On-site non-invasive condition assessment for cement mortar-lined metallic pipelines by time-domain fluid transient analysis

Abstract

Pipeline condition assessment is essential for targeted and cost-effective maintenance of aging water transmission and distribution systems. This article proposes a technique for fast and non-invasive assessment of the wall condition of cement mortar–lined metallic pipelines using fluid transient pressure waves (water hammer waves). A step transient pressure wave can be generated by shutting off a side-discharge valve in a pressurised pipeline. The wave propagates along the pipe and reflections occur when it encounters sections of pipe with changes in wall thickness. The wave reflections can be measured by pressure transducers as they are indicative of the location and severity of the wall deterioration. A numerical analysis is conducted to obtain the relationship between the degree of change in wall thickness in a cement mortar–lined pipe and the size of the corresponding pressure wave reflection. As a result, look-up charts are generated for any specific cement mortar–lined pipeline to map this relationship. The wall thickness of a deteriorated or distinct section can be determined directly and quickly from the charts using the size of the reflected wave, thus facilitating on-site pipeline condition assessment. The validity of this time-domain pipeline condition assessment technique is verified by numerical simulations and a case study using the field data measured in a mild steel cement mortar–lined water main in South Australia. The condition of the pipe as assessed by the proposed technique is generally consistent with ultrasonic measurements.