PWHT

OWNER

CLIENT: Sabz Engineering Company

National Iranian Gas Company IGAT 5 Gas Compressor Stations DOCUMENT TITLE

DOCUMENT No.

TASHA DOC. NO.

602-106602106-TSHTSH-VD-0 VD-015 15 Rev. 0 PWHT PROCEDURE

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CONSURTIUM:

TASHA Manufacturing Company SABZ Engineering Company FBM Hudson Italiana FBM KNM FZCO.

PWHT PROCEDURE FOR SPY-2-1106/2106/3106/4106-EA-101

TASHA DOC. NO.

TOTAL PAGES:

602-106-TSH-VD-015 602-106-TS H-VD-015 Rev. 4

8 (EXCLUDING COVER SHEET)

4

22/02/2006

FOR APPROVAL

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M.S.KH.

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S.P.Z.

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8/1/2006

FOR APPROVAL

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2

12/11/2005

FOR APPROVAL

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M.S.KH.

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28/09/2005

FOR APPROVAL

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M.S.KH.

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0

17/08/2005

FOR APPROVAL

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S .P.Z. S.

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DESCRIPTION

PREPARED

CHECKED

APPROVED

CONSURTIUM

OWNER



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602-106-TSH-VD-015 Rev. 0 PWHT PROCEDURE

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Contents

Introduction 1- Scope 2- Reference 3- Heat Treatment Specification 4- Heat Treatment Facilities 5- Heating System 6- Thermo Couple (T/C) 7- Interruption of Heating during P.W.H.T. 8- Operating of Post Weld Heat Treatment 9- Header Boxes 10- Hardness Test 11- Q.C. Form

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Introduction:

This procedure covers the minimum requirement for shop post weld heat treatment (SPWHT) of the headers boxes (SPY--1~4(106)-EA-101) relevant to IGAT-V Air Coolers.

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Scope: This Procedure is contained general requirements of post weld heat treatment, which shall be applied for Air Cooler headers.

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Reference: ASME Sec.VIII Div.1 Ed.2001 / Welding Spec. (602-000-ME-SP-003-D00)

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Heat Treatment Specification:

3-1) The method of applying, checking and controlling preheat and interpass temperature shall be stated on the WPS. 3-2) the minimum preheat temperature to be applied prior to the commencement of thermal cutting or welding shall meet requirements of the code, which ever is the highest. 3-3) when welding dissimilar metal welds having different preheat temperature requirements the more stringent preheat requirement shall normally be applied. This temperature shall be established during the welding procedure qualification. 3-4) preheat may be applied by any suitable method. Where fuel gas or oil is used, the gas or oil shall be sulphur free. The fuel/air mixture shall produce a neutral flame to ensure that no carbon deposit is left on the weld area. 3-5) Preheat shall be applied in a uniform manner and maintained throughout welding. Once preheat is applied, welding shall not be interrupted or stopped (other than for rest break) until a minimum of 30% of the final weld depth has been completed. On completion of welding, the weld area shall be cooled slowly under insulation to ambient temperature or, if required by paragraph 3-7 subject to an intermediate de-hydrogenation heat treatment. 3-6) Preheat and interpass temperatures shall be measured as follows by the use of temperature indicating crayons, thermocouples or contact pyrometers:  For nominal thickness at the weld preparation less than 50 mm, prheat temperature shall be maintained for a distance of 4t or 51mm, whichever is less, from the edge of the weld preparation.  For nominal thickness greater than or equal to 50mm at the weld preparation, preheat temperature shall be maintained for a distance of 75mm, from the edge of the weld preparation.  Preheat temperature shall be measured only after sufficient time has elapsed for temperature equalization (based on two minutes per 25mm thickness) 

Interpass temperature shall be measured on the weld metal or the base material immediately adjacent to the weld.

