2. 2
This Manual is compiled by
Mr K S Rao (QA),
Mr S P Ghiya (Inspection ) and
Mr N M Bodalia (M FS)
Under the guidance of
Mr P D Lohidakshan (Weld Engg & Prod Engg )
HEAT TREATMENT MANUAL
3. 3
INDEX
TOPIC PAGE NO.
1 . INTRODUCTION ON HEAT TREATMENT 4- 24
2 . FURNACE PARTS AND ATTACHMENTS 25- 37
3. STD. OPERATING PROCEDURES(HFS) 38- 47
4 . STD. OPERATING PROCEDURES(PFS) 48- 56
5 . STD. OPERATING PROCEDURES(MFS) 57-69
6 . STANDARD PRACTICES FOR LSR 70-74
7 . GOOD ENGINEERING PRACTICE 75-88
8 . CODE EXTRACT(REFERENCE ONLY) 89- 101
9 . ANNEXURES 102- 118
4. 4
General
• Only qualified supervisors and operators including
LSR operators shall be authorised to operate furnace.
• A list of qualified personnel shall be prepared by QA
and published periodically.
• Thjs manual is prepared on the basis of experience
and feedback, taken from various personnel.
• This manual is for reference only.
5. 5
HEAT TREATMENT
• WHAT IS HEAT TREATMENT ?
• WHY IS IT REQUIRED ?
• TYPES OF HEAT TREATMENT
• HEAT TREATMENT AT HZW
6. 6
WHAT IS HEAT TREATMENT
• MATERIALS TREATED BY
APPLICATION OF HEAT NORMALLY
DONE IN SOLID STATE
• VARIOUS SOURCES OF HEAT
• PARAMETERS ARE HEATING
RATE,SOAKING TEMP,SOAKING
TIME,COOLING RATE AND COOLING
MEDIA
7. 7
WHY IS IT REQUIRED ?
• TO ENHANCE MATERIAL PROPERTIES /
EASE IN FABRICATION BY CHANGING
– Strength,Improve corrosion resistance
– Toughness/Ductility
– Hardness,Dimensional stability etc
– Remove diffusible hydrogen to avoid
hydrogen cracking
• CARRIED OUT IN FABRICATION
INDUSTRIES ,STEEL PLANTS, FOUNDRY,
FORGING SHOPS etc..
14. 14
NORMALIZING
• The steel is heated to 40° C above the upper
critical temperature(910 ºc) followed by cooling
in the still air.
Normalizing is done to achieve the following :
• To get Uniform structure and reduce chemical
gradients
• To change Mechanical properties,
– UTS,YS
– Hardness
– Impact properties
• To refine the grains
15. 15
ANNEALING
• In this process, the steel is heated from 10 to
50°C above the upper critical
temperature(910ºc) and held for the desired
length of time; followed by very slow cooling
in the furnace
Annealing is done to achieve following :
• to soften the steel and improve ductility
• to relieve internal stresses caused by previous
treatment
16. 16
SOLUTION ANNEALING
In Stainless steels , it is heated to 1050°C or
above ,and held for the desired time; followed by
quenching/blowing the air(cooling to room
temperature within few minutes).
Solution annealing is done on stainless steel and
non ferrous alloys to achieve following:
• To soften the material
• To dissolve carbide precipitation formed at grain
boundaries during manufacturing process
• To improve Corrosion Resistance
17. 17
AGING
The Material is heated to a certain temperature,
and held for the desired time; followed by
normally for precipitation hardened alloys or
cooling in air
Aging is done on materials susceptible for
aging characteristics : Maraging Steels
• Normally increase in strength
• To Improve Toughness/Ductile-brittle transition
temp.
19. 19
STRESS RELIEVING
The steel is heated to a temperature below or
close to the lower critical point, followed by
desired rate of cooling and there is no change
in grain structure.
