Pipeline Inspection Gauge Research Articles

A new measurement system using magnetic flux leakage method in pipeline inspection

Today, natural gas and oil, called main energy sources, are transported by pipelines at long distances. Defects (corrosion, cracks, dents) in the buried pipelines can cause loss of life, environmental pollution and economic loss. Recently, devices called “Pipeline Inspection Gauge (PIG)” are used for non-destructive evaluation (NDE) of defects in pipelines. In these devices, the magnetic flux leakage (MFL) technique comes into prominence as the inspection method. However, when the literature is examined, a study that examines the speed variable for defect detection has not been found. In this study, two new PIGs which can be used to investigate the speed variable while determining defects in pipelines are designed. For these new designs, a new magnetic measurement system with KMZ51 AMR sensors is developed. The voltage values of the sensors in the measurement system are saved to the computer by using LabVIEW-based software in sequential order via the NI USB-6210 data acquisition card. This data is also displayed on LCD screens by using MyRIO 1900. In the article, the mechanics of the developed system, its electronics and its software are examined in detail. Moreover, the usability of these new designs in determining pipeline defects are examined through an example experiment result with the Origin analysis program.

Stress Distribution of the Power Section Cup of Pipeline Inspection Gauges by Finite Element Method

AbstractThe pipeline inspection gauges (PIGs) are often blocked in actual operation. As the PIG ran in the straight pipeline, elbow, and anomaly, the large deformation and stress state of the power...

A New Sensitive Excitation Technique in Nondestructive Inspection for Underground Pipelines by Using Differential Coils

In general, a magnetic flux leakage (MFL) pipeline inspection gauge (PIG) has been applied to nondestructive testing for investigating ferromagnetic materials, such as underground gas pipelines. Although MFL PIG is efficient to the inter-city large-scale pipelines, it is hard to apply to small-size pipelines that are usually installed in the city, because the permanent magnet for MFL PIG is too big and heavy to operate inside the small pipe. The strong adhesive magnetic force of permanent magnet to the pipe wall also prevents the usage of MFL PIG in small pipelines. In this paper, we propose a new technology of nondestructive inspection by using a differential coil, which is easy to be manufactured with lightweight, low cost, and simple structure for operating inside the underground pipelines. Comparing with the conventional permanent-magnet MFL PIG, the results of the proposed system could also maximize the detection sensitivity of defect signals and minimize the magnetic adhesive force on the pipe wall simultaneously.

PIG's Speed Estimated with Pressure Transducers and Hall Effect Sensor: An Industrial Application of Sensors to Validate a Testing Laboratory.

The pipeline inspection using a device called Pipeline Inspection Gauge (PIG) is safe and reliable when the PIG is at low speeds during inspection. We built a Testing Laboratory, containing a testing loop and supervisory system to study speed control techniques for PIGs. The objective of this work is to present and validate the Testing Laboratory, which will allow development of a speed controller for PIGs and solve an existing problem in the oil industry. The experimental methodology used throughout the project is also presented. We installed pressure transducers on pipeline outer walls to detect the PIG’s movement and, with data from supervisory, calculated an average speed of 0.43 m/s. At the same time, the electronic board inside the PIG received data from odometer and calculated an average speed of 0.45 m/s. We found an error of 4.44%, which is experimentally acceptable. The results showed that it is possible to successfully build a Testing Laboratory to detect the PIG’s passage and estimate its speed. The validation of the Testing Laboratory using data from the odometer and its auxiliary electronic was very successful. Lastly, we hope to develop more research in the oil industry area using this Testing Laboratory.

