Patent Publication Number: US-6992594-B2

Title: Pipeline monitoring system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 60/292,211 filed on May 18, 2001. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention is related to an improvement to the process of monitoring the protective voltage placed on buried steel pipelines subject to corrosion. Natural gas pipelines are of that type. At present, a sacrificial electrode (anode) is connected to gas pipelines at selected locations along their length. The sacrificial electrode prevents galvanic action from corroding the pipeline. It is necessary to periodically evaluate the integrity of the sacrificial anode electrode. This is done through an electrical lead connected to the pipeline (cathode). An electrical potential is generated between pipeline and a ground reference cell. A potential difference above a certain threshold, i.e. negative 0.85 volts, indicates an operable cathode. Impressed DC current from a fixed AC rectifier can also supply the cathodic protection voltage. 
     BRIEF SUMMARY OF THE INVENTION 
     Corrosion of buried pipelines including gas pipelines is abated by inducing a low power current in the pipeline through a buried anode. A properly protected pipeline will show a voltage of approximately −1 V. In one common configuration, it is measured through a process which requires a field technician to locate the test point, uncover it, attach a voltmeter to the test line, record the reading, disconnect and replace the cover. The corrosion status is monitored in this manner one or two times per year. These test points are often hard to find and require metal detectors and shovels to locate and expose. Other test points are difficult to access. For example, if a test point is located on a busy street, any testing will require traffic stoppage permits and testing may be limited to Sundays in the early hours. Some test points are above ground but in areas so remote as to be accessible only by all terrain vehicles or by air. 
     The successful reading and recording of the buried pipeline corrosion status is mandated by federal law and essential to the safe transmission of gas through buried metal pipelines. Due to the difficulties resulting from the location and reading of these test points, it is desirable to provide a system that allows for remote and efficient testing of the integrity of a pipeline. 
     Accordingly, the system of the present invention uses a radio frequency identification (RFID) type tag transponder. The device is installed in a protective housing near the cathode connection test point. The device has an internal lithium battery and remains in a sleeping state until it awakens with an internal timer and takes reads on a preset schedule. On interrogation by a wake-up radio frequency from a hand-held computer, the device broadcasts a signal with an encoded voltage reading, preferably on a 900 MHz wide spectrum band. This system would enable a vehicle to drive by a location and send out interrogation signals for nearby transponders. These transponders would in turn produce signals providing cathode protection voltage levels. The process can be executed entirely from a vehicle driving by the test site. This approach would be safer, save labor in a significant way, and would further provide a means for documenting readings. 
     The data gathered by the interrogation hand-held computer is uploaded to a central database using cell phone connection, via the internet, or via direct connection to the database computer. Data is then analyzed and out of tolerance readings transmitted to the operator via email or other suitable means. Similarly, once repairs are made, confirmation readings showing the appropriate protective charge could be quickly gathered. The database storage of out-of-tolerance and repaired test point voltages, in combination with the multiple readings per test point, creates a system more easily and thoroughly monitored by the pipeline system operator and regulatory agencies resulting in greater integrity to the pipeline system. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a functional block diagram of the components of the cathodic voltage test point monitor in accordance with this invention. 
         FIG. 2  is a functional block diagram of the test point interrogator of the system in accordance with this invention. 
         FIG. 3  is a pictorial view illustrating a manner of interrogating a cathodic voltage test point monitor. 
         FIG. 4  is an enlarged view of the hand held unit also shown in  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The invention described herein combines GPS (global positioning system) technology, RF (radio frequency) narrow band and Spread Spectrum communications, and extremely low power use components in a new system which would accomplish the automatic reading of the test points. 
     The system includes a Test Point Monitor (TPM), designated by reference number  10  in  FIG. 1 , installed above or below ground in a test point housing (not shown). The TPM  10  will automatically turn itself on and take voltage readings at scheduled intervals, for example every month, and record them in its memory. A technician receives the voltage readings at a location remote from the TPM  10  location. The technician is guided towards the TPM  10  by a handheld Test Point Interrogator (TPI), shown in  FIG. 2  and designated by reference number  50 . The TPI  50  includes a GPS function discussed further herein, and when the technician is in range of the TPM  10 , the TPI  50  will call for the stored TPM data. The TPM  10  is adapted for storing in its memory past voltage readings, and transmitting current and past voltage readings to the TPI  50 . The TPI  50  will store data from several thousand such TPM  10  units for download into a main database via direct connection or via the internet. 
     Details of the TPM  10  are shown in  FIG. 1 . As shown, the TPM  10  is coupled to a reference cell  12 . A potential difference between a cathodic voltage measurement point  14  and the reference cell  12  is measured at an A to D converter  16  which produces a digital output signal inputted into a CMOS microcontroller  18 . The microcontroller  18  receives power from a battery  20  and a power regulator  22 . An antenna  24  receives a “wake-up” signal which activates the microcontroller  18  through a wake-up circuit  26 . The interrogation signal would be initially processed by a command receiver  28 . Once activated to output its encoded voltage signal, the microcontroller  18  transmits the signal via a data transmitter  30  to antenna  24  for broadcast and receipt by the TPI  50 . 
