ABSTRACT

In this article we present experimental results of measurements of the wave attenuation coefficient in trunk pipelines, analyzing and comparing theory with experiment. We propose an approximation for the attenuation coefficient as a function of nondimensional parameters. We also identify criteria that allow optimizing the number of pressure detectors for a pipeline based on a cost-to-effectiveness ratio of leak detection, and determine the maximum permissible distance between pressure detectors registering pressure waves.

INTRODUCTION

In view of the increasingly greater focus on sensitivity and other parameters of Leak Detection Systems (LDS), requirements for measuring equipment are becoming especially high. This in turn raises the cost of its delivery and installation. The cost of measuring equipment itself is only a part of the problem, as installation of a pressure detector requires installing additional telemetry systems in what is a very labor-intensive and costly process. This raises a pivotal issue as to where and how to install pressure detectors. The key to this problem lies in methods and algorithms used to detect a leak and its location. The pressure surge method is one of the most common methods of leak detection. It is founded on the use of pressure detectors (PD) that detect a negative-pressure wave (downsurge) caused by the pipeline leak. However, the wave amplitude diminishes the farther it moves from the leak point in a process known as wave attenuation, which means that if pressure detectors are installed too far apart, the leak of a certain quantity will not be detected. The problem of wave attenuation and the spacing of pressure detectors along the pipeline are the focus of research in this article.

EXPERIMENT

While it is possible to imagine the operation of a pipeline in a laminar flow mode, in practice this can happen only in exceptional cases. For instance, when the pipeline's operation is suspended, at one point the flow velocity will become so slow as to cause a laminar flow that will exist until the flow stops entirely. In pipelines we most often deal with a turbulent flow. When analyzing the propagation of waves in a turbulent flow, we faced the difficulty of isolating the signal of a disturbance wave against the background of constant hydrodynamic noise. For this reason, when processing experiment results we selected only those processes of disturbance propagation that had a strongly pronounced steep wave front and large amplitude. Such processes in the pipeline happed for reasons of:

  1. real leaks,

  2. closing of line valves,

  3. shutting down and starting of pumping units.

Experiments were conducted only on straight-line pipeline sections without loops or with closed loops. The objects of our research were three pipeline sections. Table 1 shows physical properties of pumped fluid and flow parameters for each pipeline section.

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