1
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
BHEL – POWER SECTOR 5
BHEL – POWER SECTOR 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 RESPECTIVE MANUFACTURING UNITS SPECIFIC TO
THE PROJECT.
BHEL – POWER SECTOR 7
STATUS OF AMENDMENTS
Sl.No. Description Remarks
BHEL – POWER SECTOR 8
TABLE OF CONTENTS
Chapter Description Page No.
1 Heat Treatment Procedure - Boiler and Auxiliaries 8 - 23
2 Heat Treatment Procedure - Steam Turbine, Turbo- Generator and Auxiliaries
24 - 25
3 General 26
1. Testing of Temperature Indicating Crayons 27
2. Compatibility Test for Heat Treatment System 28 - 29
4 Pre heat & PWHT of Critical Piping with Turbine & Auxiliaries 30
BHEL – POWER SECTOR 9
CHAPTER-1
HEAT TREATMENT PROCEDURE - BOILER AND AUXILIARIES
HEAT TREATMENT MANUAL FOR POWER SECTOR CHAPTER -1
BHEL – POWER SECTOR 10
1.0 PURPOSE:
1.1 This procedure provides information, method and control for Pre-Heat, Post Heat 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
- Contractual obligations, if any.
2.2.1 Where parameter for Pre-Heat ,Post Heat 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 :
3.1.1 When parts of two different thicknesses are welded together, the preheating requirements
of the thicker shall rule
HEAT TREATMENT MANUAL FOR POWER SECTOR CHAPTER -1
BHEL – POWER SECTOR 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 It is recommended to use thermocouples with temperature recorder for recording
pre heating . Where temperature recorder is not possible to use, Preheating shall be
checked using thermal chalk (temperature indicating crayons) prior to start of
welding as well as at frequent intervals during welding
3.1.4 In case of any power interruption during welding, the joint shall be wrapped with dry
thermal insulating blankets to ensure slow and uniform cooling. Requirement of
uninterrupted power supply shall be ensured for materials like P-91, T-91 &
BS EN 10025
3.1.5 Preheating & Post Heating Methods:
3.1.5.1 Preheating & Post Heating 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 ) on each side from the centre of the weld. 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.
HEAT TREATMENT MANUAL FOR POWER SECTOR CHAPTER -1
BHEL – POWER SECTOR 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 Pre-Heat / PWHT.
3.4 Temperature Measurement for PWHT:
3.4.1 Post weld heat treatment temperature cycle 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 joint.
3.5.1.3 Thermocouples located 180° apart.
3.5.1.4 Thermocouples located at top and bottom of weld joint.
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.
HEAT TREATMENT MANUAL FOR POWER SECTOR CHAPTER -1
BHEL – POWER SECTOR 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.
HEAT TREATMENT MANUAL FOR POWER SECTOR CHAPTER -1
BHEL – POWER SECTOR 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 actual parameters shall 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
HEAT TREATMENT MANUAL FOR POWER SECTOR CHAPTER -1
BHEL – POWER SECTOR 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 Structural.
Table-VI Preheat for Flame Cutting.
7.1 Pertinent Records like Job card, PWHT Charts, shall be maintained.
7.0 RECORDS :
HEAT TREATMENT MANUAL FOR POWER SECTOR CHAPTER -1
BHEL – POWER SECTOR 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
HEAT TREATMENT MANUAL FOR POWER SECTOR CHAPTER -1
BHEL – POWER SECTOR 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
P1 Gr 2 9 Nil Nil
> 9 Nil 620 - 650
P3 Gr 1 13 Nil Nil
> 13 80 (Note 2) 620 - 650
P4 Gr 1 13 150 Nil (Note 3)
> 13 150 640 - 670
P5 A Gr 1 8 150 Nil (Note 3)
> 8 150 680 -710
P15 E Gr 1
(Note 4) All 220 750 – 770
P8 All Nil Nil
12 x 1M All 220 730 - 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 . Note 4 : 9 Cr 1 Mo ¼ V Steel ( P-91, T-91 )
HEAT TREATMENT MANUAL FOR POWER SECTOR CHAPTER -1
BHEL – POWER SECTOR 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
P1Gr 1
t 19 Nil Nil Nil
19 < t 5 Nil Nil 595 - 625
25 < t 75 100 Nil 595 - 625
t > 75 150 Nil 595 - 625
P1Gr 2
t 9 Nil Nil 620 – 650
19 < t 5 Nil 150
for 2 hours 620 - 650
25 < t 75 100 150
for 2 hours
620 - 650
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 220 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.
