Abstract: 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.

Abstract: An emergency shutdown system includes an emergency shutdown valve, a control line to carry a signal determinative of positioning of the emergency shutdown valve, a solenoid assembly coupled to the control line to effectuate the positioning of the emergency shutdown valve, and a junction device coupled to the control line and the solenoid assembly. In some embodiments, the junction device includes a switch, such as a relay, responsive to the signal to control whether the solenoid assembly is coupled to the control line and, therefore, energized.

Abstract: Disclosed herein is a controller and method useful for transferring control of a process control device between first and second control modes. The controller includes first and second servo control modules that generate first and second drive signals based on feedback information from first and second sensors for control of the process control device in accordance with first and second control modes, respectively. The controller also includes a feedback control transfer module that transfers control of the operation of the process control device from the first control mode to the second control mode based on the feedback information from the first sensor. In certain embodiments, such control transfer involves a control routine that initially generates the second drive signal based on the first drive signal to effectuate a smooth, bumpless transfer between the control modes.

Abstract: A digital valve positioning system is disclosed. The system comprises a valve, a valve controller having a controller microprocessor and a controller memory and a valve actuator having an output coupled to the valve to control the position of the valve over a range of motion in response to an output from the valve controller. The system further comprises a first position sensor for determining the position of the valve actuator and an intelligent limit switch for generating a limit switch state signal indicative of a state of the valve being above or below a threshold set point. The limit switch comprises a second position sensor generating an output signal indicative of the position of the valve, a limit switch memory, a limit switch microprocessor communicatively coupled to the limit switch memory, an isolated communication link between the controller microprocessor and the limit switch microprocessor for transferring the set point data from the controller to the limit switch.