PWHT

HEAT TREATMENT OF

PRESSURE VESSELS

2

WHAT IS HEAT TREATMENT?

• MATERIALS TREATED BY APPLICATION

OF HEAT - NORMALLY DONE IN SOLID

STATE

• HEATING BY VARIOUS SOURCES

• PARAMETERS

– RATE OF HEATING

– SOAKING TEMP.

– SOAKING TIME

– COOLING RATE

– COOLING MEDIA

WHY HT REQUIRED ?

• TO ENHANCE PROPERTIES

–Strength

–Toughness

–Hardness

TO BRING THE PROPERIES SUITABLE FOR

FABRICATION

• CARRIED OUT IN

–FABRICATION INDUSTRIES

–STEEL PLANTS

– FOUNDRY

– FORGING SHOPS

4

MATERIALS HEAT TREATED

• METALS & ALLOYS

– SINGLE PHASE

– MULTIPHASE

• ALLOYS

– Single Phase : Copper Nickel

– Multiphase : Steels

• METALS (Single phase )

– Titanium

HEAT TREATEMENT

CRITERIA

• COLD WORKED to NORMAL

– All materials

• UNEQUILIBRIUM PHASES to

EQUILIBRIUM

– Stainless Steels ,Maraging Steels

• STRESSED to UNSTRESED

6

MATERIALS HEAT TREATED

• CS

• C-Mn , C-Mo , Cr-Mo , Cr-Mo-V, Ni -Steels

• Stainless Steels

7

TYPES OF HEAT TREATMENT

• NORMALIZING

• ANNEALING

• STRESS RELIEVING

• SOLUTION ANNEALING

• HARDENING

• TEMPERING

• AGEING

8

NORMALIZING

• The steel is heated to 40° C above the

upper

critical temperature

followed by cooling in the

still air.

To achieve

• Uniform structure

• Change in Mechanical properties,

– UTS & YS

– Hardness

– Impact properties

10

ANNEALING

• Steel is heated 10 to 50°C above the

upper

critical temperature

and held for the desired

length of time followed by very slow cooling

within the furnace

To achieve:

• Softness & better ductility

• Stresses free material – Stress generated due

to mechanical working / previous HT

11

SOLUTION ANNEALING

• Austenitic Stainless steels is heated to above

1050°C and held for the desired time followed by

cooling to room temperature within few minutes

by quenching / blowing the air.

Solution annealing is done on stainless steel and

non ferrous alloys to achieve following:

• To soften the material

• To remove carbide precipitation formed at grain

boundaries during manufacturing process

12

AGEING

The Material is heated to a certain temperature,

and held for the desired time; followed by

quenching or cooling in air

Ageing is done on materials susceptible for

ageing characteristics : Maraging Steels

• Normally increases strength

• Improve Toughness

AGEING

Maraging Steels

M250

• Temperature : 485° C

• Normally 3 Hrs 15 mts

• Heating Rate : 200 C per hr per inch thick

14

STRESS RELIEVING

The steel is heated to a temperature

below or close to

the lower critical temperature

with a specific

rate of

heating

. It is

held at the temperature

for a desired

length of time

, followed by cooling with a specific

rate up to certain temperature.

There is no change in grain structure.

Stress relieving is done Fabricated Components of

CS & LAS:

• To reduce Internal Stresses

• To soften the steel partially

• To soften HAZ

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 thick

• Heating Rate : 200° C per hr per inch thick

• Cooling Rate : 260° C per hr per inch thick

16

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 thick

• Heating Rate : 200° C per hr per inch thick

• Cooling Rate : 260° C per hr per inch thick

Ni -Steels

• Nickel Steels : 1,2,3% Ni

– SA 203 GrA ,D

• Temperature : 593° C Min

– Normally 600 - 640° C,

• Time : 60 mts min

– Time : 1 hr / inch thick

• Heating Rate : 200° C per hr per inch thick

• Cooling Rate : 260° C per hr per inch thick

18

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 thick

• Heating Rate : 200° C per hr per inch thick

• Cooling Rate : 260° C per hr per inch thick

LAYOUT OF A TYPICAL

FURNACE

(Electrical or Gas fired )

RECORDER _P.I.D. FURNACE JOB COMPENSATING CABLE THERMOCOUPLE

20

THERMOCOUPLES

• PRINCIPLE OF A THERMOCOUPLE

• THERMOCOUPLE MATERIAL

• TYPES OF THERMOCOUPLE BEING

USED IN HZW

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.

22

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

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.

24

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

recorder

pid

CONSTRUCTION OF A

K TYPE THERMOCOUPLE

26

‘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 .

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

28

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 )

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)

30

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 • GENERALLY KEEP 25 MM / HOUR.

31

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.

32

STANDARD OPERATING

PROCEDURE FOR HFS-1

1650 3575

14300.

3575 3575 3575 ( ZONE-1 ) ( ZONE-3 ) ( ZONE-5 ) ( ZONE-7 ) ( ZONE-2 ) ( ZONE-4 ) ( ZONE-6 ) ( ZONE-8 )

1640 1650 7900 (BOGIE WIDTH ) BURNER

34 7900 BOGGIE WIDTH 8700 1050 9500 9000 1195 1. PROJECT NO: 2. SECTION NO : 3. CHARGE NO : 4. H. T. REQ. NO : BURNER

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.

