Inline Inspection for the Determination of Unknown Material Properties and the Detection of Material Inhomogeneities in Pipelines

Thale, Werner; ROSEN Technology and Research Center GmbH; Germany

Hühn, S.; ROSEN Technology and Research Center GmbH; Germany
Thale, W.; ROSEN Technology and Research Center GmbH; Germany

ID: ECNDT-0206-2018
Download: PDF
Session: Oil & Gas 2
Room: H2
Date: 2018-06-11
Time: 15:20 - 15:40

Operation and maintenance of ageing pipelines or replaced pipeline segments represent enormous challenges for pipeline operators. To ensure safe, profitable and code-compliant operation of a pipeline throughout its life cycle, pipeline operators must provide traceable, verifiable and complete design and construction records of the entire pipeline. In the case of incomplete records, a frequent problem is the missing of the relevant parameter for operation pressure, i.e. the pipe grades of the built-in joints or pipeline segments. Furthermore, material inhomogeneities such as variations of metallurgical hardness — so called hard spots — can also compromise integrity. These anomalies are susceptible for crack formation, especially at varying pressure cycles. The fact that most pipelines are underground makes it even more difficult and cost-intensive to determine material properties such as pipe grade, or material inhomogeneities like hard spots.
In order to solve this problem efficiently, we use inline inspection tools outfitted with sensors for nondestructive material characterization. We advanced and adjusted different electromagnetic methods, or a combination of them, to work well with the specific conditions of inline inspection, e.g. high inspection velocities of up to 3m/s, and sensor lift-off due to rough surface conditions. We work with static or alternating magnetic excitation of the pipe wall, and use active and passive coils and hall elements as sensors.
For pipe grade determination, a specific eddy current technique was developed that is calibrated on pipe samples covering steel qualities from grade B to grade X80 per API 5L specification. The sensors for hard spot detection are calibrated on steel samples with different heat treatment corresponding to different grades of hardness and different hardening depths. While volumetric hard spots can already be detected with the classic magnetic flux leakage technique using low static magnetization, surface-sensitive electromagnetic methods with alternating fields are necessary for the detection of shallow hard spots.
This holistic inline inspection service suite is a first step in replacing destructive testing requirements in integrity verification processes.