Corrosionunderinsulation cui refers to the external corrosion of piping and vessels that occurs underneath externally cladjacketed insulation as a result of the penetration of water. Save energy control process temperatures protect workers from high temperatures nace standard rp0198981 is a good source of. Because the corrosion is hidden under the insulation, cui tends to. Inspections have been carried out on equipment both with and without metal weather sheeting around the insulation. The water can come from rain water, leakage, deluge system water, wash water, or swearing from temperature cycling or lowtemperature operation such as refrigeration units. Simulation specimens with large area thinning, localized grovelike corrosions and pitlike corrosions are machined, and probes are designed and manufactured. Corrosion under insulation cui is a major safety threat to chemical processes with pipes and pressure vessels for moving and storing fluids where anions and cations are transported via water to pipe surfaces to corrode away pipe surfaces. Corrosion under insulation cui is one of the most well known phenomena in the process industries, and yet it still makes up an inordinately large percentage of global maintenance expenditures. Assessment of corrosion under insulation and engineered. The water can come from rain water, leakage, deluge system water, wash water, or sweating from temperature cycling or low temperature operation such as refrigeration units. We use this fast and cost effective electromagnetic inspection technique along with guided wave testing, real time radiography and digital radiography for honing in on cui suspect areas without stripping insulation. Pulsed eddy current pec corrosion under insulation cui. The resistive part is the part that causes corrosion in the same manner as direct current corrosion. Pulsed eddy current testing pect is an inspection technique used for corrosion under insulation cui screening on carbon steel structures as pipes, vessels.
Apr 14, 2011 corrosion under insulation cui is the corrosion of piping and vessels that occurs beneath insulation as a result of water penetration. Corrosion under insulation cui is the corrosion of piping and vessels that occurs beneath insulation as a result of water penetration. Perform 100% visual inspection and selectively strip suspect areas 6. These cover deep pitting, as well as general corrosion, that have occurred on galvanized steel. A pulsed eddy current testing probe consisting of a circular excitation coil and an amrsensor. Thermo12 gold with xox inhibits corrosion technical bulletin. Jun 12, 2017 for the love of physics walter lewin may 16, 2011 duration. Pulsed eddycurrent pec inspection through insulation. Pulsed eddycurrent detecting corrosion under insulation. Free water can destroy that corrosion barrier and result in. Corrosion under insulation cui cui is a particularly severe form of localized corrosion that has been plaguing chemical process industries since the energy crisis of the 1970s forced plant designers to include much more insulation in their designs intruding water is the key problem in cui.
Vapor phase corrosion inhibitors preventing corrosion under. Introduction pulsed eddy current pec is a versatile nondestructive testing technique uniquely suited to detect corrosion under insulation, one of the most important issues facing the petrochemical industry today,5,6. Measurements can be made through any material not conducting electricity including coatings, insulation materials, weather sheeting and even corrosion products. Corrosion under insulation cui is a problem in the industrial sector, including refining, petrochemical, power, industrial, onshore and offshore industries and it is a real threat to the on stream reliability of many of todays plants. Corrosion detection and measurement using eddy current methods. Detection of corrosion under insulation cui using ndt techniques. This technology has proven to be an efficient screening tool, allowing for. Some of our coatings are used to solve the problems associated with corrosion under insulation cui, but before addressing our solutions to cui, we present a simplified model of what happens. Corrosion under insulation occurs in isolated lines due to liquid. Development of a pulsed eddy current instrument for. Corrosionpedia what is corrosion under insulation cui. Aug 31, 2017 definition what does corrosion under insulation cui mean.
Corrosion under insulation cui is a special form of external corrosion, it refers the corrosion of piping and vessels that occurs beneath insulation following water ingression. This form of corrosion occurs when water is absorbed by or collected under insulation. By its very nature cui tends to remain undetected until the insulation and claddingjacketing is removed to allow inspection or when leaks occur. Save energy control process temperatures protect workers from high temperatures nace standard rp0198981 is a good source of information, but electrolytes will eventually find their way. What is alternating current corrosion ac corrosion. Patiphon suksawat slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. Such products are often heated for more efficient transport, thus the pipe is wrapped with foam insulation over the coating, and then further covered with a tape wrap over the insulation. It occurs mainly due to ingress of water through the insulation which then comes in. A pulsed eddy current system for flaw detection using an. Charles tremblay as we discussed in our previous article, corrosion under insulation cui is one of the most difficult corrosion processes to prevent.