Enhanced MEMS SINS Aided Pipeline Surveying System by Pipeline Junction Detection in Small Diameter Pipeline

Pipeline is one of the most important tools to transport gases or liquid substances from the starting point to the destination. There are large numbers of small diameter pipelines under urban areas, which require to be inspected regularly to prevent their leakage. Pipeline Inspection Gauge (PIG) carries the pipeline defects detection sensors and localization sensors to discover the pipeline defects and the corresponding positions by its spiral motion inside the inspected pipeline. The low-accuracy property of Micro-Electro-Mechanical System (MEMS) based inertial sensors is the main limitation that influences the positioning precision of pipeline defects. This paper studies a method to enhance the positioning precision of MEMS Strap-down Inertial Navigation System (SINS) aided pipeline surveying system by pipeline junction detection to correct the azimuth and pitch errors induced PIG positioning error. The verification experiment results show that the positioning precision of MEMS SINS aided pipeline surveying system would improve about 54.42% after adding azimuth and pitch errors correction in each straight pipeline segment with the pipeline junction detection result.

Experimental Investigation and Simulation of Magnetic Flux Leakage from Metal Loss Defects

Magnetic flux leakage (MFL) principle is widely used in detecting defects in cross-country pipelines. The tools based on the MFL techniques termed as instrumented pipeline inspection gauge (IPIG) are frequently used as per statutory requirement. The tool identifies the location of metal loss and also characterizes the size of metal loss defects in terms of length, width along circumference and depth in terms of percentage loss. Tool velocity in terms of frequency of data acquisition is important parameter whose effect on the MFL signal and on the defect quantification has been studied. Operation of linear pull through rig under various combinations of MFL tool parameters such as velocity, frequency and spatial sampling has been developed. A set of experiments by varying velocity from 0.25 to 2 m/s keeping frequency constant at 450 Hz have been carried out. MFL signals obtained from all known defects have been analyzed for its nature and quantifying the dimension of defect. The effect of velocity on individual dimensions of the defect has been studied in this work. Within the limitation of the experiments carried out, the present work indicates that smaller defects cannot be reported with better accuracy. Also, the velocity is seen to have a significant effect in characterizing the length of the defect using IPIG especially for defects of larger area.

Speed simulation of bypass hole PIG with a brake unit in liquid pipe

Periodic pigging of oil and gas pipelines for dewatering, cleaning and inspecting has become a standard industry procedure. A pigging operation requires the pipeline inspection gauge (PIG) to move at a nearly stable, moderate speed; otherwise, inspection data could be missed, and the PIG could break down. In this paper, a brake unit for the active control of the PIG speed and the working principle of the brake unit are presented. Two cases are discussed in this paper to present the characteristics of the brake unit. The speed governing equations of each case are simplified and solved using a numerical solution utilizing the Euler-Cauchy method. The results from the two studies indicate that an undesirably high travel speed of a PIG can be prevented because the drag force of the brake increases sharply with increases in PIG travel speed. A PIG would travel with more stability and at slower speeds when utilizing the brake unit. Moreover, the number of wheels on the brake unit has a great impact on the results because the more wheels that are present, the higher the control force of the brake unit.

Experimental Research on the Frictional Resistance of Fluid-Driven Pipeline Robot with Small Size in Gas Pipeline

Pipeline inspection gauge (pig), as a kind of pipeline robot, is commonly used in oil and gas pipelines during different stages of operation to perform functions such as dewatering, cleaning and inspecting. Predicting the motion of a pig to estimate its velocity, position and required driving pressure is essential before pigging. A precise evaluation can greatly help the operator to control the motion of the pig and reduce the pigging risks. The frictional resistance between a pig and the pipeline is a key determinant of the prediction accuracy, and research on the contact behaviour of sealing disc can help to understand the frictional resistance well. As a result, in this paper, an experimental rig for measuring the frictional resistance of the bidirectional pig with high accuracy was developed, and the effects of the sealing disc’s interference, thickness and clamping rate on the sliding friction of the pig were experimentally studied. The corresponding normal force between the sealing disc and the pipeline was obtained by a 2D axisymmetric nonlinear finite element model, and the frictional coefficient with the variation of the sealing disc’s size was presented. Research results show different effects of the sealing disc’s sizes on the frictional force, normal force and the frictional coefficient. In addition, different contact behaviours can be observed by the indication of the frictional coefficient curve. The contact behaviour can be grouped into several conditions, depending on the size of the sealing disc.

