Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
  • G01N29/04—Analysing solids
  • G01N29/07—Analysing solids by measuring propagation velocity or propagation time of acoustic waves
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N17/00—Investigating resistance of materials to the weather, to corrosion, or to light
  • G01N17/04—Corrosion probes
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
  • G01N29/04—Analysing solids
  • G01N29/11—Analysing solids by measuring attenuation of acoustic waves
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2291/00—Indexing codes associated with group G01N29/00
  • G01N2291/02—Indexing codes associated with the analysed material
  • G01N2291/024—Mixtures
  • G01N2291/02458—Solids in solids, e.g. granules
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2291/00—Indexing codes associated with group G01N29/00
  • G01N2291/02—Indexing codes associated with the analysed material
  • G01N2291/025—Change of phase or condition
  • G01N2291/0255—(Bio)chemical reactions, e.g. on biosensors
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2291/00—Indexing codes associated with group G01N29/00
  • G01N2291/04—Wave modes and trajectories
  • G01N2291/044—Internal reflections (echoes), e.g. on walls or defects
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2291/00—Indexing codes associated with group G01N29/00
  • G01N2291/26—Scanned objects
  • G01N2291/263—Surfaces
  • G01N2291/2634—Surfaces cylindrical from outside

Definitions

• the present invention relates to corrosion detection. More specifically, the invention relates to a method for detecting and determining corrosion properties, such as type, location, size, and growth rate in metals and the like in a corrosive environment using a corrosion sensing probe.
• the invention is also capable of distinguishing between different types of corrosion such as uniform corrosion, and localized corrosion, such as pitting, crevice, and stress corrosion cracking.
• Uniform corrosion generally includes corrosion of large areas of a corrodible material at a roughly uniform rate.
• Localized corrosion such as pitting or cracking, is generally smaller scale corrosion which is harder to detect.
• Localized corrosion occurs initially in a microscopically small area on a material surface, which eventually becomes larger and deeper, forming pits or cracks in the surface.
• Localized corrosion, particularly pitting is hazardous because material is removed in a concentrated area that is not easily recognized.
• One of the most dangerous consequences of pitting corrosion is a leak in a containment vessel such as a tank or pipeline. The leak typically occurs at a pinhole in a wall of a containment vessel. The majority of the wall will have adequate thickness to contain the vessels contents. However, the resulting leak can be especially dangerous where the contained material is under pressure, at high temperature, or both.
• ECN electrochemical noise
• Various statistical analyses may be performed on these noise signals to distinguish corrosion type and corrosion rate in a corroded article. Examples of this ECN approach are described in U.S. patent 5,139,627, U.S. patent 5,425,867, and U.S. patent 6,015,484.
• Electrochemical noise generated by localized corrosion is small and difficult to detect. Environmental noises from motors, circuit breakers, switches, and radio frequency generators in or near the corroded article may mask or obscure the corrosion noise signal, resulting in inaccurate ECN readings.
• Another known method involves the use of a radioactive probe to detect pitting corrosion as described in U.S. patent 4,412,174.
• a radioactive probe is placed into a corrosive stream. As pitting corrosion occurs, pieces of the radioactive probe break off and enter into the stream. The presence of radioactive material is detected by a downstream radiation detector, which allows for the analysis of the probe's corrosion rate.
• a disadvantage of this approach is that it does not have the capability to differentiate between different types of localized corrosion, such as crevice and pitting.
• Acoustic emissions can also be used to detect surface corrosion of an insulated pipe. This method is described in U.S. patent 5,526,689. This approach involves a transmission of acoustic emissions along the surface of an insulated pipe to locate corroded areas of the pipe. This approach, however, does not include the ability to distinguish between different types of corrosion.
• U.S. patent 5,719,503 involves electromagnetic pulse propagation. According to this method, two electromagnetic sensors are mounted onto a corrodible article. Two pulses are sent from these sensors, and anomalies are examined at the intersection of the two pulses to locate areas of corrosion on the article itself. This approach also does not include the ability to distinguish between different types of corrosion.
• a corrosion sensor which comprises a metal probe attached to a transducer element.
• the metal probe is inserted into a corrosive environment together with a corrodible article to be tested.
• the probe and the corrodible article are composed of a substantially identical metal material.
• a transducer element attached to the probe sends an ultrasonic or radio frequency signal through the probe, and receives any ultrasonic or radio frequency signals which have been reflected by corroded areas of the probe. These reflected signals are analyzed to determine the type, size, location, and growth rate of corrosion conditions in the probe, and thus the corrodible metal article.
• the invention provides a method for detecting corrosion conditions of a corrodible metal article in a corrosive environment which comprises: a) placing a corrosion sensor into the corrosive environment, which corrosion sensor comprises: i) a metal probe comprised of a metal which is substantially identical to that of the corrodible metal article; and ii) a transducer element attached to said probe, which transducer element is capable of projecting and receiving ultrasonic or radio frequency signals through the probe; b) projecting ultrasonic or radio frequency signals from the transducer element through the probe; and c) receiving reflected ultrasonic or radio frequency signals with the transducer element, which reflected ultrasonic or radio frequency signals are reflected by corroded areas of the probe, and generating an electrical response signal to the reflected ultrasonic or radio frequency signals, which indicates a corrosion condition of the probe.
