It is well known in the hot rolled steel making business that nonmetallic inclusions play critical
role in defining steel performance. The objective of this paper is to study laminations that were
detected via Phased Array UT system in X60MS Class-C High Frequency Welded Pipe intended for
offshore application. The linear intermittent laminations appear along the pipe and adjacent to
the weld seam from both sides at a width of 30 to 40 mm with various depths. Technical review
was carried out on 5 available pipes, pertaining to the same heat of the original pipe identified
earlier with lamination, through model experiments; both on the laboratory and on the industrial
scale. At the beginning, depth and distribution of detected laminations were analyzed by manual
UT mapping using normal beam probe. Metallurgical analysis via Energy Dispersive X-ray (EDX)
was carried out on three samples to determine the chemical composition as well as the
morphology of the lamination. The type of inclusion which turned out to be type B (Alumina-
Al2O3) inclusion was identified by evaluating EDX results using Method A per ASTM E45. As it is
a pure material based incident, failure analysis was carried out by the steel maker to identify the
associated root causes from process control prospective and the appropriate preventive
measures to avoid reoccurrence. Eventually, the applied quality control measures during
manufacturing process of HFW pipes, represented in the deployment of UT systems, were
reviewed to identify the reason behind missing such important defect before pipes are being
shipped to the client.
Composite repairs have been applied to pipelines and piping systems for structural reinforcement after external corrosion. Such repairs may consist of glass or carbon fibers embedded in a matrix of epoxy. Typically, these repairs are hand applied using either wet lay-up systems or prefabricated rolls of composite sleeve. In some applications, pipeline continued corrosion growth under composite repairs were reported using Inline Inspection (ILI) which raises a concern about the integrity of the metallic piping under composite repairs. When continued corrosion is detected by ILI, a difficulty is typically faced due to the inability to measure pipeline remaining thickness under such repairs. To resolve this challenge, this paper will discuss multiple inspection and corrosion monitoring techniques for metal loss under composite repairs. To measure the pipeline wall thickness due to internal corrosion, one or more of the three (3) Non-Destructive Testing (NDT) technologies namely; Dynamic Response Spectroscopy (DRS), Multi-skip Ultrasonic (MS-UT) and digital radiography were evaluated and found capable. To monitor for external corrosion, a scheduled visual inspection of the composite repair would be the first inspection step. If the composite repair appears to be intact then the visual inspection would suffice and the repair should be acceptable to its design life. If the original defect is external corrosion and a scheduled visual inspection of the composite repair shows damage to the composite repair then inspection to assess the integrity of the substrate must be used before permanently fixing the composite repair. For this scenario, digital radiography or MS-UT are recommended to assess the condition of the substrate
Four 48-inch diameter cast iron outfall pipelines were inspected and rehabilitated in the San Francisco Bay. The inspections included internal and external inspections pipe structural supports and the ductile iron diffusers. Visual and ultrasonic inspections were conducted on the pipe exterior. Internal inspection was conducted by divers.Rehabilitation included removal of the lining and relining of the pipe and cathodic protection of the pipe external surfaces.The case study describes the testing and inspection procedures utilized and challenges faced during ultrasonic thickness measurements of old cast iron pipe cleaning & lining of pipe and deployment of galvanic anode sleds in seawater.
Stress Oriented Hydrogen Induced Cracking (SOHIC) is recognized as an individual cracking mechanism in NACE MR0175/ISO 15156-2. SOHIC occurrence is rare and the mechanism not fully understood but thought to be restricted to carbon and low-alloy steels with low strength and low hardness. Several SOHIC resistance test methods have been reported but none of the test methods is currently standardized. The newly developed “twist and bend” test is currently under standardization in NACE TG 536.Within this work SOHIC resistance tests using the “twist and bend” test method were performed on SAWL large-diameter pipes of grades X52 and X65. All relevant sampling positions (base material heat-affected zone longitudinal weld) were investigated and the results were compared to standard four-point bend SSC tests without additional twist. A new test geometry using reduced specimen dimensions that allows testing of smaller specimens for weld regions has also been developed.The SOHIC performance is discussed based on grade microstructure and hardness of the investigated pipe materials. The investigated SAWL large-diameter pipes revealed excellent SOHIC resistance.
This paper describes independent testing to assess the curing characteristics and fitness-for-service of liquid-applied oil and gas pipeline coatings applied at low temperatures. The curing rates and time to cure to a “back-fill” ready condition at various temperatures were determined for eleven coating products using differential scanning colorimetry (DSC). These curing schedules were compared to those provided by the manufacturers.Selected coating products were applied to blast cleaned steel in simulated winter field conditions. Steel substrate and air temperatures were maintained at 0 °C during application curing and measurement of durometer hardness impact flexibility and adhesion. The cold temperature cured coating samples were then tested in accordance with the laboratory methods specified in CSA Z25.30 Table 1. Based on the test results it was concluded that the selected products were suitable for maintenance application to excavated oil and gas pipelines when the lines are operating at temperatures as low as 0 °C.
Erosion of mild steel lines and equipment during the production of hydrocarbons from underground reservoirs is a complex and not fully quantitatively understood phenomenon becoming even more intricate when electrochemical corrosion is included. Oil and gas companies have always tried to account for this phenomenon with simple models. Over the last 40 years the American Petroleum Institute recommended practice 14E (API RP 14E) erosional velocity equation has been used by many operators to estimate safe production velocities in erosive-corrosive service. The widespread use of API RP 14E is a result of it being simple to apply and requiring little in the way of inputs. However there is very little scientific backing for this approach. The API RP 14E erosional velocity equation is often quoted to be overly conservative and to unjustifiably restrict the production rate or overestimate required pipe sizes.The present workprovides a review of literature on the origin of the API RP 14E erosional velocity equation its limitations misuses applications and known alternatives. This review suggests that a proper erosion model would provide a better description for the vast majority of conditions in oil and gas production systems to determine the safe operating velocity while maintaining a maximum production capacity and using cheaper materials or smaller diameter pipelines. However these models are more complex and are therefore not as widely applied. Overall there are currently no simple and readily available alternative formulae for calculating the erosional velocity and resort in many cases is a semi-empirical approach that includes operational experience.Keywords:erosion API RP 14E erosional velocity erosive-corrosive service operational experience
Galvanized steel pipe is protected by a layer deposited by hard water, but may suffer corrosion in soft water. Presented are case studies of corrosion in galvanized water piping in a stadium, hotel, and county government building. Details of corrosion mechanism and mitigation strategies are also discussed.