Wear of a polyurethane rubber used in dry gas pipeline as inspection gauges

Pipeline inspection gauges (PIGs) are essential for regular maintenance in natural gas exploration in cleaning and inspection. Their sealing discs, made of polyurethane rubber (UR), are often found to be worn quickly due to rubbing against steel surfaces. The damage in the UR sealing disc would cause a PIG stuck in operation (pigging). In this research, we investigate the frictional behavior and wear mechanisms of the UR sealing disc. Experimental study was carried out on UR samples against steel pipe materials using a pin-on-disc tribometer. The morphology and wear modes were studied using an optical microscope combined with finite element method (FEM). Results showed the completing mechanisms of abrasion, oxidation, and surface fatigue. The inter-correlation between these three modes and test conditions are discussed here. The understanding obtained in this research is beneficial for the improvement of pipeline design and operation.

Collisional vibration of PIGs (pipeline inspection gauges) passing through girth welds in pipelines

The continuous collision between a running PIG (pipeline inspection gauge) and girth welds in a pipeline can induce significant vibrations on the PIG, which can harm its mechanical structure. The vibration response caused by the collision between a running PIG and a girth weld was studied both experimentally and theoretically. A two-dimensional dynamic model of the PIG is introduced to explain and understand the collisional vibration. Our results demonstrate that the girth weld, which can be regarded as an obstacle, can greatly affect the dynamic behaviour of a running PIG. The instantaneous acceleration when the PIG passed over the girth weld is larger than that of the PIG that collided with the girth weld. The distinct and regular vibration response signal of a PIG passing through a girth weld can be used to identify the obstacles inside a pipe to calculate and correct the pigging mileages with the help of a special algorithm based on the function of odometers during the pigging or inspection process.

Characterization of the pressure loss coefficient using a building block approach with application to by-pass pigs

A building block strategy for modelling the pressure loss coefficient of flow through a complex geometry is presented. The approach relies on decomposing a complex flow geometry into geometrical building blocks of which the pressure loss coefficients are characterized individually. The different contributions are subsequently combined to describe the pressure loss of the geometry as a whole. This approach is applied and tested to an industrially relevant application: a by-pass pig (Pipeline Inspection Gauge). This is a cylindrical device that travels inside a pipeline and is commonly used in the oil and gas industry for pipeline maintenance. An important factor in determining the ultimate velocity of the device is the pressure drop over the by-pass pig, which is characterized by a pressure loss coefficient due to the by-passing fluids. In this study the pressure loss coefficient of three frequently used by-pass pig geometries in a single phase pipeline is investigated with Computational Fluid Dynamics (CFD). The CFD results are used to validate the simple building block approach for systematic modelling of the pressure loss through the by-pass pigs, which takes the geometry and size of the by-pass opening into account. It is shown that the pressure loss models can capture the CFD results for each of the three pig geometries. The pressure loss models can be combined with pig/pipe-wall friction models to predict the velocity of a by-pass pig in a single phase pipeline, which is important for a safe and effective pigging operation. The applied building block approach may also be suitable to characterize pressure loss coefficients of complex geometries in general.

A Novel Method to Enhance Pipeline Trajectory Determination Using Pipeline Junctions.

