A novel smart caliper foam pig for low-cost pipeline inspection—Part A: Design and laboratory characterization

Pipeline pigging for in-line inspection is a fundamental practice in the oil and gas industry. Yet, the so-called “smart pigs” used for this purpose are expensive and delicate and the risk related to their possible blocking inside the pipeline is non-negligible, hence their deployment is rather infrequent (generally, just once in several years). In this paper, we present a new, low-cost and low-risk foam pig with inspection capabilities similar to those of a multi-channel caliper pig (i.e. able to detect, locate and size inner diameter changes and deformations) together with additional features that allow to detect internal roughness changes (e.g. due to corrosion) and perform some pH/salinity determinations, also useful for corrosion assessment purposes. One implementation of the new tool makes use of a foam pig “carrier”, providing the required push with a good capability to surpass restrictions, equipped with specialized sensors and modules for data acquisition and storage. Another implementation, called “skeleton caliper pig” and suitable to prevent the massive displacement of condensates from gas lines, deploys the light plastic system without any foam pig carrier, pushed by the gas velocity alone. In the paper we will discuss the design, construction and field testing of this new low-risk inspection pig.