Material Technology Trends to Improve Multi-Layer Coatings: Challenges to Traditional Thinking

Current Global acceptance of the three layer polyethylene coating system for the exterior coating of steel pipelines (for almost any environment on-shore/off-shore for oil, gas or water pipelines) has helped to expand the present coating use. The focus of this paper will be on coating material changes by technology, to up-grade the end use of the coating system and to present those changes to the engineering and corrosion community to the benefit of the end user or client.

Unleashing the Hidden Value of a Pipeline Through the Use of Visual Communications

How does the communication of information affect the pipeline industry? People are becoming more aware of the pipeline industry and how it may affect individuals and landowners in the future. Corporations are producing commuications tools to alleviate the lack of knowledge and the hidden value of energy pipelines. This case study examines two projects: “Passing through Edson” examines a winter pipeline construction job in Edson, Alberta. The story is told by the people on the job. We examine the environmental issues, economic impact, Native employment, and winter construction techniques. The “Boy Chief” video examines the impact of an archaeological dig on the prairies. In this program we have insight into the aboriginal history of the area and how the pipeline company is helping people learn more about the Native way of life. The paper examine how communication tools like these, allow employees access to information when communicating to stakeholders.

Tar-Polyurethane Joint Coating for the Three-Layer Polyethylene Pipeline Coating

This article describes a new joint coating system implemented by Bechtel for a major international, 48 inch diameter gas pipeline. Despite the long history of use as a pipe and valve coating, the new implementation is the industry’s first significant use of a thermoset hot spray coating applied to field weld areas of pipe, mill coated with a three layer polyethylene system. In the laboratory and in field trials, the coating demonstrated integrity, was applied much quicker than the traditional heat shrink sleeve, and eliminated several application contingencies. Laboratory investigations undertaken in Houston, Texas and Lyon, France were key steps in selecting the 100% solids tar-polyurethane coating. Additionally, the testing assisted in developing the surface preparation technique, and demonstrating the coating’s ability to adhere to the polyethylene coating as well as the steel pipe. Serious localized corrosion, and cathodic protection shielding associated with other joint coatings are less probable with the new joint coating system. Actual field cathodic protection testing indicated very low current consumption for the completed pipeline. The efficient joint coating operation contributed to setting new construction records.

Quantitative Examination of Segregation in Slabs for the Production of Sour Service Linepipe

Segregation is a major problem to be overcome by producers of HIC resistant steels. Primary segregation is an inherent and unavoidable feature of the solidification process. The constitutive relationship between solid and liquid stage determines microsegregation and it is influenced by the chemical composition of the steel and its cooling rate. Macrosegregation occurs when microsegregated liquids collect and shift through liquid flow. OREGON STEEL MILLS has conducted systematic measurements on pressure-cast slabs using a computer assisted micro analyzer. This microprobe measures element concentrations over a large area of the specimen. A statistical evaluation based on the frequency distribution of the concentrations forms the basis of a quantitative analysis. From this, characteristic parameters such as the segregation factor and maximum concentration can be derived. This paper discussed the influence of carbon on segregation structure and on segregation properties of manganese, and compares the results with those of continuously cast slabs.

The Investigation of Pipeline Accidents, Canada’s Approach

The Transportation Safety Board of Canada (TSB/C) is the short name, or applied title, for the federal agency mandated to carry out independent safety investigations of accidents and incidents of the marine, pipeline, rail and air modes of transportation. Our official name is the “Canadian Transportation Accident Investigation and Safety Board” reflecting the legislation under which we operate. The CTAISB Act was passed by Parliament in June 1989 and promulgated in March 1990.

Limit Loads for Pipelines With Axial Surface Flaws

The limit loads for pipelines with axial surface flaws have been evaluated by using a strip yield model at levels of ligament yield and ligament collapse. The former was defined as that at which the plastic zone first reaches the back surface, and the later is that at which the plastic zone spreads over the entire ligament. The evaluated collapse load has been used to estimate the failure stress of pipelines containing axial surface flaws. Predictions have been compared with existing experimental data.

