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  • [会议] Hydrogen induced stress cracking (HISC) resistance and improvement methods for super duplex stainless steels
    摘要:The paper reviews the history of HISC failures of duplex and superduplex stainless steels when deployed subsea and subject to cathodic protection (CP) at potentials around -1V SCE. The test methods applied to investigate the problem and subsequently used to develop current design codes that deal with HISC are reviewed. Data from these investigations is compared with other testing using the same cast and batch of bar product, but where controlled shot peening is used to induce compressive residual stresses in the surface of the test samples. Parent pipe material and cross welded samples of seamless pipes were also tested. Peened material showed a 10 to 15% improvement in the threshold stress to initiate HISC. The paper also discusses an Advanced Forging Process (AFP) production route, recently developed to provide both increased notch toughness at low design temperatures and improved resistance to HISC in forgings used to make 10k weld neck and swivel ring flanges for subsea manifolds. Data is presented showing an increase in the threshold stress ratio (applied stress divided by the actual 0.2% proof strength) from 85% to 97.5%. We also find a corresponding increase in impact toughness of AFP material, allowing use of the products at design temperatures down to minus 70°C. This is attributed to the dissolution of detrimental nitride precipitates within ferrite grains in the forgings and transforming these into advantageous intergranular reformed austenite.
  • [会议] Round-robin evaluation of ISO 20340 annex a test method
    摘要:Among available standardized test methods for evaluating the performance of marine and offshore coatings, ISO 20340 Annex A is widely used.1 It is well known that tests performed on presumably identical materials in presumably similar circumstances do not in general yield to identical results. Such deviation is attributed to unavoidable random errors inherent in every test procedure and the fact that the parameters that may influence the outcome of a test cannot all be completely controlled. One consequence of such deviation is that different coating selection may be obtained upon where and how the test is performed, as ISO 20340 Annex A includes acceptance criteria for the selection of coating systems. Thus, to establish the precision of ISO 20340 Annex A, six laboratories participated in a round-robin evaluation of ISO 20340 Annex A test method for the first time. The aim was to estimate the repeatability and the reproducibility of this test upon laboratory, and eventually to determine how to improve the test method and the standard for the further revision of the standard. Five different painted systems applied on abrasive blasted steel were selected so that it included good and poor systems. The results of this study in terms of scribe creep and pull-off strength data were analyzed regarding the repeatability within a laboratory and lab-To-lab reproducibility.
  • [会议] Investigations about a new heavy metal free, low p-content corrosion inhibitor for evaporative cooling systems based on phosphorous modified organic acid (PMOA)
    摘要:State of the art corrosion inhibitor programs for evaporative cooling systems are based on phosphate, phosphonates, zinc and combinations thereof. Although generally satisfying control of corrosion can be achieved, all programs have drawbacks such as lack of biodegradability and content of heavy metals. Consequently, there is a need for corrosion inhibitors with an improved environmental profile and/or improved performance. This contribution shows the results obtained with a newly developed corrosion inhibitor, phosphorous modified organic acid (PMOA). It is free of heavy metals and has an excellent environmental profile. Corrosion tests have been carried out in dependence of important application parameters, applying electrochemical methods, beaker tests and long term tests in cooling circuit simulating devices. The results show excellent efficiency and significant synergies between the new substance and other inhibitors. Pilot plant studies of a formulation based on the new inhibitor show the same or better performance compared to commercially available products, but a marked reduction of the phosphorous entry into the waste water. The improved performance can be transferred directly into savings. The positive results were confirmed in a cooling water system of a German refinery.
  • [会议] Methodology for the evaluation of cleaning pigs on sludge deposits from corrosion pits
    摘要:For decades pipelines have been operated in remote and environmentally sensitive areas as well as within populated locations. Proper maintenance of pipelines can prevent internal corrosion to a remarkable degree. The methods employed are primarily mechanical cleaning (pigging) and chemical treatment (corrosion inhibitors, biocides), often used in combination. Corrosion issues arise in areas of the pipeline typically under localized areas containing sediments that tend to be an agglomeration of solids, waxes and water. The resulting corrosion defects can then become ideal locations for sediment and water to continue to gather and create deep, dirt filled localized pitting that cannot be protected through chemical treatment without the aid of mechanical cleaning (pigging). In an effort to increase the knowledge of the cleaning efficiency of typical pig designs at removing sludge and debris from pre-existing corrosion pits, a novel test setup and method has been devised. A recirculating flow loop was constructed with the capabilities of launching a 102 mm (4") diameter cleaning pig using either crude oil or water as the pumped fluid. During the test, a pig would be passed through a test apparatus which housed flush mounted coupons with variously sized pits, packed with manufactured sediment (sludge). Following the pigging operation, the coupons were removed and analyzed via laser scanning techniques to measure sludge volume removal and maximum depth of cleaning. The pigs' cleaning abilities were compared based on both metrics and information was gathered based on the profile of the sludge's surfaces post pigging, as well as images of the pigs with adhered sludge.
