Journal of Pipeline Systems Engineering and Practice

North America is traversed by many high-pressure oil and gas transmission pipes and the stability of that essential buried infrastructure must be maintained under a variety of earth-loading conditions. In the research reported in this paper, a series of pipe-bending experiments have been conducted on 105-mm (4.1-in.) outside diameter and 1,830-mm (6-ft) long steel pipes buried in dense sand placed in a $\mathrm{4,000}\times \mathrm{2,000}\times \mathrm{2,000}\text{-}\mathrm{mm}$ ($157.5\times 78.7\times 74.7\text{-}\mathrm{in.}$) test pit. The pipe ends were pulled by two parallel cables attached to a spreader beam outside the test region, which was pulled by a hydraulic actuator. The research reported in this paper investigated burial depth-to-diameter ratios of 3, 5, and 7 as well as two horizontal extents for the soil behind the pipe distances of $3D$ and $9.5D$. Special consideration was made to assess the influence of friction between the pulling-cables and soil. This friction is significant and may contribute about 20% of the maximum pulling load for the case of a depth-to-diameter ratio of 3. Consistency of results was established using four test repetitions for some cases. Whereas the horizontal extent of soil behind the pipe tested in the research reported in this paper had an insignificant influence on the pulling forces, the burial depths significantly influenced the ultimate pulling forces for the system. The failure mechanism controlling the limiting pulling force in these tests was consistently governed by the soil and the pipe remained elastic.

With an increase in trenchless methods being used for the installation of natural gas lines in urban areas, unmarked sewer service laterals present a risk of accidental and unknown cross-bores with these distribution lines. Although the physical damage to underground facilities is always unwanted, a cross-bored plastic natural gas distribution pipeline in a sewer is vulnerable to mechanized sewer cleaning tools that may be used in the event of a backup, with potential explosive consequences. Mainline sewers and storm sewers are also at risk from cross-bores; however, the scope of this paper is sewer service laterals. Although good practices exist for operators of horizontal boring equipment, these assume that the existing underground structures are marked and/or located. State legislation mandates the marking and locating of underground infrastructure; however, the question of who assumes responsibility for marking and locating sewer service laterals is a contentious issue. Sewer system owner/operators generally place the responsibility of locating and marking in the hands of unsuspecting property owners claiming that the laterals are on private property. In reality, property owners lack the expertise and equipment to mark and locate these service laterals. This paper describes the challenges with respect to natural gas cross-bores in unmarked sewer service laterals and presents data obtained from a survey of 43 contractors involved in the distribution contracting industry. The results further support the need for immediate action related to unmarked underground sewer service laterals.

As part of an experimental program, a large number of in-service culverts were tested to investigate the influence of several parameters on field performance of culverts. These parameters included cover depth, load application, size, shape, and other properties of corrugated metal culverts. Response of 14 test culverts was simulated using a two-dimensional finite element program and a three-dimensional finite difference program. Deflections predicted from the two-dimensional analyses were larger than the deflections measured in the field. However, the experimental and calculated thrust forces were similar. Deflections and thrust forces predicted from the three-dimensional analysis were similar to the experimental results. The critical factors affecting the response of the culverts include cover depth, culvert size, metal thickness, and elastic modulus and other properties of backfill soil. The influence of these parameters on the culvert behavior is investigated through numerical simulations using the established modeling properties.

The New Jersey DOT (NJDOT) operates and maintains a network of thousands of kilometers of conduits, many carrying fiber-optic cables that are vital to the state’s communication system. These primarily nonmetallic conduits frequently must be located and marked to avoid damage from construction. By design they can be located using a system of trace wires (TW) and radio-frequency detection. However, for various reasons the TW are missing and thus not functioning over a significant portion of the network. The purpose of the research reported in this paper was to analyze and improve the inventory information base, and find and compare effective methods for locating these conduits. Any candidate solution had to meet requirements for accuracy and depth sensitivity, be practical to implement, cost-effective, work with both metallic and plastic conduits, and be reliable. Innovative methods for locating underground conduits were investigated and evaluated with respect to various conditions. Validated approaches include enhancements to current TW methods, a new acoustic transmission (AT) method, and the ground-penetrating radar (GPR) method. The benefits of optimized location include the following: (1) reduced cost and time from more expedient systems for locating conduits, (2) less accidental damage to conduits, (3) avoidance of connectivity problems and loss of crucial communications, and (4) preservation of the fiber-optic network. A decision process identifying the optimal solution with respect to various conditions was developed and is presented in this paper. To enable the best application of the decision approach, the underlying conduit and surrounding-environment data was improved using cross-referenced geographic soil map data to enable proper selection of location technologies.

Condition assessment of wastewater collection systems is a vital part of a utility’s asset management program. Reliable information on pipe condition is needed to prioritize rehabilitation and replacement projects, given the current state of our nation’s infrastructure. Although inspections with conventional closed-circuit television (CCTV) have been the mainstay of pipeline condition assessment for decades, other technologies are now commercially available. Five of these innovative technologies were selected for field trials under the U.S. Environmental Protection Agency (USEPA) demonstration program: zoom camera, electroscanning, digital scanning, laser profiling, and sonar. The goal of the field demonstration was to evaluate the technical performance and cost of these technologies. The field demonstration was conducted in August 2010 and was hosted by the Kansas City, Missouri Water Services Department. The innovative technologies were compared to CCTV inspection. Each technology identified maintenance and structural defects by collecting data or images of the pipe condition. The camera technologies (i.e., digital scanning, zoom camera, and CCTV) and laser scanning provided pipe condition above the water line, whereas sonar assessed conditions below the water line. Electroscanning detected leakage-related defects anywhere along the pipe circumference. Costs were compared for different inspection technologies based on actual costs for planning, field work, data analysis, and reporting. Total costs for the multisensor (digital, laser, and sonar scanning) inspection were $14.71 per m of pipeline inspected as compared to $10.31 per m for electroscanning, $3.46 per m for zoom camera, and $9.78 to $10.48 per m for CCTV.

In natural gas transmission network analysis, the general gas pipeline equation and its common design variations (Weymouth, Panhandle A, Panhandle B, IGT/AGA) typically assume an average compressibility factor $Z_{av}$ across pipeline sections. In this work, it is shown that errors in the selected $Z_{av}$ value result in design specification errors biased toward pipe sections further downstream of the network. These errors are especially pronounced in large pressure change systems and can have significant cost implications given standardized pipeline sizing. Consequently, a new natural gas transmission model is developed towards improved natural gas pipeline network analysis. The new model is based on quartic characterization of the $P/Z$ integral term in pseudoreduced form. The pseudoreduced framework serves to preserve the simplicity level of prevailing design equations while improving the accuracy in the handling of the $P/Z$ integral computation by up to 100% with improved design specifications and cost-saving implications.

Pipeline failures cause significant environmental and property damage and fatalities every year. Current methods have a lack of sensitivity to pinpoint the leak location with sufficient accuracy when the leak is at the stable regime. The acoustic emission (AE) method relies on propagating elastic waves caused by the leak turbulence. The current AE leak detection methodology relies on two neighbor sensors, and requires either a long wiring system or a wireless system with clock synchronization, which raises many other challenges. In this paper, the new leak localization approach is proposed to detect the leak from a single point measurement with two sensors designed to be sensitive to the wave motions generated in pipes at two orthogonal directions (radial and axial). The approach is demonstrated on a laboratory-scale steel pipe in comparison with the conventional two-neighbor sensor approach. The result indicates that the proposed localization approach successfully pinpoints the leak location with good accuracy, which enables the implementation of single-point wireless acoustic emission sensing in long-range pipeline networks.