Simple HydrodynamicModels for the Prediction of Pig Motions in Pipelines

Abstract

Abstract This paper reports results of an ongoing research project on fundamental aspects of the mechanics of pig motions in pipelines. This is a joint research program between PUC-Rio (Pontificia Universidade Catolica do Rio de Janeiro) ad PETROBRAS in Brazil, and in the first phase reported here it has been directed towards the development of simple, analytical hydrodynamic models thereby pass through the pig. In this study, only incompressible, steady state flow has been considered Foam pigs, flat discs, and piston-type cups have been analyzed. Computational fluid dynamic and finite element techniques have been employed in order to provide a solid fundamental basis for the simplified models. This paper has been previously presented in the 7th International Pipeline Pigging Conference& exhibition, held in Houston Texas, February 1995. Introduction Pigging of pipelines has been perform fix nearly a century. The use of pigs fm cleaning dewatering batching, and more recently, inspection d pipelines, has become a standard industry procedure. This expanding demand has driven the manufacturers to produce a great variety of pig models. Yet, a difficultly often by the engineer where designing a pigging operation is the lack of reliable tools for the prediction of the many variables related to the motion of the pig through the pipeline. Most of the available knowledge is based on field experience, Hence, selecting the best pig, estimating its speed and the amount of back and forward bypass, often involves some guesswork and, consequently, a high degree of uncertainty. Although one can not overlook the kind uncertainties often associated with complex engineering field operations, such as the passage of a pig through a pipe, there is certainly a need for more scientific based knowledge in pipeline pigging. Results of research on the motion of pigs in pipelines are Scarcely found in the literature. One may refer to related work by Ellis et al/. in the sixties on the pipeline flow of capsules. Although some of their results can be extended to the flow& pigs. it does not consider important variables such as contact forces or bypass through holes. References 3 and 4 treat the dynamics of pigs in gas lines. MOE recently, an experimental research programs, which address some of the fundamental problems related to pipeline pigging, has been conducted by CALTEC in the U.K. Among other topics, this study focus on the relationship of flow variables with cleaning efficiency and cup wear. The present contribution reports results of on going research on the dynamics of pig motion in pipelines. This is a University/industry joint effort, carried on by PUC-Rio (Pontificia Universidade Catolica do Rio de Janeiro) and the PETROBRAS R&D Center in Brazil. The goal of this initiative is to develop simple hydrodynamic models to be employed in predictions of bypass, differential pressure velocities associated with pipeline pigging operations.