Andreas DOWE, Dr. Christian BARON, Reinhardt BÜSSING**

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1 X Międzynarodowa Konferencja Techniczna: 2-21 września, 27, Płock Zarządzanie Ryzykiem w Eksploatacji Rurociągów New VESTAMID (Polyamide 12) grades to manufacture products with large geometrical dimensions for oil and gas applications Andreas DOWE*, Dr. Christian BARON*, Reinhardt BÜSSING** *Degussa GmbH, High Performance Polymers Paul-Baumann-Str. 1, Marl, Germany, andreas.dowe@degussa.com, Christian.baron@degussa.com **SB Projektentwicklung, Oberer Ahlenbergweg 8a, Herdecke, Germany, sbprojekt@hotmail.com Abstract PA 12 is a high performance polymer with outstanding mechanical properties and excellent chemical stability. It is the preferred material in many demanding applications, e. g. in the automotive industry for fuel lines of passenger cars or for air brake tubing s in trucks. In recent years PA 12 pipes undergo approval processes for the use in high pressure gas distribution and offshore oil explorations. Also the applications lining and rehabilitation of pipes are under investigation. Especially the swelling behavior and the outstanding resistance to oil and other petrochemicals make VESTAMID to the material of choice for rehabilitation and lining applications. The authors will give an introduction to the excellent technical performance of PA 12 and the new application possibilities using the very high melt viscosity and stiffness of the new developed PA12 grades. 1. PA 12 A high performance thermoplastic material Due to the specific carbon-amide group in the polymer chain polyamides (PA) have strong intermolecular actions which induce high mechanical strength, high melting temperatures and chemical stability. The long chain PA 12 with 11 carbon atoms between carbon-amide groups has the lowest water absorption of all commercial available PA and represents the best compromise in thermal and mechanical properties. That is why PA 12 is the material of choice for some challenging applications relied on already for decades, e. g. in the automotive industry for fuel lines of passenger cars or for airbrake tubing of trucks. Compared with medium and high density polyethylene (MDPE, HDPE) in use for low pressure gas supply, long chain polyamides like PA 12 provide naturally superior performance due to their described chemical structure (table 1). Besides PA 12 only PA 11 is commercially available with almost identical properties. PA 11 supplied by one manufacturer is based on a planted feed stock, castor bean, while PA 12 is synthesized from butadiene, a crude oil by-product, in a multi-step process. Degussa is the only company of the four PA 12 suppliers who is fully back-integrated to butadiene.

2 Table 1: Basic properties of PA 12 vs. PE Property Unit PA 12 HDPE MDPE Melting temperature C Tensile strength at yield Tensile elongation at break Flexural Modulus MPa % MPa 45 2 > > >8 7 Charpy impact strength kj/m 2 No break 3 2 Hardness, Shore D Permeability(23 C, mm 3 /bar/day) Methane Hydrogen (data for PA 12 pending) <.5 < New PA 12 designed for large pipe extrusion Controlling molecular weight and intermolecular interacting forces is a Degussa core competence to design PA 12 extrusion grades with optimized processing and performance properties. Degussa PA 12 is sold under the registered trade mark VESTAMID L (L for laurolactam, the monomer for PA 12). When Degussa decided to start with large pipe projects a new high molecular PA 12 grade for extruding pipes with bigger sizes was designed. The most outstanding property of the newly developed PA12 is its high melt stiffness at typical extrusion temperatures of 21 to 25 C. The melt stiffness of standard PA12 grades is not high enough to yield constant pipe geometries for large diameter pipes. In order to achieve good processing conditions for large diameter pipe with standard PA12 grades the extrusion temperature would have to be reduced. However, this would result in high residual stresses in the pipe. It should be emphasized that for these reasons a standard commercial PA12 grade cannot be used for large diameter tubes. The outstanding properties of the new VESTAMID LX92 and LX93 grade have been achieved by combining the well known good hydrolysis resistance and the mechanical behaviour of other PA 12 grades with significantly higher melt stiffness. This combination of properties makes these new products an ideal material for the production of large diameter pipe. In Fig. 1 the maximum pulling forces of this new grades at elevated temperatures are shown in comparison to a standard grade. The pulling force measured on the hot polymer is an indication of the melt stiffness, which is significantly increased for the new grade. Increase of melt stiffness of PA 12 measured with a strain viscosimeter 2 C 22 C 24 C m ax. p ull fo rce in cn Standard PA 12 High viscous PE New PA 12 Fig. 1: Increased melt stiffeness of PA12

