FIRST OF A KIND PIPE-IN-PIPE SPOOL DESIGN AND FABRICATION TECHNOLOGY FOR ITER-BURIED COOLING WATER SYSTEM

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1 International Journal of Mechanical Engineering and Technology (IJMET) Volume 8, Issue 9, September 2017, pp , Article ID: IJMET_08_09_053 Available online at ISSN Print: and ISSN Online: IAEME Publication Scopus Indexed FIRST OF A KIND PIPE-IN-PIPE SPOOL DESIGN AND FABRICATION TECHNOLOGY FOR ITER-BURIED COOLING WATER SYSTEM Mahesh Babu P, Murugula Sai Sandeep and Deepak Menon Engineering Design and Research Centre, Nuclear Design, Heavy Civil Infrastructure IC, L&T Construction, Chennai, India ABSTRACT The Project ITER, the International Thermonuclear Experimental Reactor is to demonstrate the scientific and technological feasibility of nuclear fusion energy for peaceful purposes. ITER is being constructed at St. Paul lez Durance, Cadarache, France. ITER Cooling Water System (CWS) serves as a medium of transferring the heat from nuclear reactor to atmosphere. The cooling water system includes both buried (surrounded by soil) and above ground piping with Carbon steel and Stainless steel as pipe material. Codes and standards such as ASME, ASTM and AWWA have been referred in designing the Piping system in according to Flow, Pressure and Temperature requirement. As per pipe stress analysis, some of the branch connections are found to be having higher stress values than that of allowable as per ASME B31.3 in the buried piping of ITER-CWS due to limited flexibility. In order to limit the stress values at these branch connections, first of a kind pipe-in-pipe concept has been developed to allow flexibility, a research and analysis has been performed on piping system using piping stress analysis software CAESAR II. Resulting stress values found to be reduced by great extent (20%) and infer satisfactory performance of innovative pipe-in-pipe concept. Additionally, a new fabrication technology has been developed for these pipe-in-pipe spools based on which the pipe-in-pipe spools are successfully fabricated and shipped to ITER site. This pipe-in-pipe concept is a cost and time effective solution for the buried piping where additional flexibility is to be introduced with constraints like congested environment around the piping. Keywords: Buried piping, Cooling water system, Pipe Flexibility, ITER, Piping stress analysis, CAESAR II Cite this Article: Mahesh Babu P, Murugula Sai Sandeep and Deepak Menon, First of a Kind Pipe-In-Pipe Spool Design and Fabrication Technology for Iter-Buried Cooling Water System, International Journal of Mechanical Engineering and Technology 8(9), 2017, pp editor@iaeme.com

2 First of a Kind Pipe-In-Pipe Spool Design and Fabrication Technology for Iter-Buried Cooling Water System 1. INTRODUCTION The Design of cooling water system in ITER project is performed according to ASME B 31.3 code. The extremes of ambient temperature of the ITER site layout are -25 C and 40 C. Selection of piping materials and pipe fittings are done as per ASTM standards based on Fluid s design pressure and temperature requirements. Carbon steel and Stainless steel materials are selected based on the project requirements. Piping layout of all the cooling water systems have both buried and above ground piping and analysis has been performed with the requirements of piping stress using CAESAR II software and for pipe supports using STAAD PRO V8 software. In the pipe stress analysis, piping system is checked for sufficient flexibility based on thermal expansion. As the Buried piping is completely surrounded by soil and due to limited flexibility, stresses induced at some branch connections exceeded the allowable stress values of the pipe material as per ASME B31.3. In order to reduce the stress values at the branch connections, first of its kind pipe in pipe concept has been developed for the corresponding piping spools of CWS buried piping. 2. PROBLEM DESCRIPTION Piping layout of cooling water systems should be performed with the requirements of piping stress and pipe supports i.e., sufficient flexibility for thermal expansion; proper pipe routing so that simple and economical pipe supports can be constructed; and piping materials and section properties commensurate with the intended service, temperatures, pressures, and anticipated loadings. As a typical example, one of the branch connections of ITER-CWS buried piping is described below: The required volumetric flow rates of Demineralized water in the Run pipe and branch pipe in one of the ITER-CWS piping in buried portion are m 3 /hr and m 3 /hr respectively. The pipe sizing calculations has been performed based on the required flow and velocity as per Continuity Equation given below: = Where, Q = Fluid flow (m 3 /s), V= Velocity of the fluid (m/s) and A= Area of the pipe (m 2 ). The Nominal pipe size is selected based on the standard sizes as per ASME B for Carbon steel and ASME B for Stainless steel piping. The pipe sizes DN 1200 and DN 750 are selected for the run and branch pipes respectively restricting velocity to an approximate value of 2.5 m/s. The temperatures of process fluid and ambient for buried piping is considered to be 50 C and 10 C respectively to check with thermal expansion in operating conditions. The thickness of DN 1200 and DN 750 pipes are selected as mm and 9.53 mm as per ASME B (Clause 304.1) calculation given below: Thickness = PD 2(SEW+Py) +C.A Where, D = Outer Diameter (mm), S = Allowable Stress (MPa), E= Joint Efficiency, W= Weld joint Strength reduction factor, Y= Coefficient, C.A. = Corrosion Allowance. Pipe stress analysis has been conducted using CAESAR II software using the available inputs. Due to the limited flexibility in buried portion, the stresses obtained in this branch connection exceeded the allowable stresses as per ASME B In order to reduce the stresses, pipe-in-pipe concept has been proposed, where outer pipe and compressible Poly Urethane Foam (PUF) material is selected over the process piping at the junction. This helps editor@iaeme.com