Stress relieving is done to achieve following :
• To reduce Internal Stresses (residual Stresses)
• To soften the steel partially
• To improve ductile-brrittle transition temp. and
equalize impact values
20. 20
STRESS RELIEVING
C-Mn , C-Mo , Cr-Mo (< 2% Cr)
• C - Mn Steels , C - Mo Steels,Cr-Mo Steels
– SA 515Gr 70 , SA204GrA, SA387GR11CL1
• Temperature : 593 C Min
– Normally 600 - 640 C,650-690 C
• Time : 15 minutes min
– Time : 1 hr / inch
• Heating Rate : 200 C per hr per inch
• Cooling Rate : 260 C per hr per inch
21. 21
Cr-Mo Steels
Cr - Mo Steels (Cr >2%)
– SA 335P22 ,SA335P5
• Temperature : 676 C Min
– Normally 680 - 700 C 2.25Cr
– 704 - 720 C 5 Cr
• Time : 15 mts min
– Time : 1 hr / inch
• Heating Rate : 200 C per hr per inch
• Cooling Rate : 260 C per hr per inch
STRESS RELIEVING
22. 22
Ni -Steels
• Nickel Steels : 1,2,3% Ni
– SA 203 GrA ,D
• Temperature : 593 C Min
– Normally 600 - 640 C,650-690 C
• Time : 60 mts min
– Time : 1 hr / inch
• Heating Rate : 200 C per hr per inch
• Cooling Rate : 260 C per hr per inch
STRESS RELIEVING
23. 23
Steels enhanced by Heat Treatments
• Q&T Steels :
– 9.5% Ni Steels , SA 517 Gr E
• Temperature : 538 C Typ
– Normally < 600 C
• Time : Minimum 15 minutes to 2 Hr
– Time : 1 hr / inch
• Heating Rate : 200 C per hr per inch
• Cooling Rate : 260 C per hr per inch
STRESS RELIEVING
27. 27
PRINCIPLE OF THERMOCOUPLE
The basic principle of thermoelectric
thermometry is that a thermocouple develops
an emf which is a function of the difference in
temperature of its measuring junction &
reference junction. If the temperature of
reference junction is known, the temperature
of the measuring junction can be determined
by measuring the emf generated in the circuit.
28. 28
THERMOCOUPLE MATERIAL
REQUIREMENT
1. High coefficient of thermal emf.
2. Continuously increasing relation of emf to temperature over
a long range.
3. Freedom from phase changes or other phenomenon giving
rise to discontinuity in temperature emf relationships.
4. Resistance to oxidation, corrosion and contamination.
5. Homogeneity and reproducibility to fit an establish
temperature & emf relationship.
SPEED OF RESPONSE MAY BE IMPROVED AND
RADIATION & CONDUCTION ERRORS MAY BE REDUCED
BY THE USE OF SMALL DIAMETER THERMOCOUPLES.
29. 29
TYPES OF THERMOCOUPLE
BEING USED IN HZW
K type :
Material : Chromel + Alumel
Nickel based ( 10 %Cr ) + ( 2 % Al )
Properties : Non-Magnetic + Magnetic
In this type of thermocouple, the wires are
joined at one end only to form a point-type
temperature sensor. Instrumentation converts
the millivolt signal to related temperature.
30. 30
TYPES OF THERMOCOUPLE
BEING USED IN HZW contd...
K type :
Dia : 2.5 mm 0. 7 mm
Insulation Bare(ceramic) Refractory
coated
Attachment Mech Capacitor
Usability Reusable Disposable
Location PIT F/c except PIT F/c
Color - Red & Yellow
32. 32
‘S’ TYPE THERMOCOUPLE
• ‘S’ TYPE THERMOCOUPLE ARE THE STANDARD
THERMOCOUPLES.
• IT IS USED FOR CALIBRATING “K” Type
THERMOCOUPLES.
• MATERIAL OF CONSTRUCTION
90% PLATINUM + 10% RHODIUM
PLATINUM
• OXIDATION RESISTANCE , SO MORE LIFE .
Accuracy : 0.25 %
33. 33
ISSUE METHODOLOGY
For DISPOSAL TYPE
• Users will send their requirement of thermocouple
through Consumable slip ( mentioning HTR No ) to
QA
• QA shall issue the same .
• QA shall issue identification sticker duly attached
• Users shall ensure availability of identification sticker
on unused wire .
• See Annexure-12 for further details
34. 34
COMPENSATING CABLE
COMPENSATING CABLE IS DEFINED AS A PAIR OF WIRES
HAVING SUCH EMF TEMPERATURE CHARACTERISTICS
RELATED TO THE THERMOCOUPLE WITH WHICH THE
WIRES ARE INTENDED TO BE USED, THAT WHEN
PROPERLY CONNECTED TO THERMOCOUPLE THE
EFFECTIVE REFERENCE JUNCTION IS IN EFFECT
TRANSFERRED TO THE OTHER END OF THE WIRES.
MATERIAL ==> +ve COPPER ( white )
-ve COPPER NICKEL (blue ) for “ K “ TYPE .
See Annexure-9 (Annexure Page 1-4) for further details
35. 35
P.I.D.
