Technical Polymers Oil & Gas Offshore
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Since 1972, Rilsan® Polyamide 11 based flexible piping has been used in the following applications:
- Offshore oil & gas production and test lines
- Gas & water injection lines
- Gas lift lines
- Production risers
- Choke & kill lines
- Nitrogen lines
- Hydraulic lines
Rilsan® PA 11 is used as the liner material in flexible pipe and provides these benefits:
- Leak proof pipe
- Corrosion and abrasion resistance
- Continuous manufacturing of pipe
- Temperature and pressure resistance up to 100°C and 172 Mpa
- A permeation rate to hydrogen sulfide, carbon dioxide and methane 50 to 500 times less than that of nitrile rubber, and polyolefin materials.
In 1958 the Institut Francais du Petrole began a 14 year research program to develop a new concept of polymeric flexible pipe. Rilsan® PA11 was selected from over one hundred various thermoplastics. The OTC paper 5231 "Improved Thermoplastic Materials for Offshore Flexible Pipes" clearly explains the performance of Rilsan® PA 11.
In a test of aging properties of Rilsan® PA 11 Liners in Crude Oil the tensile properties, particularly the yield point evolution of Rilsan® PA11, were monitored at temperatures ranging from 120°C to 150°C. The yield point is extremely important in production risers where the Rilsan® PA11 liner is exposed to dynamic stress cycles created by sea motion. Test results conclude that Rilsan® PA11 will perform in dry crude oil applications for a period of 10 years at a continuous temperature of 100°C. Obviously, the life will increase if the service temperature is lower and if the liner is not exposed to dynamic stress cycles.
A field test was performed in a sour gas environment (9.3 wt % of CO2 and 15.3 wt % of H2S) in Lacq, France. After 3 years at 50°C and a pressure of 90 bars, the Rilsan® PA11 properties remained outstanding.
It is common for thermoplastic piping materials to swell when exposed to oil at high temperature and pressure. If the pipe is exposed to sudden variations in pressure, the polymer liner will blister, tear or crack. Flexible pipe made from Rilsan® PA11 will not blister, tear or crack under similar conditions. It displays superior resistance to blistering compared to other materials.
Rilsan® PA11 has been used for at least 15 years in umbilical applications. An umbilical is a group of hydraulic fluid lines and/or electrical cables reinforced with metal wires. Rilsan® PA11 was introduced successfully in 1970 as a liner material. However, the use of Rilsan® PA11 increased rapidly in the 1980's because of concerns due to new control fluids as well as new well service chemicals. Rilsan® PA11 has superior corrosion resistance and stress aging capabilities. It has a proven service life in excess of 20 years for temperatures up to 40°C. Comparatively, thermoplastic polyesters exhibit problems of stress cracking and hydrolysis when exposed to lubricant and biocide additives in control fluids. The more demanding fluids have led to specific grades of Rilsan® PA11 for this market. As a reference, the OTC paper 7272 describes the use of Rilsan® PA11 in umbilical systems. Rilsan® PA11 meets SAE J517 (100 R7 & R8), the old reference standard, and the recently developed API 17 E standard that more specifically addresses subsea umbilical issues. Tests were conducted at the National Laboratory in Glasgow. Reinforced aramid braided hoses made of Rilsan® PA11 and thermoplastic polyester elastomer were submitted to repeated internal pressure cycles at 70°C and 40°C.
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