Calibration of the AC Potential Dropping System (ACPD) for Determination of Crack Growth in API 5L X65 Steel under Cathodic Protection Effect

2020 ◽  
Vol 1012 ◽  
pp. 412-417
Author(s):  
Misael Souto de Oliveira ◽  
Antonio Almeida Silva ◽  
Marco Antonio dos Santos ◽  
Jorge Antonio Palma Carrasco ◽  
João Vitor de Queiroz Marques
Keyword(s):  
Crack Growth ◽  
Marine Environment ◽  
Cathodic Protection ◽  
Sea Water ◽  
Potential Drop ◽  
Mechanical Tests ◽  
Flow Density ◽  
Type Specimens ◽  
X65 Steel ◽  
Api 5L X65 Steel

In this work the calibration of an Alternative Current Potential Drop (ACPD) system was performed to monitore laboratory mechanical tests on marine environment under cathodic protection. The calibration was done on CT type specimens of API 5L X65 steel dimensioned according to ASTM E1820 standard., The crack propagation during a tensile test with displacement control in an ACPD equipment was monitored through the performs points collection by two channels: one that monitors the crack growth and another that monitors a region free of crack. Using a profile projector and graphical data processing and analysis software, the area of ​​the fracture surface of the specimen was meansured, which allowed to correlate a crack size with a corresponding value of potential drop and the calibration curve. In order to verify verify the efficacy and precision of the technique, step loading tests were performed on API 5L X65 steel test specimens, submerged in synthetic sea water under the overprotection potential of-1300mVAg/AgCl. The results of the calibration showed few dispersed errors, and the main factors of this dispersion may be related to the geometry of the specimen and with variations in current flow density, which is influenced by corners and edges and by the presence of pick-up inductive. The calibration and its effectiveness can be verified through the results of the tests in marine environment, presenting crack lengths close to the actual values, confirming the effectiveness of the ACPD technique.

Crack Growth in Pipes Under Service Contortions

2009 ◽  
Author(s):  
Oddvin O¨rjasaeter ◽  
Richard Verley ◽  
Per Egil Kvaale ◽  
Tor Gunnar Eggen
Keyword(s):  
Crack Growth ◽  
Cathodic Protection ◽  
Growth Rates ◽  
Fatigue Cracks ◽  
High Growth ◽  
Potential Drop ◽  
Fatigue Tests ◽  
Full Scale ◽  
Small Scale ◽  
Loading Frequency

At the A˚sgard field a leak on a 10″, 13Cr production pipeline was discovered in December 2000 during pressure testing. The cause was a crack at an anode pad fillet weld (pads are connectors for the cathodic protection system). Later, a similar leak occurred on another A˚sgard flowline. During pigging inspection (AUT) several smaller crack indications were found at similar locations. Propagation of such cracks will depend on loading and environmental conditions. To investigate this further, a test programme was carried out using 13Cr pipe materials. Both small scale tests and full scale pipes were used. Specimens were prepared with small initial fatigue cracks at the pad weld. The propagation of the cracks was then recorded under various environmental and loading conditions. The loading was selected to cover a crack growth rate range of ∼10−6 to 10−3 mm/cycle for various crack depths and for two loading frequencies. Tests were conducted under cathodic protection (hydrogen in the material measured) and for temperatures up to 140°C and pressures up to 30bar. The crack growth was recorded by the potential drop method (ACPD). For the full scale pipe tests, specially developed equipment was used for simultaneous measuring at up to 24 individual locations. The results showed that low loading frequency (0.1 Hz) enhances the growth rates; elevated temperature gave equal or lower propagation rates than at 25°C and a pressure of 30bar did not influence the results. A few cracks were also initiated during the corrosion fatigue tests and exhibited high growth rates; possibly due to the so-called “small crack” effect and possibly in synergy with the influence of hydrogen.

Experimental Study of Crack Growth in HDPE PE100 Pipes

2013 ◽  
Author(s):  
Raul Machado ◽  
Marco Gonzalez ◽  
Jeanette Gonzalez
Keyword(s):  
Experimental Study ◽  
Crack Growth ◽  
Extrusion Process ◽  
Mechanical Tests ◽  
Piping System ◽  
Type Specimens ◽  
Fracture Characterization ◽  
Elastic Plastic ◽  
Operation Conditions ◽  
Hdpe Pipes

The operation conditions of a piping system such as impact loads, cyclic loadings and discontinuities cause damages, cracking or weakening in the material. The High Density Polyethylene (HDPE) is amply used in the fabrication of pipes due to its versatility, low cost and lightweight. In this study, an experimental study of fracture mechanics of HDPE PE100 specimens obtained directly from extruded pipes is developed. The research is aimed at characterizing the pipe mechanical behaviour under operation loadings, for which elastic-plastic mechanical tests under the ASTM D-5045, E-1820, E-399 and E-813 standards and ESIS protocol are carried out. The influence of the orientation induced by the extrusion process (circumferential or longitudinal direction) on pipes fracture resistance is established. SENB type specimens (three point bending) are used for the fracture characterization and J-R Curves (J vs. Δa) for elastic-plastic analysis are generated according to ESIS protocol. The PE100 fracture characterization throughout the J vs. Δa curves indicates that in both circumferential and longitudinal directions require similar quantities of energy to generate new fracture surfaces on HDPE pipes. Indeed, the orientation of the polymer chains as a result of pipe extrusion process could be not so relevant for predicting the direction of crack growth in HDPE pipes.