PID = PROPORTIONAL INTEGRAL DERIVATIVE
• PID FUNCTIONS BOTH AS PROGRAMMER AND
CONTROLLER
• PID CONTROLLER CAN BE ZONE WISE
• PROGRAMME IS MADE IN SEGMENTS AS PER
DIFFERENT STAGES OF HEAT TREATMENT
• DIGITAL DISPLAY IS AVAILABLE FOR PROGRAMME
TEMPERATURE AND FURNACE TEMEPERATURE
• TYPICAL OR REPETITIVE HEAT TREATMENT CYCLE
CAN BE STORED IN PID(PROGRAMMER)
36. 36
RECORDER
TYPES OF RECORDER
PAPERLESS -- WITH COLOUR DISPLAY SCREEN ,HARD DISC AND FLOPPY DRIVE.
NOT USED IN HZW.
•WITH PAPER -- CURRENTLY BEING USED IN HZW.
•24 CHANNEL -- CURRENTLY BEING USED IN PFS( CHINO MAKE-- model no.I003
/Graph ET 001).
•12 CHANNEL -- CURRENTLY BEING USED IN MFS1 AND HFS1
( CHINO MAKE -- model no. EH100 / Graph ET 201).
COMPENSATING CABLES ARE CONNECTED BEHIND THE RECORDER SCREEN IN
CHANNELS.
•X-AXIS IS FOR TEMPERATURE (RANGE = 0 TO 1200’C)
•THE SCALE ON X-AXIS IS NON-LINEAR.
•Y-AXIS IS FOR GRAPH SPEED.
•VARIOUS SPEED OF GRAPHS ARE 12.5, 25, 50, 100 MM / HOUR
•WE GENERALLY KEEP 25 MM / HOUR.
37. 37
GRAPH PAPER
• GRAPH PAPERS ARE USED FOR PLOTTING THE
FURNACE TEMPERATURE VIA THERMOCOUPLE.
THEY ARE FITTED ON THE RECORDER.
• GRAPH PAPER RECOMMENDED ON RECORDER ONLY
TO BE USED
• GRAPH PAPER FOR MFS1 AND HFS1 FURNACE
==> ET 201 CHINO MAKE, JAPAN
GRAPH PAPER FOR PFS FURNACE
==> ET 001 CHINO MAKE, JAPAN
• THE LENGTH OF ONE BUNDLE OF GRAPH PAPER IS
GENERALLY 2000 MM.
• DOTTING TYPE RECORDER INK (CHINO MAKE, JAPAN)
IS USED IN RECORDER FOR PLOTTING OF GRAPH.
USUALLY , 6 COLOURS ARE FILLED FOR PLOTTING.
• SEE ANNEXURE-10 FOR FURTHER DETAILS
41. 41
STANDARD OPERATING PROCEDURE FOR HFS-1
FURNACE
1. Receive the job as per HT request.
2. Receive heat treatment request duly approved by
metallurgy engineer.
3. Ensure that Insp. Clearance is available prior
to loading for job.
4. Load the supporting arrangement as per the attached
annexure -3
5. Ensure the spider arrangement as per attached
annexure - 5
6. Fix the thermocouples at locations shown in furnace
charge.
7. Check the entire job as per check list (annex.-I).
42. 42
STANDARD OPERATING PROCEDURE FOR HFS-1
FURNACE
9. Move the bogie inside the furnace
10. Pass the thermocouples through ports and
connect it with compensating cables
11. Set the program as per heat treatment request.
Secure it and then run it in fast mode as check.
Bring it back to the initial segment and hold.
12. Insert heat treatment chart in recorder and adjust
the speed of the graph.
13. Clear inspection of job and get the signature of
inspector on graph paper for firing the furnace.
14. Check LPG level, pressure and temperature in the
storage tanks and note down in logbook.
43. 43
STANDARD OPERATING PROCEDURE FOR HFS-1
FURNACE
15. Switch on the power supply
16. Close the bogie door
17. Follow the procedure for startup of furnace in zone-I
18. Start the blower from the field push button station
provided
19. Give power supply to the ignition panel
20 When the “system healthy” contact comes from the
instrument panel, the lamp for the “system healthy”
signal is on. This indicates that the combustion air
pressure and gas pressure are within the specified
limits
21. Now the firing on the cycle can start.
44. 44
STANDARD OPERATING PROCEDURE FOR HFS-1
FURNACE
22. Open the pilot and main gas valves
23. Press start cycle button on doing so the cycle starts
and purging start indicator lamp is on.
24. After 3 minutes ( time adjusted through timer ) the
purging is completed and ignition start lamp is ON
At the same time the purging start lamp gets OFF.
25. After 10 seconds the ignition start lamp gets OFF
By this time the pilot burner should have been fired
and the pilot flame is established.
26. Flame healthy signal LED gets on which is provided
on the flame sensor relay. This can be viewed through
the glass window provided in the ignition panel.
