For more than 25 years HDPE pipe made from PE 3408 pipe-grade resins have provided long-term solutions to many of the power industries’ piping needs. Recent advances in HDPE resins have increased the engineering characteristics of the material. The upgraded resin, PE 4710, offers superior slow crack resistance, excellent abrasion resistance and higher working pressure capability to name a few of the improved characteristics. The use of PE 4710 resin to make HDPE pipe was approved for industrial applications in 2007 under ASTM F 714.

AmerenUE Callaway plant engineers needed to replace approximately 2000 feet of 30-inch carbon steel pipe used as their Essential Service Water (ESW) system for the plant. Similar to the original steel blow-down line which was installed in the 1980s, the 30-inch ESW carbon steel pipe had reached the end of its useful life due to internal corrosion of the pipe wall. Time was a major factor in the replacement of the line and long lead times for ASME Class III steel pipe put project completion past Callaway’s installation window. AmerenUE engineers were looking for options. Because of the successful ongoing installation of the 36” HDPE blow-down line, AmerenUE engineers and project managers were interested in the use of HDPE pipe to solve their ESW line issue. PE 4710 HDPE pipe was discussed during a presentation by Steve Sandstrum, Director of Business Development, and Shane Schuessler, both with ISCO Industries. One major hurdle existed – approval of PE 4710 HDPE pipe by ASME and the Nuclear Regulatory Commission (NRC).

The ESW line was a replacement project occurring between buildings in the secure area of the Callaway Nuclear Plant and is an ASME Section III, Division 1; Class 3 buried water piping system. This line replacement was the first such HDPE piping installation of its kind in the United States and included 2000 feet of 36-inch IPS DR 9.5 PE 4710 HDPE pipe. Because the replacement project involved a safety system of the Callaway plant, the NRC had to approve the use of HDPE in such an application. A group of qualified experts in ASME Class 3 piping systems including AmerenUE engineers and engineering consultants worked to create ASME Code Case N-755. Dudley Burwell of ISCO Industries was included in the group as the HDPE expert and was an integral part of the team to get acceptance of the code case. ASME Code Case N-755 covers the use of HDPE materials in ASME Class 3 water piping systems. It outlines system design, training, fabrication, installation, examination and testing. Approval within ASME was reached on Code Case N-755 in 2007. The technical information in Code Case N-755 became the basis for Callaway’s request to the NRC (and ultimate approval) for use of the HDPE in an ASME Section III, Class 3 system. ASME’s approval of Code Case N-755 provides the opportunity for nuclear power facilities across the United States to obtain NRC approval and receive the long term advantages of HDPE pipe in buried systems.

Installation of AmerenUE Callaway plant’s ESW piping system presented several complex challenges including a short installation timing window, numerous physical obstacles above and below grade, and the unfamiliarity with HDPE pipe fusion and installation. Once again, ISCO Industries provided training, supplied the pipe and fittings, and provided the McElroy fusion equipment for this project. Corrigan Company, a mechanical contractor based in St. Louis, Missouri, was the installing contractor for the ESW line replacement while Bloomsdale Excavating completed the excavation and backfill work. On-site training started in June 2008 and the lines were installed and hydro-tested by December 2008. One train of the new piping was tied-in and made operational in December 2008. The second train became operational in April 2009.