Page 437 - Pipelines and Risers

404 Chapter 21

21.5 Improving Design Codes and Guidelines

21.5.1 General
IS0 standards for subsea equipment and risers in deepwater are presently being prepared. As
part of this work, integration of MI and IS0 standards and preparation of adequate design
codes for deepwater applications are ongoing. A new International Standard for flexible pipe,
API spec 17J(ISO 13628-2) has been issued. Furthermore, DEEPRISER JIP (Kirkemo et al.
(1999)) project establish design codes for deepwater steel risers (all types of risers ranging
from drilling to production).
21.5.2 Flexible Pipes

1. Flexible Pipe Guidelines
flexible pipes have been used for decades. The early pipes and hoses were of the bonded type
(vulcanized rubber and armoring). The designs were primarily governed by the ratio burst to
design pressure.

From the early seventies, large resources were put into the development of reliable non-
bonded flexible pipes. As a result of the product development work, the confidence in flexible
pipes increased, and flexible pipes are considered attractive for many applications. The use of
flexible pipes was, however, still limited partially because no general industry standard was
available. In the middle eighties, Veritec (1987) developed a general design standard for
flexible pipes, in a JIP. These guidelines were based on the design methods used by the
manufacturers and the offshore design codes. API followed by preparing the recommended
practice 17B.

These design codes represented the state of the art of flexible pipe design. With the exception
of Brazil, the use of flexible pipes was still moderate during this period. There was, however,
a continuous growth in demand and requirements (temperature, pressure and diameter) to
flexible pipes. Many oil companies developed their own specifications for flexible pipes and
the industry faced the following problems:

- Many operators had their own design standards.
- The manufacturers used their in-house standards for design. To prepare additional
documentation conforming with the operators’ standards was often cumbersome and
expensive.
- The general design standards were not updated and were considered to be increasingly
inadequate.

A general consensus had emerged in that the industry would benefit from a standard
specification. As a consequence, a JIP project headed by MCS was conducted during 1994
and 1995. A draft specification was issued in May 1995 and has now been accepted by API as
the general design specification for flexible pipes. Most oil companies and main offshore
contractors are expected to accept this specification which is now named API Spec 17J. The