U22011 Structural Integrity Assignment Sample

Table of Contents

Introduction 

Literature Review

Analytical Analysis

Conclusion and Recommendation

References

Introduction

Header distributes fluid through heat exchanger matrix (Headers, Nozzles and Turnarounds - Heat Exchanger Design Handbook, Multimedia Edition, 2020) as shown in figure1

Figure 1: Heat Exchanger with headers

The most critical high-temperature and high-pressure component of a power boiler is super heater header. During operation (start-up, shut-down and cyclic loads), the header experiences sustained load operation which results in induction of creep and fatigue that damages the components. This reduces the life of a header (Barbera, Chen and Liu, 2017). To operate header and other high-temperature and high-pressure components in an economical way, it is essential to assess these irreversible damages in order to assess the remaining life in this component.

The super-heater header of a fossil-fired boiler that operates in creep domain experiences high stresses at certain sections (girth welds, shell nozzle junctions etc). The major stream exits the boiler from the super-heater header and it will enter high-pressure turbine through main-steam piping in order to generate electric power.

The major purpose of this study is to estimate life assessment of super-heater header with given dimensions and operating conditions. In this study, the fatigue and creep life of a header with given stub configuration is estimated using pressure vessel design codes such as the EN12952 or ASME B31.1.

Operating Conditions

Pressure (P) = 14 MPa

Temperature (T)= 565°C

Total in-service time= 82000 hrs

Dimensions

Material of Header and tube= 2¼CrMo (P22)

Outer diameter of header = Do =390 mm

Header thickness=t= 56 mm

Tube stub outer diameter = do= 57 mm

Tube thickness = tb= 9 mm

Pitch between tube holes = L1=336 mm

Pitch between tube holes=L2= 400 mm

Literature Review

The fatigue life is a function of strain range, applied stress range, and mean stress. According to methods that are based on stress range or strain range, fatigue life refers to total number of cycles to create fatigue damage and to start a dominant fatigue flaw leading to ultimate failure.

Different pressure vessel and piping design codes have been used in literature to determine the fatigue and creep life of super heater header (NiesÅ‚ony and Böhm, 2015) such as ASME Boiler and Pressure Vessel Code Section III Subsection NB and Section VIII Division 2, EN 12952, EN 13445, EN 13480, PD 5500,RCC-M, RCC-MRx, JSME, PNAEG and R5 (Shi et al., 2016).

Many design codes are based on stress-range methods such as the ASME Boiler and Pressure Vessel Code Section III Subsection NB, Section VIII Division 2, BS EN 12952-3, BS EN 13445-3, BS EN 13480-3, BS EN 1993-2 and PD 5500. The design codes which are based on strain range based methods ASME Section III Subsection NH and the structural integrity assessment procedure R5. RCC-M is a combination of stress and strain approach (Shi et al., 2016).

Analytical Analysis

A ligament (TUBE ARRANGEMENT, 2020) is defined as follows

Ligament = Tube pitch - tube hole diameter

Figure 2: Ligament

As the pitch of tube on every tube row is equal, the ligament efficiency is determined as follows

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