3 3. PA 12 - A material of choice for high pressure gas supply The above shown advantages in terms of mechanical strength of PA 12 vs PE are also reflected by higher maximum operation pressures (MOP) at pressure pipe applications. Long term hydrostatic strength investigations according to ASTM D2813 [1] and ISO98 [2] have proven that in a 5 years extrapolation PA 12 is able to operate at pressures up to 18 bar using a safety factor of 2 for gas. MOP in bar (SDR-11 pipes) 23 C 6 C 8 C MDPE 4 4 HDPE 1 7 PA Table 2: Maximal allowable operation pressures for PA 12 and PE based gas pipes with considering a safety factor of 2 (data for VESTAMID gas pipe grade still under evaluation) These figures demonstrate the superior performance of PA 12 over PE at ambient temperatures and the safety reserve at elevated temperatures. One major concerns about thermoplastic materials used for pressure pipes is the slow crack propagation. In contrast to PE PA 12 is highly resistant against stress cracking in general and slow crack growth and passes easily all the relevant tests originally created for this weakness of PE. For example the notched pipe test acc. to ISO [3] was performed at 8 C and 2 bar internal pressure without any failures even after 2h. Also an increased notch depth of 3% of the wall thickness instead of 2 % didn t result into failures after 2h Degussa cooperation with E.ON Ruhrgas in Germany on evaluating PA 12 for high pressure gas supply Degussa and E.ON Ruhrgas decided in 25 to set up together a high pressure test installation on the E.ON Ruhrgas Technical Center site in Dorsten. Degussa had to deliver 6 m of 11 mm SDR-11 PA 12 pipe on a coil and some straight pipes for assembling a system including two butt fusion and two electro-fusion joints. Degussa also had to provide electro-fusion end caps. For the extrusion and coiling of the requested pipe Degussa cooperated with the company Egeplast in Greven, Germany. Although having PA 12 the first time on their production line Egeplast was able to extrude the pipe within the tolerances and with excellent appearance without any problem. The online coiling on a 2.5 m diameter drum was running smooth without cranking the pipe on the coil at all.

Fig. 2: Coil of 6 m PA 12 gas pipe, 11 mm, SDR-11 for test installation, manufactured at Egeplast, Greven/Germany For the development of electro-fusion fittings and

Using the PA 12 gas pipe material they manufactured the required components for the test installation in a perfect manner. Fig.

ON Ruhrgas site a burst pressure test was carried out with a 3 m test pipe including a butt fusion and an electro-fusion joint and electro-fusion end caps.

4 Fig. 2: Coil of 6 m PA 12 gas pipe, 11 mm, SDR-11 for test installation, manufactured at Egeplast, Greven/Germany For the development of electro-fusion fittings and end-caps Degussa cooperated with the company Friatec AG in Mannheim, one of the world leading companies in electro-fusion fittings. Using the PA 12 gas pipe material they manufactured the required components for the test installation in a perfect manner. Fig. 3: PA 12 electro-fusion fittings for test installation, manufactured by Friatec, Mannheim, Germany Before the test installation on the E.ON Ruhrgas site a burst pressure test was carried out with a 3 m test pipe including a butt fusion and an electro-fusion joint and electro-fusion end caps. In a short term burst pressure test the system bursts at 93 bar in a ductile crack in the tube region, while the fittings withstand the loads unaffected (fig. 4). Fig. 4: PA 12 gas pipe with butt fusion and electro-fusion joint and electro-fusion end caps for quick burst pressure test at E.ON Ruhrgas in Essen, Germany,

Fig. 5: PA 12 gas pipe 11 mm, SDR-11, unrolled for test installation on Technical Center site of E.