  • [会议] Abrasion-corrosion resistance of stainless and wear-resistant steels for oil sands applications
    摘要:Oil sands operations may give rise to various corrosion risks such as pitting corrosion, crevice corrosion, microbiologically influenced corrosion and abrasion-corrosion. These risks are mainly related to the chemical composition of the slurry and the presence of abrasive particles or rocks. That is why the corrosion resistance is a critical parameter that has to be taken into account for material choice to avoid regular maintenance of the process equipment. This paper focuses on the abrasion-corrosion resistance of various stainless steels and wear-resistant carbon steels. The abrasion-corrosion tests were conducted by means of an innovative test method in environments containing chlorides in a pH range from 3 to 9. The results show that wear-resistant steels are more resistant to abrasion-corrosion than stainless steels in environments containing a low amount of chlorides when the pH is basic. On the contrary, in more corrosive environments, wear-resistant steels are susceptible to corrosion. In such environments, duplex stainless steels are more resistant to abrasion-corrosion and can be considered as excellent candidate materials for various applications like piping systems for instance.
  • [会议] Are you trained, certified and qualified to assess corrosion and related defects?
    摘要:Hazardous liquid and gas pipeline operators are tasked with the responsibility of complying with the federal and state regulatory requirements to ensure that personnel are trained, certified and operator qualified to gather information and data of pipeline defects that are to be assessed properly after in-line inspection runs, direct assessment or other maintenance activities. This requires that technical personnel be qualified in many tasks and experienced in all phases of direct examination of corrosion, gouges, dents, weld defects, cracks, wrinkle bends, SCC, construction defects, etc.
  • [会议] Remaining strength of corroded pipe direct assessment process
    摘要:Remaining Strength of Corroded Pipe Direct Assessment (RSCP DA) process can be used as an assessment metal loss technique to verify In-Line-lnspection (ILI), External/Internal Corrosion Direct Assessment (EC/ICDA) and other inspection data which is used in determining the safe pressures and thereby validate the operator's ongoing integrity management program. This is accomplished by evaluating and verifying the metal loss defects such as corrosion and mechanical damage such as a gouge with the stress cracking concentrator removed. The RSCP DA process provides a pipeline operator with a basis for the determination for repairs or not.
  • [会议] Improvements to cathodic protection performance using DCVG prioritization
    摘要:Due to the serious consequences of corrosion and leaks in underground pipelines, external corrosion direct assessment (ECDA), as described in ANSI<1)/NACE(2) SP0502 was developed in an attempt to proactively prevent external corrosion and ensure the integrity of oil and gas pipelines that are difficult to pig. This standard requires a minimum of two indirect inspections to confirm the most susceptible locations on a pipeline for external corrosion to occur. Cathodic protection close interval survey (CP CI PS) and direct current voltage gradient (DCVG) are usually complementary indirect inspection techniques used for assessing the effectiveness of the cathodic protection and coating conditions. DCVG detects coating anomalies due to voltage gradient created as a result of direct current flow to coating anomaly. Coating severity index or DCVG % IR is used to prioritize coating anomalies for repair with the intent of improving the cathodic protection performance. Coating anomalies with large DCVG %IR are thought to have greater risk for external corrosion during ECDA; possibly due to large exposed metal to corrosive environment. However, considering that a large coating anomaly would consume more CP current, the tendency for corrosion is expected to be minimal. This paper will show improvements in interpretation of DCVG % IR and how accurate selection of pipeline coating rehabilitation location based on this concept would lead to improvements in cathodic protection performance. Case studies from previous ECDA digs are presented.
  • [会议] Improving the controlled humidity protection systems by addition of vapor phase corrosion inhibitors
    摘要:Controlled Humidity Protection (CHP) reduces corrosion created by exposing items to high relative humidity (exceeding 40%). Although, controlled humidity protection systems, in theory, can suppress the cathodic reaction and lower the corrosion rate, in reality, the amount of moisture and oxygen in presence of corrosive species like chloride that is required to initiate the corrosion reaction for steel is extremely low, and once corrosion reaction starts there is no defense mechanism to stop it. Addition of the vapor phase corrosion inhibitors to the CHP provide a more effective corrosion protection for materials exposed to the environment during short term storage. A dry air controlled humidity system can reduce the moisture level, but it will not be able to prevent corrosion. The advantage of the vapor phase corrosion inhibitor addition to CHP system is the creation of a strong physisorption to the material surface that minimizes any surface contact with corrosive species or water due to its hydrophobic film. Therefore, vapor phase corrosion inhibitors addition can provide superior advantages over the controlled humidity protection system in the presence of aggressive environments that contain excessive salt, oxygen and moisture.
  • [会议] Compatibility behavior of elastomers for PCP applications
    摘要:With the aim of understand the performance of elastomeric materials used in progressive cavities pumps to face operational conditions presented in Venezuelan oil wells, it was carried out a compatibility study of two elastomers with low and high nitrile content in environments such as H2S, CO2 and different crude oils to simulate real conditions in the lab. This study is based in the evaluation of the mechanical behavior of the elastomers before and after being in contact with different fluid and gases. NACE and ASTM standards were used to evaluate mechanical properties of the elastomers such as yield strength, elongation at break, Shore A hardness, permanent deformation and volumetric swelling. Characterization techniques such as thermal gravimetric analysis (TGA) and scanning electron microscopy (SEEM) were employed. The effect of crude oils, hydrogen sulfide (H2S) and carbon dioxide (CO2) in the elastomer helps to predict the performance behavior of the material when it is in service. Upon completion of the different evaluation techniques, it was observed how different fluids conditions (Temperature, H2S and C02 concentration) affect the mechanical properties of the elastomers studied. It is recommended to continue the evaluation with different elastomers which provide a range of support to various aggressive environments to which the material is subjected during its operation.

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