AMIGOS TECHNICAL SERVICES ( S ) PTE LTD POST WELD HEAT TREATMENT PROCEDUREDoc No : ATS-PWHT-001 Revision No : 01 Date : POST WELD HEAT TREATMENT PROCEDURE DESCRIPTION NAME SIGNATURE PREPARED BY REVIEWD BY APPROVED BY REVISION STATUS S.NO REVISION No. DATE DESCRIPTION Page 1 of 11 . 10. 6. 11.AMIGOS TECHNICAL SERVICES ( S ) PTE LTD POST WELD HEAT TREATMENT PROCEDURE Doc No : ATS-PWHT-001 Revision No : 01 Date : CONTENTS Page 1. Important Measures During PWHT……………………………………….. 9. Scope…………………………………………………………………………… Heating Item / Work Volume. Location... 7.. 3.. Applicable Code & Specification…………………………………………….. 3 3 3 3–4 4 4 5 5 6 6 6 7 Appendix 1 Appendix 2 Sketch : Width of Heated & Insulted Zone ( LOCAL PWHT ) Thermocouple Locations ( LOCAL PWHT ) Attachments : PWHT Report Form ( Specimen ) Page 2 of 11 . Report / Documentation……………………………………………………… Heat Treatment Equipment…………………………………………………...……………………………………………………… Temperature Control System………………………………………………… Personnel‟s Qualification……………………………………………………. 5. Schedule…………………………. 4. Heat Treatment ( PWHT ) Method…………………………………………… Temperature Monitoring………………………………………………………. 12.. 8. 2. Temperature Ranges. Precautions……………………………………………………………………. 5ѵRT on each side of the Bent or formed area. 4. chapter UCS-56 ASME B31. shall extend 2. 5. T = pipe wall thickness in mm ) 2. 2. SCHEDULE HEATING ITEM Various sizes of piping welds range from Ø0. the minimum Width of the heated band shall extend at least 2.AMIGOS TECHNICAL SERVICES ( S ) PTE LTD POST WELD HEAT TREATMENT PROCEDURE Doc No : ATS-PWHT-001 Revision No : 01 Date : 1. HEATING ITEM / WORK VOLUME. measured from CENTRE of the Weld. ( R = inside Diameter in mm . In Local PWHT of Butt Weld Joint. 2.8mm Also structural weld joints of varying thickness 3.1 2001 ED . 3. ASME code Section VIII Div.3 DNV-OS-C101 or DNV-OS-C201 AWS D1. Scope This document covers the procedure for PWHT Work of High Pressure Piping system Weld joints by localized heating method for carbon and manganese steel. in accordance with the codes specifications stated in the above section 3. APPLICABLE CODE & SPECIFICATION 1. 3.75” ~ Ø16” Thickness range : Less than 50.1 Client‟s Specification 4. Page 3 of 11 . 4–2 Minimum Required Heated Band Width: 1. alloy steel materials and castings.5ѵRT beyond The edge of the weld joining the branch or attachment to the run pipe. In local PWHT of Bend or formed sections. In Local PWHT of welded Branch Connection. the minimum width Of the heated band shall extend to 2. LOCATION.5ѵRT beyond the edge of the weld. the minimum width of the Circumferential Heat Band. HEAT TREATMENT ( PWHT ) METHOD 4–1 Weld Joints shall be locally heat-treated in such manner that the entire Band be brought up uniformly to the required temperature and held for the specified period of time. whichever Distance is the smallest. (e) After heat treatment . the ends of piping should be sealed to Prevent internal air currents from creating excessively high Thermal gradients through the thickness of the piping. or in ¼ of the outer Circumference.AMIGOS TECHNICAL SERVICES ( S ) PTE LTD POST WELD HEAT TREATMENT PROCEDURE Doc No : ATS-PWHT-001 Revision No : 01 Date : 4. measured from the center of the weld. A demonstration will be carried out upon client‟s Request. Protected from rain and draught. Shall extend at least 5ѵRT beyond the edge of the weld. (c) All thermocouple attachments shall be adequately insulated by High temperature misreading caused by the effect of radiation. arc strike. (b) When tack welding thermocouple onto the work piece. all materials shall be cooled in still air. (b) Density of 128Kg/m3 Ceramic fiber insulation