A New High Temperature Pressure Rated HDPE Pipe Resin Expands the Capability of Polyethylene Pipe

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1 A New High Temperature Pressure Rated HDPE Pipe Resin Expands the Capability of Polyethylene Pipe Dane Chang, PhD The Dow Chemical Company Freeport, Texas USA Carl Baker, PE The Dow Chemical Company Freeport, Texas USA SHORT SUMMARY (One paragraph, ~6 sentences) A bimodal high density polyethylene (HDPE) resin with an 82 C (180 F) pressure rating has recently been developed for demanding pipe applications. This resin qualifies in the highest pressure rating category with both ISO PE100 and ASTM PE4710 listings. In addition, it has excellent resistance to both slow crack growth and rapid crack propagation. It expands the capability of traditional polyethylene material to more severe service environments and has been used successfully in North American O&G gas gathering and transporting applications in both solid wall and composite pipe structures KEYWORDS (Obligatory, please give ~3-5 keywords) Pipe, High Temperature, PE4710, PE100 ABSTRACT Due to its flexibility, toughness, and good resistance to corrosion and abrasion, polyethylene pressure pipe has been widely used for several decades in a variety of applications, including gas and water distribution, oil and gas gathering, and many industrial pipe segments. A significant limitation for polyethylene pipe in these applications is its temperature capability. Typically, polyethylene pipe can be safely used at temperatures up to 60 C (140 F). Projects that involve higher temperatures have historically required alternative materials. A bimodal high density polyethylene (HDPE) resin with an 82 C (180 F) pressure rating has recently been developed for demanding pipe applications. This resin qualifies in the highest pressure rating category with both ISO PE100 and ASTM PE4710 listings. In addition, it has excellent resistance to both slow crack growth and rapid crack propagation. It expands the capability of traditional polyethylene material to more severe service environments and has been used successfully in North American oil and gas gathering and transporting applications in both solid wall and composite pipe structures. Key physical and performance properties will be discussed. 1 Copyright 2016 by The Dow Chemical Company

2 INTRODUCTION A proprietary gas phase dual reactor process is allowing commercial production of an advanced, high temperature pressure rated bimodal high density polyethylene (HDPE) resin. Compared to traditional unimodal polyethylene (PE) technology, this bimodal technology provides increased design flexibility through resins with an even broader range of molecular weight distribution (MWD) and a wider window of high performance characteristics. As shown in Figure 1, the bimodal structure includes a low molecular weight (LMW) fraction, which maximizes crystallinity for stiffness and tensile properties, and a high molecular weight (HMW) fraction, which maximizes comonomer incorporation for improved toughness, stress crack resistance, and melt strength. This unique molecular structure, combined with an enhanced additive package, imparts excellent long-term hydrostatic strength at higher temperatures without the need to cross-link the material. Figure 1: Basic Structural Comparison (1) (1) Data shown is simulated and does not represent actual measurements of MWD or comonomer distribution. DISCUSSION Elevated Temperature and Pressure Ratings While pipelines used in municipal and industrial applications must often endure extreme temperatures, oil and gas pipe is widely regarded to have one of the highest, most rigorous requirements. As a result, the materials in these experiments were tested according to those standards. Results showed that pipes made with this advanced bimodal HDPE resin offer the industry s highest elevated temperature ratings among non-crosslinked polyethylene pipes, enabling safe operation up to 82 C (180 F), which easily surpasses both competitive materials and industry standards. This exceptional high temperature performance is matched by high pressure ratings. A maximum operating pressure (MOP) can be determined for a pipeline at various temperatures using the following ratings: hydrostatic design basis (HDB), hydrostatic 2 Copyright 2016 by The Dow Chemical Company