Measurement of corrosion under insulation and effectiveness of protective coatings dharma abavarathna william g. The extent and rates of corrosion can vary widely and be caused by environment, third party damage or the service conditions. To simulate the insulation and cladding, acrylic plates and an aluminum sheet were used. Pdf incotest, a method for detection of corrosion under. If you continue browsing the site, you agree to the use of cookies on this website. The other commonly used methods are radiography, and complete insulation removal. Compared with conventional eddycurrent testing, pulsed eddycurrent inspection requires no direct contact with the object being tested.
Such products are often heated for more efficient transport, thus the pipe is wrapped with foam insulation over the coating, and then further covered with a tape wrap over the insu. Vapor phase corrosion inhibitors preventing corrosion. Corrosion under insulation cui is a localized corrosion occurring at the interface of a metal surface and the insulation on that surface. For the love of physics walter lewin may 16, 2011 duration. Eddy currents testing of a component under coating 5. Development of a pulsed eddy current instrument for corrosion. Inspection for insulated pipevessel wall thinning may.
Corrosion under insulation cui is one of the most important unresolved issues facing the petrochemical industry today. The equipment begins to corrode as it is exposed to water and oxygen. Inspection techniques for detecting corrosion under insulation. Cui is a subject that is well researched and understood. Definition what does corrosion under insulation cui mean. Cui can be a particularly severe form of corrosion because of the difficulty in detection due to the corrosion occurring beneath the insulation. This article was originally published in the january 1988 national board bulletin. It is a top culprit for piping leaks and near misses and results in significant maintenance costs. Pulsed eddy current testing pect inspection technique. Corrosion inspection using pulsed eddy current semantic scholar. Pulsed eddy current pec has been promoted for screening corrosion under insulation cui, however the sensitivity is often operatordependent, and the overall accuracy can be poor 4, 5,6. Corrosion under insulation cui guidelines 2nd edition.
The technique of pulsed eddy current pec, pulsed eddy current has proven to be able to. Preventing corrosion under insulation cui a chlorine. It occurs mainly due to ingress of water through the insulation which then comes in contact with the metallic pipes underneath. Cui is difficult to detect until the insulation is removed for inspection or when corrosion damage leads to the failure or leaks. Pulsed eddy current, nondestructive testing, defect detection, finite element method. Pulsed eddy current testing of carbon steel pipes wall. Corrosion under insulation cui is a major safety threat to chemical processes with pipes. This is a localized external corrosion occurring in equipment made of insulated carbon and lowcarbon steels.
The pulsed eddy current technique has been under developtnent at iowa state uniyersit. Pulsed eddy current testing of inner wall flaws in pipe under insulation. For this corrosion to occur, water must collect in the insulation and oxygen must be present. Corrosion under insulation a large range of insulated and coated equipment, including pipes, vessels, columns, heat exchanger shells and storage tanks, has been inspected for corrosion under insulation cui. Corrosion under insulation cui is a severe form of localized external corrosion that occurs in carbon and low alloy steel equipment that has been insulated. Corrosion under insulation cui cui has been recognized as a problem in many industries insulation is a necessary component of the system and is designed to.
Corrosion under insulation loop steam drum present by. Pdf on oct 10, 2007, hamed malekmohammadi and others published incotest, a method for detection of corrosion under insulation using pulsed eddy current technique find, read and cite all the. For one, the industry as a whole has become more complex. Pulsed eddy current testing pect is an inspection technique used for corrosion under insulation cui screening on carbon steel structures as pipes, vessels, tanks and spherical tank legs without the need of.
Corrosion under insulation has become more critical in the industry for a number of reasons. Pulsed eddycurrent has been identified as a potential ndt method for this application. Thermo12 gold with inhibits corrosion under insulation cui thermo12 gold with xox inhibits corrosion technical bulletin since the inception of the industrial insulation group in 2002, thermo12 gold calcium silicate hightemperature pipe and block insulation has incorporated, a unique process and formulation, that. Corrosion under insulation cui is, as the name indicates, the corrosion or corrosionrelated cracking that occurs under insulationandor fireproofing. Perform external inspection of insulation to identify areas of staining, bulging, breakdown damage that could result in water ingress agt.
