The document provides guidelines for pre-heat (PH) and post-weld heat treatment (PWHT) of welds during construction activities at sites for boilers and auxiliaries. It specifies requirements for pre-heating temperature based on material thickness and type, methods for pre-heating and PWHT, temperature measurement and control during PWHT using thermocouples. The width of heat treatment band, number and location of thermocouples depends on the component being welded and treated. Proper procedure is to be followed in case of interruptions during any stage of heat treatment.

1. 1
BHARAT HEAVY ELECTRICALS LIMITED
POWER SECTOR - CORPORATE QUALITY

2. 2
INDEX
Sl.No. Description Page No.
01 Cover Sheet 01
02 Index 02
03 Preface 03
04 Foreword 04
05 Approval Sheet 05
06 Important Note 06
07 Status of Amendments 07
08 Table of Contents 08

3. 3
PREFACE
Construction activities at field are dominated by welding processes for assembly
and building critical products like boiler, boiler auxiliaries, electrostatic precipitator
and piping. Various welding processes are adopted at the field based on the
product requirements and reliability of the welds.
This document has been prepared to provide basic guidelines to all construction
personnel in ensuring effective process management of welding and allied
activities. The various aspects of process control covering the stages of planning &
preparation for welding, controls during welding and post welding requirements are
brought out in the form of specifications, norms and procedures/instructions in this
document. This manual has been updated to reflect the newer materials and
processes developed by BHEL.
The requirements specified in this document are based on the relevant codes/
specifications like IBR, ASME and AWS and also consolidates the experience of
BHEL good welding practices based on more than three decades of manufacturing
and erection. The document also provides DO s and DON’T s for the benefit of
users, which would help in better process control and prevention of defects.
I am sure that this Manual would enable the construction activities in a big way to
manage their welding processes effectively to produce defect free quality.
A.V. Krishnan
General Manager (Corporate Quality)

4. 4
Page 4
F O R E W O R D
The present revision of the Heat Treatment Manual has been made with the contribution
from a team of BHEL Engineers having long experience in the areas like Construction Management,
Quality, Welding Technology & Heat treatment of manufacturing units and Power sector.
In this revision, the comments / suggestions offered by Power Sector / Regions, BHEL
HPBP Trichy, Piping Centre, HPEP Hyderabad & HEEP Haridwar and the minimum requirements of
reference codes have been taken care.
This manual deals with, apart from Heat Treatment requirements for BHEL-Trichy complex,
HEEP Haridwar & HPEP Hyderabad packages also. Heat treatment requirements for the new
material P91/T91 are dealt in detail for the benefit of site engineers.
We hope that the present volume will be very much handy and useful for all our site
engineers.
Any further feedback or suggestion is welcome to improve upon the the present
volume in due course.
Place : Chennai (D.Indran)
Date : 09.11.2006 Executive Director
Power Sector - Southern Region

5. 5
Page 5
HEAT TREATMENT M A N U A L
F O R
POWER SECTOR
BHARAT HEAVY ELECTRICALS LIMITED
POWER SECTOR / CORPORATE QUALITY
NAME DESIGNATION / DIVISION
V.KANDHSAMY AGM/ PSSR –QLY, Chennai
UM DESHPANDE AGM/ CQ, SECUNDRABAD
Dr. K.P.DHANDAPANI DGM / WTC-TIRUCHY
P.ELANGOVAN DGM / PC- Chennai
A.SUKUMARAN Manager/ SAS Cell - TIRUCHY
D.DEVASAHAYAM Manager/ PSSR-QLY, Chennai
PREPARED BY
R.JANARTHANAN Dy. Manager/ PC-Chennai
APPROVED BY
A.V.KRISHNAN
GENERAL MANAGER
/ CQ, NEW DELHI
DOCUMENT NO. PSQ-HTM-COM
R01 / 11 – 06
ISSUE DATE 13.11.2006
COPY NO.
ID No. : 1078
DATE OF ISSUE CONTROLLED COPY /
INFORMATION COPY
ISSUED BY
ISSUED TO :

