API TR 17TR2-2003 pdf free download

API TR 17TR2-2003 pdf free download.The Ageing of PA-11 in Flexible Pipes.
Introduction In the construction of a ßexible pipe, an inner polymeric pressure sheath is the only layer which seals the conveyed ßuid within the pipe structure. Therefore, its integrity is cru- cial to safe and reliable operation. Polyamide 11 (PA-11) is the most commonly used pressure sheath material (1) , other options being polyvinylidene ßuoride and polyethylene. This document provides comprehensive guidance on mate- rials and pipe issues regarding the use and operation of PA-11 in ßexible pipe applications, typically in production and gas handling applications up to 100¡C. The document concentrates on the use of PA-11 in the inter- nal sheath of ßexible pipes, although similar considerations may also apply to other uses of PA-11 within ßexibles, e.g., anti-wear layers, intermediate sheathes and outer sheathes. The collective goal of this document is to prevent failure of the internal pressure sheath, as a result of ageing and associ- ated loss of mechanical properties, by determining and dis- seminating the necessary scientiÞc and practical information. API SpeciÞcation 17J and Recommended Practice 17B (2,3) contain only limited information with respect to these phe- nomena, and this report supplements and updates the data in the Third Edition of API RP 17B (3) . PA-11 is also used in umbilicals. However, the exposure temperatures are frequently lower than production tempera- tures. In cases of higher temperature exposure, the informa- tion contained in this document applies. 2 The Ageing of PA-11 2.1 BACKGROUND The main ageing concern regarding PA-11 in ßexible pipe applications, in the absence of oxygen in the bore ßuids, is the effect of water at elevated temperature. The hydrolysis reaction breaks the polyamide links within the polymer, and leads to embrittlement of the material. There is a long history of detailed study of this process, and key references are listed in Appendix A.
The rate of the PA-11 ageing reaction is highly dependent on a number of operational factors including the water con- tent of the ßuid, temperature, acidity (due to carbon dioxide, hydrogen sulphide, organic acids, inorganic acids), oil com- position, and presence of oilÞeld treatment chemicals, such as methanol. Considerations regarding the chemical ageing of PA-11 are detailed in Appendix A, and summarised in the sections which follow. Outline guidelines for conducting lab- oratory ageing experiments are given in Appendix B. It should be noted that other aspects of performance, unrelated to chemical ageing, may inßuence the use of any polymeric material in a ßexible pipe, e.g., mechanical prop- erties, fracture toughness, creep, blistering performance, coefÞcient of friction, thermal expansion, dynamic proper- ties, etc. These other aspects of performance are outside the scope of this document. 2.2 THE EFFECT OF WATER IN SATURATED & UNSATURATED CONDITIONS Experimental results derived through JIP projects and in- house research along with fundamental chemistry consider- ations conÞrm that the process affecting the ageing of PA-11 in a water environment is reduction in the molecular weight due to hydrolysis. This process is independent of the sheath thickness in typical pipe designs. There is now good agree- ment on this aspect of ageing from different sources. The chemical mechanisms are discussed in Appendix A. If there is free water in a production stream, the PA-11 will age as if immersed in 100% water. It has also been found that a free water phase is not necessary for such ageing to occur. Conditions should be regarded as ÒwetÓ for the consideration of PA-11 ageing if water levels are > 80% of saturation in any given liquid or gas environment ßowing within the pipe (3) .