Fault-Tolerant Pressure Relief System for Drilling

Abstract

A fault-tolerant system relieves pressure of fluid flow in a drilling system. Redundant pressure relief valves can open to relieve fluid flow from a discharge outlet of a manifold when over pressurization is detected. A hydraulic arrangement operably connected to the redundant relief valves provides hydraulic motive force in redundant hydraulic circuits respectively to the redundant relief valves. The redundant circuits are cross-connected to one another. Pressure transducers distributed in the hydraulic arrangement measures operational pressures of the hydraulic arrangement. Redundant controllers can both control the hydraulic motive force provided in the redundant circuits respectively to the redundant relief valves to open and close the relief valves in response to the pressure level measurement.

What is claimed is: 
     
         1 . An assembly for relieving pressure of fluid flow in a drilling system in response to a pressure level measurement of the drilling system, the assembly comprising:
 pressure relief valves disposed in fluid communication between the fluid flow and at least one discharge outlet, each of the pressure relief valves operable to open and close fluid communication of the fluid flow with the at least one discharge outlet;   hydraulic circuits being cross-connected to one another and being operably connected to the pressure relief valves, the hydraulic circuits providing hydraulic motive force respectively to the pressure relief valves; and   controllers operably connected to the hydraulic circuits, each of the controllers receiving the pressure level measurement of the drilling system, both of the controllers in a standard condition simultaneously controlling the hydraulic motive force provided in the hydraulic circuits respectively to the pressure relief valves to independently open and close the respective pressure relief valve in response to the pressure level measurement,   in response to a first failure condition of either one of the controllers, the other one of the controllers independently controlling the hydraulic motive force provided in the hydraulic circuits respectively to the pressure relief valves to simultaneously open and close the respective pressure relief valves in response to the pressure level measurement.   
     
     
         2 . The assembly of  claim 1 , wherein, in response to a second failure condition of either one of the hydraulic circuits, either one of the pressure relief valves automatically faults closed regardless of the pressure level measurement. 
     
     
         3 . The assembly of  claim 1 , comprising a manifold having one or more flow inlets disposed in fluid communication with an upstream portion of the drilling system and receiving the fluid flow therefrom, and having one or more flow outlets disposed in fluid communication with a downstream portion of the drilling system and delivering the fluid flow thereto. 
     
     
         4 . The assembly of  claim 1 , further comprising sensors communicatively connected to the controllers and providing readings for the pressure level measurement of the drilling system. 
     
     
         5 . The assembly of  claim 1 , further comprising a plurality of sensors distributed in the hydraulic circuits and measuring a plurality of operational parameters, both of the controllers receiving the operational parameters, either one of the controllers detecting a second failure condition associated with the operational parameters from one of the hydraulic circuits and automatically faulting the respective pressure relief valve closed in response to the second failure. 
     
     
         6 . The assembly of  claim 5 , wherein the hydraulic circuits comprise pumps connected to a pneumatic supply and pumping the hydraulic motive force; and wherein a first of the sensors comprises a first pressure transducer measuring pressure of the pneumatic supply as one of the operational parameters. 
     
     
         7 . The assembly of  claim 6 , wherein the pumps connected to the pneumatic supply pump the hydraulic motive force to a common hydraulic input for the hydraulic circuits. 
     
     
         8 . The assembly of  claim 7 , wherein a second of the sensors comprises a second pressure transducer measuring the common hydraulic input as one of the operational parameters. 
     
     
         9 . The assembly of  claim 7 , comprising one or more accumulators connected to the common hydraulic input. 
     
     
         10 . The assembly of  claim 6 , wherein the hydraulic circuits provide the hydraulic motive force in the event of failure of either one of the pumps. 
     
     
         11 . The assembly of  claim 5 , wherein a third of the sensors comprises a third pressure transducer measuring pressure of the hydraulic motive force to a first of the pressure relief valves as one of the operational parameters, either one of the controllers detecting the measured pressure below a first threshold as the second failure condition and automatically faulting the first pressure relief valve closed in response thereto. 
     
     
         12 . The assembly of  claim 11 , wherein a fourth of the sensors comprises a fourth pressure transducer measuring pressure of the hydraulic motive force to a second of the pressure relief valves as one of the operational parameters, either one of the controllers detecting the measured pressure below a second threshold as the second failure condition and automatically faulting the second pressure relief valve closed in response thereto. 
     
     
         13 . The assembly of  claim 1 , wherein each of the controllers is communicatively connected to a position sensor of each of the pressure relief valves, either one of the controllers detecting either one of the pressure relief valves failing to open as the second failure condition. 
     
     
         14 . The assembly of  claim 1 , wherein each of the hydraulic circuits comprises an electrically-driven directional control valve having a default no-flow state and an active flow state, both of the electrically-driven directional control valves being connected to a common hydraulic input. 
     