6. 6
Page 6
I M P O R T A N T
THIS HEAT TREATMENT MANUAL PROVIDES BROAD BASED
GUIDELINES FOR HEAT TREATMENT WORK AT SITES. HOWEVER,
SITES MUST ENSURE ADHERENCE TO THE PRIMARY DOCUMENTS
LIKE CONTRACT DRAWINGS, ERECTION WELDING SCHEDULE, PLANT
/ CORPORATE STANDARDS, WHEREVER SUPPLIED, STATUTORY
DOCUMENTS, WELDING PROCEDURE SPECIFICATIONS,
CONTRACTUAL OBLIGATIONS, IF ANY AND SPECIAL INSTRUCTIONS
ISSUED BY MANUFACTURING UNITS SPECIFIC TO THE PROJECT.

7. 7
Page 7
STATUS OF AMENDMENTS

8. HEAT TREATMENT MANUAL FOR POWER SECTOR 8
CHAPTER - 1
Page 8
TABLE OF CONTENTS
Chapter Description Page No.
1 Heat Treatment Procedure - Boiler and Auxiliaries 8-22
2
Heat Treatment Procedure - Steam Turbine, Turbo-
Generator and Auxiliaries
23-24
3 General 25
1. Testing of Temperature Indicating Crayons 26
2. Compatibility Test for Heat Treatment System 27-28

9. HEAT TREATMENT MANUAL FOR POWER SECTOR 9
CHAPTER - 1
Page 9
CHAPTER-1
HEAT TREATMENT PROCEDURE - BOILER AND AUXILIARIES

10. HEAT TREATMENT MANUAL FOR POWER SECTOR 10
CHAPTER - 1
Page 10
1. HEAT TREATMENT PROCEDURE - BOILER AND AUXILIARIES
1.0 PURPOSE:
1.1 This procedure provides information, method and control for Pre-Heat (PH) and Post
Weld Heat Treatment (PWHT) of welds at sites.
2.0 DOCUMENT:
2.1 The following documents are referred in preparation of this procedure:
2.1.1 ASME Sec.I
2.1.2 ASME B31.1
2.1.3 Indian Boiler Regulations
2.1.4 AWS D1.1
2.1.5 Welding Manual
2.2 The following are to be referred as Primary Documents:
- Contract drawings
- Erection Welding Schedule or equivalent
- Plant / Corporate standards, where supplied
- Welding procedure specification, where supplied
- Contractual obligations, if any.
2.2.1 Where parameter for preheating and PWHT are not available in the primary documents,
reference may be made to this procedure.
2.2.2 Where such parameters are not contained either in the primary documents or in this
procedure, reference may be made to Manufacturing Units.
3.0 PROCEDURE:
3.1 Pre Heating (PH):
3.1.1 When parts of two different thicknesses are welded together, the preheating requirements

11. HEAT TREATMENT MANUAL FOR POWER SECTOR 11
CHAPTER - 1
Page 11
3.1.2 When parts of two different P numbers are joined together, the material requiring higher
preheat shall govern (please refer Welding Manual for P numbers).
3.1.3 Preheating shall be checked using thermal chalk (temperature indicating crayons) prior
to start of welding as well as at frequent intervals during welding. It is preferable to
have a thermocouple and a temperature recorder in case of alloy steels of
thickness > 50 mm.
3.1.4 In case of any interruption during welding, preheating temperature shall be maintained
at joint by wrapping dry thermal insulating blankets to ensure slow and uniform cooling.
3.1.5 Preheating Methods:
3.1.5.1 Preheating shall be applied by any of the methods given below:
a. Electrical resistance heating
b. Induction heating
c. Oxy-acetylene or other gas torches
3.2 Post Weld Heat Treatment (PWHT):
3.2.1 The method shall be by locally heating a circumferential band including the entire weld
and adjacent area of base metal, by induction or electrical resistance heating.
3.2.2 Heat band for PWHT.
3.2.2.1 For Boilers:
a. When heat treating welded joints in components in the boiler proper, width of the
heated circumferential band (W) on either side of the weld, W = 3 times the width
of the widest part of the weld groove but in no case less than twice the width of
weld at reinforcement.
b. When used in post weld heat treatment in sections - W = 3 times the plate
thickness.
c. For nozzle and other welded attachments - W must be wider than the nozzle or
attachment or 3 times the wall thickness.
3.2.2.2 For Piping:
W = 3 times the wall thickness of thickest part. In case of nozzles and attachment
welds, the width of the heat band shall extend beyond the nozzle or the attachment wall
on each side by at least twice the higher thickness and shall extend completely around
the header.

