Abstract

Pipeline installation by Horizontal Directional Drilling (HDD), has progressively gained a lot of popularity over the last three decades. Sound engineering practices, site condition, client preference and safety considerations can dictate the use of HDD methodology for installing a pipeline segment. HDD has gained global recognition and it is sometimes recommended by regulatory agencies and governmental agencies to avoid contamination, disturbance and flow interruption of water bodies and especially in environmentally sensitive area. Nowadays, it is the preferred method for trenchless installation of pipelines across major natural and manmade obstacles such as water bodies and roadway, ravines, rail way, run ways and other structures. Sometimes HDD can be very convenient and may be the only option from constructability stand point.

Introduction

The case history will discuss HDD methodology and precautions. With all the benefits of HDD comes the disadvantages especially from pipeline maintenance, corrosion control and integrity management point of view. Pipelines segments installation by HDD can impose additional strain on the pipeline during pull through and can significantly increase both installation stress and operational stress of the pipeline. HDD installed pipelines are relatively deep and could easily become low points for liquid hold up causing flow issues. Such low points tend to accumulate corrosive species thereby causing internal corrosion problems. HDD installation increases the likelihood of external coating damage during pull through of the carrier pipeline. Significant external coating damage can easily expose the pipeline to corrosive species in the soil. Depending on the depth, conventional methods of detecting coating damage and monitoring possible external corrosion conditions of the pipeline may not suffice. Above ground techniques such as Direct Current Voltage Gradient (DCVG), Alternating Current Voltage Current (ACVG) and Close Interval Potential Survey (CIPS) may not be efficient. Each HDD installation should be uniquely designed and installed to suit site conditions, such that it will not present pipeline integrity nightmare down the road, especially for un-piggable pipelines. Precautions were taken in planning, engineering, design and installation of the pipeline to make sure the HDD segment does not turn out to be problems from pipeline maintenance, corrosion control and integrity point of view.

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