The 3 major effects of galvanized steel on pulsed eddy current in corrosion under insulation inspection. Chemical, petroleum and food processing facilities, to name a few, require more sophisticated equipment, instruments and piping arrangements see figure 4. Although the extent and resultant cost of corrosion under insulation cui are not known exactly, j. Corrosion under insulation occurs in isolated lines due to liquid infiltration or humidity retained between the metal and insulating material. The incident the failure of a 8 inch carbon steel, high pressure hydrocarbon line due to corrosion under insulation on march, 2008, at a dows lhc plant, an 8 inch, schedule 20, carbon steel hydrocarbon line failed. While coatings on the metal can be effective for extended periods, once the coating begins to break down, moisture held in or under the insulation will inevitably find an opening and begin its counterproductive work. Pulsed eddy current testing of inner wall flaws in pipe under. Pdf pulsed eddy current testing of inner wall flaws in pipe.
Pulsed eddy currents, corrosion under insulation, gmr sensor. The localized inner wall corrosions in the pipe under insulation are especially hazardous to pipelines. Preventing corrosion under insulation cui a chlorine institute perspective frank reiner. Advisory bulletin warns about corrosion under insulation. Pdf pulsed eddy current testing of inner wall flaws in. Jul 07, 2010 corrosion under insulation loop steam drum present by. Compared with conventional eddy current testing, pulsed eddy current inspection requires no direct contact with the object being tested. The most common and straightforward way to inspect for corrosion under insulation is to cut plugs in the insulation that can be removed to allow for ultrasonic testing.
Delahunt in corrosion control under thermal insulation and fireproofing 1 shows the seriousness of the problem by presenting case histories. It has shown tnuch protnise for detecting corrosion and cracks in tnultilayered aircraft structures, and has elidt. Pulsed eddy current testing of wallthinning through cladding and insulation was studied from both theoretical and experimental aspects. Pulsed eddycurrent has been identified as a potential ndt method for this. The association between the resistive and capacitive current is a vital decisive factor for alternating current corrosion since massive resistance currents leads to immense corrosion. Pulsed eddy current pec has been successfully deployed over the last decades for a variety of corrosion related applications, most notably for corrosion under insulation cui inspections. The analytical solution was derived for a simplified fourlayered structure and was used to conduct simulations to ascertain the feasibility of this method. Corrosion under insulation is caused by the ingress of water into the insulation, which traps the water like a sponge in contact with the metal surface. Corrosion under insulation inspection and prevention. Detection of corrosion under insulation cui using ndt.
Appendix d case studies of 1 a national oil company, 2. Irisndt uses stateoftheart highperformance pulsed eddy current pec systems to inspect for corrosion under insulation cui. Corrosion under insulation cui refers to the external corrosion of piping and vessels that occurs underneath externally cladjacketed insulation as a result of the penetration of water. This paper addresses the corrosion under insulation cui issue, which occurs. The duration of the eddycurrents, within the enclosed. Pulsed eddy current pec has been successfully deployed over the last decades for a variety of corrosionrelated applications, most notably for corrosion under insulation cui inspections. A recent phmsa advisory bulletin warns the pipeline industry about corrosion under insulation cui, which is frequently used on pipe transporting heavy crude oil. Jun 24, 2016 a recent phmsa advisory bulletin warns the pipeline industry about corrosion under insulation cui, which is frequently used on pipe transporting heavy crude oil.
Corrosion under insulation cui and monitoring of degradation under engineered temporary wraps has proven to be a challenge to reliably detect and monitor using ndt methods. Spare chlorine recycle line put into service during maintenance activity leak quickly developed. External corrosion of carbon steel piping, pressure vessels and structural components resulting from water trapped under insulation in conjunction with other variables that accelerate and drive the corrosion external chloride stress corrosion cracking of austenitic and duplex stainless steel under. Vapor phase corrosion inhibitors preventing corrosion under insulation corrosion under insulation cui is a serious concern both in terms of monetary loss and danger to personnel safety. This project evaluates the effectiveness of the currently available equipment to detect and assess the anticipated. The following article is a part of the national board technical series. Corrosion under insulation, and 4 examples from the u.
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