The purpose of this paper is to give the rationale for the development of an ISO standard on "Reliability-based limit state methods" for application to pipeline transportation systems. This standard is complementary to the traditional pipeline design standard under development by ISO, "Petroleum and Natural Gas Industries - Pipeline Transportation Systems", DIS 13623. The development of a new international standard dealing with reliability-based methods is outlined, followed by a discussion of the various limit state design concepts of relevance, which basically would cover both the so-called "deterministic method" and the "probabilistic method". The main objective and the basic safety philosophy as will be implemented in this ISO standard are given. The standard as described is applicable to both offshore and onshore pipeline systems.
The use of structural reliability techniques by means of a reliabilitybased limit state procedure is referred to as a design option in the new pipeline standard (ISO DIS 13623). This standard represents a valuable framework for a common technical basis according to various existing national standards. However, some guidance and specifications how to apply the reliability-based design principles to pipelines has been found necessary and is at present lacking. The new ISO standard with the title: "Petroleum and Natural Gas Industries - Pipeline Transportation Systems - Reliability-based Limit State Methods" is going to serve this purpose and gives supplementary information and specification on the use of the methods. This standard is now under development by a work group under the mandate of ISO TC67/SC2. A committee draft is planned to be ready by the end of 1999. The work group (WG12) is represented by about 20 expert members from ten ISO members countries, i.e. Brazil, Canada, Denmark, France, Germany, Italy, Netherlands, Norway, UK and USA.
