WORK WITH US
  • About CADE
  • Sectors

    Thermosolar and Renewables

    More info

    Oil & Gas

    More Info

    Power Generation

    More Info

    Other Industries

    More Info
  • Consultancy

    Heat Transfer Equipment Technology

    Process Technology
    Thermal & Hydraulic Design
    Mechanical Design
    Detail Engineering
    Performance Assessment

    More info

    Simulation Engineering

    FEA - Finite Element Analysis
    CFD - Computational Fluid Dynamics
    CHT - Conjugated Heat Transfer

    More info

    Engineering Analysis

    Fitness For Service Assessment
    Mechanical Integrity Remaining Life
    Evaluation Failure Root Cause Analysis
    Performance Assessment

    More info

    Process & Mechanical Consulting

    3rd Party Engineers
    Expert Witness
    Due Dilligence Assessment
    Warranty Resolution

    More info

    Structural Engineering

    Design verification / validation by structural calculation
    Study and definition of loads
    Structural design (conceptual and detailed 3D-2D)

    More info
  • Engineering

    Basic & Detail Engineering

    Data Sheets
    Valve Specifications
    Control valves
    Detailing Engineering
    Plant Layouts and General Arrangement drawings
    Much more

    More info

    Process Engineering

    Chemical Processes
    Thermodynamic Processes
    Heat Transfer
    Hydraulics

    More info

    Equipment Engineering

    Pressure Vessels
    Heat Exchangers
    Reactors, Columns and Towers
    Tanks

    More info

    Piping Engineering

    2D / 3D Design Piping Design
    Flexibility Analysis
    Advanced Piping Flexibility
    Analysis (Finite Element Analysis)

    More info

    3D Laser Scanner

    Assessment of Existing Industrial Assets
    Equipment Manufacturing Dimensional Control
    Brownfield Projects and As-Built Engineering

    More info
  • R&D
    Edit Content

    Eclosion

    Generation, storage and transport of renewable hydrogen and biomethane.

    More info
    On going
    TES4Trig logo

    Tes4trig

    Innovative solution for the generation of heat, cold and electricity from solar energy

    More info
    On going
    Edit Content
    logo cade engineering cade soluciones de ingeniería - Servicios de Ingeniería y Consultoría

    Research, Development and Innovation

    CADE has develop its own R&D activities since 2009 around new disruptive technologies and industrial applications related to renewables and clean-tech industries

    Further information
    logo cade engineering cade soluciones de ingeniería - Servicios de Ingeniería y Consultoría

    Investigación, Desarrollo e Innovación (I+D+i)

    Desde 2009, CADE desarrolla actividades de Investigación, Desarrollo e Innovación (I+D+i) en torno a nuevas tecnologías disruptivas y aplicaciones industriales relacionadas con energías renovables e industrias de tecnología limpia.

    Más información
  • Technologies
    Edit Content

    process CSP

    Custom solutions for the integration of thermosolar heat in the industry

    More info

    solidTES

    Thermal energy storage system in concrete

    More info

    zeroSD

    Zero-Sludge-Disposal - Zero-Sludge-Disposal Solution using SCWG Technology

    More info

    zeroLD

    Zero Liquid Discharge - Zero Liquid Discharge Solution for Wastewater Treatment

    Más información
    Edit Content

    Cade Cobots

    CADE Cobots is a business line framed in our portfolio of solutions in Industry 4.0 of CADE for optimization of industrial processes, through collaborative robots or cobots, comprehensive process consulting, artificial vision, as well as development and supply and integration of complete turnkey solutions in hand. CADE Cobots allows us to respond to our idea of intelligent industrial models that are adaptable to needs and processes, applied to companies of all sizes.

    Más información
  • Publications

STRUCTURAL INTEGRITY ASSESSMENT DURING LOCAL PWHT

Post weld heat treatment (PWHT) is a thermal treatment usually  performed in steels that have been welded. Its object is to ensure that the welding properties are suitable for its expected operation according to the mechanical and structural requirements prescribed in the corresponding design codes. This kind of treatment is usually performed on pressure equipment and pipes within refineries, petrochemical and power plants.  

Depending on used material and thickness of the welded parts, PWHT might become a mandatory requirement, according to the design codes commonly used for pressure equipment and piping design (ASME VIII, B31.3, EN -13445, AD-2000, etc.).

What is meant by PWHT? How is PWHT done?

By means of a proper PWHT, temperature is raised around welded area in order to eliminate residual stresses generated during the welding process (stress relief) and thus reducing the hardness of the heat-affected zone (HAZ).

In case of application of a non-adequate PWHT, residual stress or excessive hardness may appear in the joint area after welding. This phenomenon, in combination with the stresses caused by the regular equipment operation (pressure, temperature, etc.) might lead to a mechanical instability or generate, in the worst case scenario, plastic collapse failures, fatigue damage or stress corrosion cracking phenomena.

PWHT parameters (temperature and time) to be applied will be defined by internal fluid, material and thickness, as well as by the requirements of design code or owner/licensor’s specifications.

welding-pwht-tratamiento-termico-post-soldadura

PWHT in manufacturing stage

pwht-tratamiento-termico-post-soldadura
Post Welding Heat Treatment at workshop

Along manufacturing stage, PWHT treatment is usually carried out at the workshop facilities with specialized furnaces aimed for such process. Depending on furnace’s capacity, thermal treatment can be performed for the one-piece equipment. This way, significant thermal gradients are avoided and thus the appearance of residual stress and excessive hardness in the joint zone are considerably minimized. In general terms, when the PWHT is conducted along manufacturing stage, a detailed evaluation of its impact on equipment’s mechanical behavior does not result strictly mandatory.

