proposed new asmeb31p standard on preheat & pwht.pdf

8/10/2019 Proposed New ASMEB31P Standard On Preheat & PWHT.pdf

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PROPOSED NEW ASME B31P

STANDARD ONPREHEAT & PWHT

AWS Heat Treating ConferenceAugust 1213, 2014 Arlington, TX

Richard D. Campbell, PE ([email protected])

Bechtel

Phillip D. Flenner, PE ([email protected])

Flenner Engineering Services, LLC


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ASME B31 Pressure Piping Code is comprised of 7 individual

Sections:

ASME B31.1 Power Piping

ASME B31.3 Process Piping

ASME B31.4 Pipeline Transportation Systems for

Liquids and Slurries ASME B31.5 Refrigeration Piping and Heat Transfer

Components

ASME B31.8 Gas Transmission and Distribution Piping

Systems

ASME B31.9 Building Services Piping ASME B31.11 Slurry Transportation Piping Systems

(incorporated into B31.4 in 2012)

ASME B31.12 Hydrogen Piping and Pipelines

Why is a New Standard Needed?


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Each Section serves specific areas of the piping industry

Each Section has different: Applications

Operating Pressures, Temperatures, Conditions

These Code Sections have diverged through the years in some

of their requirements, such as preheat and postweld heattreatment (PWHT)

Rules in B31 Code Sections are different than those in the

Boiler and Pressure Vessel Codes

The result is a diversity of these requirements that are

confusing and difficult to administer and oversee



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The ASME B31 Standards Committee has made attempts to

provide consistency between various Sections by establishingtechnical committees to oversee similar chapters in different

Sections

The B31 Committee approved a new Standard tentatively

titled ASME B31P Standard on Preheat and PWHT toprovide nearly identical rules for B31.1, B31.3, B31.5, and

B31.12

To begin this process, revisions have been made to B31.1 and

B31.3 for the 2014 Editions to provide consistent rules in

these Sections These rules will provide the basis for the proposed Standard

Task assigned to B31 Fabrication and Examination

Committee and chaired by Phil Flenner



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P-Number 1 Steels:

ASME B31.1-2012 175F for > 1 in. and > 0.30% C

ASME B31.3-2012

175F for 1 in. (no carbon limit)

ASME B31.5-2013 175F for > 3/4 in. (no carbon limit)

Does a 1 in. thick pipe know the difference?

Varying Preheat Requirements


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P-Numbers 5A and 5B Steels:

ASME B31.1-2012 400F for SMTS > 60 ksi or > 1/2 in. and % Cr > 6.0

300 F for all others

ASME B31.3-2012

350 F minimum preheat for all thicknesses ASME B31.5-2013

300 F or 400 F minimum, but thickness ranges are

different than in B31.1

ASME B31.4-2012 and B31.9-2014

The WPS shall specify the minimum preheat temperature& the method of heating (but provide no specific

temperatures)

Why are requirements different for same strength & thickness?



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B31.3-2010


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B31.3-2012

1stStep

EliminateRecommended


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Preheat Requirements

Preheat requirements are mandatory values

Minimum preheat is 50F

Base metal temperature at or above minimum temperature in

all directions from point of welding for a distance the larger

of 3 in. or 1.5X the greater nominal thickness

Base metal temperature for tack welds shall be at or abovethat required for a distance not less than 3 in. from the point

of welding

Two different P-Nosminimum preheat is higher of the two

Nominal material thickness is thickness of the pressure-retaining materials being joined at the weld (slight

clarification from 2012 to 2014)

For P-Nos. 3, 4, 5A, 5B, 6, & 15E preheat shall be maintained

until PWHT performed (with some exceptions)


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B31.1-2012All in paragraph layout (no tables)


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B31.1-2014Put specific preheat requirements in a new Table 131.4.1


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60 ksi

60 ksi

60 ksi

175

175

175

>1/2 %Cr > 6.0 400

B31.12014 Table with changes from 2012 requirements shown in red

2014 also added allowance to attach thermocouples

using low-energy capacitor discharge welding


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Preheat Requirements

Minimum preheat is 50F

Preheat zone shall be at or above minimum temperature in

all directions from point of welding for a distance the larger

of 3 in. or 1.5X the greater nominal thickness (added in 2014

to match B31.1-2014)

Base metal temperature for tack welds shall be at or abovethat required for a distance not less than 3 in. from the point

of welding (added in 2014)

Preheat requirements apply to all types of welding, including

tack welds, repair welds, and seal welds on threaded joints


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Preheat Requirements (cont.)

Two different P-Nosminimum preheat is higher of the two

(shall in 2014 compared with recommended in 2012)

Nominal thickness is thickness of the thicker component

(slight clarification in 2014 from 2012 of thicker component

measured at the joint)

Allowance of attaching thermocouples with low energydischarge welding (clarification in 2014 from that in 2012)

For P-Nos. 3, 4, 5A, 5B, 6, & 15E preheat shall be maintained

until PWHT performed (with some exceptions) (B31.3-2014

added several paragraphs from B31.1-2014)


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B31.3-2012


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B31.3-2014 Approved, but not yet published

The bad news is the preheat table has been drastically revised

from the 2012 Edition, including:

Thickness cutoffs (e.g. P-1 1 in. is now < 1 in.)