Effect of Asphaltene Deposition on the Internal Corrosion in Transmission Lines

Crude oil from Norte de Monagas field, in Venezuela, contains large amounts of asphaltenes, some of them are very unstable with tendency to precipitate. Because of liquid is carried over from the separation process in the flow stations, asphaltenes are also present in the gas gathering and transmission lines, precipitating on inner wall of pipelines. The gas gathering and transmission lines contain gas with high partial pressures of CO2, some H2S and are water saturated; therefore inhibitors are used to control the internal corrosion. There is uncertainty on how inhibitors perform in the presence of asphaltene deposition. To protect the pipelines from external corrosion, cathodic protection is used. Since asphaltenes have polar properties, there exists an uncertainty on whether it enhances asphaltene precipitation and deposition. The purpose of this paper to describe the causes that enhance asphaltene deposition on gas and some of the preliminary result from an ongoing research project carried out by Intevep and Corpoven.

Evaluation of Stray Current Effect on the Cathodic Protection of Underground Pipeline

Two types of stray current which affect the cathodic protection of underground pipeline are discussed. One is the stray current by DC transit system and the other is that originated from the nearby cathodic protection system. The popular evaluation methods of the pipe-to-siol potential measurement was undertaken to evaluate the corrosion activity of pipeline. In case when the pipe was affected by the stray current, the measured pipe-to soil potential was significantly deviated from the mean value resulting in normal distribution. Analysis of such distribution pattern has revealed that the pipe under investigation was in the condition of insufficient protection (noble mean potential and high asymmetry coefficient) due to the considerable effect of stray current (high standard deviation value). It was also confirmed that the efficiency of drainage system was so low (<10%) due to the improper selection of drainage point. Simultaneous measurement of the magnitude and direction of the sheath current resulted in information about the place where stray current entered into pipe and escaped to soil. For the second case of stray current problem, it is shown that it has been caused by the combined interference from nearby CP system.

Residual Strength of 48-Inch Diameter Corroded Pipe Determined by Full Scale Combined Loading Experiments

To provide a data base for the confirmation of computational and classical residual strength analyses of corroded pipelines subjected to combined loads, full scale experiments of 48-inch diameter pipe sections with artificial corrosion were conducted. Design of the experiments was guided by the prerequisite of testing pipe sections in full scale such that subsequent corrections for the uniform depth and extent of the degraded region, and D/t ratios were not required. The testing and analysis procedures were progressively developed through three distinct phases of the program: 1) one proof of concept experiment performed on smaller diameter pipe with artificial corrosion subjected to internal pressure and axial bending, 2) five 48-inch diameter pipe tests, each with artificial corrosion, subjected to internal pressure and axial bending, and 3) eight 48-inch diameter pipe tests, each with artificial corrosion subjected to pressure, axial bending, and axial compression. Combined loading on the test specimens followed a predetermined path until failure by either rupture or global buckling occurred, while the elastic-plastic load-deflection and large strain behavior was recorded. The uniform depth, axial length, and circumferential length of the degraded region were selected to represent commonly observed general corrosion dimensions found among in-service pipelines, with the maximum and minimum extents reflecting the typical wall loss characteristics at the girth and seam weld locations. The pipe behavior during the experiments and analyses was ultimately modeled and verified by an elastic-shell model capable of defining failure pressure and curvature for a corroded pipe subjected to combined service loads. This paper presents details on the test procedures, specimen preparation and design, and complex data acquisition techniques utilized in the generation of required global and location response information. In addition, significant experimental results from the program which enabled the development and validation of a new procedure for the assessment of corroded pipes under combined loads are reviewed.

Inspection Challenges: Pigs Versus Pipes

As the size of the international pipeline network grows, and systems age (by the year 2000, over 50% of US gas transmission pipelines will be over 40 years old), and as environmental pressures increase, the demand for inspection is ever more apparent. Pipeline operations’ experience has revealed many “new” defects and “new” inspection problems, many of which have challenged in-line inspection technology and stimulated further developments. This paper describes what pipeline inspection needs to find, the available technology and some examples of the inspection challenges.