blanket shall be Used the thermal insulation. (d) The miminum number/location of the thermocouple to be Attached to the work place shall be as follows: Weld sizes ( NPS ) (a) D≥6” No. 4–4 Thermocouple Location: (a) Thermocouple shall be firmly attached to the center of the Weld zone using a capacitance-discharge type thermocouple Welder. (pls refer to APPENDIX-2) Page 4 of 11 . Precautions shall be taken so as not to create defects such as Undercuts. etc and the welded zone shall be Smoothly finished by grinder after heat treatment. (d) Wherever possible. HEAT TREATMENT ( PWHT ) METHOD – CON’T 4–3 Thermal Insulation: (a) The insulation width. (c) The insulation blanket will be kept in position with iron or steel Wire.of T/C 1 no Locations 9 O‟clock ( center ) (b) 6”<D<16” 2 no 1800 apart ( top & bottom ) (c) D≥ 16” 3 or more Every 600mm from each other. Exposed. 6. IMPORTANT MEASURES DURING PWHT Upon the occurrence of below-mentioned problems during LOCAL PWHT Operation. PRECAUTIONS 6–1 It is vital to highlight the need for adequate support of work piece Prior to commencing any heat treatment to minimize possible Misalignment.AMIGOS TECHNICAL SERVICES ( S ) PTE LTD POST WELD HEAT TREATMENT PROCEDURE Doc No : ATS-PWHT-001 Revision No : 01 Date : 4-4-1 For Structural Joints : Thermocouple can be placed as per the clients requirement or at a Regular intervals of 0. machined and threaded surface shall be protected from Oxidation by applying Anti-Seize and Lubricating Compound prior to PWHT. the following should be observed: FAULT / PROBLEM ACTION NOT ALLOWED No weather protection Provided before heating CORRECTIVE ACTION Provide proper and Adequate weather Protection before heating RAIN Page 5 0f 11 . collapse or deformation. 6–2 7. TEMPERATURE MONITORING 5–1 Temperature monitoring shall be done by the thermocouples and Temperature shall be recorded continuously on temperature record Chart.5m whichever is suitable 5. distortion. AMIGOS TECHNICAL SERVICES ( S ) PTE LTD POST WELD HEAT TREATMENT PROCEDURE Doc No : ATS-PWHT-001 Revision No : 01 Date : 8. TEMPERATURE RANGES : The procedure for PWHT has to be followed for the various steel grades as mentioned below. Material Grade Alloy Steels ASTM A 335 P4 Temperature Range 705° .749° Heating / Soaking TIme 2 Hrs / 25mm wall Thickness soaking 2 hrs minimum 2 Hrs / 25mm wall Thickness soaking 2 hrs minimum 2 Hrs / 25mm wall Thickness soaking 2 hrs minimum 2 Hrs / 25mm wall Thickness soaking 2 hrs minimum 1 Hrs / 25mm wall Thickness soaking 1 hrs minimum Rate of Heating 100°C / Hrs / 25mm wall thickness 100°C / Hrs / 25mm wall thickness 100°C / Hrs / 25mm wall thickness 100°C / Hrs / 25mm wall thickness 222°C / Hrs / 25mm wall thickness Rate of Cooling 100°C / Hrs / 25mm wall thickness 100°C / Hrs / 25mm wall thickness 100°C / Hrs / 25mm wall thickness 100°C / Hrs / 25mm wall thickness 222°C / Hrs / 25mm wall thickness 705° .650° .749° 730° .760° 705° .790° 590° . Schematic Sketch of Heat Treatment process Workpiece Power Source „k‟ type mV Program Setter (1) Temperature Controller pulse (2) On/off pulse Power Regulator (3) Heater (4) + Temperature Recorder 10. . TEMPERATURE CONTROL SYSTEM Temperature will be controlled by combination of program setter (1) which Generates voltage (mv) equivalent to the electromotive force of “k” Thermocouple with temperature controller (2). and the Heater (4) will be Controlled by the difference of thermal electromotive force of thermocouple (5). PERSONNEL’S QUALIFICATION Heat Treatment operator shall have at least one year of field experience in the Heat treatment work described in this Procedure.AMIGOS TECHNICAL