12. HEAT TREATMENT MANUAL FOR POWER SECTOR 12
CHAPTER - 1
Page 12
3.2.2.3 Other Pressure Vessels:
Heat bandwidth, placement of thermocouple, preheat and PWHT information shall be
obtained from the supplier.
3.3 Condition of Welded Joints:
3.3.1 The weldment shall be free of grease, oil etc. prior to PH/PWHT.
3.4 Temperature Measurement for PWHT:
3.4.1 Post weld heat treatment temperature shall be measured and monitored by use of
thermocouples with calibrated recorders.
3.4.2 The periodicity of calibration of the equipment shall be as per calibration procedure.
3.4.3 Where the soaking temperature is found to be lesser than specified, the PWHT cycle
shall be repeated.
3.4.4 In case of interruption during PWHT, the following actions are to be taken, depending
on the stage during which interruption occurred.
a.Interruption during heating cycle:
- The whole operation to be repeated from the beginning.
b.Interruption during soaking:
- The joint can be treated subsequently for the balance left over soaking
period.
c.Interruption during cooling:
-Ensure slow cooling by covering with insulation to a minimum width of 1.5 times
the outer diameter applied equally about the centre line of weld, till the
temperature reaches around 300°C.
3.5 Thermocouple (t/c) Fixing:
3.5.1 Thermocouples shall be used for recording Post Weld Heat Treatment temperatures.
3.5.1.1 Following are guidelines regarding number and placement of thermocouples:
3.5.1.2 Minimum of two thermocouples per weld.
3.5.1.3 Thermocouples located 180° apart.
3.5.1.4 Thermocouples located at top and bottom of weld.
3.5.1.5 Thermocouples located at a distance of approximately 1.5 times of the wall thickness
about the centre line of weld.
3.5.1.6 One point of the 6/12 points recorder shall be used for recording ambient temperature.

13. HEAT TREATMENT MANUAL FOR POWER SECTOR 13
CHAPTER - 1
Page 13
3.5.2 The following guidelines may be used for attaching thermocouples to job:
a. For capacitor discharge method: Thermocouple elements should be attached
within 6 mm of each other.
b. For other type of t/c: Insert the elements in a SS tube of internal diameter
approximately 6 mm. Apply force on tube and crimp it. Place this t/c and weld
the crimped button to the pipe in area of interest. Do not weld the elements.
c. Insulate the t/c leads suitably and protect t/c ends from direct radiation from
heating elements.
3.5.3 For Bunched Tubes:
3.5.3.1 Where a bunch of closely placed tube welds (e.g. Super Heater/Reheater Coils)
require to be Post Weld Heat Treated, the same shall be grouped together as if they
form a single component.
3.5.3.2 In such cases attachment of a minimum of three thermocouples, two at the end tubes
and one at the middle is recommended.
3.6 Soaking Time:
3.6.1 Wherever not specified the soaking time shall be as per Tables I, II and III.
3.6.2 The following guidelines shall be used to determine the thickness and subsequent
selection of the soaking time of PWHT:
a. For butt welds, the thickness shall be the thickness of the material at the weld.
For bar stock, the thickness shall be the diameter.
b. For fillet welds, the thickness shall be the throat thickness.
c. For partial penetration branch welds, the thickness shall be the depth of the
groove prior to welding.
d. For repairs, the thickness shall be the depth of the groove as prepared for repair
welding.
e. For combination of different welds in a component, the maximum thickness in
the definitions given above shall govern.
3.6.3 Soaking time is to be reckoned from the time temperature of the joint crosses the
recommended lower temperature of the cycle, to the time it comes down below the
same recommended lower temperature of the cycle.
3.7 Heating and Cooling Rates:
3.7.1 Wherever not specified, the heating rate above 300°C and cooling rate after soaking
upto 300°C shall be as follows: This is applicable for all materials.