45. 45
STANDARD OPERATING PROCEDURE FOR HFS-1
FURNACE
27. Due to certain length of pipe between the burner and
solenoid valves, which may contain air, the burner
may not light up in the first attempt. In that case,
repeat the above mentioned procedure.
28. Once the main flame is established, the control is
passed on to the temperature controller.
29. For startup of furnace in other zones, follow the same
steps no 16 to 27 mentioned above.
30. After all zones are started, start recording time and
temperature from recorder every 30 minutes in the
logbook.
31. Conduct spot checks for heat treatment every 4hours
and fill the spot check format.
46. 46
STANDARD OPERATING PROCEDURE FOR HFS-1
FURNACE
32. Monitor the heat treatment process and graph till
the completion to ensure that it is as per program
and heat treatment request.
33. After heat treatment cycle is completed, shut off
all LPG supply valves and let furnace run with
blowers on for 15 minutes.
34. Open the bogie door. Disconnect thermocouples
from compensating cable.
35. Submit the graph and duly filled spot check formats
to inspection for approval of heat treatment.
47. 47
36. Retrieve the thermocouples from the ports and the
bogie out of the furnace.
37. Allow the job to reach room temperature.
38. Remove the thermocouples from the job carefully
without damaging the junction of thermocouples and
without making impression on parent material of job.
39. Unload the job from the bogie and move the bogie
inside the furnace.
40. Close the furnace. Shut off the main power supply.
STANDARD OPERATING PROCEDURE FOR HFS-1
FURNACE
51. 51
STANDARD OPERATING PROCEDURE FOR PFS
FURNACE
1. Receive the job as per HT request.
2. Receive heat treatment request duly approved by
metallurgy engineer.
3. Ensure that Insp. clearance is available prior to
loading for job.
4. Load the job on the bogie as per the heat treatment
furnace request.
5. Ensure the supporting arrangement as per the
attached annexure-I.
6. Ensure the spider arrangement as per annexure- II.
7. Fix the thermocouples at locations shown in furnace
charge.
52. 52
STANDARD OPERATING PROCEDURE FOR PFS
FURNACE
8. Check the entire job as per check list attached as
annexure-III
9. Move the bogie inside the furnace.
10. Pass the thermocouples through ports and
connect it with compensating cables.
11. Insert heat treatment chart in recorder and adjust
the speed of the graph.
12. Clear inspection of job and get the signature
of inspector on graph paper for firing the furnace.
13. Check LPG level, pressure and temperature in
the storage tanks and note down in logbook.
53. 53
STANDARD OPERATING PROCEDURE FOR PFS
FURNACE
14. Switch on the power supply.
15. Close the bogie door.
16. Switch on ID blower first and then the air blower
and maintain pressure at about 800mm WG by
slowly opening the suction valve.
17. Ensure that pressure of LPG from yard to inlet
of pressure regulator is always less than 20psi
(1.5kg/CM2).
18. Open the inlet valve to the regulator and open
the outlet valve.
19. If pressure exceeds 1600 mm WG , isolate the
pressure by lifting the handle of safety shut off
valve.
54. 54
STANDARD OPERATING PROCEDURE FOR PFS
FURNACE
20. Immediately start lighting the pilot burners and adjust
the flame with the air valve .
21. Open the isolating valve for pressure gauge and
adjust the pressure regulator by turning the screw
provided in the stem so that the pressure is
maintained at about 1000mm WG.
22. Light up alternate main burners and adjust the flame
lengths uniformly.
23. Lock the doors by pneumatic locking.
24. After all zones start, record time and temperature
from recorder every 30 minutes in the logbook.
55. 55
STANDARD OPERATING PROCEDURE FOR PFS
FURNACE
25. Conduct spot checks for heat treatment every
4 hours and fill the spot check format. Monitor the
heat treatment process and graph per heat
treatment request.
26. After the heat treatment cycle is completed, shut off
all LPG valves and let furnace run with blowers on
for 15 minutes.
27. Open the bogie door. Disconnect thermocouples
from compensating cables.
28. Submit the graph and duly filled spot check formats
to inspection for approval of heat treatment.
56. 56
29. Retrieve the thermocouples from the ports and move
the bogie out of the furnace.
30. Allow the job to reach room temperature.
31. Remove the thermocouples from job carefully and
without marking impression on parent material of
job.
32. Unload the job from bogie and move the bogie inside
the furnace.
33. Close the furnace. Shut off the power supply.
STANDARD OPERATING PROCEDURE FOR PFS
FURNACE
59. 59
STANDARD OPERATING PROCEDURE
FOR PIT FURNACE
1. Receive heat treatment request duly authorized
by metallurgy engineer.