36

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.

37

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

38

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.

39

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.

40

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.

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

42

STANDARD OPERATING

PROCEDURE FOR PFS

44 BOGGIE WIDTH 4100 2650 5600 1050 1235 1460 5500 BURMER

PFS FURNACE SKETCH

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

46

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

47

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.

48

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.

49

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.

50

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

STANDARD OPERATING

PROCEDURE FOR PIT

52 BLOW ER 37 00 1/D OF BA F F L E 41 50 ( RE F RA CT O RY I/S ) 4961 1000 250 125 1380 4020 TROLLEY STRUCTURE CERAMIC BLANKET ROOF BAFFLE HEATING ELEMENT CERMIC FIBER SLABER BLOCK INSULATING CASTABLE FIRE BRICK OUTER SHELL CERMIC BLANKET GROUND LEVEL

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.

54

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

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

56

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

57

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 00C to 10000C in steps of 500C is fed to the indicator / controller.

3. After the millivolt value / temperature reading displayed is steady, the reading of

58

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 ( +/- 10C ), 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.

PROCEDURE FOR EMPTY FURNACE

CALIBRATION

2. The millivolt output for various temperature ranging from 400 C to 10000C 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.

60

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) +/- 10C

6. Recorder +/- on temperature scale. +/- minutes on time scale.

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.

62

7. Set the temperature of controller to 4000C.

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

12. The temperature is then raised in steps of 50 C up to 10000C. ( I. e. 4000C, 4500C, …….., 9500C, 10000C. ) 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 +/- 50C up to 8000C and +/- 100C above 8000C.

14. This is allowed to plot on the graph and thus obtained for time and temperature values.

64

STANDARD OPERATING

PRACTICES FOR LOCAL

65

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

•

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

66

LSR -BAND WIDTH

t

67

LOCAL STRESS RELIEVING SET UP

1. Provide multitonne roller on one end of vessel during LSR of circular 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.

68

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

GOOD ENGG. PRACTICES

FOR FURNACE CHARGES

70

SUPPORTING ARRANGEMENTS

1. Minimum distance between wall of furnace and the job shall be 600mm.

2. Minimum distance between floor of the furnace and lower most part of the job shall be 300mm.

3. The distance between the flame of burner and saddle support shall be 600mm.

4. Minimum 90 degree saddle to be used, however 120 degree saddle is desirable.

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

72

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

Zero gap

Supporting arrangement

SUPPORTING ARRANGEMENTS

11. Locking/clamping of job, restricting the movement (axial/lateral) during heat treatment shall be avoided. 12. All long nozzles projecting outside job surface shall

74

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

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

76

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.

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.

78

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

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

80

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.

THERMOCOUPLES

ATTACHMENTS

THERMOCOUPLES

ATTACHMENT UNIT

82

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.

CODE EXTRACTS

•FURNACE PWHT

• L S R

84

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.

85

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.

86

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.

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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.

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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).

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.

90

( 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.

SERVICE CONDITION

• LETHAL SERVICE PWHT IS MANDATORY • EXEMPTIONS ARE FEW

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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”.

CODE EXTRACT FOR HEAT TREATMENT

• The temperature of furnace shall not exceed 800‟F ( 4270C) at the time when the vessel or part is placed in it.

• Above 8000F( 4270C), the rate of heating shall not be more than 4000F Per hour (2000C/Hour) divided by the maximum metal thickness of the shell or head plate in inches, but in no case more than 4000F Per hour( 2220C 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 2500F( 1390C) within any 15 feet ( 4.6m) interval of length.

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CODE EXTRACT FOR HEAT TREATMENT

• During the holding period, there shall not be a greater difference than 1500f ( 830c) 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 8000F ( 4270C), The rate of cooling shall not be more than 5000F Per hour (2780C/Hour) divided by the maximum metal thickness of the shell or head plate in inches, but in no case more than 5000F Per hour ( 2780C Per hour).

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.

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SELECTION OF SPIDERS AT OPEN ENDS FOR HEAT TREATMENT

10000 10 20 30 40 50 60 70 80 90 100 9500 9000 8500 8000 7500 7000 ISMB 250

6500 ISMB 250 BOX SEC ISMB 250

6000 5500 5000 4500 4000 3500 ISMB 150 3000 2500 2000 ISMB 125 ISMB 150 1500 1000 500 ISMB 125 ISMB 150 10 20 30 40 50 60 70 80 90 100

DATA FOR ABOVE CHANNELS:

WEB HT FLG WD FLG THK WEB THK S H E L L D IA M E T E R WT/ MTR.(KG) 13 SHELL THICKNESS ISMB 125 75 ISMB 250 14.9 37.3 SHELL THICKNESS ISMC 250 DESIGNATION 30.4 125 150 250 250 ISMB 150 80 125 80 7.6 7.6 12.5 14.1 4.4 4.8 6.9 7.1 Annexure-5

102 HT REQUEST