14. HEAT TREATMENT MANUAL FOR POWER SECTOR 14
CHAPTER - 1
Page 14
Thickness of Material Maximum Heating Rate Above
300°C
Maximum Cooling
Rate Upto 300°C
≤ 25 mm
> 25 ≤ 50 mm
> 50 ≤ 75 mm
> 75mm
220°C/hour
110°C/hour
75°C/hour
55°C/hour
220°C/hour
110°C/hour
75°C/hour
55°C/hour *
* For structural - 65°C/ hour (Max.)
3.8 Temperature Records:
3.8.1 All the heat treatment cycles may be controlled within ±10°C around the
midpoint of the recommended range of temperature for the material.
4.0 POST WELD HEAT TREATMENT (PWHT) JOB CARD:
4.1 Prior to start of PWHT operations, a job card may be prepared including details of weld
reference, soaking time, soaking temperature, maximum rates of heating and cooling,
temperature recorder details, date of PWHT as per sample format.
4.2 On completion of PWHT the actuals may be recorded on the job card.
4.3 A chart number shall be given to each chart.
5.0 HEAT TREATMENT OF P-91 WELDS :
5.1 Please refer Welding Manual vide document No. PSQ-WDM-COM for heat treatment of
welds in P-91 materials.
5.2 HEAT TREATMENT OF T-91 WELDS:
5.3 Please refer Welding Manual vide document No. PSQ-WDM-COM for heat treatment of
welds in T-91 materials

15. HEAT TREATMENT MANUAL FOR POWER SECTOR 15
CHAPTER - 1
Page 15
5.4 HEAT TREATMENT OPERATOR REQUIREMENTS:
The operator for the Heat Treatment shall be a qualified Electrician and should be
conversant in the operation & maintenance of heat treatment machines & Process. He
should be trained properly by the concerned Welding / Electrical Engineer in order to
handle/ maintain the machines / process without any trouble / problem.
6.0 LIST OF TABLES:
Table-I Weld preheat and PWHT for tubes and pipes outside diameter ≤ 102 mm.
Table-II Weld preheat and PWHT for Boiler Header welds.
Table-III Weld preheat and PWHT for pipes outside diameter > 102 mm.
Table-IV P Number and Group Number for Base Materials.
Table-V Pre-heat and PWHT for Non-Pressure Parts including Structurals.
Table-VI Preheat for Flame Cutting.
7.1 Pertinent Records like Job card, PWHT Charts, shall be maintained.
7.0 RECORDS :

16. HEAT TREATMENT MANUAL FOR POWER SECTOR 16
CHAPTER - 1
Page 16
POST WELD HEAT TREATMENT (PWHT) JOB CARD
Project : ____________________
Card No. : ____________________ Date : ________________________
Unit No. : _____________________ Package : _____________________
Description :___________________ Temp. Recorder Details :
Weld Reference :_______________ 1. Make : _____________________
Material Spec. : ________________ 2. Type : _____________________
Size : Dia __________________ mm 3. Sl.No.: _____________________
Thick (t) ______________ mm 4. Chart speed: ________ mm / hour
NDE Cleared on :_______________ 5. Calibration Due on : __________
Report No. : _______________
Thermocouple Locations :
Minimum 2
d = 1.5 x t from weld centre
Heating Band = 6 x t
Insulation Band = 12 x t
Date of PWHT _________________ Chart No. : _____________________
Start Time : ___________________ End Time :_____________________
Required Actual
Rate of Heating (Max) °C/h
Soaking Temperature °C
Soaking Time (Minutes)
Rate of cooling (Max)° C
Ambient temperature recorded on the PWHT Chart: ____________
Contractor BHEL
Results : Accepted / Not Accepted Released for further processing