     
         15 . The assembly of  claim 14 ,
 Wherein each of the controllers is communicatively connected to the electrically-driven directional control valves of both of the hydraulic circuits to provide a control signal thereto;   wherein in the second failure condition, either of the controllers is configured to automatically fault a respective one of the pressure relief valves closed in response to a failure of the respective electrically-driven directional control valve; and/or   wherein the hydraulic motive force is provided in the open circuit of a first of the hydraulic circuits in the event of a failure of the electrically-driven directional control valve in a second of the hydraulic circuits, the pressure relief valve of the second hydraulic circuit defaulting to a closed condition.   
     
     
         16 . The assembly of  claim 14 , wherein each of the hydraulic circuits comprises a pair of open and close hydraulically-driven directional control valves connected to the common hydraulic input, the open hydraulically-driven directional control valve having a default closed state and an active opened state, the close hydraulically-driven directional control valve having a default opened state and an active closed state, the active opened state providing an open output of the hydraulic motive force to open the respective pressure relief valve, the default opened state providing a close output of the hydraulic motive force to close the respective pressure relief valve, the open and close hydraulically-driven directional control valves each having the respective default state in response to the electrically-driven directional control valve having the default no-flow state and each having the respective active state in response to the electrically-driven directional control valve having the active flow state. 
     
     
         17 . The assembly of  claim 16 , wherein each of the hydraulic circuits comprises a pair of discharge hydraulically-driven directional control valves, a first of discharge hydraulically-driven directional control valves connected to the open output and having a default open state and an active close state, the default open state communicating with a discharge, a second of the discharge hydraulically-driven directional control valves connected to the close output of the close hydraulically-driven directional control valve and having a default closed state and an active opened state, the active opened state communicating with the discharge, the discharge hydraulically-driven directional control valves each having the respective default state in response to the electrically-driven directional control valve having the default no-flow state and each having the respective active state in response to the electrically-driven directional control valve having the active flow state. 
     
     
         18 . The assembly of  claim 16 , wherein each close output comprises a pilot-operated check valve piloted by the respective open output. 
     
     
         19 . An assembly used with a buffer manifold for relieving pressure of fluid flow in a drilling system, the drilling system having a pneumatic supply, the buffer manifold having one or more flow inlets, one or more flow outlets, and first and second pressure relief valves, the one or more flow inlets disposed in fluid communication with an upstream portion the drilling system and receiving the fluid flow therefrom, the one or more flow outlets disposed in fluid communication with a downstream portion the drilling system and delivering the fluid flow thereto, the first and second pressure relief valves disposed in fluid communication between the one or more flow inlets and the one or more flow outlets and disposed in fluid communication with at least one discharge outlet, each of the first and second pressure relief valves operable to open and close fluid communication with the at least one discharge outlet, wherein the control assembly comprises:
 a hydraulic arrangement operably connected to the first and second pressure relief valves and connected to the pneumatic supply, the hydraulic arrangement powered by the pneumatic supply and providing hydraulic motive force in two hydraulic circuits respectively to the first and second pressure relief valves, the two hydraulic circuits being cross-connected to one another;   a plurality of sensors distributed in the hydraulic arrangement and measuring a plurality of operational parameters of the hydraulic arrangement; and   a pair of controllers operably connected to the hydraulic arrangement, each of the controllers receiving the operational parameters from the sensors and receiving a pressure level measurement of the drilling system, both of the controllers controlling the hydraulic motive force provided in the two hydraulic circuits respectively to the first and second pressure relief valves to open and close the first and second pressure relief valves in response to the pressure level measurement.   
     
     
         20 . A method of controlling fluid flow in a drilling system, the method comprising:
 receiving the fluid flow from an upstream portion of the drilling system at one or more flow inlets of a manifold assembly;   in response to a first pressure level measurement of the drilling system, flowing the fluid flow out one or more flow outlets of the manifold assembly to a first downstream portion of the drilling system in response thereto;   in response to a second pressure level measurement of the drilling system, flowing the fluid flow out at least one discharge outlet of the manifold assembly to a second downstream portion of the drilling system, instead of out the one or more flow outlets, by simultaneously controlling, with controllers, hydraulic motive force provided in hydraulic circuits respectively to pressure relief valves to independently open the respective pressure relief valve;   in response to a first failure condition of either one of the controllers, independently controlling, with the other one of the controllers, the hydraulic motive force provided in the hydraulic circuits respectively to the pressure relief valves to simultaneously open and close the respective pressure relief valves in response to the first and second pressure level measurements; and   in response to a second failure condition of either one of the hydraulic circuits, automatically faulting either one of the pressure relief valves closed regardless of the first and second pressure level measurements.