P-Nos. 7, 8, and 21-52 are now replaced with All other

materials

The greatnews is the preheat table is IDENTICAL to B31.1-2014!


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P-Number 1 Steels:

ASME B31.1-2012

175F for > 1 in. and > 0.30% C

ASME B31.3-2012

175F for 1 in. (no carbon limit)

Replaced with:

ASME B31.1-2014 and B31.3-2014

200F for > 1 in. and > 0.30% C



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P-Numbers 5A and 5B Steels:

ASME B31.1-2012

400F for SMTS > 60 ksi or > 1/2 in. and % Cr > 6.0

300 F for all others

ASME B31.3-2012

350 F minimum preheat for all thicknesses

Replaced with:

ASME B31.1-2014 and B31.3-2014

400F for SMTS > 60 ksi (5A & 5B)

400F for > 1/2 in. and % Cr > 6.0 (5B only)

300 F for all other 5A and 5B



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Post Weld Heat Treatment Requirements

Must qualify WPS to Section IX, including PWHT

Welds with ferritic filler metal with > 3% Cr shall receive a

PWHT

The upper limit of PWHT temperature range is a

recommended valuemay be exceeded provided the actual

temperature does not exceed the lower critical temperature ofeither material

When 2 different P-Nos. are welded, PWHT shall be for the

material requiring the higher PWHT

Use of material transition joints may be required (new in2014)

PWHT is notrequired for nonferrous materials


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PWHT Requirements (cont.)

Control thickness is lesser of:

Thickness of weld

Thickness of material being joined at the weld

Thickness of weld is:

Groove weldsthicker of the two ends after weld

preparation, including I.D. machining Fillet weldsthroat

Partial penetration weldsdepth of weld groove

Repair weldsdepth of cavity to be repaired

Branch weldsvarious options Heating and Cooling Requirements

> 600F heating and cooling at no greater than 600F/hr


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Furnace Cooling

Should be used when practical

May be PWHT in more than one heat provided at least 1

ft. overlap

Furnace shall be calibrated so PWHT can be controlled

within the required temperature range (new in 2014) Local Heating

Width of band shall be at least 3X wall thickness

Nozzle and attachment welds, width shall extend on each

side at least two times the run pipe thickness andcompletely around the run pipe

Guidance for placement of thermocouples per AWS

D10.10

Keep above lower critical temperature

Care with P15E


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B31.1-2014Consolidated and Revised from 2012 Edition


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B31.1-2014Table 132 Notes:


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B31.1-2014Modifications to lower limit:


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B31.1-2014


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B31.1-2014


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B31.1-2014


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Post Weld Heat Treatment Requirements

PWHT shall be as required by the WPS

When dissimilar ferritic materials are welded, PWHT shall

be for the material requiring the higher PWHT

Use of material transition joints may be required (new in

2014)

For ferritic to austenitic weldments, PWHT shall be for theferritic materials


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Control thickness is lesser of:

Thickness of weld

Thickness of material being joined at the weld

Thickness of weld is:

Groove weldsthicker of the two ends after weld

preparation, including I.D. machining Fillet weldsthroat

Partial penetration weldsdepth of weld groove

Repair weldsdepth of cavity to be repaired

Branch weldsvarious options Heating and Cooling Requirements (new in 2014)

> 600F heating and cooling at no greater than 600F/hr


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Furnace Heating

May be PWHT in more than one heat provided at least 1

ft. overlap

Furnace shall be calibrated so PWHT can be controlled

within the required temperature range (new in 2014)

Local Heating (all new in 2014) Width of band shall be at least 3X wall thickness

Nozzle and attachment welds, width shall extend on each

side at least two times the run pipe thickness and

completely around the run pipe Guidance for placement of thermocouples per AWS

D10.10

Keep above lower critical temperature

Care with P15E


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B31.3-2014 Approved, but not yet published

Similar to preheat tables, the bad news is the PWHT table

has been drastically revised from the 2012 Edition The greatnews is the preheat table is IDENTICAL to B31.1-

2014!


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ASME B31P Draft

Proposed Sections:

Introduction

Glossary

Temperature Measurement

May expand on AWS D10.10 requirements

Temperature Control

Preheating methods

PWHT methods Furnace

Local


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ASME B31P Draft

Proposed Sections (cont.):

Welding Preheat

Table 5.1 (instead of text)

PWHT

Table 6PWHT

Table 6.1Alternate PWHT Requirements for Carbonand Low Alloy Steels, P-Nos. 1 and 3

Table 6.2Exemptions to Mandatory PWHT

Alternatives to Preheat and PWHT Requirements andExemptions


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proposed new asmeb31p standard on preheat & pwht.pdf

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