3 design strength (HDS) obtained from HDB, minimum required strength (MRS), or categorized required strength (CRS). The following is a summary of the ASTM pressure rating listings received by this advanced bimodal HDPE resin: 1600 psi HDB at 23 C (73 F) 1000 psi HDS at 23 C (73 F) 800 psi HDB at 82 C (180 F) Figure 2: ASTM D2837 Regression for the Advanced Bimodal HDPE The advanced bimodal HDPE resin offers higher temperature creep resistance up to 82 C (180 F) for improved fitting integrity in spoolable composite pipe for oil and gas applications. Figure 3 compares the maximum operating pressures of standard dimension ratio (SDR) 11 pipe made with the advanced bimodal HDPE resin (ASTM PE4710) and conventional unimodal ASTM PE3608/PE3408 materials. Measured at 23 C (73 F), the advanced bimodal HDPE offers PE4710 pipe a 26 percent higher MOP than unimodal PE3608/PE3408. At 60 C (140 F), the advantage grows to nearly 60 percent, with the added potential of increasing operating temperatures up to 82 C (180 F). 3 Copyright 2016 by The Dow Chemical Company

Figure 3: Comparison of MOP Ratings for SDR 11 Pipe Table 1 lists the pressure ratings of the advanced bimodal HDPE resin at various temperatures and SDRs when used as PE4710 (ASTM) pipe.

4 Figure 3: Comparison of MOP Ratings for SDR 11 Pipe Table 1 lists the pressure ratings of the advanced bimodal HDPE resin at various temperatures and SDRs when used as PE4710 (ASTM) pipe. Table 1: Pressure Ratings of Advanced Bimodal HDPE Resin for PE4710 Water Pipe per ASTM D2837 (2) (2) Based on a 0.63 design factor for PE4710 and PPI TR-4 HDB listing of 1600 psi/23 C (73 F), 1000 psi/60 C (140 F), and 800 psi/82 C (180 F) (3) LTHS (long term hydrostatic strength) 4 Copyright 2016 by The Dow Chemical Company

5 Slow Crack Growth Resistance One of the most important measurements that determine a pipeline s life expectancy is resistance to slow crack growth (SCG). As illustrated in Figure 4, at a nominal stress of 2.4 MPa (350 psi), the advanced bimodal HDPE resin offers 10,000 hours in the ASTM F1473 Pennsylvania Notch Test (PENT), compared to the ASTM D3350 requirement of 10 hours for PE3408, 100 hours for PE3608 and 500 hours for PE4710 pipe, the advanced bimodal HDPE offers resistance 20 times longer. Its excellent resistance to SCG also allows installation using trench or trenchless (HDD) methods and helps reduce the need for expensive bedding and embedment during trench installation. Figure 4: ASTM F1473 PENT Test at 80 C (176 F)/2.4 MPa (350 psi) Rapid Crack Propagation Resistance In addition to excellent slow crack growth resistance, the advanced bimodal HDPE resin also offers strong resistance to rapid crack propagation (RCP). This is important because while RCP failure is rare, under favorable conditions, a crack can propagate at speeds up to 984 feet (300 meters) per second. Figure 5 shows that the advanced bimodal HDPE resin is much more resistant to RCP than the typical PE2708 and PE3608 resins when measured in accordance with ISO requirements. With a critical temperature of -17 C (~1 F) and a critical pressure of 12 bar (converted to a full scale critical pressure of 664 psig in accordance of ISO 4437), RCP failure is highly unlikely for pipe made with the advanced bimodal HDPE resin. In comparison, RCP failure is possible for typical PE2708 pipe at temperatures below 15 C (59 F) or pressure above 90 psig and PE3608 pipe is vulnerable to RCP failure at temperatures below 9 C (48 F) or pressure above 142 psig. 5 Copyright 2016 by The Dow Chemical Company

Figure 5: ISO 13477 S-4 RCP Test (10-inch IPS, SDR 11 Pipe) (4) Full scale critical pressure (Pc) calculated in accordance with ISO 4437 Resistance to Water Hammering Pressure surge (or water hammer)

6 Figure 5: ISO S-4 RCP Test (10-inch IPS, SDR 11 Pipe) (4) Full scale critical pressure (Pc) calculated in accordance with ISO 4437 Resistance to Water Hammering Pressure surge (or water hammer) can be as much as 200 percent of the MOP for liquid transportation such as water. Quick burst testing of pipe produced with the advanced bimodal HDPE has shown resistance to water hammering up to four times the MOP. Table 2 shows the results for 22-inch SDR 9 and 20-inch SDR 11 butt-fusion jointed pipe, respectively. The hoop stress of 4264 psi for 22-inch SDR 9 pipe and 4522 psi for 20-inch SDR 11 pipe are more than 400 percent of the maximum design stress of 1000 psi. 6 Copyright 2016 by The Dow Chemical Company

