Design of Contraflow Cleaning PIG for Pipeline Maintenance

• Main Author: Kresnajaya , Prasetia Pancakarsa
• Format: Thesis
• Language: English
• Published: 2009
• Subjects: TJ Mechanical engineering and machinery
• Online Access: http://utpedia.utp.edu.my/9265/1/2009%20-Design%20Of%20Contraflow%20cleaning%20PIG%20For%20Pipeline%20Maintenance.pdf; http://utpedia.utp.edu.my/9265/

Conventional Pipeline Inspection Gauge (PIG) is a device used to remove solid deposit from the pipeline wall and driven by the fluid flow. For single offshore pipeline application, it needs to be launched from the manifold at the seabed which has drawbacks on the water depth restriction and requires intervention from the surface to launch the PIG. The current trend on the PIG design to overcome this challenge is to develop a counter flow PIG for single offshore pipeline application which is unequipped with the PIG launcher at the manifold. Two of the commercial counter flow prototypes are contraflow tetherless mechanical crawler developed by the Astec Development Ltd. which has a drawback of poor traveling speed and Durham Pipeline Technology (DPT) crawler developed by University of Durham which has a drawback of discontinued motion. In this research, it is focused on the generation of a model of PIG with the function of wax removal. The requirement of the PIG design includes the ability to travel in both forward and reverse direction at a constant speed. In order to come out with the expected results, the scope of the research work is limited to the generation of the conceptual design of the PIG, product architecture and configuration design defined of the proposed concept and generation of Computational Aided Design (CAD) model of the proposed concept. A systematic design based on Dieter's approach is adopted to design a PIG. It consists of conceptual and embodiment phases. In the conceptual design phase, the PIG design starts with problem definition, generating number of possible concepts using functional decomposition method and selecting the most promising concept using conceptscreening method. The most promising concept of PIG design consists of five modules, specifically: drive mechanism, turbine for drive mechanism, flow control, turbine for wax removal and wax removal module. Furthermore, a layout and configuration of critical components of the most promising concept is performed in the embodiment phase. The PIG is designed with reference to the product design specification document of the pipeline operating condition ofpressure of 15 MPa, fluid velocity of 1 m/s and a pressure drop across the PIG of 31 kPa. The PIG design begins with the analysis of the impeller to determine the maximum power that can be generated from the fluid flow. The turbine module has a function to provide power to drive the drive mechanism and the wax removal module. Dimension of the impeller that can generate maximum power is calculated based on the meridional and cascade flow analysis. Furthermore, to ensure the valid assumption of the design parameter that is used to determine the dimension of the impeller, a CAD model of impeller is simulated using the Fluent software. In order to travel in a constant speed, the turbine for drive mechanism module is attached with flow control module which uses a perpetual mechanism of a poppet valve and a spring in the crawling mode and a magnetic mechanism in the return mechanism. For the drive mechanism device, a cam follower with bristle is used in the PIG design. The calculation of the cam follower mechanism follows the bristle theory that has been developed by Stutchbury. For wax removal, a cutting tool is used in the PIG design where the design of the cutting tool refers to the cutting tool standard used for machining process. Based on the preliminary analysis, the PIG design can move in a counter flow at speed of 0.03 m/s with the time ratio between the PIG movements in forward direction and stationary condition of 4.28. The PIG design can remove wax solid deposit with a maximum shear strength of 81 kPa. The outcome of this research is an assembly drawing of the PIG design.