HEAT TREATMENT MANUAL FOR POWER SECTOR CHAPTER -1
BHEL – POWER SECTOR 19
TABLE - III WELD PREHEAT AND PWHT FOR PIPES
OUTSIDE DIAMETER >102 mm
P No. of
Material
Thickness
(mm)
BUTT WELDS Stub and Attachment welds
Note 1 & 2
Post
heat
C
(Note
3)
Preheat
C
PWHT
C
Throat 19 mm Throat > 19 mm
Preheat
C
PWHT
C
Preheat
C
PWHT
C
P1 Gr 1 & SA106 Gr C
19 Nil Nil Nil Nil Nil 595 - 625
Nil
>1925 Nil 595 - 625
Nil Nil Nil 595 - 625
Nil
>2575 150 595 - 625
150 Nil 150 595 - 625
Nil
>75 150 595 - 625
150 595-625
150 595 - 625
Nil
P1 Gr 2 & SA 106 Gr C
9 Nil Nil Nil Nil Nil 620 - 650
Nil
>919 Nil 620 - 650
Nil 620-650
Nil 620 - 650
Nil
>19 150 620-650
150 620-650
150 620 - 650
150 for 2 hrs
P4 Gr 1 All 150
640-670
150 640-670
150 640-670
Nil
P5 A
Pipes
Castings &
Forgings
150 680 - 710
150 680-710
150 680-710
250 for 2 hrs
P15 E Gr1
All 220 750-
770 220
750-
770 220
750-
770
280
for 2
hrs
P15 E Gr1 +
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.
HEAT TREATMENT MANUAL FOR POWER SECTOR CHAPTER -1
BHEL – POWER SECTOR 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 710°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.
HEAT TREATMENT MANUAL FOR POWER SECTOR CHAPTER -1
BHEL – POWER SECTOR 21
TABLE - IV P NUMBER AND GROUP NUMBER FOR BASE MATERIALS
P.No Group No.
Common Name Tubes Pipes Plates Forgings Castings Fittings
P1 1
Carbon Steels
SA192 SA106GRB SA36 SA266CL
1
SA216WC
A
SA234
WPB SA210GRA1 SA515GR55 SA352LC
A
SA515GR60 SA352LC
B
SA515GR65
SA516GR55
SA516GR60
SA516GR65
P1 2
Carbon Steels
SA210GRC SA106GRC SA515GR70 SA266CL
2
SA216WC
B
SA105
SA516GR70 SA216WC
C
SA234
WPC SA299 SA352LC
C
P3 1 Carbon-Moly Steels
SA209T1 SA335P1 SA217WC
1
P3 1 ½Cr½Mo Steels
SA213T2 SA335P2 SA387GR2
P4 1
1Cr½Mo/ 1¼Cr½Mo Steels
SA213T12/ SA335P12 SA387GR12 SA182F1
2
SA217WC
6
SA234
WP12 SA213T11 SA335P11 SA387GR11 SA182F1
1
SA234
WP11 P5A 1 2¼Cr1Mo Steels
SA213T22 SA335P22 SA387GR22 SA182F2
2
SA217WC
9
SA234
WP22 P15
E
Gr 1
2
9Cr1MoV Steels SA213T91 SA335P91 SA387GR91 SA182F91 SA234
WP91
P8 1
18Cr-8Ni Steels SA213TP304 SA376TP304 SA240TP304 SA182F3
04
SA351CF
3
SA403
SA213TP304
H
SA376TP304H SA240TP321 SA182F3
21
SA351CF
8
SA213TP347 SA376TP321 SA240TP347 SA182F3
47
SA351CF
3M
SA213TP347
H
SA376TP347 SA336F3
04
SA351CF
8M
SA213TP321 SA376TP347H SA336F3
21
SA351CF
10
SA336F3
47
SA351CF
10M
P8 2 25Cr-20Ni Steel (Type 310)
SA240TP310 SA182F310 SA351CK
20
Note : IS1239 & API 5L GR B Pipes, IS2062 Plates may be treated as P No.1 Gr No.1 material.