• the invention further provides a method for detecting corrosion conditions of a corrodible metal article in a corrosive environment which comprises: a) placing a corrosion sensor into the corrosive environment, which corrosion sensor comprises: i) a metal probe having an elliptical or circular cross section, which probe is comprised of a metal which is substantially identical to that of the corrodible metal article; ii) a metal crevice ring attached around the probe; and iii) a transducer element attached to said probe, which transducer element is capable of projecting and receiving ultrasonic or radio frequency signals through the probe; b) projecting ultrasonic or radio frequency signals from the transducer element through the probe; c) receiving reflected ultrasonic or radio frequency signals with the transducer element, which reflected ultrasonic or radio frequency signals are reflected by corroded areas of the probe, and generating an electrical response signal to the reflected ultrasonic or radio frequency signals, which indicates a corrosion condition of the probe; d) collecting a series
• the invention still further provides a corrosion sensor for detecting corrosion conditions of a corrodible metal article in a corrosive environment, which corrosion sensor comprises: a) a metal probe comprised of a metal which is substantially identical to that of the corrodible metal article to be tested; and b) a transducer element attached to said probe, which transducer element is capable of projecting and receiving ultrasonic or radio frequency signals through the probe.
• FIG. 1 shows a corrosion sensor of the invention having one external transducer.
• FIG. 2 shows a corrosion sensor of the invention having two external transducers.
• FIG. 3 shows a corrosion sensor of the invention having one internal transducer.
• FIG. 4 shows a corrosion sensor of the invention having two internal transducers.
• FIG. 5 shows a side view of a corrosion sensor of the invention attached to a pipe containing a corrosive environment.
• FIG. 6 shows a side view of a corrosion sensor of the invention attached to a wall of a vessel containing a corrosive environment.
• FIG. 7 shows a graphical representation of a reflected ultrasonic pulse projected through a probe having corrosion defects.
• the invention provides a method for detecting corrosion conditions of a corrodible metal article in a corrosive environment.
• a corrosive environment includes any environment containing a corrosive medium which may cause corrosion of an object or article exposed to that environment.
• corrosive media nonexclusively include flowing or non-flowing chemicals including gases such as air, natural gas, process exhaust fumes, and liquids such as acids, bases, organic and inorganic solvents, oils, water, and the like.
• a corrodible metal article includes any object or article comprising a metal, which is capable of becoming corroded in a corrosive environment containing a corrosive medium as described above.
• the term "metal" includes any metal, metal alloy, or combinations of metals and non- metals.
• Suitable metals nonexclusively include iron, steels such as stainless steel and super alloy steels, copper, zinc, aluminum, titanium, and alloys and combinations thereof.
• the corrodible metal article may be in any shape or form. In the practice of the present invention, such articles are typically in the form of metal pipes or vessel walls.
• a corrosion sensor 8 of the invention is a device which comprises a metal probe 2 attached to a transducer 4.
• the metal probe 2 may comprise any metal, metal alloy, or combinations thereof such as those described above for the corrodible metal article. It is important that the material of the metal probe 2 is substantially identical to that of the corrodible metal article to be tested, h a preferred embodiment, the metal probe 2 comprises stainless steel, most preferably stainless steel 304.
• the metal probe 2 may be in any shape or form, and may be solid or hollow.
• the metal probe 2 is of a shape having a circular or elliptical cross section. In a most preferred embodiment, the metal probe 2 is of a shape having an elliptical cross-section. This shape serves to induce stress points on the metal probe 2 for the formation and detection of stress corrosion cracking, which is described below.
• the probe may optionally include one or more stress inducing features which serve to induce stress on the probe, thus providing fixed locations for corrosion formation and detection.
• stress inducing features may include stress inducing shapes, and stress inducing attachments.
• a stress inducing shape is a particular shape or configuration of the metal probe which may induce stress on probe itself for the formation and detection of corrosion, particularly stress cracking corrosion.
• the probe includes a bent portion which may induce stress on the probe.
• stress may be induced on a probe which is of a shape ⁇ having an elliptical cross section.
• a stress inducing attachment includes objects which may be attached onto or around the probe, which may induce stress on the probe for the formation and detection of corrosion. Stress inducing attachments preferably comprise substantially the same material as that of the probe.
• the probe may also comprise a metal crevice ring 6, preferably of the same material as the probe which is attached around the probe to provide fixed locations for the formation and detection of crevice corrosion, as described below.
• a transducer element is attached to the metal probe 2.
• the transducer element preferably comprises at least one transducer 4, 4' as shown in FIGS. 1-6.
• Suitable transducers nonexclusively include piezoelectric transducers, electromagnetic acoustic transducers (EMAT), magnetorestrictive transducers, interdigital ultrasonic transducers, and active transducers such as millimeter wave transducers. Piezoelectric transducers are preferred, the most preferred being angled piezoelectric transducers. Suitable piezoelectric transducers are commercially available from Tektrend International of Montreal, Canada. Suitable methods of attaching the transducer elements to the probe nonexclusively include gluing, welding, soldering, and the like.
• the transducer element may be attached to the metal probe 2 internally or externally, and may be done in any arrangement and by any suitable means known in the art which would allow the transducer element to be capable of projecting and receiving ultrasonic or radio frequency signals through the metal probe 2.
