Air in pipelines - a literature review

The entry, control and release of air from pipelines is a major, though often, hidden problem in pipelines used for water supply, foul water drainage and effluent discharge. Considerable cost can be incurred in providing air valves and chambers, and in deepening trenches so as to provide the minimum gradients that are thought necessary to enable air bubbles and pockets to move towards the valves. This report is the first output of a research study commissioned by the Department of Trade and Industry (DTI), to be carried out between October 2003 and November 2005. The study is aimed at producing a guidance manual for designers and operators of pipelines in order to reduce the number and cost of problems caused by air in water and wastewater pipelines. The detailed objectives of the study can be summarised as follows: • To collect and review existing knowledge and experience relating to air problems in pipelines. • To carry out targeted experimental and numerical studies to obtain information necessary for the preparation of the guidance manual. • To combine information from the knowledge review with results from the experimental and numerical studies to produce practical design guidelines for use in the manual. • To produce a guidance manual for designers and operators of water and wastewater pipelines on how to avoid or eliminate problems due to air. This report summarises the findings of a review of published data and practical experience relating to the movement and effects of air in water and wastewater pipelines. Available information on the use, sizing and location of air valves is also reviewed. A first version of this report was published in July 2004 and later amendments were introduced in the current, final, version. The conclusions of this review had implications for the design of test facilities for studying air bubble or pocket movement in pipelines, which were taken into account in the experimental work carried out in the latter half of 2004