On the basis of Iran's strategic development plan, natural gas industry must develop the capacity of gas transmission up to 1300millionm3 per
day until 2025. For this purpose, gas pipeline length should be doubled during the next 15years; however, experience shows a remarkable delay in
nearly all gas pipeline projects. The main goal of this paper is to identify and rank the causes of delay in these kinds of projects in Iran. In this
regard, 24 executed gas pipeline projects were studied and then extracted delay factors were conferred with 10 experts from several disciplines. The
result was a 43-item list of factors which then was ranked by means of a questionnaire survey. The result reveals that the 10 major delay factors are:
“imported materials, unrealistic project duration, client-related materials, land expropriation, change orders, contractor selection methods,
payment to contractor, obtaining permits, suppliers, and contractor's cash flow”.