MS POST WELD HEAT TREATMENT

MESAIEED A 2000 CCPP PROJECT PROJ ECT

Document Number 14T2-00-MA-ONM-SOM-036

Page Rev Date

Document Title Method Statement for Post Weld Heat Treatment

1 of 8 00

Method Statement For Post Weld Heat Treatment

MESAIEED A 2000 Combined Cycle Power Project

00

For Review & Approval

04.05.08

REV

DESCRIPTIO N

DATE

PREPARED BY SOMI

APPROVED BY SOMI

VERIFIED

BY

IBERDROLA

VERIFIED

Client

BY

MESAIEED A 2000 CCPP PROJECT



Page Rev Date

2 of 8 00

INDEX 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18.

PURPOSE SCOPE REFERENCES RSPONSIBILITIES SPECI AL EQUIPMENTS GENERL REQUIREMENTS HE ATING METHOD TIME AND TEMPER ATURE REQUIREMENTS HE ATING AND COOLING R ATES JOINT PREPAR ARION AND WR APPING THERMOCOUPLE EXTENSION LE ADS TEMPER ATURE RECORDING PWHT OF DISSIMILAR P-NUMBER WELDS NON-PRESSURE TO PRESSURE RETAINING PARTS SAFETY INSPECTION DOCUMENTATION



1.0


Page Rev Date

3 of 8 00

PURPOSE

The purpose of this procedure is to provide requirements for Post Weld Heat Treatment (PWHT) of weld joints for the MESAIEED A IPP PROJECT .

2.0

SCOPE

This procedure refers to following documents for performing PWHT of shop & field welded piping system components in accordance with ASM E / ANSI B31.3, B31.1 and Client.

3.0

REFERENCES

The following reference documents have been utilized in preparing this procedure and shall be referred to for additional technical information as necessary. ASME B31.1: Chemical Plant and Refinery Piping. 3.1

ASME B31.1 Power Piping.

3.2

ASME Boiler and Pressure Vessel Code, Section IX, Welding and Brazing Qualifications.

3.3

American Welding Society (AWS) D10.10 -75, Local Treatment of Welds in Piping and Tubing.

4.0

RESPONSIBILITIES

4.1

The SOMI Welding Supervisor / Foreman has the responsibility for implementing and ensuring this procedure

4.2

The SOMI Supervisor / Foreman shall determine the PWHT requirements, based on project specification and other refere nce documents.

4.3

The SOMI Welding Supervisor / Foreman shall be responsible for initiating PWHT operations in accordance with the specification.

5.0

SPECIAL REQUIREMENTS

5.1

Welding Procedure Specifications (WPS) utilized in performing the affected we lds shall be qualified for PWHT when required by the applicable code.

5.2

All temporary attachments within the heat -affected zone shall be removed




Page Rev Date

4 of 8 00

6.0

GENERAL REQUIREMENTS

6.1

PWHT shall be in accordance with the applicable WPS, ASM E B31.3, and B31.1, or design drawings and this procedure. Specific requirements of the WPS or this procedure shall govern.

6.2

Prior to the start of work, a detail table -listing of joints or components requiring heat treatment shall be prepared for review. The table shall include the information for each joint or component, location, Drawing No., diameter, wall thickness, material, heating rate, cooling rate, soaking temperature & time, number and location of thermocouple.

7.0

HEATING METHOD

The heating shall be done by resistance or induction methods by application of electrical resistance elements in the form of ceramic heater pads.

8.0

TIME AND TEMPERARURE REQUIREMENTS

8.1

Attachments µA¶ defines requirements for PWHT applications based on the materials P numbers listed in ASME Section IX.

8.2

The minimum holding time shall be in accordance with Attachments µA¶.

8.3

When members being joined and of unequal thickness, the nominal section thickness at the location of the Weld heat affected zone in the heavier section shall be the governing thickness for determining the holding time and heating / cooling rates.