SERVICES ( S ) PTE LTD POST WELD HEAT TREATMENT PROCEDURE Doc No : ATS-PWHT-001 Revision No : 01 Date : Page 6 of 11 9. etc (b) Number of Thermocouples (c) Time and Date Started (d) Chart Speed ( inches/hr) (e) Heating / cooling Rates. HEAT TREATMENT EQUIPMENT’S 12 – 1 Temperature Recorder It is Chino 12pts recorder calibrated for type “k” chromel / alumel Temperatures. glass fiber varnish finished) for temperature range up to 900°C. Unit. Thermocouple will be attached directly onto metal surface of the work piece Using a thermocouple Welder.2mm to 0.3mm. including date of calibration (g) Name of operator (h) The Approval signature of Client‟s site representive 11 – 2 A copy of Thermocouple Certificate provided by the supplier and Calibration Certificate of Temperature Recorder will be attached Together with the heat treatment Report and temperature chart. 12 – 3 . 12.8mmØ. 12 – 2 Program Controller It consists of Chino Program Setter and Chino Temperature Controller. Each chart is to show: (a) Item Identification Number ( Job. Tag/Piece No. REPORT / DOCUMENTATION 11 – 1 A Time-Temperature Record Chart shall be provided for each heat Treatment operation. Calibration Certificate shall be submitted to Clients before commencing Work. 0. ISO. Soak Temperature & Soak Time (f) Model & serial number of temperature recorder .AMIGOS TECHNICAL SERVICES ( S ) PTE LTD POST WELD HEAT TREATMENT PROCEDURE Doc No : ATS-PWHT-001 Revision No : 01 Date : Page 7 of 11 11. Thermocouple It shall be Chromel-Alumel type “k” thermocouple (consumable type. This consumable type of thermocouple gives The greatest accuracy and weld penetration will be only 0. The instrument shall be calibrated every 12 months by a third party. System. 7Kw Ceramic Pad Heaters. so as to avoid Temperature misreading caused by the effect radiation. 12 – 5 Thermocouple Compensating Lead It shall be Copper / Constantan when used in conjunction with type “k” Thermocouple. 12 – 6 Electric Resistance Heater 2.AMIGOS TECHNICAL SERVICES ( S ) PTE LTD POST WELD HEAT TREATMENT PROCEDURE Doc No : ATS-PWHT-001 Revision No : 01 Date : Page 8 of 11 12 – 4 Thermocouple Welding Unit When counsumable type of thermocouple is to used for monitoring Temperature. 12 – 9 Insulation Blanket Density of 128Kg/m3 ceramic fiber blanket Size: 7200L x 600W x 25T (mm) per roll Maximum services temperature: 1200°C . it will be attached to the metal surface by capacitance Discharge from this instrument. 12 – 7 Power Regulator 60Kva Step down Transformer c/w built in ELCB x 6 channels 60 Kva output 12 – 8 High Temperature Ceramic Putty This is used to insulate the hot junction of thermocouple. T = Pipe Wall thickness in mm.AMIGOS TECHNICAL SERVICES ( S ) PTE LTD POST WELD HEAT TREATMENT PROCEDURE Doc No : ATS-PWHT-001 Revision No : 01 Date : Page 9 of 11 APPENDIX – 1 WIDTH OF HEATED & INSULATED ZONES ( FOR LOCAL PWHT ) Heated Band Width Weld Centre Line Heating Element 2.5ѵRT Insulation 5ѵRT 5ѵRT Insulation Width Where R = Inside Diameter in mm.5ѵRT 2. . 1) D ≤ 6” : 1 thermocouple – 9 O‟ clock ( CENTRE) 2) 6” < D < 16” : 2 thermocouple ( TOP & BOTTOM ) 3) D ≥ 16” : 3 or more thermocouples ( Every 600mm from each other or in ¼ of The outer circumference. whichever Distance is the smallest ) 600mm 600mm .AMIGOS TECHNICAL SERVICES ( S ) PTE LTD POST WELD HEAT TREATMENT PROCEDURE Doc No : ATS-PWHT-001 Revision No : 01 Date : Page 10 of 11 APPENDIX – 2 THERMOCOUPLE LOCATIONS ( LOCAL PWHT ) All thermocouples are to be attached on the center of the weld. AMIGOS TECHNICAL SERVICES ( S ) PTE LTD POST WELD HEAT TREATMENT PROCEDURE Doc No : ATS-PWHT-001 Revision No : 01 Date : Page 11 of 11 .