ASME Heat Treatment by Eng. Ibrahim Eldesoky

8/10/2019 ASME Heat Treatment by Eng. Ibrahim Eldesoky

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airo Inspection ompany

Eng. Ibrahim Eldesoky

ASNT

NDT-LEVEL III

ASME AUTHORIZED INSPECTOR


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Post weld Heat Treatment

Any heat treatment subsequent to welding.

Normalizing

A process in which a ferrous metal is heated to a suitable

temperature above the transformation range and is

subsequently cooled to below the transformation range.

Stress Relieving

Uniform heating of a structure or portion thereof to a

sufficient temperature to relieve the major portion of the

residual stresses, followed by uniform cooling.

Transformation Range

A temperature range in which ferrous materials undergo

internal atomic changes affecting their material properties.

2Cairo Inspection Company (CIC) Www. CIC-Egypt.com Eng. Ibrahim Eldesoky


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a) When vessels are to contain lethal substances,

either liquid or gaseous, all butt welded joints shall

be fully radiographed, .. When fabricated of

carbon or low alloy steel, such vessels shall be post

weld heat treated.

When a vessel is to contain fluids of such a nature

that a very small amount mixed or unmixed with air

is dangerous to life when inhaled, it shall be the

responsibility of the user and/or his designated

agent to determine if it is lethal.

UW-2 SERVICE RESTRICTIONS



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UW-10 Postweld Heat treatment

Pressure vessels and pressure vessel parts shall be

heat treated as prescribed in UW-40 when PWHT is

required in the applicable part of Subsection C.

UW-40 Procedures of PWHT

a)

In the procedures that follow, the minimum soak

band shall contain the weld W), heat affected zone

HAZ) and a portion of the base metal adjacent to the

weld being heat treated.



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d) When pressure parts of two different P-Number Groups are

joined by welding, the PWHT shall be that specified according to

UCS-56 or UHA-32, for the material requiring the higher PWHT

temperature.

e) PWHT, when required, shall be done before the hydrostatic

test and after any welded repairs except as permitted by

UCS56 f).

A preliminary hydrostatic test to reveal leaks prior to PWHT is

permissible.

f) The term nominal thickness is the thickness t) of the welded

joint as follows. For pressure vessels or parts being post weld heat treated in

a furnace charge, t is the greatest weld thickness in any vessel

or part which has not previously been post weld heat treated.



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f) Nominal

Thickness



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f) Nominal Thickness continued...

UW-49 Check of PWHT Practice

The Inspector shall satisfy himself that all PWHT has been

correctly performed and that the temperature readings

conform to the requirements.



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UCS-56 a) Requirements for PWHT

Requires WPS qualification per Section IX. Everything requires

PWHT unless exempted by Tables UCS-56 or UCS-56.1.

Exemptions to PWHT do not apply when:

PWHT is a service requirement UCS-68),

joining material of certain P-Numbers and thicknesses welded

with either the electron beam, inertia and continuous drive friction,

electroslag or electrogas welding processes.

Heating and cooling rates do not apply for P-No. 1 welded materials

heat treated in the austenitizing range.

UCS-56 b) Requirements for PWHT

Holding times and temperatures may exceed stated values unless

prohibited by Table UCS-56.

Intermediate PWHT need not conform to Table UCS-56.

Heat treatment may be performed in multiple PWHT cycles.



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UCS-56 c) Requirements for PWHT

When welding pressure parts of different P-Numbers, use the table

with the higher PWHT temperature.

When welding non-pressure parts to pressure parts, the PWHT

temperature for the pressure part shall govern. Furnace temp, shall

not exceed 800F 425C) at the time the vessel or part is placed in

it.

Above 800F 425C), the heat up rate shall not exceed 400F per

hour 222C) divided by the maximum metal thickness of the shell

or head in inches, but in no case more than 400F per hour

222C).

During the heating period, there shall not be a variation in

temperature greater than 250F 120C) throughout the vessel

within any 15 foot 4.6 meter) interval of length.

Holding times and temperatures per Table UCS-56orUCS56.1.

UCS-56 d) Requirements for PWHT



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UCS-56 d) Requirements for PWHT

During the holding period, there shall not be a greater

difference than 150F 83C) in temperature between the

highest and lowest readings.

During the heating and holding periods, the furnace

atmosphere shall be so controlled as to avoid excessive

oxidation of the vessel surface.

The furnace shall be designed as to prevent flame

impingement on the vessel. Above 800F 425C), cooling

shall be done in a closed chamber or cooling chamber.

Cooling rates above 800F 425C) shall not exceed 500F

per hour 278C) divided by the maximum shell or head

thickness in inches, but in no case more than 500F per hour

278C).

From 800F 425C) the vessel may be cooled in still air.


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ASME Heat Treatment by Eng. Ibrahim Eldesoky