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Temperature indicating crayons for use on 300 series stainless steel shall be certified free from injurious contaminants(e.g. sulphur, halides ) 3-7) where the specified minimum preheats t emperature are 150 C or higher an intermediate dehydrogenation post weld heat treatment shall be applied in accordance alternatively for equipment subject to PWHT, preheat shall be maintained without interruption until the start of PWHT. Post weld heat treatment 

3-8-1) PWHT shall be performed in accordance with code and welding spec. 3-8-2) PWHT in an enclosed furnace is the preferred method, with the electric resistance or muffle furnace PWHT for local closing welds. 3-8-3) all machined surface shall be protected from scaling during PWHT using a suitable protective coating. 3-8-4) for equipment subject to PWHT in an enclosed furnace, thermocouples shall be located on both the inside and outside surfaces at the following locations, as a minimum, to ensure the correct temperature is attained: The thickest and thinnest members (including nozzles)  The top and bottom of the equipment (as positioned in the furnace)  3-8-5) for weld subject to a local or partial PWHT, four thermocouples shall be equally spaced around the weld joint on both the inside and outside surfaces. Where electric resistance elements are used for local or partial PWHT, a minimum of one control thermocouple shall be used for each heating circuits. 3-8-6) for local PWHT, the minimum width of the heating band shall be a minimum of 6t or 150mmeithersideof the weld, whichever is greater, or the code requirement if this results in a greater, or the code requirement if this results in a greater heating band width. Insulation shall extend a minimum of 250mm beyond the edge of the heating band or the code requirements if this results in greater insulation width. For flanges weld, the entire flange surface inside and out, shall be insulated. Whenever practical, the inside surface over the area of the heating band shall be insulated, or if this is not practical, the ends shall be sealed to prevent draughts and minimize convection currents. 3-8-7) Pressure retaining welds of equipment in sour, amine and caustic services shall be subject to PWHT after all welding is complete. Attachment welds to pressure retaining components, and any areas subject to heating for bending, correction of misalignment etc. for equipment in amine and caustic services shall be subject to PWHT. 3-8-8) Where PWHT is a service requirement in accordance with 3-8-7 welding after PWHT is not permitted without additional PWHT with the exception of minor, external attachment welds to equipment in sour service only, providing the PQR complies with the hardness testing requirements. 3-8-9) Where PWHT s a code requirement only welding after PWHT without additional PWHT is permitted only for the following:

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Heat Treatment Facilities:

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The heat treatment operation of this project will carried out by Reactorsaz Co or Artash Co. Reactorsaz Co. has a heat treatment furnace with the following capacity. Length : 18 meter Width : 6 meter Height : 6 meter Temperature range : 100-120 C Main fuel : Natural gas Control System : Automatic & monitoring system Temperature Control : Automatic Control

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Heating System 4-1) for heating of the box to be treated; it shall be place on the bogie and push bogie into the furnace. 4-2) during the firing, the flame shall not be harmful and not be react with base metal. 4-3) Flames shall not be directly contact with the any part of box or box attachment.

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Thermocouple (T/C) According to furnace category monitoring facilities, control panel and suitable thermocouple (T/C) are predicted for temperature measurement. T/C location and its contacts type are met the UW-40 design code. The location of thermocouple connection shell is covered by proper insulation material with minimum dimension 50 x 50mm.

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Interruption of Heating During PWHT: If heating is interrupted at any stage of the heat cycle, precaution should be taken to minimize the cooling rate. Subsequent heating shall be in accordance with the relevant heat cycle.

6.1- Interruption in heating period: Wait until to 600 C, and go on reheating. 6.2- Interruption within soak period: If the temperature drops below the lower limit, it shall be increased to correct range at specified heating rate for the material and thickness, and then hold period should be restarted. 6.3- Interruption during cooling period: In this case if the temperature is within cooling rate, then acceptable. But that is beyond, applying additional insulation shall be taken on furnace gate until the cooling rate reach to acceptable cooling rate.

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Operating of Post Weld Heat Treatment: The operation of the shop post weld heat treatment should be generally performed in accordance with the sequence prescribed hereafter. 1- Review the procedure of the heat treatment work and assembly drawing. 2- Check the weld line number, cleaning condition, and other requirement to be performed for post weld heat treatment. 3- Measure the skin temperature of bare parts.

