ASME Section VIII Div 2 PWHT Requirements

ASME Section VIII contains comprehensive requirements for the design, fabrication, inspection, testing and certification of fired or unfired pressure vessels with internal or external operating pressures exceeding 15 psig. In addition, this standard provides mandatory and nonmandatory appendices that detail additional design criteria, nondestructive examination standards and acceptance standards that apply.

Division 1

As its name implies, Division I of ASME Section VIII code deals specifically with pressure vessels. It specifies the mandatory and nonmandatory construction requirements, along with welding specifications such as WPSs (Welding Procedure Specifications), PQRs, and welder performance qualifications; making certain these documents are correctly documented before placing vessels into service is important.

Post-weld heat treatment (PWHT) is a controlled process in which material that has been welded is heated up below its lower critical transformation temperature, held there for an extended period, to remove residual stresses and microstructural changes caused by welding process. ASME Section VIII Code provides table that lists PWHT requirements for different materials.

PWHT requirements depend on both the chemical makeup of the material and its thickness; some codes mandate PWHT for materials exceeding certain thickness limits while others only if a material is susceptible to stress corrosion cracking.

The ASME Section VIII Div 1 table details PWHT requirements for different steels. This table includes details on minimum preheat temperature and duration requirements as well as maximum allowable carbon levels per steel material type; for instance, for 2.25%Cr-0.5%Mo and 1.20%Cr-0.14%Mo steels the required preheat temperature is higher than other alloys.

Division 2

The ASME Section VIII Div 2 PWHT requirements provide rules and standards that regulate the design, fabrication, inspection, and testing of pressure vessels. This section of American Society of Mechanical Engineers’ Boiler and Pressure Vessel Code covers every aspect of vessel creation from material choice through structural integrity calculations to corrosion/erosion allowance calculations as well as MDMT toughness testing requirements for weld filler material as well as any metallurgical phenomena which might compromise their safety.

This section also includes both mandatory and non-mandatory appendices as guidelines that can help avoid costly mistakes, including minimum weld thickness requirements, welding procedures and helium tests. They also offer guidance on conducting pressure testing and stamping procedures and for verifying the compliance of pressure vessels.

ASME Section VIII’s latest revision aims to promote consistency and clarity when designing and fabricating pressure vessels, with changes such as adding paragraph UG-84(d)(3) for diffusion welding impact test requirements, realigning Part 4.18 to ensure consistency when it comes to heat exchangers, removing UHX altogether in favor of its revised “PRT VIII-1” designation – increasing consistency while simultaneously improving maintenance of pressure vessels.

Division 3

ASME Section VIII provides rules and regulations for designing, fabricating, inspecting, testing and marking pressure vessels in all industries including oil. The standard includes appendices containing additional design criteria and nondestructive examination standards that help ensure vessels meet safety regulations. Observing these guidelines isn’t mandatory but can ensure vessels meet required safety criteria.

ASME Section viii PWHT requirements are laid out in various code sections and their appendices, providing details such as design criteria, inspection acceptance standards and nondestructive examination techniques applicable to pressure vessels. Furthermore, this code sets rules for stamping and labeling pressure vessels with one ASME certification mark bearing U-M-V designators as well as stamping/labeling rules and establishes standards relating to single ASME certification marks that contain U-M-V designationators.

Section VIII training courses equip engineers with a thorough knowledge and comprehension of pressure vessel construction and design. These courses can provide substantial benefit for mechanical, maintenance, inspection/QAQC engineers looking to excel in pressure vessel design or operation – for instance PetroSync’s ASME Section VIII Div 1 and 2 training course is one such solution that can enhance engineers’ capabilities while helping promote safe and compliant pressure vessels.

Appendixes

The ASME Code Section VIII contains mandatory requirements, prohibitions and guidance related to pressure vessel materials, design, fabrication, examination, inspection, testing, certification and pressure relief. There are nonmandatory appendices such as Part UG (general fabrication requirements) as well as Parts UW, UF and UB that cover welding methods of construction respectively.

Post-weld heat treatment (PWHT) is required by ASME Code Section VIII and can be performed using either furnace or in-shop methods. Tables in UCS-56 outline heating cycle data required to meet PWHT for various materials according to their P No and Gr No; some low alloy steels, however, may fall under different jurisdictional jurisdiction such as US piping and pressure vessel codes whose requirements for PWHT may resemble BS 2633 in terms of standards compliance requirements.

For example, the piping and pressure vessel code stipulates a minimum soaking temperature of 1200 deg F for steels containing 1.5%Cr and 0.5%Mo (including ASME P4 and P5 group 1) while BS 2633 also specifies similar minimum soaking and minimum preheat requirements for these steels. Furthermore, full radiography of welds in lethal service service is mandatory under both codes.