2. Receive the job for heat treatment with
inspection clearance.
3. Put the job either on support or on heat
treatment fixture inside the furnace.
4. Ensure that equal clearance is available on all
sides between job and baffle.
5. Ensure that the furnace is calibrated.
6. Connect thermocouples with compensating
cable to PID.
60. 60
7. Set the program in the programmer as per heat
treatment request.
8. Take a trial run of program to ensure the accuracy.
9. Calibrate all 5 PID’s prior to starting the furnace.
10. Insert the graph inside the recorder and take the
signature of inspector on the graph paper.
11. Close the furnace door.
12. Start the furnace by giving power supply ‘ON’
STANDARD OPERATING PROCEDURE
FOR PIT FURNACE
61. 61
13. Start recording the time and temperature in the
logbook every 30 minutes.
14. Ensure that the cycle is functioning as per program.
15. After the heat treatment is over, open the furnace
cover.
16. If the job calls for water quenching, lift the job and
dip it in quench tank.
17. It the job calls for air cooling in still air, lift the job
and put it outside on supports in open air.
STANDARD OPERATING PROCEDURE
FOR PIT FURNACE
62. 62
18. It the job doesn’t call for anything above, allow the
job to cool down in furnace.
19. Keep the job outside after removing from furnace.
20. Submit the heat treatment graph to inspection for
approval of heat treatment cycle.
21. Close the furnace cover after the furnace is cooled
down to room temperature.
STANDARD OPERATING PROCEDURE
FOR PIT FURNACE
63. 63
PROCEDURE FOR EMPTY FURNACE
CALIBRATION
Calibration of PIDS ( indicator & controller )
1. Connect the millivolt source to the temperature
indicator or controller by a compensating cable.
Care should be taken to clean the wires and
terminals thoroughly before connections are
made.
2. The millivolt output for various temperature
ranging from 00
C to 10000
C in steps of 500
C is fed
to the indicator / controller.
3. After the millivolt value / temperature reading
displayed is steady, the reading of
indicator/controller shall be noted.
64. 64
PROCEDURE FOR EMPTY FURNACE
CALIBRATION
Calibration of recorder
1. Connect the millivolt source to the recorder by a
compensating cable. Care should be taken to
clean the wires and terminals thoroughly before
the connections are made.
4. If the error in the indicated readings is more than
the specified accuracy ( +/- 10
C ), then correction
to be carried out for the indicator / controller and
points 1 to 4 shall be repeated till the specified
accuracy is obtained is obtained.
65. 65
PROCEDURE FOR EMPTY FURNACE
CALIBRATION
2. The millivolt output for various temperature
ranging from 400 C to 10000
C is fed to the
recorder and is allowed to plot on a graph.
3. The graph thus obtained is reviewed for time
and temperature values. These values should
meet the accuracy requirements.
4. If there is error in the values plotted on the
graph, then correction to be carried out for
the recorder and points 1 to 4 shall be
repeated till the specified accuracy is
obtained.
66. 66
PROCEDURE FOR EMPTY FURNACE
CALIBRATION
EQUIPMENT REQUIRED ACCURACY
1. 20 Nos. big K-type thermocouples +/- 0.25%
2. 10 Nos. small K-type thermocouples +/- 0.25%
3. Millivolt source (wahl unit )
( 1 micro volt at 1000 micro volts )
4. Heat treatment fixture.
5. Temperature indicators (PID) +/- 10
C
6. Recorder +/- on temperature scale.
+/- minutes on time scale.
67. 67
PIT FURNACE CALIBRATION PROCEDURE
1. Ensure that the PIDs are calibrated as mentioned above.
2. Ensure that the recorder is calibrated as mentioned
above.
3. Ensure that all the thermocouples used are calibrated.
4. Ensure that the thermocouples are attached to the heat
treatment fixture as shown in sketch-I.
5. Place the heat treatment fixture inside the furnace with
thermocouples in position.
6. Close the furnace lid. Start the furnace and the recorder.
68. 68
7. Set the temperature of controller to 400
0
C.
8. After reaching the set temperature, it is allowed to
stabilize for half an hour.
9. Measure and record the temperature indicated by
each of the 20 thermocouples. The temperature is to
be read through WAHL UNIT.
10. Three sets of readings are to be taken for each
thermocouples at an interval of 10 minutes.
11. Also record the readings indicated by each of the
thermocouples at an interval of 10 minutes.
