Emergency shutdown test system

Details Emergency shutdown test system Emergency shutdown test system

1999-03-04

2001-02-13

Huson, Gregory L. (Department: 3753)

Fluid handling

Line condition change responsive valves

Pilot or servo controlled

C137S456000

Reexamination Certificate

active

06186167

ABSTRACT:

This invention relates to emergency shutdown systems used in process control systems and to the testing of emergency shutdown valves used in such systems.
BACKGROUND OF THE INVENTION
Process control systems incorporate emergency shutdown valves which are normally in a fully opened or fully closed state. In order to assure that such emergency shutdown valves can properly function, they are periodically tested by partially opening or closing these valves. Since these tests are typically performed with pressure in the pipeline of the process control system, it is important to perform any test quickly and then return the valve to its normal state.
In such prior emergency shutdown systems, in order to perform a short test, a complicated panel of pneumatic valves and switches are normally used by an operator to partially open or close the emergency shutdown valve under test. In particular, this requires an operator to observe and understand a panel of pneumatic valves and switches and then to operate the particular associated valves and switches in order to partially open or close the desired emergency shutdown valve being tested. It is also important that any emergency shutdown system provide the ability to be able to move the emergency shutdown valve to its safe condition when commanded by the emergency shutdown controller, in the unlikely, but possible situation where a failure event has occurred during a valve test interval, and the valve under test must now be properly commanded by the emergency shutdown system.
SUMMARY OF THE INVENTION
In accordance with the principles of the present invention, there is provided an emergency shutdown system which includes an emergency shutdown controller for commanding the operation of an emergency shutdown valve between a normally fully opened or fully closed state to an emergency state when a failure event is detected in the process control system. The emergency shutdown system includes a solenoid valve coupled to the emergency shutdown controller for responding to the controller and venting the emergency shutdown valve actuator to a fail state. A digital valve controller or positioner includes an output pressure coupled through the solenoid valve to the valve actuator of the emergency shutdown valve so that the emergency shutdown valve can be quickly ramped up and down in order to test the emergency shutdown valve. As an example, a digital signal sent to the digital valve controller moves the emergency shutdown valve from its normal fully opened or fully closed state to a partially opened or partially closed state, and then quickly returns the valve to its normal state. If an emergency occurs during the test procedure or at any other time, the emergency shutdown system acts through the emergency shutdown controller to de-energize the solenoid valve, causing the solenoid valve to vent the emergency shutdown valve actuator to a fail state.
In a preferred embodiment of the invention, the powering of the solenoid valve and of the digital valve controller is provided by the emergency shutdown controller on the same pair of wires. Also, it is preferred that a digital communicating device, such as a hand held digital unit is coupled to the digital valve controller to provide the required digital signals for moving the emergency shutdown valve during the test procedure. The digital communicator can be coupled to the same pair of wires powering both the solenoid valve and the digital valve controller with the use of an impedance boosting device inserted on the pair of wires between the emergency shutdown controller and the digital units. The impedance boosting device enables dc power such as 24 volts dc to be supplied to power the solenoid valve and the digital valve controller on the same pair of wires, while also permitting the digital communicator to reliably communicate with the digital valve controller over the same pair of wires.


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Applicant-FUJI ELECTRIC CO LTD; inventor-Tanakura Nobuyuki; Title-Stem Free Testing Device Of Main Steam Stop Valve.

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