• the transducer element comprises one transducer 4 which is externally attached to a first end of the metal probe 2.
• the transducer element comprises two transducers, 4 and 4', wherein one is externally attached to a first end of the metal probe 2 and the other is externally attached to a second end of the metal probe 2.
• the transducer element comprises one transducer 4 which is internally attached to the metal probe 2.
• the transducer element comprises two transducers, 4 and 4', wherein both are internally attached to the metal probe.
• the corrosion sensor is placed into a corrosive environment. This is typically done by attaching the sensor to the corrodible metal article in the corrosive environment. This may be done in any suitable manner which would expose the metal probe to the corrosive environment, such as by inserting the probe through the corrosive metal article and into the corrosive environment, or by flush mounting the sensor to the corrosive metal article.
• a sensor 8 is attached via a seal 10, through a wall 11 of a corrodible metal pipe 12, wherein the transducer 4 is on the outside of the pipe 12, and the metal probe 2 is exposed to a corrosive environment inside the pipe 12.
• FIG. 5 shows a sensor 8 is attached via a seal 10, through a wall 11 of a corrodible metal pipe 12, wherein the transducer 4 is on the outside of the pipe 12, and the metal probe 2 is exposed to a corrosive environment inside the pipe 12.
• a sensor 8 is attached to a corrodible metal vessel 18 wherein the probe 2 is attached via a seal 10 within a wall 16 of the vessel 18, which vessel 18 contains a corrosive environment.
• ultrasonic or radio frequency signals such as ultrasonic waves, radio waves, millimeter waves, and the like, are projected from the transducer element, through the metal probe.
• the voltage, frequency, incident angles, length, and other parameters of these signals may vary depending on the size of the probe and the type of transducer used, and may be determined by those skilled in the art.
• an ultrasonic transducer may generate an ultrasonic pulse through a probe, said pulse having a frequency ranging from about 1 MHz to about 10 MHz, more preferably from about 1.5 MHz to about 8 MHz, and most preferably from about 2 MHz to about 5 MHz.
• Radio frequency transducers may generate pulses having frequencies ranging from about 1 gigahertz to about 5 gigahertz. Radio frequency transducers are available from Prolyx, L.L.C. of San Jose, California.
• the ultrasonic or radio frequency signals sent through the probe to those areas by the transducer element will be reflected by the corrosion, and sent back to the transducer element.
• These reflected ultrasonic or radio frequency signals, if any, are received by the transducer element, which then generates an electrical response signal to the reflected ultrasonic or radio frequency signals, indicating a corrosion condition of the metal probe.
• Corrosion conditions include any properties of corroded areas, such as corrosion size, location, growth rate, and type.
• Types of corrosion nonexclusively include stress corrosion cracking, uniform corrosion, and localized corrosion such as pitting corrosion and crevice corrosion.
• Stress corrosion cracking is the formation of fine cracks due to the combined influence of tensile stress and a corrosive medium. Uniform corrosion is generally characterized as an even thinning of a corrodible article over a large surface area. Pitting corrosion is a localized form of corrosion by which small cavities or holes are produced in the corrodible article. Crevice corrosion is a localized form of corrosion typically formed in crevices such as under washers, gaskets, clamps, and the like.
• a series of such electrical response signals may be collected by a signal data collector which may be electrically connected to the transducer element.
• the signal data collector includes an ultrasonic testbed including a broadband receiver which receives the ultrasonic electrical response signals sent from the transducer. These signals are then sent to a digitizer which changes the response signals from analog to digital, and displays the signals on an oscilloscope or graphic processing information display.
• the graphically displayed signals are a function of echo receive time and amplitude which are indicative of the distance along the probe and the amount of corrosion at that distance.
• a preferred signal data collector comprises a computer microprocessor for system operation and control, and for using corrosion algorithms for calculating type, location, size, and growth rate of corrosion. This determination of corrosion conditions can be analyzed to survey the structural integrity of corrodible metal articles which are subjected to corrosive environments. The parameters of importance depend on the environment conditions, and are easily determinable by those skilled in the art.
• a corrosion detector is assembled by externally bonding a piezoelectric transducer to one end of a metal probe.
• the probe is composed of a stainless steel rod having an elliptical cross section.
• Fig. 7 This graph shows an initial ultrasonic pulse which is reflected from the simulated corrosion at the drilled hole points as well as the back wall of the probe.
• a corrosion detector is assembled by externally bonding a piezoelectric transducer to the end of a metal probe.
• the probe is composed of a stainless steel rod having an elliptical cross section.
• the corrosion detector is securely placed through an opening in a sidewall of a stainless steel pipe such that the transducer remains outside of the pipe.
• Natural gas is allowed to flow through the pipe such that the metal probe is in contact with the natural gas.
• Ultrasonic waves are projected from the transducer through the probe. Reflected waves are received and collected by the transducer. The received ultrasonic waves then induce a voltage from the transducer, which is analyzed by a signal data collector which is electrically attached to the transducer. These analyzed signals are used to establish a baseline.
• Ultrasonic waves are then projected and received in the same manner through the probe once an hour for 30 days. Reflected ultrasonic signals are collected and analyzed, and compared to the baseline in order to estimate the degree of corrosion of the probe, and hence on the inside wall of the pipe.

