ABSTRACT

This paper presents observations and guidelines associated with conducting hydrostatic pressure tests of pipelines and/or process equipment, such as vessels. The potential concerns for hydrostatic pressure tests relate to the water itself, including any suspended solids, dissolved oxygen, or any Sulfate Reducing Bacteria (SRB) or Acid Producing Bacteria (APB) that may be present in the test water. Recommendations of several major crude oil and natural gas producers, pipeline companies, chemical suppliers and service companies have been reviewed, including “best practices.” Hydrostatic pressure test water should be completely removed from the system within 28 days, including any small remnants of water from low spots or deadlegs. However, if the period of time following the introduction of the test water and the beginning of operations exceeds 28 days, then it would be appropriate for a “dry” or “wet” lay-up in order to preserve the integrity of the base metals and prevent internal corrosion. This paper presents general observations and recommendations related to “dry” and “wet” lay-ups, including filtration requirements and specific treatments for oxygen scavengers, biocides, and corrosion inhibitors

INTRODUCTION

Hydrostatic pressure tests are conducted on new pipelines or associated process equipment used in crude oil or natural gas gathering and production systems before they begin operations. This is to demonstrate the physical integrity of the piping system and associated process equipment. The tests consist of filling the system with hydrostatic test water, and holding it under pressure for a certain period of time. Pressures are typically conducted at 125% of the planned maximum allowable operating pressure, but may range from 110 to 150%. The duration of the hydrostatic pressure tests may vary, depending on the system being tested and the relevant codes. Although the pressure tests are intended to demonstrate system integrity, the tests also introduce potential threats to the system if the liquid (most typically water) is not completely removed from the system following completion of the tests. This paper will identify and discuss the primary threats to the long term integrity of the pipelines or process equipment if some quantity of the test fluids remains within the system. It will also summarize guidelines used by some major crude oil and natural gas producers or pipeline companies in order to maintain the system integrity if the fluids used for the hydrostatic pressure tests remain within the pipeline for an extended period of time. The latter will also discuss “wet lay-ups” or “pickling” of pipelines in order to preserve them for extended periods of time, until they will again be activated for service

CONSIDERATIONS IN HYDROSTATIC PRESSURE TESTS

There are a number of considerations when planning and conducting hydrostatic pressure tests for pipelines.

This content is only available via PDF.
You can access this article if you purchase or spend a download.