HEAT TREATMENT MANUAL FOR POWER SECTOR CHAPTER -1
BHEL – POWER SECTOR 22
TABLE - V PREHEAT AND PWHT FOR NON PRESSURE PARTS INCLUDING STRUCTURALS
P.No. of Material / Material
Specification
Gas Cutting Welding
Thickness (mm)
Preheat °C
Thickness (mm)
Preheat °C
PWHT °C
P1 / IS 2062
25
> 25
Nil
100
38
> 38 63
> 63
Nil
100
150
595-625
a) All butt welds > 50 mm thick
b) Any welds to a tension member
IS 8500 – Fe 540
( Ceiling Girder )
– – 150 620- 650 ( Soaking time 2.5 Mts. Per mm. Minimum 120 Mins)
BS EN 10025 Gr
420 N ( Ceiling Girder )
- - 220
620 – 650 ( Soaking time 2.5 Mts. Per mm.
Minimum 120 Mins. )
P4 Gr 1 All 150 All 150
640-670
a) All butt welds in tension member
b) All fabricated com-ponents > 16mm thick (Note 3)
(Note 3) P5 A All 150 All 150
680-710 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 A material shall be post heated at 250°C for 2 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.
HEAT TREATMENT MANUAL FOR POWER SECTOR CHAPTER -1
BHEL – POWER SECTOR 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 All 150
(Note 1)
P3 All 150
(Note 1)
P4 All 150
(Note 1)
P5 A All 150
(Note 2)
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 A materials, except when the part is scheduled for hot forming, shall
be inter stage heat treated at 680-710°C for 30 minutes minimum after
flame cutting and prior to any welding. Subsequent to this heat
treatment, a minimum 3 mm of the gas cut edge shall be removed by
machining / grinding.
HEAT TREATMENT MANUAL FOR POWER SECTOR CHAPTER -2
BHEL - POWER SECTOR 24
CHAPTER -2
HEAT TREATMENT PROCEDURE -
STEAM TURBINE, TURBO-GENERATOR AND AUXILIARIES
HEAT TREATMENT MANUAL FOR POWER SECTOR CHAPTER -2
BHEL – POWER SECTOR 25
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
HEAT TREATMENT MANUAL FOR POWER SECTOR CHAPTER -3
BHEL - POWER SECTOR 26
CHAPTER - 3
GENERAL
HEAT TREATMENT MANUAL FOR POWER SECTOR CHAPTER -3
BHEL - POWER SECTOR 27
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.
HEAT TREATMENT MANUAL FOR POWER SECTOR CHAPTER -3
BHEL - POWER SECTOR 28
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 is stabilized.
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 :
4.1 Records pertaining to the test shall be prepared and maintained.
HEAT TREATMENT MANUAL FOR POWER SECTOR CHAPTER -3
BHEL - POWER SECTOR 29
Compatibility Test for HT System
Site: Report No.
Date :
Details Temperature Recorder Thermometer
Make:
Model:
Sl. No.:
Range:
Test Results
Sl. No. t/c No. C/C. No. Temperature Reading °C
Difference °C Results* Recorder Thermometer
Record results (Accepted/Rejected) where rejected, record the faulty component as
required by 3.7.1
Witnessed by
(Name & Signature)
HEAT TREATMENT MANUAL FOR POWER SECTOR CHAPTER -3
BHEL - POWER SECTOR 30
Notes :- Rate of heating 50 Deg. C per hour above 300 °C
Rate of cooling 30 Deg. C per hour up to 300 °C
This is as per BHEL HEEP - Hardwar recommendation. ***********
Pre heat & PWHT of Critical Piping with Turbine & Auxiliaries
Sl no
Material Spec 1
Material Spec 2
OD Thickness
Type of Weld
Pre heat Deg. C
PWHT Temp. Deg. C
Holding time minimum (minutes)
1 GS 17 CrMoV 511
SA335 P91
≥110 >30 G 200 TO 300
690+10 (Notes)
240
2 G17 CrMo 9 10
SA335 P22
≥110 >30 G 200 TO 300
690+10 (Notes)
240
3 21 Cr Mo Ni V47
SA335 P22
≥110 >30 G 200 TO 300
690+10 (Notes)
240