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• Physics & Mathematics (AREA)
• Life Sciences & Earth Sciences (AREA)
• General Physics & Mathematics (AREA)
• Immunology (AREA)
• Chemical & Material Sciences (AREA)
• Analytical Chemistry (AREA)
• Biochemistry (AREA)
• General Health & Medical Sciences (AREA)
• Pathology (AREA)
• Health & Medical Sciences (AREA)
• Acoustics & Sound (AREA)
• Biodiversity & Conservation Biology (AREA)
• Ecology (AREA)
• Environmental & Geological Engineering (AREA)
• Environmental Sciences (AREA)
• Testing Resistance To Weather, Investigating Materials By Mechanical Methods (AREA)
• Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)
• Investigating And Analyzing Materials By Characteristic Methods (AREA)

Priority Applications (5)

Applications Claiming Priority (2)

Publications (2)

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Family Applications (1)

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Cited By (1)

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• 2000
  • 2000-12-22 US US09/746,095 patent/US6490927B2/en not_active Expired - Lifetime
• 2001
  • 2001-12-18 EP EP01987411A patent/EP1344044B1/en not_active Expired - Lifetime
  • 2001-12-18 AT AT01987411T patent/ATE437357T1/de not_active IP Right Cessation
  • 2001-12-18 AU AU2002239629A patent/AU2002239629A1/en not_active Abandoned
  • 2001-12-18 WO PCT/US2001/048872 patent/WO2002052247A2/en not_active Ceased
  • 2001-12-18 JP JP2002553096A patent/JP2004522948A/ja active Pending
  • 2001-12-18 DE DE60139340T patent/DE60139340D1/de not_active Expired - Lifetime
  • 2001-12-21 TW TW090131870A patent/TW576917B/zh not_active IP Right Cessation

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