Butt fusion was carried out with standard equipment and slightly adjusted temperature profiles. For the electro-fusion fittings standard power generators from Friatec AG were used.

The system with one butt fusion and one electro fusion joint and two electro-fused end caps was installed and sealed in a 5 mm steel pipe.

5 Fig. 5: PA 12 gas pipe 11 mm, SDR-11, unrolled for test installation on Technical Center site of E.ON Ruhrgas in Dorsten, Germany For the test installation the coiled tube was unrolled in the field without any mechanical stretching tool. Butt fusion was carried out with standard equipment and slightly adjusted temperature profiles. For the electro-fusion fittings standard power generators from Friatec AG were used. The adjusted fusion conditions were read from a bar code adhered to the fittings. The system with one butt fusion and one electro fusion joint and two electro-fused end caps was installed and sealed in a 5 mm steel pipe. For 72 hours 36 bar natural gas was applied for checking the tightness of the system. Then the pressure was lowered to 24 bar. This pressure will be applied for 2 years and the installation is supervised continuously with respect to constant pressure, leakages and gas permeation [4]. Fig. 6: Butt fusion joint and electro-fused end cap with gas connection 4. PA12 for flexible pipe applications for oil transportation Testing has been performed in ISO 91 certified and accredited laboratories in the UK, The Netherlands and Germany. The different material characterisation tests were performed according to those standards required by ISO [5] and API 17 J [6]. In some cases alternative standard test procedures were used Crude oil compatibility Fluid compatibility tests have been performed with PA12 (VESTAMID LX92) in crude oil which was provided by Petrobras. Any possible oxygen contamination of the oil has not been removed since this would also extract other components from the oil. Tensile specimens were aged in the oil at 8 C for a total period of 28 days. After 1, 2, 41, 62, 83 and 28 days specimens were retrieved from the ageing environment and tensile tests performed.

6 The mean value of the elongation at break is shown in Fig. 7 as a function of the ageing time. The corrected inherent viscosity (CIV) was also determined and is shown in Fig. 8. The CIV of both materials declines but after 28 days remains higher for PA 12. These tests are still ongoing [7]. 35 Elongation at break [%] PA12 (Low TAN) PA11 (Low TAN) Ageing time [d] Fig. 7: Elongation at break of PA12 as a function of ageing time in crude oil (TAN = 1.1 mg KOH/g) at 8 C CIV in dl/g PA12 (Low TAN) PA11 (Low TAN) Ageing time [d] Fig. 8: Corrected inherent viscosity (CIV) of PA12 as a function of ageing time in crude oil (TAN = 1.1 mg KOH/g) at 8 C 4.2. Ageing in water (hydrolysis) Ageing experiments have been performed by Shell Global Solutions in the Netherlands. These tests are required by ISO and API 17J. A long term ageing program has been initiated in 24, which implies exposure of PA12 samples to two different environments and three different temperatures. Chemical ageing of polyamides involves hydrolysis and oxidation. In oil and gas applications the transported media are usually oxygen free. Therefore, only hydrolysis contributes to the chemical ageing process, which requires that the ageing environment is oxygen free. PA12 and PA11 were simultaneously exposed to exactly the same conditions in the same autoclave. For each environment and temperature the samples were aged for four different times. The longest exposure times reported in this document were 818 days. Additional tests with even longer times are still ongoing. In order to avoid contamination of the environment with oxygen, special care was taken to remove oxygen before the temperature was raised. An oxygen sensor was used to ensure that the