Pipeline inspection gauges (pigs) have been used for many years to perform various maintenance operations in oil and gas pipelines. Different pipeline parameters can be inspected during the pig journey. Although pigs use many sensors to detect the required pipeline parameters, matching these data with the corresponding pipeline location is considered a very important parameter. High-end, tactical-grade inertial measurement units (IMUs) are used in pigging applications to locate the detected problems of pipeline using other sensors, and to reconstruct the trajectories of the pig. These IMUs are accurate; however, their high cost and large sizes limit their use in small diameter pipelines (8″ or less). This paper describes a new methodology for the use of MEMS-based IMUs using an extended Kalman filter (EKF) and the pipeline junctions to increase the position parameters’ accuracy and to reduce the total RMS errors even during the unavailability of above ground markers (AGMs). The results of this new proposed method using a micro-electro-mechanical systems (MEMS)-based IMU revealed that the position RMS errors were reduced by approximately 85% compared to the standard EKF solution. Therefore, this approach will enable the mapping of small diameter pipelines, which was not possible before.

Finite Element Modeling of Magnetic Flux Leakage from Metal Loss Defects in Steel Pipeline

Magnetic flux leakage is a nondestructive method for inspection of steel pipelines carrying petroleum products, and is most widely used technique. The inspection tool used for this purpose is called instrumented pipeline inspection gauge (IPIG) which moves with the pressure of fluid inside the pipeline. In this paper, a three-dimensional finite element modeling and static simulation of the magnetic circuit of a magnetic flux leakage-based IPIG has been carried out. A FEM-based MagNet software has been used. Rectangular defects of different dimensions on a plate have been modeled, and the magnetic flux leakage response from each of these defects has been studied. Appropriate properties and boundary conditions have been imposed in the simulation. The dependency of some of the characteristic defect dimensions and the leakage flux signal has been studied. In addition, the effect of sensor liftoff on the leakage flux values for specific defect geometry has been studied and understood. Furthermore, the effect of defect orientation on the internal or external surface as against the sensor positioning has also been studied. A comparison of the FEM-simulated flux values with that of experimental leakage flux values has been made.

Pipeline Inspection Gauge Position Estimation Using Inertial Measurement Unit, Odometer, and a Set of Reference Stations

This paper presents a low-cost methodology to estimate the position of a pipeline inspection gauge (PIG). The environment in which the PIG navigates is inside the thick walls of a metallic pipeline, where it is not possible to receive a global positioning system (GPS) signal. As a consequence, it is necessary to use other means of navigation. A technique is presented in the paper that uses an inertial measurement unit (IMU), a speedometer, and a set of reference stations. A Kalman filter is used to fuse the measurements from the IMU, the speedometer, and the reference stations. The reference stations, with known GPS coordinates, are installed for every set interval to correct the PIG’s state estimate from the errors that accumulate due to the integration of the IMU measurements. The paper presents three scenarios. These scenarios differ in the way the update step of the Kalman filter is performed. Experimental results are presented along with a 100-run Monte Carlo test to verify the estimator’s consistency.

Pipeline Bending Strain Measurement and Compensation Technology Based on Wavelet Neural Network

The bending strain of long distance oil and gas pipelines may lead to instability of the pipeline and failure of materials, which seriously deteriorates the transportation security of oil and gas. To locate the position of the bending strain for maintenance, an Inertial Measurement Unit (IMU) is usually adopted in a Pipeline Inspection Gauge (PIG). The attitude data of the IMU is usually acquired to calculate the bending strain in the pipe. However, because of the vibrations in the pipeline and other system noises, the resulting bending strain calculations may be incorrect. To improve the measurement precision, a method, based on wavelet neural network, was proposed. To test the proposed method experimentally, a PIG with the proposed method is used to detect a straight pipeline. It can be obtained that the proposed method has a better repeatability and convergence than the original method. Furthermore, the new method is more accurate than the original method and the accuracy of bending strain is raised by about 23% compared to original method. This paper provides a novel method for precisely inspecting bending strain of long distance oil and gas pipelines and lays a foundation for improving the precision of inspection of bending strain of long distance oil and gas pipelines.

