FIRST OF A KIND PIPE-IN-PIPE SPOOL DESIGN AND …€¦ · software and for pipe supports using...

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International Journal of Mechanical Engineering and Technology (IJMET) Volume 8, Issue 9, September 2017, pp. 495–501, Article ID: IJMET_08_09_053

Available online at http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=8&IType=9

ISSN Print: 0976-6340 and ISSN Online: 0976-6359

© 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. 495–501.

http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=8&IType=9

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 7914.88 m3/hr and 2457.97 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 (m3/s), V= Velocity of the fluid (m/s) and A= Area of the pipe

(m2

).

The Nominal pipe size is selected based on the standard sizes as per ASME B 36.10 for

Carbon steel and ASME B 36.19 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 11.91 mm

and 9.53 mm as per ASME B31.3-2012 (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 31.3. 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



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 C205.

3. 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 31.3.


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



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.


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.

Figure 8 Fabricated Pipe-in-Pipe spool at Work

shop, India Figure 9 Pipe-in-pipe spool installed at ITER-

site, 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.

Pipe-in-pipe

spool



[5] ASTM C920, Standard Specification for Elastomeric Joint Sealants.

[6] DIN 30672 - 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

60000 PSI Tensile Strength.

[8] ANSI B18.2.1 - Square, Hex, Heavy Hex, and Askew Head Bolts and Hex, Heavy Hex,

Hex Flange, Lobed Head, and Lag Screws (Inch Series).

[9] ANSI B18.2.2 - 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. 01–12

[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. 1144– 1158.

[12] Rahul K. Menon. Metal Hydride Based Cooling Systems, International Journal of

Mechanical Engineering and Technology, 6(12), 2015, pp. 73-80.

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