Flameproof Apparatus Using Non-Grounded Energy-Limiting Barrier

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 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.

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.