Abstract

The paper describes the key properties of the bonded flexible pipes, including the recent development of bonded flexible pipes; especially for choke and kill systems as well as for continuous high pressure gas service. The construction and the qualification procedures acc. to API specifications 16C [1], 17K Draft5 [2] and RP 17B [3] are discussed. An interesting application example is introduced, which is believed to be the first integrally floating high pressure line for live crude oil. The advantages and limits of the bonded flexible pipesare presented.

Introduction

The oil industry uses large quantities of flexible pipes, basically for offshore oil drilling and production, but frequently onshore as well. Their onshore application can be explained with the possibility of easier assembly and the unequal subsidence of the equipment due to the production, but for offshore production in many cases there is no other solution at all. The connection between the fixed equipment placed on the seabed and the floating drilling or production units can only be achieved by flexible pipes. There are two basic flexible pipes: "unbonded flexible pipe" described in API (American Petroleum Institute) Standard 17J [4] and "bonded flexible pipe"; at the date of submission of the manuscript the relevant API 17K Standard is in Draft5 stage [2].

The unbonded flexible pipe construction consists of separate unbonded polymeric and metallic layers, which allows relative movement between layers. In the bonded flexible pipes the steel reinforcement is integrated and bonded to a vulcanized elastomeric material. Both constructions are spoolable; the bonded construction is generally used in short lengths up to 30-40 m, but it is available upto 200 m single pieces. Longer lines can be assembled with intermediate couplings.

The bonded flexible pipe is a very special composite structure, where the reinforcing material is steel cable or wire laid in specific angles and the continuous phase is rubber. The modulus difference between the reinforcement and the continuous phase is much bigger than in any other composite, 5 orders of magnitude. This results in unique properties of bonded flexible lines.

The flexible lines are used in numerous applications e. g. as rotary drilling hoses, choke and kill lines, production flow lines, gas or water injection, pile driving etc. In the present paper we focus our attention to those applications, where the lines are exposed to high pressure gas service. This is the case with choke and kill lines intermittently, and with production, gas injection and gas export lines continuously. The experiments were carried out on particular design of cable reinforced flexible pipes. More details can be found in references [5;6;7;8;9]. Since bonded flexible pipe manufacturers use different components, coupling designs etc. special care had to be taken in generalization of the statements, especially if the reinforcing material is solid wire, not cable.

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