PWHT on-site

Along plant scheduled turnarounds or shutdowns due to repairs or modifications, welding operations and the subsequent PWHT must be performed on-site. Such interventions will be generally localized on specific zones of the equipment thus Local PWHT might generate significant thermal gradients between the treated areas and the rest of the areas not be affected by the thermal treatment.

These thermal gradients can lead to mechanical instability issues (residual stress, excessive joint hardness, stress corrosion cracking, etc.). In most cases, these defects are not straight detected, which could result in future mechanical issues throughout the equipment’s service life. (e.g. Stress corrosion cracking).

Failures or breaks in operating equipment, which may lead to a unit shutdown, imply a serious tricky issue that could be prevented and even avoided, with the corresponding control and analysis of local post-weld heat treatments.

welding-pwht-during-turnover
Preparation of welding works.
grafic-pwht-tratamiento-termico-postsoldadura
PWHT procedure (Temperature Vs Time curve)

CADE’s experience in this type of analysis. Examples.

Therefore, and in case of heat treatments on-site, definition and validation of the right parameters of PWHT result highly recommendable in terms of mechanical integrity compliance and code requirements.

From a technical point of view, such evaluations are usually approached through a transient analysis using the finite element method, which considers treatment temperatures, geometries to be treated and transition temperatures, based on the guidelines and recommendations of WRC-452 “Recommended practices for local heating of welds in pressure vessels”, and ASME VIII Division 1 UCS-56 design code.

pwht-analisis-transitorio-elementos-finitos-1
pwht-analisis-transitorio-elementos-finitos-2

In and out temperatures during transient analysis with finite element.

Results validation is conducted according to design code ASME VIII Division 2, Part 5 “Design by analysis requirements” / API 579-1 ASME FFS-1 “Fitness for service, evaluation of protection against local failure in elastic-plastic range”, so that residual stress and permanent plastic deformations (if any) should be below the limits established by these codes.

local pwht-tensiones-y-deformaciones
pwht-tensiones-y-deformaciones-2

Finally, a buckling analysis is performed to ensure the equipment or vessel stability during the Post Weld Heat Treatment (PWHT) for wind/seismic loads.

pwht-buckling-example-pandeo

  • Conclusions derived from the analysis will allow to validate the mechanical integrity of the equipment during and after the PHWT treatment. Moreover, these conclusions will determine and validate the parameters of the thermal treatment to be applied: both heating and cooling ramps and treatment times. The analysis will also help to reduce the instability risks of the equipment against wind / seism loads during the process.
  • Likewise, the analysis will allow to define in advance the required means for the right performance of the Post Weld Heat Treatment (heating blankets, electricity generators, auxiliary machinery, etc.), in order to ease appropriate resources and time planning.
  • It is usual practice to evaluate circumferential welding of vertical equipment, welding of skirts or welding of support cradles, among other examples.

CADE has a wide experience as an engineering and consulting company specialized in design of pressure equipment and evaluation of mechanical integrity in critical operating equipment. CADE provides comprehensive engineering and consulting services to plant owners, EPC contractors, and equipment suppliers: thermal, hydraulic, process and mechanical design, preparation of design specifications and technical requirements, procurement, owner’s engineering, performance evaluation, integrity assessment consultancy or expert witness services, among other capabilities.

Author: Pedro José Montes Marín

OTHER PROJECTS

CADE Engineering Contact

Seeking engineering and consulting services? Tell us about your project on the following form and one of our specialists will reach out to you as soon as possible.

Also, you can call +34 967 19 01 72 or send an email to cade@cadesoluciones.com.

Follow us in our social networks

Linkedin Youtube Instagram

SERVICES

TECHNOLOGIES

SECTORS

ABOUT US

legal notice

CADE Engineered Technologies

CADE Soluciones de Ingeniería, S.L.

HEADQUARTERS

Parque Científico y Tecnológico
Paseo de la Innovación 3, 02006 Albacete – Spain

Tel. +34 967 19 01 72

CADE FACTORY

Av. Adeca, 55, 02007 Albacete - Spain

MADRID OFFICE

C/Raimundo Fernández Villaverde, 53 (Entreplanta), 28020 – Madrid

© Copyright 2003-2024 Cade Soluciones de Ingeniería S.L. - Terms and Conditions of Use

Albacete

Parque Científico y Tecnológico

Paseo de la Innovación 3, 02006 Albacete – España

Tel. +34 967 19 01 72

Madrid

C/Raimundo Fernández Villaverde, 53 (Entreplanta)

28020

Madrid – España

Cargar más

Albacete

Parque Científico y Tecnológico

Paseo de la Innovación 3, 02006 Albacete – España

Tel. +34 967 19 01 72

Madrid

C/Raimundo Fernández Villaverde, 53 (Entreplanta)

28020

Madrid – España

Contact us

I guess you are interested in what we do

If you please, contact us and tell us about your project to inform you what we can do for you

Can we call you?

We inform you about our engineering solutions