17. HEAT TREATMENT MANUAL FOR POWER SECTOR 17
CHAPTER - 1
Page 17
TABLE - I
WELD PRE HEAT AND PWHT FOR TUBES & PIPES
OUTSIDE DIAMETER ≤ 102 mm
(Applicable For Butt Welds And Socket Welds)
P. No. of
Material
Thickness
(mm)
Preheat °C PWHT °C
P1 Gr 1& SA 106
Gr C (Note 1)
≤ 19 Nil Nil
≤ 9 Nil Nil
P1 Gr 2
> 9 Nil 620 - 650
≤ 13 Nil Nil
P3 Gr 1
> 13 80 (Note 2) 620 - 650
≤ 13 125 Nil (Note 3)
P4 Gr 1
> 13 125 650 - 670
≤ 8 150 Nil (Note 3)
P5 A Gr 1
> 8 150 700 - 750
P5 B Gr 2 All 220 730 - 760
P8 All Nil Nil
12 x 1M∅ All 200 730 - 760
Note 1 : For SA 106 Gr .C with less than 0.25 % carbon content .
Note 2 : Pre-heating is necessary for t>16mm.
Note 3 : Less than 0.15 % carbon content .

18. HEAT TREATMENT MANUAL FOR POWER SECTOR 18
CHAPTER - 1
Page 18
TABLE - II
WELD PREHEAT AND PWHT FOR BOILER HEADER WELDS
(NOTE - 3)
(Applicable For Welding of Header to Header Joints)
P. No. of
Header Material
Thickness
(mm)
Preheat
°C
Post Heating
°C
PWHT
°C
t ≤ 19 Nil Nil Nil
19 < t ≤ 25 Nil Nil 595 - 625
25 < t ≤ 75 100 Nil 595 - 625
P1Gr 1
t > 75 150 Nil 595 - 625
t < 19 Nil Nil 620 – 650
19 < t ≤ 25 Nil
150
for 2 hours
620 - 650
19 < t ≤ 75 100
150
for 2 hours
620 - 650
P1Gr 2
t > 75 150 150
for 2 hours
620 - 650
P4 Gr 1 All 150 Nil 640 - 670
P5 A (Note 1) All 150 250 for 2 hours 680 - 710
12 x 1M ∅ All 200 Nil 710-740
Note :
1. All P5A headers shall be inter stage heat treated at 700 - 750°C for 30 minutes
soaking prior to any cold straightening operation. In lieu of this, the straightening
can be done after final PWHT. Any P5A Header with weld thickness above
50mm requires inter stage H.T. at 700-750°C for 30 minutes soaking minimum
(max. shall be limited to 2.5 minutes/mm of thickness).
2. Soaking for PWHT shall be at the rate of 1 hour per 25 mm of thickest weld (but
not less than 30 minutes for carbon steel and 1 hour for alloy steel). Soaking
time for 12 x 1 M∅ header material shall be 4 minutes per mm of the applicable
thickness with a minimum of 180 minutes.
3. Seal welding of Hand Hole Plates, Radiographic plugs and Screws can be
carried out after final PWHT, provided the preheat is carried out as per the
table.
4. For P number and Group number refer Table - IV.

19. HEAT TREATMENT MANUAL FOR POWER SECTOR 19
CHAPTER - 1
Page 19
TABLE - III
WELD PREHEAT AND PWHT FOR PIPES
OUTSIDE DIAMETER >102 mm
BUTT WELDS Stub and Attachment welds Note 1
& 2
Throat ≤≤≤≤ 19 mm Throat > 19 mm
P No. of
Material
Thickness
(mm) Preheat
°°°°C
PWHT
°°°°C Preheat
°°°°C
PWHT
°°°°C
Preheat
°°°°C
PWHT
°°°°C
Post
heat °°°°C
(Note 3)
≤ 19 Nil Nil Nil Nil Nil
595 -
625
Nil
>19≤25 Nil
595 -
625
Nil Nil Nil
595 -
625
Nil
>25≤75 150
595 -
625
150 Nil 150
595 -
625
Nil
P1 Gr 1
&
SA106
Gr C
>75 150
595 -
625
150
600-
650
150
595 -
625
Nil
≤9 Nil Nil Nil Nil Nil
620 -
650
Nil
>9≤19 Nil
620 -
650
Nil
600-
650
Nil
620 -
650
Nil
P1 Gr 2
&
SA 106
Gr C
>19 150
620-
650
150
600-
650
150
620 -
650
150 for
2 hrs
≤75 125
640-
670
125
650-
680
125
640-
670
Nil
P4 Gr 1
>75 150
640-
670
150
650-
680
150
640-
670
Nil
Pipes 150
680 -
750
150
700-
750
150
680-
750
250 for
2 hrs
P5 A
Castings &
Forgings
220 680-
750
150 700-
750
150 680-
750
250 for
2 hrs
P5B Gr2
+
P5B Gr2,
All 220
750-
770
220
750-
770
220
750-
770
280 for
2 hrs
P5B Gr2
+
P5 A
All 220
730-
760
220
730-
760
220
730-
760
280 for
2 hrs
Note :
1. Irrespective of the stub or attachment materials, the PWHT cycle shall be governed by the pipe
material.
2. Throat shall be specified in the drawing. Wherever flanges are welded to pipes combined throat
shall be taken into consideration.
3. Post heating shall be done immediately after welding.