3 Mahesh Babu P, Murugula Sai Sandeep and Deepak Menon in avoiding direct contact of process pipe with the soil and also allows flexibility during thermal expansion and pressure loadings. The typical cross section of pipe-in-pipe spools is illustrated in Figure 1. Figure 1 Sectional view of pipe-in-pipe spool With reference to Figure 1, Outer sleeve pipes and fittings for both inner carbon steel and stainless steel piping are fabricated from two halves of ASTM A516M GR70 plates. Thickness of outer sleeve pipe is selected as 8 mm to qualify the pipe against soil load. Inner diameter of the outer sleeve pipe is selected such that the annular space between the inner and outer pipes is 40 mm as recommended by the pipe stress analysis. The annular space between the inner and outer sleeve pipes is filled with compressible PUF conforming to ASTM C591. At the ends of the outer sleeve pipe, Poly sulphide sealant as per ASTM C920 is applied to avoid the ingress of water from sideways. Outer sleeve spool and soil exposed portion of inner pipe spool are provided with a protective layer of 25 mm thick Cement Mortar Lining or Coating (CMLC) as per AWWA C RESULTS Figure 2 and 3 are the glimpses of pipe stress analysis by CAESAR-II software, to illustrate the stress values of pipe junction with and without pipe-in-pipe respectively. Since the buried piping is covered by the soil around it, the expansion due to thermal or pressure loadings are not allowed and thus the stresses are developed at the corresponding point. In Figure.2, the marked pipe junctions 1, 2 without having pipe-in-pipe are with high stress levels of more than 80% of allowable stress values which is not acceptable as per ASME B editor@iaeme.com

4 First of a Kind Pipe-In-Pipe Spool Design and Fabrication Technology for Iter-Buried Cooling Water System Figure 2 Stress levels at the pipe junctions without pipe-in-pipe This increase in stress values is mitigated and found to be in allowed limit i.e. 60% of allowable stress values by introducing pipe-in-pipe as shown in Figure 3. This is due to the flexibility created by the compressible material like Poly Urethane Foam that allows the expansions due to thermal or pressure loadings. Hence, the pipe-in-pipe spool arrangement is proved to be an effective solution for mitigating the pipe stresses in an environment like buried portion. Figure 3 Stress levels at the pipe junctions with pipe-in-pipe 4. FABRICATION TECHNOLOGY In order to overcome the constraints like maintaining the uniform annular space between inner process pipe and outer sleeve pipe during fabrication, filling with PUF material, handling the pipe spool and transporting it to ITER-site, a detailed and effective fabrication methodology has been developed. The outer sleeve pipe is developed to be a flange kind of arrangement with bottom and top halves over the inner process pipe. Plate material ASTM A516M GR70 with width 50 mm and thickness 8.0 mm is drilled with 12 mm dia. hole for M10 hexagonal head bolt to the editor@iaeme.com

