Analysis on the Leakage of the Flange Connection of the Water-Containing Hydrofluoric Acid Pipeline

Kun Lu,Bingjun Gao,Aoqing Zhang,Junhua Dong

doi:10.3390/pr9111986

Abstract

Leakages of bolted pipe flange connections of water-containing hydrofluoric acid pipelines were frequently reported by the extraction section in the fluorine chemical industry. Water-containing hydrofluoric acid can cause severe injuries to human beings due to its strong causticity. The water-containing hydrofluoric acid pipe was a short lined pipe, so a lot of flange connections and supports were adopted in the pipeline. In this paper, the finite element models of the pipeline were established to analyze the internal force of the pipeline under conditions including internal pressure, temperature, self-weight, and so on. Based on this, the equivalent design pressure of the flange connections was determined. The results of the stress analyses of the pipeline showed that leakages were mainly caused by a large bending moment, due to the unreasonable layout of the piping supports under self-weight. When the pipeline was supported on the beam of the pipe gallery, which is not necessarily beneficial to reduce the bending moment of the pipeline, and the flange connection was close to the supporting beam at the same time, leakages frequently occurred in this flange connection. To support the pipeline reasonably, the flange connection should be placed at zero bending moment positions. Therefore, the positions with zero bending moments of the pipeline with equal and unequal spacing supports were obtained under gravity load, to provide a basis for the rational support of lining piping.

Highlights

Flanges were often reported to leak for various reasons, such as internal pressure [1], piping load due to thermal deformation [2,3], aging of gaskets [4], and creep or stress relaxation of the bolt and flange under high temperatures and high pressures [5,6,7]
Leakage analysis is required for piping systems under relatively high temperatures and pressures [9]
Water-containing hydrofluoric acid can cause severe injuries to human beings due to its strong causticity, but leakages of bolted pipe flange connections of the water-containing hydrofluoric acid pipeline were frequently reported in the fluorine chemical industry

Summary

Introduction

Flanges were often reported to leak for various reasons, such as internal pressure [1], piping load due to thermal deformation [2,3], aging of gaskets [4], and creep or stress relaxation of the bolt and flange under high temperatures and high pressures [5,6,7]. Pipeline stress analysis focuses on the maximum bending moment point to check the pipeline strength or the sealing performance of the flange connection at corresponding positions. The internal force of the water-containing hydrofluoric acid pipeline will be analyzed under conditions of internal pressure, temperature, and self-weight to find the main cause of the bending moment and methods of reducing the bending moment to ensure good performance of the flange sealing. The pipeline works under a pressure of 0.9 MPa (the conveying ing pump is 90 m)aand a temperature °C It was a carbon steel pipe withlining. Vibration of the pipeline was not considered in the current study For this kind of pipeline, the length of the lining pipe was short and many flange.

Finite

The Calculation Results

Analysis and Discussion

Analysis andare

Conclusions