20. HEAT TREATMENT MANUAL FOR POWER SECTOR 20
CHAPTER - 1
Page 20
4. For butt welds of different P group combinations, PWHT temp. may be as follows:
P1 + P3 - 620 to 650°C
P1 + P4 - 640 to 670°C
P4 + P5A - 680 to 720°C
(For other P Group combinations, refer to Engineering)
5. a. For P1 & P3 materials soaking time shall be 1 hour per 25mm up to 50mm
thickness and 2 hours + 15 minutes for each 25mm thickness over 50mm.
b. For P4 & P5 materials, soaking time shall be 1 hour per 25mm up to 125mm
thickness and 5 hours + 15 minutes for each 25mm thickness over 125mm.
6. For P number and Group number refer Table IV.

21. HEAT TREATMENT MANUAL FOR POWER SECTOR 21
CHAPTER - 1
Page 21
TABLE - IV
P NUMBER AND GROUP NUMBER FOR BASE MATERIALS
P.No Group
No.
Common
Name
Tubes Pipes Plates Forgings Castings Fittings
SA192 SA106GRB SA36 SA266CL1 SA216WCA SA234WPB
SA210GRA1 SA515GR55 SA352LCA
SA515GR60 SA352LCB
SA515GR65
SA516GR55
SA516GR60
P1 1
Carbon
Steels
SA516GR65
SA210GRC SA106GRC SA515GR70 SA266CL2 SA216WCB SA105
SA516GR70 SA216WCC SA234WPCP1 2
Carbon
Steels
SA299 SA352LCC
SA209T1 SA335P1 SA217WC1
P3 1
Carbon-Moly
Steels
P3 1
½Cr½Mo
Steels SA213T2 SA335P2 SA387GR2
SA213T12/ SA335P12 SA387GR12 SA182F12 SA217WC6 SA234WP12
P4 1
1Cr½Mo/
1¼Cr½Mo
Steels
SA213T11 SA335P11 SA387GR11 SA182F11 SA234WP11
P5A 1
2¼Cr1Mo
Steels SA213T22 SA335P22 SA387GR22 SA182F22 SA217WC9 SA234WP22
P5B 2
9Cr1MoV
Steels SA213T91 SA335P91 SA387GR91 SA182F91 SA234WP91
18Cr-8Ni
Steels SA213TP304 SA376TP304 SA240TP304 SA182F304 SA351CF3 SA403
SA213TP304H SA376TP304H SA240TP321 SA182F321 SA351CF8
SA213TP347 SA376TP321 SA240TP347 SA182F347 SA351CF3M
SA213TP347H SA376TP347 SA336F304 SA351CF8M
SA213TP321 SA376TP347H SA336F321 SA351CF10
P8 1
SA336F347 SA351CF10M
P8 2
25Cr-20Ni
Steel (Type 310) SA240TP310 SA182F310 SA351CK20
Note : IS1239 & API 5L GR B Pipes, IS2062 Plates may be treated as P No.1 Gr No.1 material.