       FIG. 2  illustrates the Test Point Interrogator (TPI)  50 . The TPI  50  includes a microprocessor  52  which displays information via an LCD display  54 . The LCD display  54  also includes an input/output function operable through a touch screen display. A power switch and special function keys  66  provide an additional input function in conjunction with a touch screen display  54 . 
     The microcontroller  52  is powered either by an external power input  56  or a rechargeable battery pack  58 , both which are regulated through a power regulating and control circuit  60 . Memory for data and operating system software is retained on flash EEPROM memory  62  and RAM memory  64 . A GPS receiver  68  receives GPS positioning signals via a GPS antenna  70  that provides location fixing information and status information concerning the TPM  10  to the microcontroller  52 . In this manner, the system can identify test points in the immediate locality of the TPI  50 . 
     The identification tags for each of the test points being interrogated can also be stored within the EEPROM memory  62  and the RAM memory  64 . A wake-up signal is sent via a wake-up transmitter  72  and the antenna  74  to the TPM  10 . The antenna  74  also receives encoded cathode voltage readings from TPM  10  through a data receiver  76 . Transmission of data stored within the TPI  50  to a central control center (not shown) may take place via telephone line modem  78  connected with phone jack  80 , or by wireless transmission using a cell phone (not shown). Alternatively, the TPI  50  may be coupled directly or indirectly to the central control center via a corn port  82 . 
     The TPI  50  also includes the ability to monitor a TPI rechargeable battery  62  reserve level for uninterrupted service. A vehicle mount (not shown) will be used to provide TPI  50  power and remote antenna features for improved sensitivity. On removal from the vehicle mount there will be a transmission power reduction and a manual call signal trigger activated in the TPI  50  to protect the operator. The GPS  68  mapping features of the TPI  50  provide both visual and audio signals to a user indicating test point locations. Additionally, the TPI  50  is configured such that if the GPS  68  system locates a proximal TPM  10 , the GPS  68  cooperates with the TPI  50  to automatically interrogate the proximal TPM  10  and thus automate the process of reading the cathodic voltage measured by the TPM  10 . 
     The life of the TPM  10  is extended by scheduling the interrogation signal listening mode for a predetermined time interval. Moreover, the life of the TPM is extended by enabling the TPI  50  to store the read history and thereby not unnecessarily interrogate a TPM  10  which has already been read within the established time interval. In an alternative embodiment, the TPM may have a replaceable battery for extended life. 
     The TPM  10  may also interrupt measurements to estimate the polarized potential. This is accomplished by a TPM function that breaks the circuit between two of its lead wires and within one second, takes an off-voltage reading. The TPM  10  also allows for this interrupt feature to work with a coupon that is protected in the normal operating state and disconnected from the protective DC circuit for measurement. This interrupt or instant-off measurement can also be accomplished for structures protected by impressed current by using the GPS receiver  60  of the TPI  50  as a highly accurate timing piece. By synchronizing the TPI  50  with an impressed current interrupter, more than one TPM  10  used on that structure can be interrogated at precisely the correct time to give an “on” potential reading followed by an “off” potential reading. 
     In a preferred embodiment, the present invention is adapted to analyze the voltage readings and, if a critical problem exists, the TPM  10  initiates a emergency beacon or other suitable signal without being activated by the interrogation signal. 
       FIG. 3  illustrates a truck  84  that may drive in the proximity of a nearby test point monitor  10  to interrogate that test point. 
       FIG. 4  illustrates a preferred TPI unit  50 . This illustration shows the display  54 , which is depicted as displaying a map that is used for locating a nearby TPM  10 . 
     The present invention provides the following benefits over the existing method. First, the frequency of voltage readings would be greatly increased so that a more thorough history is established. Secondly, the ease and speed of locating the test points using GPS and RF communications, especially in rural settings, would greatly reduce the man-hour requirements of testing and compliance. Thirdly, the ability to remotely receive data from units located in high traffic areas would reduce or eliminate the traffic problems associated with the current methodology. Fourthly, the TPI  50  will allow direct voltage readings from a test point where no TPM  10  is utilized. This type of reading is verified by ensuring that the GPS location of the TPI matches the database position for the test point being tested. Lastly, the database of precise GPS positions for each TPM  10  will allow for more rapid responses to pipeline emergencies. 
     In alternative embodiments, the TPM  10  and TPI  50  of the present invention may be utilized to measure the cathodic voltages of other buried assets, as well as in difficult to access areas such as storage tanks or silos. For example, with a reconfigured antenna, the TPM  10  could be placed at an above ground test point for enabling data transmission to a TPI  50  located in an airplane or helicopter. 
     Although this invention has been described in connection with pipelines for supplying natural gas, the concepts herein are equally applicable in other environments. For example, pipelines that transmit oil, petroleum, or water and that are made from steel or structural steel assets protected by cathodic voltage are also candidates for this invention. Numerous other applications will likely be available. It should be apparent to those skilled in the art that the above-described embodiment is merely illustrative of but a few of the many possible specific embodiments of the present invention. Numerous and various other arrangements can be readily devised by those skilled in the art without departing from the spirit and scope of the invention as defined in the following claims.