PIT FURNACE CALIBRATION PROCEDURE
69. 69
PIT FURNACE CALIBRATION PROCEDURE
12. The temperature is then raised in steps of 50 C up to
10000
C. ( I. e. 4000
C, 4500
C, …….., 9500
C, 10000
C. ) The
measured temperature is stabilized for 30 minutes.
PID reading are also to be recorded along with this.
13. The allowed temperature variation with respect to the
set temperature is +/- 50
C up to 8000
C and +/- 100
C
above 8000
C.
14. This is allowed to plot on the graph and thus
obtained for time and temperature values.
15. Calibration of furnace is valid for 1 year.
71. 71
LOCAL STRESS RELIEVING
WHY
• Local SR to be done only when furnace SR not feasible
• When only certain components to be PWHT
HOW
• Can be done by Electrical / Gas / diesel / Induction etc..
• DETAILS ON ENSURING PWHT TEMP. IN WELDMENT AREA
• Soaking band(SB) = Widest weld width ‘x’+ ’t’ or 2 inches
whichever is less from edge of weld
• Heating band width (HB)
• Induction stress level
• Through thickness criteria
• SB + 4 rt where r = Inside radius, t = thickness
• Insulation band width (IB)
• Axial gradient
• HB + 4 rt
72. 72
LSR -BAND WIDTH
Weld width ‘X’ +
lesser of 1T or 2”
X
t
Soak band
Insulation band
Heating band
73. 73
LOCAL STRESS RELIEVING SET UP
1. Provide multitonne roller on one end of vessel during
LSR ofcircular seam when job is horizontal.
2. If both ends are open during LSR, provide insulation
from inside. If not possible , prevent airflow so that
temperature on inside surface do not drop down.
3. Spider/prop shall be provided in such a way that upper
portion of spider / prop is not welded with inside
surface to allow contraction/expansion of shell surface.
4. Spider/prop shall be between 200- 500mm from heating
zone.
5. Temporary attachments, provided for holding insulation,
shall be within soak band only.
6. Minimum two thermocouples shall be provided from
inside, when accessible.
74. 74
LOCAL STRESS RELIEVING
No Welding at top
Multitonne roller
200 to 500mm from heating band
LSR of C/S
SB+HB+IB
Spider or
prop
76. 76
SUPPORTING ARRANGEMENTS
1. Heat Treatment request shall be as per Annexure-7
and Annexure-8.
2. Minimum distance between floor of the furnace
and lower most part of the job shall be 300mm.
3. The distance between burner flame and saddle
support as well as furnace wall and job
shall be 600mm.
4. Minimum 90 degree saddle to be used, however
120 degree saddle is desirable.
77. 77
600mm
900
600mm
SUPPORTING ARRANGEMENTS
450mm
5. Saddle shall be arranged in such away that open
end of the vessel is maximum 450mm from saddle
support.
6. Saddle shall be located as close to spiders
(temporarily arranged to control deformation) as
possible.
burner
300mm(point no:2)
78. 78
SUPPORTING ARRANGEMENTS
7. Spiders shall be provided as per annexure-5
8 Saddle supports shall be selected as per annexure.-3
9. Spiders or vertical prop shall be provided at open
ends, center and below man way/nozzles above 24”
10. Avoid gap between saddle support and job surface
80. 80
13. Checklist shall be prepared and attached with HT
request before furnace is fired as per Ann-1
14. Spot check report shall be filled by supervisor as
per Annexure-2 during job is being heat treated.
15. Moonplate support and welding inside surface
prior to release for Heat treatment as per
Annexure-4
16. General idea about thermocouple locations and its
attachments is as per Annexure-6
SUPPORTING ARRANGEMENTS
81. 81
GENERAL
1. Blocking the flame of the burner is not desirable
2. Burner shall have blue flame and not yellow
3. Flame shall not directly impinge on job
4. All burners shall be fired at a time
5. Keep all job nozzles open during heat treatment
6. Above “24” nozzles / manways shall be located
towards bottom
82. 82
GENERAL
Temp. support
Furnace floor
Gasket machined surface
7. Deoxidization agent shall be applied on all
machined and gasket faces
8. Gasket / machined face of loose assemblies
shall not be touching any object.
83. 83
THERMOCOUPLES
1. All the thermocouples shall be
tagged with aluminum sheet
and identification hard punched
on it.
(For PIT furnace only)
2. Minimum two thermocouples to
be attached for any charge.
84. 84
3. Minimum 8 thermocouples to be used for a charge in
HFS- I furnace if the job occupies all 8 zones
4. Maximum distance between two thermocouples for a
sample job is as shown in annexure- 6
5. PTC shall have separate thermocouple
THERMOCOUPLES
85. 85
1. Use only TAU-90 capacitor Discharge Welding
machine for thermocouple connection
2. Use WPS:999-154 R0 for attachment of
thermocouple for cs/alloy steel material
3. Only trained person by welding engineering shall
attach thermocouple
4. A list of qualified person shall be by Welding
Eng.