Chatter vibration phenomenon of pipeline inspection gauges (PIGs) in natural gas pipeline

Pipeline inspection gauges (PIGs) are needed for operations such as cleaning and internal inspection of the natural gas pipelines to facilitate improvement in efficiency and safety. There is chatter vibrations appeared in PIGs when they run in the dry pipe with the wear of rubber sealing disc. Dry friction-induced self-excited vibration between sealing disc and pipe is the source of chatter vibration on PIG. In this paper, an experimental setup for measuring chatter vibration response signal of a typical bi-directional PIG running in a real dry steel pipe was implemented. The reason that cause self-excited vibration which manifest as chatter vibration on PIG, was explained through the analysis of classic dry-friction model. A self-excited vibration model based on LuGre friction model was proposed for better understanding of the phenomenon of chatter vibration during the process that PIG running through the natural gas pipeline, and the model was solved by MATLAB/SIMULINK. Our results show that the PIG runs in dry pipe with chatter vibration at a certain period within micro-vibrations in the single ladder period. Dry friction-induced self-excited vibration between sealing disc and pipe is the source of chatter vibration on PIG, and lead to the wear of PIG's sealing disc in natural gas pipeline; the negative damping of system in dry friction contact is the reason that causes self-excited vibration; the simulation of the numerical model can validate the PIG's self-excited phenomenon well. These results provide a better understanding of the complex behavior of PIG motion within natural gas pipelines.

Research on Above Ground Marking of Pipeline Inspection Gauge Based on MEMS Acoustic Vector Sensor

Research on Above Ground Marking of Pipeline Inspection Gauge Based on MEMS Acoustic Vector Sensor

Multi-Diameter Pipeline Inspection Gauge for Lang Distance Industrial Application

Multi-Diameter Pipeline Inspection Gauge for Lang Distance Industrial Application

Measurement and analysis of friction and dynamic characteristics of PIG’s sealing disc passing through girth weld in oil and gas pipeline

Pipeline inspection gauges (PIGs) are needed for operations such as dewatering, cleaning and internal inspection of the oil and gas pipelines to facilitate improvement in efficiency and safety. The friction and dynamic characteristics, as the sealing disc of a PIG passes through the girth weld in a pipe, has been directly studied using a custom-built experimental setup. The contact behavior between sealing disc and girth weld was analyzed using finite element methods. A two-dimensional section analytical link model of the sealing disc is introduced here and was simulated using the mechanic dynamic analysis software Adams. Our results show that the process of the sealing disc of the PIG passing through the girth weld in the pipe can be separated into three distinct stages: (1) start-up stage, (2) climbing stage, and (3) slope stage. At first, the PIG decelerates due to the friction force and then accelerates after passing through the girth weld. The acceleration and deceleration processes produce axial vibration in PIG.

The Use of Reflection Mode Ultrasonic Transceiver Sensor in Pipeline Inspection Guage to Monitor Pipeline Internal Corrosion

Aging gas transmission pipelines are prone to internal corrosion due to the presence of carbon dioxide and hydrogen sulphide in the natural gas constituents. Commonly, the in-line inspection tool known as Pipeline Inspection Gauge (PIG) is applied to perform the corrosion inspection of the pipeline. This paper describes an ultrasonic instrumentation system for PIG to monitor internal corrosion of pipeline. The system consists of ultrasonic transceiver sensor, ultrasonic driving circuitry and data acquisition system. The hardware is equipped with a sensor carrier which is propelled along the test pipeline. The time of flight (TOF) of the ultrasonic wave is measured and was used to evaluate the internal corrosion of pipeline. An initial experimental instrument was set up to perform the distance measurement test at a frequency of 390 kHz, to simulate the changes of pipe wall thickness due to corrosion effect. Surface anomalies were created at different positions to simulate the changes of pipe wall thickness due to the corrosion effect. Variation in measured distances implied the existence of the surface anomalies. The results of the simulated surface anomalies showed that the percentage error was less than + 5%. The large value of average DC voltage gave indication of distance increment due to the depth of the surface anomalies. The developed ultrasonic instrumentation system is capable to monitor the internal corrosion of pipeline.