accordance with claim 10, wherein the further limit circuit comprises a diode connecting the connection line to the barrier output. 12. A flameproof apparatus in accordance with claim 9, wherein the further limit circuit connects the connection line to a common line such that the connection line voltage does not drop below a voltage on the common line. 13. A flameproof apparatus in accordance with claim 12, wherein the further limit circuit comprises a diode connecting the connection line to the common line. 14. A flameproof apparatus in accordance with claim 1, comprising a non-flameproof housing receiving the voltage source line from the flameproof housing, and having electrical instruments disposed therein and operatively connected to the voltage source line. 15. A method for operating systems and devices in a hazardous environment without intrinsically safe barriers and without complete enclosure by a flameproof housing, comprising: receiving an input power signal from an external power source within a flameproof housing through a first flameproof compliant input connection; converting within the flameproof housing the voltage of the input power signal to a converted output voltage that is less than or equal to a predetermined maximum output voltage; limiting within the flameproof housing the converted output voltage to be less than the maximum output voltage when the converted output voltage is greater than the maximum output voltage; and outputting the limited converted output voltage from the flameproof housing through a flameproof compliant output connection of the flameproof housing. 16. A method in accordance with claim 15, wherein limiting the converted output voltage comprises connecting the converted output voltage through a circuit to a common line when the converted output voltage exceeds the maximum output voltage. 17. A method in accordance with claim 16, wherein connecting the converted output voltage through a circuit to a common line includes connecting the converted output voltage through a diode to the common line. 18. A method in accordance with claim 16, wherein connecting the converted output voltage through a circuit to a common line includes connecting the converted output voltage through redundant diodes to the common line. 19. A method in accordance with claim 16, wherein connecting the converted output voltage through a circuit to a common line includes connecting the converted output voltage through a Zener diode to the common line. 20. A method in accordance with claim 16, wherein connecting the converted output voltage through a circuit to a common line includes connecting the converted output voltage through redundant Zener diodes to the common line. 21. A method in accordance with claim 15, comprising preventing the converted output voltage from reaching the flameproof compliant output connection when the current associated with the converted output voltage exceeds a predetermined maximum output current. 22. A method in accordance with claim 21, wherein preventing the converted output voltage from reaching the flameproof compliant output connection when the current associated with the converted output voltage exceeds a predetermined maximum output current includes forming an open circuit when the current associated with the converted output voltage exceeds the predetermined maximum current. 23. A method in accordance with claim 22, wherein forming an open circuit includes using a fuse. 24. A method in accordance with claim 15, wherein the flameproof housing includes a further flameproof compliant input connection, a further flameproof compliant output connection and a connection line extending between the further input connection and the further output connection, the method further comprising limiting the voltage on the connection line to be less than or equal to the maximum output voltage. 25. A method in accordance with claim 24, wherein limiting the voltage on the connection line includes connecting the connection line to the converted output voltage such that the connection line voltage does not exceed the converted output voltage. 26. A method in accordance with claim 25, wherein connecting the connection line to the converted output voltage includes connecting the connection line to the converted output voltage through a diode. 27. A method in accordance with claim 24, comprising operatively connecting the connection line to a common line such that the connection line voltage does not drop below ground. 28. A method in accordance with claim 27, wherein operatively connecting the connection line to a common line includes connecting the connection line to the common line through a diode. 29. A method in accordance with claim 15, comprising connecting the output connection from the flameproof housing to a non-flameproof housing such that electrical instruments disposed within the non-flameproof housing are operatively connected to the output connection. 30. A local control panel for a process control device located in a hazardous environment comprising: a flameproof housing; a flameproof compliant input connection disposed through the flameproof housing to receive a wire to connect the local control panel to an external power source; a flameproof compliant output connection disposed through the flameproof housing and having a voltage source line; a non-flameproof housing; an input device disposed within the non-flameproof housing and configured to receive input from a user; communications circuitry disposed within the housing and operatively connected to the input device, the communications circuitry configured to detect an input received from a user at the input device and to control the operation of a process control device to be controlled by the local control panel in response to detecting the input from a user at the input device, wherein the voltage output line extends through the outer wall of the non-flameproof housing and is operatively connected to the communications circuitry and the input device; a connection line operatively connected to the communications circuitry and configured for connection to a process control device to be controlled by the local control panel, the connection line extending through the non-flameproof housing; and circuitry disposed within the flameproof housing to convert the voltage from the external power source to a converter output voltage that is less than or equal to a predetermined maximum output voltage, to output the converter output voltage on the voltage source line, and to limit the output voltage at the voltage source line to be less than or equal to the maximum output voltage. 31. A local control panel in accordance with claim 30, wherein the circuitry enclosed within the flameproof housing comprises: a voltage converter having a converter input connected to the flameproof compliant input connection and having a converter output, wherein the voltage converter converts the voltage from the external power source voltage to a converter output voltage that is less than or equal to the maximum output voltage; and an energy limiting barrier operatively connected to the converter output and a barrier output operatively connected to the voltage source line, the energy limiting barrier comprising a limit circuit to limit the output voltage at the voltage source line to be less than or equal to the maximum output voltage. 32. A local control panel in accordance with claim 31, wherein the limit circuit includes a voltage limiting device disposed between the converter output and a common line such that the voltage limiting device connects the converter output to the common line when converter output voltage exceeds the maximum output voltage. 33. A local control panel in accordance with claim 31, wherein the limit circuit includes a current limiting device connected with the converter output, wherein the current limiting device operates as to form an open circuit when current from the converter exceeds a predetermined maximum output current. 34. A local control panel in accordance with claim 31, wherein the flameproof housing includes a further flameproof compliant input connection and a further flameproof compliant output connection, wherein the connection line extends between the further flameproof compliant input connection and the further flameproof compliant output connection, the circuitry within the flameproof housing comprising a further limit circuit operatively connected to the connection line and configured to limit the connection line voltage to be less than or equal to the maximum output voltage. 35. A local control panel in accordance with claim 34, wherein the further limit circuit connects the connection line to the barrier output such that the connection line voltage does not exceed the output voltage at the barrier output. 36. A local control panel in accordance with claim 34, wherein the further limit circuit connects the connection line to a common line such that the connection line voltage does not drop below a voltage on the common line. 37. A local control panel in accordance with claim 31, comprising an output device operatively connected to the communication circuitry, wherein the communication circuitry is configured to cause the output device to output a visual indication of the status of a process control device to be controlled by the local control panel. 38. A local control panel in accordance with claim 30, comprising: a further flameproof compliant input connection disposed through the flameproof housing to receive a wire to connect the local control panel to a further external power source; a further flameproof compliant output connection disposed through the flameproof housing and having a further voltage source line; further circuitry disposed within the flameproof housing to convert the voltage from the further external power source to a further converter output voltage that is less than or equal to the maximum output voltage, to output the further converter output voltage on the further voltage source line, and to limit the output voltage at the further voltage source line to be less than or equal to the maximum output voltage; and a switch disposed within the non-flameproof housing and operatively connected to the voltage source lines, to the communications circuitry, and to the input device, wherein the switch is operable to alternately connect one of the voltage source lines to the communications circuitry and the input device. 39. A local control panel in accordance with claim 30, wherein the communications circuitry is configured to control the operation of an emergency shutdown valve in response to detecting input at the input device.