7 oxygen level was less than 1 ppb in the liquid phase. The following ageing environments and temperatures were used: De-mineralised water: p (CO 2 ) = bar, p (N 2 ) = 1 bar, T = 8 C, 1 C, 12 C, tmax = 818 days De-mineralised water: p (CO 2 ) = 1 bar, p (N 2 ) = bar, T = 8 C, 1 C, 12 C, tmax = 818 days After ageing, dimensional changes, the weight, density, corrected inherent viscosity (CIV) and the tensile properties were determined. The same properties were also measured on un-aged samples. During the execution of the ageing programme the recommendations and procedures of API 17J TR2 [9] were followed, especially with respect to oxygen levels and determination of the CIV. The times to reach a critical CIV of 1.2 dl/g at different temperatures have been used to generate Arrhenius curves. For ageing in deionised water with 1 bar CO 2 the Arrhenius curves of PA12 and PA11 are shown in Fig. 9. The Arrhenius curves for ageing with 1 bar N 2 (no CO 2 ) are shown in Fig. 1. From these ageing experiments it can be concluded that PA12 has a clear advantage over PA11 with respect to ageing resistance. Since the CIV for ageing at 8 C has still not reached the critical range of 1. to 1.2 dl/g after 818 days it was decided to continue ageing a set of PA12 and PA11 samples. These samples have now been aged since June 24 and the exposure is ongoing [7]. 1. Time to reach initial acceptance criterion of CIV = 1.2 dl/g [years] ph=5 (API 17TR2) ph=4 (API 17TR2).1 PA 11 H2O/1 bar CO2 fit [years] PA 11 H2O/1 bar CO2 [years] PA 12 H2O/1 bar CO2 fit [years] PA 12 H2O/1 bar CO2 [years] T [ C] Fig. 9: Arrhenius lifetime curves, aging in water with 1 bar CO 2 1. Time to reach initial acceptance criterion of CIV = 1.2 dl/g [years] API RP 17B "Saturated" ph=7 (API 17TR2).1 PA 11 H2O/no CO2 fit [years] PA 11 H2O/no CO2 [years] PA 12 H2O/no CO2 fit [years] PA 12 H2O/no CO2 [years] T [ C] Fig. 1: Arrhenius lifetime curves, aging in water without CO 2

8 4.3 Ageing in air (oxidation) Ageing tests have been performed with PA12 in air with a relative humidity of 5%. Tensile specimens were aged at 8 C for a total period of 28 days. After 1, 2, 41, 62, 83 and 28 days specimens were retrieved from the ageing environment and tensile tests performed. In Fig. 11 and 12 the mean value of the elongation at break is shown as a function of the ageing time. From these curves the critical times to reach 5% elongation at break have been determined in an Arrhenius plot (see Fig. 13). In the case of PA12 at 8 and 1 C these times have been estimated [7]. strain at break [%] PA 12, T = 12 C PA 12, T = 14 C PA 11, T = 12 C PA 11, T = 14 C ageing time [days] Fig. 11: Aging of PA12 and PA11 in air at 12 and 14 C strain at break [%] PA 12, T = 8 C PA 12, T = 1 C PA 11, T = 8 C PA 11, T = 1 C ageing time [days] Fig. 12: Aging of PA12 and PA11 in air at 8 and 1 C 1. time to reach 5 % strain at break [years] API RP 17B "Saturated" PA 11 air PA 11 air (fit) PA 12 air PA 12 air (fit) T [ C] Fig. 12: Lifetime curve of PA12 and PA11 in air

9 5. PA12 for liner application The above mentioned results underline that PA 12 is well suitable for oil applications. But to examine whether the material may also be suitable for the specific application of lining and rehabilitation of oil pipelines additional test has to be done. One main concern of the use of thermoplastics as liner is the swelling behaviour in hydrocarbons. Fig. 13 shows the results of compatibility tests of PA12 and HDPE in three different oils. IRM 93 is a standard mineral oil used in the automotive industry. The 2 mm thick, 13 mm long and 1 mm wide samples where fully immersed in the test fluid at 6 respectively 8 C which also reflects the maximum operation temperatures of the materials. Length swelling [%] MDPE PA 12 PA 12 plasticized 4261A / 6 C / IRM 93 / Diesel oil / Crude oil low TAN LX93 / 8 C / IRM 93 / Diesel oil / Crude oil low TAN LX92 / 8 C / IRM 93 / Diesel oil / Crude oil low TAN Time [h] Fig. 13: Swelling behaviour of PA 12 grades compared to MDPE These results demonstrate that PA 12 swells less than PE in oil. The slight shrinkage of the plasticized PA 12 is caused by an exchange of the plasticizer with components of the test fluids. The above shown ageing results already underlined the very good aging performance of PA 12 in oil with low TAN. Because of the shown behaviour of plasticized PA 12 a buckling of the liner caused by length swelling is more improbable Lining process The maximum stability of the liner in the host pipe is achieved by ensuring a close fit between the two components after insertion operations are complete. In the case of HDPE liners, this is achieved by specifying the outside diameter of the liner to exceed the internal diameter of the host pipe by a small amount. The liner is then pulled through either a box containing a set of progressively reducing rollers or a reduction die, prior to insertion into the host pipe under tension. In the case of current available PA11 grades, however, the liner section tends to recover quickly after the reduction process; this means that it is not possible to specify such a tight fitting section without the risk of the liner becoming stuck during the insertion process. For this reason a neutral, or slightly loose fit is specified, which will become a slightly tight fit when warmed to the service temperature of the line [8]. Fig. 14 to 16 show the results of the recovery behaviour of different materials after compression performed on injection moulded specimens. The results indicate that PA 12 is much more comparable with PE in terms of the recovery behaviour. This will lead to easier installation of PA 12 compared to