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4- Determination the burner number and type, thermocouple type, number position and adhesion condition. 5- Confirm the calibration status (report) of temperature records. The temperature recorder shall be calibrated in accordance to the fabricator recommendation or laboratory guidance. 6- Thermocouple calibrated record shall be reviewed. 7- Connect the power cables to temperature recorder and controller, respectively. 8- Seal furnace door gap if practical. 9- Check the temporary supports for fill-up distortion due to operation, and check all of the dials instruments, knobs/ controller and indicators related to the PWHT operation. 10- Heat up unit PWHT temperature is reached at desire of the heat treatment procedure. 11- Monitor the heating rate, holding time and cooling rate during the PWHT operation. 12- Disassemble the thermocouple and temporary attached. 13- Check the time-temperature chart, and make a heat treatment report in accordance with the time-temperature chart. 14- Submit the report to inspector and client respectively. 15- Surface preparation and painting shall not be undertaken in conditions which are favorable to surface condensation when temperatures are below 10º C or the relative humidity is above 85%. 16- Paint materials shall not be applied over metal surfaces having temperature less than 3 º C above the dew point or in excess of 38 º C. 17- Paint materials shall not be applied to steel when ambient temperatures are expected to fall to 5 º C before the paint has dried. 9- Header Boxes:

The following paragraph is applicable to shop post weld heat treatment box that are fabrication by welding 9.1- Pressure vessel design data: Design code : API-661 Head material : A516Gr70 9.2- Heat treatment: Actual heat cycle to be applied to headers is as follows: 1- The rate of heating from ambient temperature up to 300 C shall be heat without recording. 2- The rate of heating from 300 C to soaking temperature shall be controlled and recorded automatically and not greater than 222 C/hr (according to table 1) 3- Soak temperature: 640± 20 C 4- Above 426C cooling shall be done in a closed furnace or cooling chamber at a rate not greater than 278C/hr dived the maximum metal thickness of the shell or head plate in inches, but in no case more than 278 C/hr. 5- During the holding period, there shall not be a greater difference than 50 C between the highest and lowest temperature throughout the portion of the weld line being heated. 6- During performance of heat treatment activity relevant graph for registering of temperature and time shall be recorded properly.

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10- Hardness Test:

10.1- For verification of correct post weld heat treatment performance at least two welded joint of each header shall be tested by checked on base hardness test instrument. 10.2- Hardness measurement shall be checked on base metal, H.A.Z and base metal. 10.3- Hardness value shall be recorded on hardness test report. 10.4- The maximum acceptable hardness is 248 H.V. (On PQR) 10.5- For each type of weld, production test requirements of Para. 14.4 of welding spec. will be considered.

FIG.1) Heat Treatment Cycle for Headers Box (Not to Scale) Table 1

Item

Max. Th'k (mm)

Heating Rate (C/hr)

Holding Time (min)

Temperature (C)

SPY-2-(1~4)106-EA-101

22

222

60

640 ± 20

Cooling Rate (C/hr)

- For any repair after P.W.H.T., it should be heat treated after repair operation locally. (Based on UCS-56) - Surface protection for raised face flanges should be considered.

222

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11- Q.C. Form All information relevant to heat treatment shall be recorded in Q.C. format and relevant graph must be attached to heat treatment report.

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Project:

Item/ Tag No.: HEAT - TREATMENT

Owner:

Report No.: REPORT

Req. No.:

Date:

We Certify That The Under mentioned Item Was Heat-Treated And Found To Be Satisfactory To:

Specification:

Drawing No.

Method of Stress Relieving:

Material:

Required Temperature:

Rate of Heating Up:

Holding Time

Method of Cooling:

Atmosphere Composition

Inspection Authority: TASHA QC. REPR.:

CLIENT QC. REPR.:

OWNER Q.C REPR.:

DATE:

DATE:

DATE:

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PWHT

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