Improved Compliance Solutions for C(T), SE(B) and Clamped SE(T) Specimens Including Side-Grooves, Varying Thicknesses and 3-D Effects

2014 ◽  
Author(s):  
Gustavo Henrique B. Donato ◽  
Felipe Cavalheiro Moreira
Keyword(s):  
Crack Growth ◽  
Plane Strain ◽  
Plane Stress ◽  
Potential Drop ◽  
Crack Size ◽  
Growth Conditions ◽  
Size Estimation ◽  
Unloading Compliance ◽  
Integrity Assessments ◽  
Elastic Unloading

Fracture toughness and Fatigue Crack Growth (FCG) experimental data represent the basis for accurate designs and integrity assessments of components containing crack-like defects. Considering ductile and high toughness structural materials, crack growing curves (e.g. J-R curves) and FCG data (in terms of da/dN vs. ΔK or ΔJ) assumed paramount relevance since characterize, respectively, ductile fracture and cyclic crack growth conditions. In common, these two types of mechanical properties severely depend on real-time and precise crack size estimations during laboratory testing. Optical, electric potential drop or (most commonly) elastic unloading compliance (C) techniques can be employed. In the latter method, crack size estimation derives from C using a dimensionless parameter (μ) which incorporates specimen’s thickness (B), elasticity (E) and compliance itself. Plane stress and plane strain solutions for μ are available in several standards regarding C(T), SE(B) and M(T) specimens, among others. Current challenges include: i) real specimens are in neither plane stress nor plane strain - modulus vary between E (plane stress) and E/(1-ν2) (plane strain), revealing effects of thickness and 3-D configurations; ii) furthermore, side-grooves affect specimen’s stiffness, leading to an “effective thickness”. Previous results from current authors revealed deviations larger than 10% in crack size estimations following existing practices, especially for shallow cracks and side-grooved samples. In addition, compliance solutions for the emerging clamped SE(T) specimens are not yet standardized. As a step in this direction, this work investigates 3-D, thickness and side-groove effects on compliance solutions applicable to C(T), SE(B) and clamped SE(T) specimens. Refined 3-D elastic FE-models provide Load-CMOD evolutions. The analysis matrix includes crack depths between a/W=0.1 and a/W=0.7 and varying thicknesses (W/B = 4, W/B = 2 and W/B = 1). Side-grooves of 5%, 10% and 20% are also considered. The results include compliance solutions incorporating all aforementioned effects to provide accurate crack size estimation during laboratory fracture and FCG testing. All proposals revealed reduced deviations if compared to existing solutions.

scholarly journals Does galvanic cathodic protection by aluminum anodes impact marine organisms?

2020 ◽  
Vol 32 (1) ◽  
Author(s):  
Anna Maria Bell ◽  
Marcus von der Au ◽  
Julia Regnery ◽  
Matthias Schmid ◽  
Björn Meermann ◽  
...  
Keyword(s):  
Marine Environment ◽  
Cathodic Protection ◽  
Algal Growth ◽  
Wind Farms ◽  
Marine Organisms ◽  
Offshore Wind ◽  
Natural Seawater ◽  
Corophium Volutator ◽  
Offshore Wind Farms ◽  
Ecotoxicological Effects

Abstract Background Cathodic protection by sacrificial anodes composed of aluminum-zinc-indium alloys is often applied to protect offshore support structures of wind turbines from corrosion. Given the considerable growth of renewable energies and thus offshore wind farms in Germany over the last decade, increasing levels of aluminum, indium and zinc are released to the marine environment. Although these metals are ecotoxicologically well-studied, data regarding their impact on marine organisms, especially sediment-dwelling species, as well as possible ecotoxicological effects of galvanic anodes are scarce. To investigate possible ecotoxicological effects to the marine environment, the diatom Phaedactylum tricornutum, the bacterium Aliivibrio fischeri and the amphipod Corophium volutator were exposed to dissolved galvanic anodes and solutions of aluminum and zinc, respectively, in standardized laboratory tests using natural seawater. In addition to acute toxicological effects, the uptake of these elements by C. volutator was investigated. Results The investigated anode material caused no acute toxicity to the tested bacteria and only weak but significant effects on algal growth. In case of the amphipods, the single elements Al and Zn showed significant effects only at the highest tested concentrations. Moreover, an accumulation of Al and In was observed in the crustacea species. Conclusions Overall, the findings of this study indicated no direct environmental impact on the tested marine organisms by the use of galvanic anodes for cathodic protection. However, the accumulation of metals in, e.g., crustaceans might enhance their trophic transfer within the marine food web.

scholarly journals Cathodic protection of structures in seawater using solar panels

2019 ◽  
Vol 121 ◽  
pp. 02004
Author(s):  
Boris Borisovich Chernov ◽  
Van Mung Vu ◽  
Anac Maskharovich Nugmanov ◽  
Lyudmila Yuryevna Firsova
Keyword(s):  
Cathodic Protection ◽  
Sea Water ◽  
Cathode Current Density ◽  
Complete Agreement ◽  
Low Alloy Steels ◽  
Solar Panels ◽  
Protective Properties ◽  
Theoretical Concepts ◽  
Alloy Steels ◽  
Cathode Current

It is well known that the cathodic protection of structures in seawater is accompanied by the formation of calcareous deposits on them. In current study, we consider the physicochemical modelling of the formation of the deposit composition against cathode current density in seawater. The reliability of the model representations is confirmed by direct experiments. The work also studied the protective properties of the deposits with a different composition for low-alloy steels in natural sea water. It has been shown that the deposits of pure Mg(OH)2 and the deposits of CaCO3 + Mg(OH)2 had better protective ability against corrosion than the deposits of pure CaCO3. However, the deposits of Mg(OH)2 dissolved faster than the deposits of CaCO3 and CaCO3 + Mg(OH)2. Theoretical concepts and experiments on the laws governing the formation of the deposits and their protective properties are in complete agreement with each other. This allows to use the obtained patterns in the cathodic protection of structures in sea water using solar panels, forming standard deviations with predetermined protective properties in the daytime.

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