22. HEAT TREATMENT MANUAL FOR POWER SECTOR 22
CHAPTER - 1
Page 22
TABLE - V
PREHEAT AND PWHT FOR NON PRESSURE PARTS INCLUDING STRUCTURALS
Gas Cutting WeldingP.No. of
Material /
Material
Specification
Thickness
(mm)
Preheat
°C
Thickness
(mm)
Preheat
°C
PWHT
°C
P1 / IS 2062
≤ 50
> 50
Nil
100
≤ 38
> 38 ≤ 63
> 63
Nil
100
120
600-650
a)All butt welds > 50
mm thick
b)Any welds to a
tension member
IS 8500 –
540
Ceiling
Girder
– – 10< τ < 200 150
600-650(Soaking time
2.5 Mts. Per mm.
Minimum 120 Mts )
P4
≤ 25
> 25
Nil
150
All 150
650-700
a)All butt welds in
tension member
b)All fabricated com-
ponents > 16mm
thick (Note 3)
P5 All 150 All 150
680-730
All welds
(Note 4)
NOTE :
1. All gas cut edges may be chipped off, ground or machined to remove the HAZ with
3mm minimum removal.
2. Clip angles above 10mm, used for beam connections, which are sheared to length,
shall require heat treatment.
3. All fabricated structural components of P-4 material, with any member above
16mm thickness, the entire assembly shall be post weld heat treated.
4. All welds of P5 material shall be post heated at 250°C for 2 hours or 150°C for
4 hours immediately following welding.
5. Soaking time shall be as below :
a. P1 and P3 materials one hour per 25mm up to 50mm thickness and
2 hours + 15 minutes for each 25mm thickness over 50mm.
b. P4 and P5 materials one hour per 25mm up to 125mm thickness and
5 hours + 15 minutes for each 25mm thickness over 125mm.

23. HEAT TREATMENT MANUAL FOR POWER SECTOR 23
CHAPTER - 1
Page 23
TABLE - VI
PREHEAT FOR FLAME CUTTING
P.No. of Material Thickness (mm) Preheat °C
P1 Gr 1 < 25 Nil
(Note 1) ≥ 25 100
P1 Gr 2
(Note 1)
All 150
P3
(Note 1)
> 100 150
P4
(Note 1)
All 150
P5
(Note 2)
All 150
NOTE :
1. For P1, P3 and P4 materials, when the flame cut edge will be machined
after cutting and when no forming operation is required after cutting, no
preheat is required for flame cutting.
2. P5 materials, except when the part is scheduled for hot forming, shall be
inter stage heat treated at 700-750°C for 30 minutes minimum after
flame cutting and prior to any welding. As an alternative to this heat
treatment, a minimum 3 mm of the gas cut edge may be removed by
machining, grinding, chipping, etc.

24. HEAT TREATMENT MANUAL FOR POWER SECTOR 23
CHAPTER -2
Page 23
2. HEAT TREATMENT PROCEDURE -
STEAM TURBINE, TURBO-GENERATOR AND AUXILIARIES
1 Procedure for Post Weld Heat
treatment of Pressure Vessel as
per ASME code Section VIII,
Div.I
Please refer Plant Standard, HEEP,
Haridwar - HW 0980814
2 For other Components Please refer Heat treatment Procedure-
Boiler and Auxiliaries of Chapter-I
CHAPTER -2
HEAT TREATMENT PROCEDURE -
STEAM TURBINE, TURBO-GENERATOR AND AUXILIARIES

25. HEAT TREATMENT MANUAL FOR POWER SECTOR 24
CHAPTER -2
Page 24
2. HEAT TREATMENT PROCEDURE -
STEAM TURBINE, TURBO-GENERATOR AND AUXILIARIES
1 Procedure for Post Weld Heat
treatment of Pressure Vessel as
per ASME code Section VIII,
Div.I
Please refer Plant Standard, HEEP,
Haridwar - HW 0980814
2 For other Components Please refer Heat treatment Procedure-
Boiler and Auxiliaries of Chapter-I