10 PA 11 by the above mentioned technique. Currently first test trials are on the way. We will show first results at the conference. Compression relaxation of VESTAMID LX92 Compression relaxation of PA 11 plasticized Compression in % Compression in % Time in s Time in s Compression relaxation of PE 45 4 Compression in % , 5, 1, 15, 2, Time in s Fig. 14 to 16: Recovery of compressed samples after release of the compression stress 6. Conclusion For Offshore applications in flexible pipes all test have been performed with a new PA12 grade concerning API 17J with a certificate obtained in June 26. The test results show the outstanding material properties and long term performance of this new material. This presentation focuses on results from long term ageing and compatibility experiments of PA 12 in air, in water with different CO2 levels, in crude oil. The ageing tests in different media demonstrate that the new PA12 performs better than the compared PA11. Also some promising results in terms of length swelling and recovery behaviour after compression could be shown. So far the new developed PA 12 grades are opening new opportunities and chances in the field of lining and rehabilitation. References 1. ASTM D2837-2, Standard Test Method for Obtaining Hydrostatic Design Basis for Thermoplastic Pipe Materials or Pressure Design Basis for Thermoplastic Pipe Products 2. ISO 98, Determination of the long-term hydrostatic strength of thermoplastics materials in pipe form by extrapolation 3. ISO 13479, Polyolefin pipes for the conveyance of fluids, Determination of resistance to crack propagation,

11 Test method for slow crack growth on notched pipes (notch test) 4. F. Jorge, A. Dowe, C. Baron, PA12 for offshore flexible pipes and high pressure gas pipes, PPS-23, Salvador 5. EN ISO , First edition, December 2: Petroleum and natural gas industries Design and operation of subsea production systems Part 2: Flexible pipe systems for subsea and marine applications 6. API 17J, second edition, November 1999: Specification for Unbonded Flexible Pipe 7. S. Buchner, T. Sheldrake, G. Bulmer, R. Tüllmann, Ch. Baron, A. Dowe, PA 12 for flexible flowlines and Risers, OMAE 27, San Diego 8. Y Giacomelli, B Howard, Qualification of plastic lined pipelines for hydrocarbon transport, Oilfield Engineering with Polymers 23, London 9. API 17 TR 2, The Ageing of PA11 in Flexible Pipes, First Edition, June Stefan Buchner, Graeme Bulmer, New polymer development for flexible flowlines and risers, Nylon grade 12, VESTAMID LX92, Rio Oil&Gas Conference ASTM D2513 6b, Standard specification for thermoplastic gas pressure pipe, tubing and fittings 12. ISO/FDIS 22621, Plastics piping systems for the supply of gaseous fuels for maximum operation pressures up to and including 2 bar Polyamid

New VESTAMID (Polyamide 12) grades to manufacture products with large geometrical dimensions for oil and gas applications

New VESTAMID (Polyamide 12) grades to manufacture products with large geometrical dimensions for oil and gas applications Andreas Dowe, Dr. Christian Baron, Reinhard Buessing Agenda: (Evonik) Degussa GmbH