Experimental investigation on sphere pig movement in multiple thickness pipe

Abstract

In the petroleum industry, using pipelines is the safest and most reliable method for crude oil or product transportation. Pipeline pigging is crucial for safe and reliable pipeline operation. The driver pressure of a pig is an important parameter of this operation. Thus, it should be known in advance. In the present survey, an experimental setup has been built to investigate the driver pressure for sphere pig motion for various material hardness as well as oversize ratios. Three spheres have been produced from 55, 65, and 75 Shore-A hardness polyurethane and they have been launched into a six-inch test spool, containing four pipes with different wall thicknesses, equipped with a reciprocating pump as well as a digital pressure measurement system. Then the driver pressures have been measured for all test cases. The uniaxial tension test results of each material along with the test spool and sphere geometries were imported into the simulation software, ABAQUS. The predicted pressure difference values by the simulation had no similar manner to the experimental results when a fixed friction coefficient has been employed. A modification of the simulation scheme is presented here, which is the use of contact pressure dependent frictional behavior in finite element simulations, as the main novelty of the work. This correction leads to close matching of the experimental and numerical results with less than 10% deviation which is an acceptable estimation in the pigging operation. Thus, the pressure-dependent coefficient of friction along with the proper hyperelastic material model can successfully evaluate the differential pressure needed for ball pig motion in a pipe. As the experimental tests are time consuming and expensive for larger pipeline pigs, this method provides a fast and economic tool for driver pressure prediction in larger pipes, based on FEM simulation.