Table 2: Quick Burst Testing of Advanced Bimodal HDPE Resin (Butt-fusion Jointed Pipe) Potential for Downgauging and Lower Costs The fact that the advanced bimodal HDPE resin meets and exceeds both

7 Table 2: Quick Burst Testing of Advanced Bimodal HDPE Resin (Butt-fusion Jointed Pipe) Potential for Downgauging and Lower Costs The fact that the advanced bimodal HDPE resin meets and exceeds both ASTM PE4710 and ISO PE100 requirements helps enable increased end-use flexibility. Using this resin for oil and gas pipe or other industrial pipe applications offers the potential to increase throughput efficiency and/or reduce pipe material costs. For example, you may increase the MOP of the pipeline to achieve higher throughput efficiency. Or, you may decide to maintain the same pressure and use a thinner wall thickness. This offers not only higher throughput efficiency due to increased inside diameter, but also lower pipe costs based on reduced material usage due to decreased wall thickness. 7 Copyright 2016 by The Dow Chemical Company

8 VALUE PROPOSITIONS OF THE ADVANCED BIMODAL HDPE RESIN The high temperature pressure rated bimodal HDPE resin creates opportunities for advantaged performance and value far beyond that of unimodal polyethylene while also improving upon the high temperature performance of traditional bimodal HDPE resins. In addition to meeting and exceeding all requirements of both ASTM D2513 and DOT CFR Title 49, Chapter I, Part 192, this advanced bimodal resin offers: Industry-leading pressure ratings Meets or exceeds ASTM PE4710 requirements Meets or exceeds ISO PE100 requirements Meets CSA Z as PE4710 PLUS material Elevated temperature performance with safe operation up to 82 C (180 F) The broadest operating temperature range continuous operation from -45 to 82 C (-49 to 180 F) with intermittent temperatures up to 95 C (203 F) Exceptional slow crack growth (SCG) resistance ASTM F1473 PENT value up to 10,000 hrs (20 times PE4710 requirements) Excellent rapid crack propagation (RCP) resistance ISO critical temperature of -17 C (~1 F) at 10 bar ISO critical pressure of >12 bar at 0 C (32 F) (calculated full scale critical pressure of >664 psig in accordance with ISO 3327) Good heat fusion and cross-fusion joint integrity with all types of MDPE and HDPE resins, including PE2406, PE2708, PE3608, PE4710, PE80, and PE100 grades Increased production output, improved flexibility (stress relaxation), and recyclability compared to cross-linked polyethylene (PEX) Trench or trenchless (HDD) installation capabilities. For trench installation, it offers the potential to significantly reduce installation costs by allowing use of natural backfill; no sand bedding required. 8 Copyright 2016 by The Dow Chemical Company

9 Table 3 compares the performance of this advanced high temperature pressure rated bimodal HDPE material to both unimodal HDPE and traditional bimodal HDPE resins. Table 3: Comparison of Selected Pipe Materials 9 Copyright 2016 by The Dow Chemical Company

10 CONCLUSIONS Advanced molecular architecture design and improved gas phase dual reactor manufacturing process flexibility coupled with an enhanced additive package successfully enabled the manufacture of advantaged high temperature pressure rated bimodal HDPE resin that qualifies both ASTM PE4710 and ISO PE100 requirements. This resin s 82 C (180 F) pressure rating along with its excellent resistance to slow crack growth and rapid crack propagation make it very well suited for oil and gas gathering, transportation, and industrial pipeline applications that face challenging higher temperature operating conditions. 10 Copyright 2016 by The Dow Chemical Company

Comparison Between PE 4710 (PE 4710 PLUS) and PE 100 (PE 100+, PE 100 RC)

Comparison Between PE 4710 (PE 4710 PLUS) and PE 100 (PE 100+, PE 100 RC) Author: Dr. Gene Palermo, President, Palermo Plastics Pipe Consulting, www.plasticspipe.com Abstract The scope of this paper is