5 Mahesh Babu P, Murugula Sai Sandeep and Deepak Menon actual length of the outer casing pipe for every interval of 100 mm (center to center distance between adjacent holes). Each bolted flange plate is welded with an outside fillet weld and inside by a welding with flush grinding into the entire length of each half of the outer casing pipe on both sides. The typical arrangement of bottom half of the outer sleeve spool is shown Figure 4. Figure 4 Bottom half of the outer sleeve The preformed PUF with 40 mm thickness is made ready for application with trimming to the size and shape. The thickness of PUF is ensured uniform throughout for the corresponding outer and inner pipe combination. Interfaces of pipe and PUF surfaces are ensured with application of adhesive before applying PUF. Bottom half of the outer sleeve spool after PUF insulation is as shown in Figure.5. Similar to the bottom half, upper half also is made available and the inner process spool after ensuring with leak tightness with rated hydro test pressure is placed over the bottom half as shown in Figure 6. Figure 5 Bottom half of the outer sleeve with PUF Figure 6 Installation of inner pipe spool over bottom outer sleeve Immediately upper half also placed over the inner pipe spool and bolt tightening to be done with 3.3 kg.m torque in proper sequential manner to ensure the both halves are securely fastened to achieve the pipe-in-pipe spool as shown in Figure 7. At the either end of the outer sleeve pipe, Poly sulphide sealant is filled 10 mm inside from the edge of outer sleeve pipe and also applied outside over the inner pipe. In order to avoid the damage to the PUF packing, the protective coating over the pipe-in-pipe is performed in-situ after the erection at site along with the field joined outer sleeve spools editor@iaeme.com

6 First of a Kind Pipe-In-Pipe Spool Design and Fabrication Technology for Iter-Buried Cooling Water System Figure 7 Final Pipe-in-Pipe spool 5. CONCLUSION The pipe-in-pipe concept is found successful in effectively reducing the pipe stress at the junction of Buried piping for ITER cooling water system by increasing the flexibility. In similar approximately 20 nos. of pipe-in-pipe spools have been designed and fabricated with respect to the requirements of ASME B31.3 code and has been accepted by ITER organization. Figure 8 and Figure 9 shows some glimpses of fabricated pipe-in-pipe spool for ITER-CWS and installed at France site respectively. Pipe-in-pipe spool Figure 8 Fabricated Pipe-in-Pipe spool at Work shop, India Figure 9 Pipe-in-pipe spool installed at ITERsite, France REFERENCES [1] ASME B31.3, Process Piping. [2] ASTM A516M, Standard Specification for Pressure Vessel Plates, Carbon Steel, for Moderate- and Lower-Temperature Service. [3] AWWA M11, Steel Pipe A Guide for Design and Installation. [4] ASTM C591, Standard Specification for Unfaced Preformed Rigid Cellular Polyisocyanurate Thermal Insulation editor@iaeme.com

7 Mahesh Babu P, Murugula Sai Sandeep and Deepak Menon [5] ASTM C920, Standard Specification for Elastomeric Joint Sealants. [6] DIN Coatings Of Corrosion Protection Tapes And Heat Shrinkable Material For Pipelines For Operational Temperatures Up To 50 Deg C. [7] ASTM A307 - Standard Specification for Carbon Steel Bolts, Studs, and Threaded Rod PSI Tensile Strength. [8] ANSI B Square, Hex, Heavy Hex, and Askew Head Bolts and Hex, Heavy Hex, Hex Flange, Lobed Head, and Lag Screws (Inch Series). [9] ANSI B Nuts for General Applications: Machine Screw Nuts, Hex, square, Hex Flange, and Coupling Nuts. [10] T. Subhashini, P. Maheswari, G. Sharmila and T.B. Gopinath, SVPWM Using SiC, GaN Power Driven Motors for Sea Water Cooling System & Ballast Water Management. International Journal of Mechanical Engineering and Technology, 8(4), 2017, pp [11] Shobha Rani Depuru, Muralidhar Mahankali and Navya Sree S, Design and Control of Standalone Solar Photovoltaic Powered Air Cooling System, International Journal of Mechanical Engineering and Technology 8(7), 2017, pp [12] Rahul K. Menon. Metal Hydride Based Cooling Systems, International Journal of Mechanical Engineering and Technology, 6(12), 2015, pp editor@iaeme.com