The Impact of Hydrostatic Pressure Test on the Interstitial Strength of Mild-Steel Pipeline Material

Adjogbe A.S,Okoronkwo C.A,Oguoma O.N,Igbokwe J.O,Ezurike O.B

doi:10.17485/ijst/2019/v12i43/144730

Abstract

Objectives: This study examined the effect of hydrostatic test practice on the mechanical properties of steel pipeline used in the oil and gas industry. Method/analysis: The method involves subjecting a 76.2 mm (3-inch) and 101 mm (4-inch) pipeline spools to predetermined maximum allowable operating pressures and designed hydrostatic pressures at designated data points. Thereafter, the spools were cut and samples prepared for experimental tests and analysis. Findings: The results showed that there is a significant change in the mechanical properties like fatigue strength and ultimate tensile strength. The result also showed a progressive increase in the fatigue strength from the control specimens to the hydrostatic pressure-tested specimens. The control specimens also exhibited a reduced fatigue strength compared to the maximum allowable operating pressure (MAOP)-tested specimens. Thus, since the hydrostatic pressure-tested specimens exhibited the highest fatigue strength, this could be reasonably attributed to the strain-hardening behaviour. Novelty/improvement: The hydrostatic pressure-testing procedure, at least, is not detrimental to the integrity of the pipeline. At best, it is beneficial since it increases the strain-hardening of the material.Keywords: Hydrostatic Testing, Service Pressures, Near Point, Far Point, Mechanical Properties, Integrity

Highlights

Hydrostatic pressure testing is a common practice in the oil industry that is used to ascertain the structural integrity of a pipeline after the completion of construction and especially when a major repair is carried out in the oil and gas industry.[1]
The results obtained in the present study revealed that the hydrostatic testing has a remarkable effect on the interstitial strength of the pipeline materials
The tensile strength of a mild-steel material is altered by hydrostatic pressure testing

Summary

Introduction

Hydrostatic pressure testing is a common practice in the oil industry that is used to ascertain the structural integrity of a pipeline after the completion of construction and especially when a major repair is carried out in the oil and gas industry.[1] It is used during the operational phase for the same purpose. In view of the factors highlighted previously, the present study aims to investigate the impact of hydrostatic pressure testing on the interstitial strength of mild-steel pipeline materials. This is, carried out in order to determine the impact of hydrostatic pressure testing on the tensile strength, fatigue strength, and hardness of pipeline materials and to establish the basis for continuity or otherwise of hydrostatic testing of pipeline systems from micro-structural impact approach.

Objectives

Methods

Conclusion