THERMOCOUPLES
ATTACHMENTS
86. 86
5. Clean surface prior to attachment.
6. Two wire of thermocouple shall be attached one
after another.
7. Gap between two wire of a thermocouple shall be
max. 3.0mm
8. Only calibrated thermocouple shall be used.
Calibration shall be by QA.
9. After PWHT, thermocouple area shall be ground
and DP shall be carried out.
10. For further details see Annexure-11 & 13-(page 1&2)
THERMOCOUPLES
ATTACHMENTS
88. 88
SPECIAL NOTE
IF THE TEMPERATURE OF HEAT TREATMENT
EXCEEEDS 650-DEGREE CENTIGRADE, THE
MATERIAL AND SIZE OF SPIDERS AND SUPPORTS
TO BE DECIDED BY PLANNING AND APPROVED BY
DESIGN.
90. 90
REQUIREMENT OF HEAT TREATMENT
AS PER ASME-SEC VIII Div.-1
• SERVICE CONDITION (UW-2)
• MATERIAL (UG-85, UW-40,UCS-56,UAT-80,UHA-32,UNF-79)
• THICKNESS (UG-85, UW-40,UCS-56,UAT-80,UHA-32,UNF-79)
• LOW TEMERATURE
OPERATION (UCS-68)
• COLD WORKING (UG-79)
• CUSTOMER SPEC.
91. 91
CODE EXTRACT FOR HEAT TREATMENT
( 1 ) The soak band shall contain the weld, heat
affected zone and a portion of base metal adjacent to the
weld being heat treated. The minimum width of this
volume is the widest width of weld plus 1T or 2 inches,
whichever is less, on each side or end of the weld. The
term ‘T’ is the nominal thickness.
( 2 ) The operation of postweld heat treatment shall be
performed either by heating the vessel as a whole in an
enclosed furnace or heating the vessel in more than one
heat in a furnace, provided the overlap of the heated
sections of the vessel is at least 5 feet ( 1.5m). When this
procedure is used, the portion outside of the furnace
shall be shielded so that the temperature gradient is not
harmful. The cross section where the vessel projects
from the furnace shall not intersect a nozzle or other
structural discontinuity.
92. 92
CODE EXTRACT FOR HEAT TREATMENT
( 3 ) When the vessel is required to be postweld heat
treated, and it is not practicable to postweld heat treat the
completed vessel as a whole or in two or more heats; any
circumferential joints not provisionally heat treated may be
thereafter locally postweld heat treated by heating such
joints by any appropriate means that will assure the
required uniformity.
( 4 ) While carrying out local postweld heat treatment,
the soak band shall extend around the full circumference.
The portion outside the soak band shall be protected so
that the temperature gradient is not harmful.
( 5 ) Heating a circumferential band containing nozzles
or other welded attachments in such a manner that the
entire band shall be brought up uniformly to the required
temperature and held for the specified time.
93. 93
CODE EXTRACT FOR HEAT TREATMENT
( 6 ) Where more than one pressure vessel or more
pressure vessel part are postweld heat treated in one
furnace charge, thermocouples shall be placed on
vessels at the bottom, center, and top of the charge or in
other zones of possible temperature variation so that the
temperature indicated shall be true temperature for all
vessels or parts in those zones.
( 7 ) Postweld heat treatment, When required, shall be
done before the hydrostatic test and after any welded
repairs. A preliminary hydrostatic test to reveal leaks
prior to PWHT is permissible.
( 8 ) For pressure vessels or parts of pressure vessels
being post weld heat treated in a furnace charge, it is the
greatest weld thickness in any vessel or vessel part
which has not previously been postweld heat treated.
94. 94
CODE EXTRACT FOR HEAT TREATMENT
( 8 contd...) The nominal thickness is the total depth of
the weld exclusive of any permitted weld
reinforcement.
For groove weld, the nominal thickness is the
depth of the groove.
For fillet welds, the nominal thickness is the
throat dimension.
If a fillet weld is used in conjunction of groove
weld, the nominal thickness is the depth of the
groove or the throat dimension, Whichever is
greater.
For stud welds, the nominal thickness shall be the
diameter of the stud.
( 9 ) For P–1 material ( carbon steel), minimum holding
temperature during postweld heat treatment shall
be 1100 Deg. F ( 593 Deg.c).