26. HEAT TREATMENT MANUAL FOR POWER SECTOR 25
CHAPTER -3
Page 25
CHAPTER - 3
GENERAL

27. HEAT TREATMENT MANUAL FOR POWER SECTOR 26
CHAPTER -3
Page 26
3. GENERAL
1. TESTING OF TEMPERATURE INDICATING CRAYONS
1.0 SCOPE :
1.1 This procedure details the method of batch testing of Temperature indicating Crayons
(Thermal chalks).
2.0 PROCEDURE :
2.1 Setup:
2.1.1 Rig a test heating arrangement including a test pipe/plate heating arrangements with
controls and a calibrated temperature recorder/thermometer.
2.2 Heat the test pipe / plate (specimen) to a temperature 10° lower than the rated
temperature of the thermal chalk in study, monitoring the temperature through
thermometer/recorder.
2.3 Stroke the thermal chalk as close to the sensing point on the specimen.
2.4 Raise the temperature of the specimen gradually up to 10% higher than the rated
temperature of the thermal chalk in study, stroking the thermal chalk on the specimen
during this period.
2.4.1 When the thermal chalk changes to the specified colour or melts (depending on the
type), within ±5° of the rated temperature, the thermal chalk is acceptable.
2.5 Consistent results for 2% of any brand and temperature will qualify the brand for the
rated temperature.
2.6 Where thermal chalks are accepted brand wise, they shall undergo this test at least
once a year.
3.0 RETESTS :
3.1 Any failure in the 2% sample chosen, will call for additional 4% for qualification of the
brand for the rated temperature.
3.2 Where retest results in further non-acceptance, the brand shall stand rejected for the
particular temperature.
4.0 RECORDS :
4.1 Records of testing and brands accepted/rejected including details of calibrated
devices used in the setup shall be maintained.

28. HEAT TREATMENT MANUAL FOR POWER SECTOR 27
CHAPTER -3
Page 27
2. COMPATIBILITY TEST FOR HEAT TREATMENT SYSTEM
1.0 SCOPE :
1.1 This procedure provides for checking the compatibility and accuracy of
thermocouples, compensating cables, temperature recorder, connected in Heat
Treatment (HT) operations at sites.
2.0 HT TEST SYSTEM :
2.1 The thermocouple (type k-chromal-Alumel is generally used at sites) attached to a test
specimen with heating arrangements and controls, compensating cables, a calibrated
temperature recorder rigged together for the test HT system.
2.2 A calibrated (accuracy ±0.5%) direct-reading thermometer (like a digital thermometer
with sensor) is used for verification.
2.0 PROCEDURE :
3.1 Attach the thermocouple as detailed in Chapter I of this manual.
3.2 Raise the temperature of the test specimen to around 200°C and maintain the same.
3.3 Place the sensor of the direct reading thermometer as close to the thermocouple
junction as possible.
3.4 Wait till the temperature stabilises.
3.5 Note reading of the thermometer and that of the temperature recorder.
3.6 Repeat steps 3.2 to 3.5 for test specimen temperatures of 400°C and 600°C
3.7 Where the temperature read by the temperature recorder is within ±10°C with respect
to the thermometer, the HT system is compatible.
3.7.1 Where the results are not within the tolerance specified above, further tests are to be
repeated to identify the fault either in thermocouple or compensating cable or both.
3.8 Adequate insulation of thermocouple, sensor from direct radiation of heat elements
shall be ensured as a precaution throughout the test.
3.9 This compatibility is recommended for each of the thermocouple available for use; this
procedure validates the thermocouple also.
4.0 RECORDS :
4.1Records pertaining to the test, shall be prepared and maintained.

29. HEAT TREATMENT MANUAL FOR POWER SECTOR 28
CHAPTER -3
Page 28
Compatibility Test for HT System
Site : Report No.
Date :
Details Temperature Recorder Thermometer
Make:
Model:
Sl. No.:
Range:
Test Results
Temperature Reading °C
Sl. No. t/c No. C/C. No.
Recorder Thermometer
Difference °C Results*
Record results (Accepted/Rejected) where rejected, record the faulty component as
required by 3.7.1
Witnessed by
(Name & Signature)