Wireless measurement of the position of a piston in an accumulator

Abstract

A measurement system including a container including an element moveable within an internal volume of the container. A sensor wirelessly measures the position of the element within the container and transmits the measured position information. Also included is an information system capable of reading the position information from the sensor.

What is claimed is: 
     
         1 . A measurement system, including:
 blowout preventers (BOPs) configured in a blowout preventer (BOP) stack;   a hydraulic fluid accumulator mounted on the BOP stack and including a piston moveable within an internal volume of the accumulator, the piston dividing the internal volume into a first chamber having hydraulic fluid and a second chamber having a gas with the volumes of the first and second chambers depending on the position of the piston, and the accumulator being capable of providing the hydraulic fluid from the first chamber to operate a BOP of the BOP stack;   a sensor capable of wirelessly measuring the position of the piston within the accumulator and transmitting the measured position information, wherein the sensor is installed on a stationary portion of the accumulator and is positioned at a fixed location within the second chamber to emit a wireless signal from the sensor through the gas toward the piston for measuring the position of the piston within the accumulator; and   an information system capable of reading the position information from the sensor.   
     
     
         2 . The system of  claim 1 , further including:
 a radio-frequency identification (RFID) tag located on the piston; and   the sensor including a radio-frequency transceiver capable of sending a radio-frequency signal to the RFID tag and reading a response signal from the RFID tag.   
     
     
         3 . The system of  claim 1 , wherein the sensor is at least one of a radio-frequency sensor, a far field electromagnetic (microwave) sensor, a near field electromagnetic sensor, and an acoustic sensor. 
     
     
         4 . The system of  claim 1 , further including:
 more than one accumulator including a piston;   transponders located on each piston and capable of communicating with the sensor to identify each piston from the other pistons.   
     
     
         5 . The system of  claim 1 , wherein the information system includes an information hub located remotely from the sensors. 
     
     
         6 . The system of  claim 1 , further including a sensor capable of measuring the temperature inside the accumulator and transmitting the measured temperature information to the information system. 
     
     
         7 . The system of  claim 1 , wherein the BOP stack is a subsea BOP stack and the hydraulic fluid accumulator, sensor, and information system are all locatable subsea. 
     
     
         8 . The system of  claim 1 , further including:
 more than one accumulator including a piston;   sensors capable of wirelessly measuring the position of the pistons within the accumulators and transmitting the measured position information; and   the information system capable of reading the position information from the sensors.   
     
     
         9 . The system of  claim 1 , wherein the sensor installed on the stationary portion of the accumulator and positioned at the fixed location within the second chamber is capable of self-calibration to account for variations in propagation speed related to changes in pressure of the gas in the accumulator. 
     
     
         10 . A measurement system, including:
 a container including an element moveable within an internal volume of the container, wherein the element includes a piston moveable within an internal volume of a hydraulic fluid accumulator, the piston dividing the internal volume into a first chamber having hydraulic fluid and a second chamber having a gas with the volumes of the first and second chambers depending on the position of the piston;   a sensor capable of wirelessly measuring the position of the piston within the hydraulic fluid accumulator and transmitting the measured position information, wherein the sensor is installed on a stationary portion of the accumulator and is positioned at a fixed location within the second chamber to emit a wireless signal from the sensor through the gas toward the piston for measuring the position of the piston within the accumulator; and   an information system capable of reading the position information from the sensor.   
     
     
         11 . The system of  claim 10 , further including:
 a radio-frequency identification (RFID) tag located on the element; and   the sensor including a radio-frequency transceiver capable of sending a radio-frequency signal to the RFID tag and reading a response signal from the RFID tag.   
     
     
         12 . The system of  claim 10 , further including:
 more than one container including a moveable element;   transponders located on each element and capable of communicating with the sensor to identify each element from the other elements.   
     
     
         13 . The system of  claim 10 , further including a sensor capable of measuring the temperature inside the container and transmitting the measured temperature information to the information system. 
     
     
         14 . The system of  claim 10 , further including:
 more than one container including a moveable element;   sensors capable of wirelessly measuring the position of the elements within the containers and transmitting the measured position information; and   the information system capable of reading the position information from the sensors.   
     
     
         15 . The system of  claim 10 , wherein the sensor installed on the stationary portion of the accumulator and positioned at the fixed location within the second chamber is capable of self-calibration to account for variations in propagation speed related to changes in pressure of the gas in the container. 
     
     
         16 . A method comprising:
 measuring a position of a piston within an internal cavity of a hydraulic fluid accumulator; and   determining a volume of hydraulic fluid remaining in the hydraulic fluid accumulator based on the measured position of the piston within the hydraulic fluid accumulator.   
     
     
         17 . The method of  claim 16 , wherein measuring the position of the piston within the internal cavity of the hydraulic fluid accumulator includes wirelessly measuring the position of the piston via a sensor. 
     
     
         18 . The method of  claim 17 , wherein wirelessly measuring the position of the piston via the sensor includes emitting a wireless signal from the sensor toward the piston. 
     
     
         19 . The method of  claim 18 , wherein the sensor is an acoustic sensor and emitting the wireless signal from the sensor toward the piston includes emitting an acoustic signal from the sensor toward the piston, and wherein measuring the position of the piston within the internal cavity of the hydraulic fluid accumulator includes receiving a reflection of the emitted acoustic signal from the piston. 
     
     
         20 . The method of  claim 18 , wherein the piston divides the internal cavity into a first chamber having the hydraulic fluid and a second chamber having a gas with the volumes of the first and second chambers depending on the position of the piston, and wherein emitting the wireless signal from the sensor toward the piston includes emitting the wireless signal from the sensor through the gas toward the piston.