95. 95
CODE EXTRACT FOR HEAT TREATMENT
P. NO. HOLDING TEMP. NOM.
THICKNE
SS
SOAKING PERIOD
1 ( CARBON
STEEL) & 3
(LOW ALLOY
STEEL)
1100 DEG. F(593’
C)
UPTO 2” 1 HR. PER INCH. ,
HOWEVER 15 MINUTES
MINIMUM
OVER 2”
TO 5”
2 HOURS , PLUS 15 MIN.
FOR EACH ADDITIONAL
INCH ABOVE 2”
OVER 5 ” 2 HOURS , PLUS 15 MIN.
FOR EACH ADDITIONAL
INCH ABOVE 2”
* POST WELD HEAT TREATMENT IS MANDATORY ON P-NO.3 GR. NO. 3
MATERIAL IN ALL THICKNESSES.
96. 96
( 10 ) Postweld heat treatment is mandatory in
Following conditions :
• For welded joints over 1. 5” nominal thickness.
• For welded joints over 1.25” nom. Thickness
through 1.5” nom. Thickness, unless preheat is
applied at a min. Temperature of 200’F ( 94‘c )
during welding.
• Vessels or parts of vessels constructed of base
material with corrosion resistant integral or weld
metal overlay cladding or applied corrosion
resistant lining material shall be postweld heat
treated when the base material is required to be
postweld heat treated. In applying this rule, the
determining thickness shall be the total thickness
of base material.
• When the PWHT is a service requirement.
CODE EXTRACT FOR HEAT TREATMENT
98. 98
CODE EXTRACT FOR HEAT TREATMENT
( 11 ) Postweld heat treatment is not mandatory for carbon
steel jobs (P1 material ) in Following conditions (UG2):
If groove welds is not over ½” in size or fillet weld
with a throat thickness of ½” or less used for attaching
non pressure parts to pressure parts provided preheat
to a minimum temperature of 200’F is applied when the
thickness of pressure Part exceeds 1.25”.
If studs are welded to pressure parts provided
preheat to a minimum temperature of 200’F is applied
when the thickness of the pressure parts exceeds
1.25”.
for corrosion resistant weld metal overlay
cladding or for welds attaching corrosion resistant
applied lining provided preheat to a minimum
temperature of 200’f is maintained during application
of the first layer when the thickness of the pressure
part exceeds 1.25”.
99. 99
CODE EXTRACT FOR HEAT TREATMENT
• The temperature of furnace shall not exceed 800’F
( 4270
C) at the time when the vessel or part is placed in it.
• Above 8000
F( 4270
C), the rate of heating shall not be more
than 4000
F Per hour (2000
C/Hour) divided by the maximum
metal thickness of the shell or head plate in inches, but in no
case more than 4000
F Per hour( 2220
C Per hour ).
• During the heating period, There shall not be a greater
variation in temperature throughout the portion of the vessel
being heat treated than 2500
F( 1390
C) within any 15 feet (
4.6m) interval of length.
100. 100
CODE EXTRACT FOR HEAT TREATMENT
• During the holding period, there shall not be a
greater difference than 1500
f ( 830
c) between the highest and
the lowest temperature the portion of the vessel being heated
• During the heating & holding periods, the furnace
atmosphere shall be so controlled as to avoid excessive
oxidation of the surface of the vessel. The furnace shall be of
such design as to prevent direct heat impingement of the
flame on the vessel.
• Above 800
0
F ( 427
0
C), The rate of cooling shall not be
more than 5000
F Per hour (2780
C/Hour) divided by the
maximum metal thickness of the shell or head plate in inches,
but in no case more than 500
0
F Per hour ( 278
0
C Per hour).
101. 101
when it is impractical to postweld heat treat at the
temperature specified in table mentioned in Sr.. No. 9, It is
permissible to carry out the post weld heat treatments at
lower temperatures for longer periods of time as shown in
table below :
CODE EXTRACT FOR HEAT TREATMENT
DECREASE IN TEMP. BELOW
MIN. SPECIFIED
TEMPERATURE IN ‘F
MINIMUM HOLDING
TIME AT DECREASED
TEMPERATURE (NOTE 1)
NOTES
50 (10’C) 2 HOURS ----
100(38’C) 4 HOURS ----
150(68’C) 10 HOURS 2
200(94’C) 20 HOURS 2
NOTES :
1. MINIMUM HOLDING TIME FOR 1” THICKNESS OR LESS ; ADD 15 MINUTES PER INCH OF
THICKNESS FOR THICKNESS GREATER THAN 1”.
2. THESE LOWER POSTWELD HEAT TREATMENT TEMPERATURES PERMITTED ONLY FOR P-
NO.1 GROUP NO. 1 AND 2 MATERIALS.