9.0

HEATING AND COOLING RATES

Above 600ÛF (316ÛC), the rate of heating and cooling shall not exceed 432ÛF (222ÛC) per hour divided by the maximum thickness of material in inches at the weld, but in no case the rate shall exceed 432ÛF (222ÛC) per hour. The welds shall be allowed to cool in still atmosphere to a temperature not exceeding 800ÛF (425ÛC). The insulation shall not be removed before the temperature has cooled below 150ÛC.

10.0

JOINT PREPARATION AND WRAPPING

10.1

The minimum width of the heated band shall be five times the thickness of the thickest component

10.2

PWHT of welded joints shall require that the entire band be brought up to a uniform temperature over the circumference of the heated pipe section. A gradual diminishing of temperature outward from the edges of the heated band shall be maintained.




Page Rev Date

5 of 8 00

10.3

Heating elements shall be securely fixed in contact with the work piece by soft iron wire, SS or mild steel banding to suit the application. Under no circumstances shall galvanized wire or other fixing material likely to detrimental to the pipe be used.

10.4

Internal

drafts or chimney cooling effect during PWHT shall be avoided. Normally, valves will be in the open or cracked position unless otherwise recommended by the valve supplier. Open-ended pipe shall be temporarily sealed off upstream and downstream of the welded joint to reduce internal heat loss by use of the end caps or other acceptable means. When post weld heat treatment is to be performed on welds between valves and piping system components, the applicable vendor must be checked or vendor contacted for special requirements.

10.5

The weldment shall be clean and free of oil, grease and dirt, prior to PWHT operation. All machined surfaces such as flange faces, bolt holes, thread etc. shall be protected from oxidation by coating with deoxaluminite or other suitable material.

10.6

Weather protection against rain and wind exposure shall be provided at all times during periods of inclement weather.

10.7

Insulation

10.8

The thermal insulation shall extend a minimum of 12 ´ beyond the heating elements on each side of the weld joint to avoid harmful temperature gradients, unless otherwise authorized by IBO Inspector. Code requirement shall however at all times to be complied with.

10.9

Prior to start PWHT the piping / components shall be checked to ensure that all restrains are removed and pipe is free to expand and contract. Also during PWHT the piping / components shall be properly supported to prevent sagging and distortion.

shall be glass wool, or other type provided by IBO. A minimum I´ thick layer of ceramic fiber or a minimum 4 ´ layer of mineral wool shall be required.

10.10 Additional information regarding joint wrapping and preparation shall be in accordance with good industry practice.

11.0

THERMOCOUPLE

11.1

Type K (Chemical alumel) or type joint J (Iron -Constantan) thermocouples are recommended. All extension cables, compensating cables and jumper cables in the measurement or control circuit shall be specified thermocouple wire.

11.2

Thermocouple shall be attached to the work piece by direct wire capacitance discharge method. The gap between the two wire / work piece junctions sha ll not exceed 6mm.

11.3

Care shall be taken to ensure that the thermocouple conductor wires do not touch each other, or metallic components, away from the hot joints.




Page Rev Date

6 of 8 00

11.4

Thermocouple hot junctions shall be protected by the application of layer of high t emperature putty, applied locally.

11.5

Wherever possible, thermocouples shall not be located under a heating pad; thermocouples shall be routed between heating pads or out through the insulations, to avoid close contact with the heating pad.

11.6

The thermocouple to compensating lead connections shall be minimum of 0.5m from the heated zone.

11.7

Following each heat treatment a minimum 150mm of wire measured from the hot zone, shall be discarded

11.8

The insulation coloring of the thermocouple / compen sating cable core wire shall be RED for positive and YELLOW for negative to verify that proper wires have been used and are connected in proper polarity.

11.9

After completion of PWHT, all thermocouples shall be removed and attachment areas ground smooth to clean sound metal. If specified by the contract, the area shall be examined by MT or PT.

11.10 All temperatures within the heated zone for furnace or localized PWHT shall exceed the specified minimum holding temperature. The actual temperature range fo r the soak period as recorded by the thermocouple shall not have a spread of more than 40ÛC. 11.11 Minimum number of thermocouple required shall be as follows: For Pipe Diameter up to 12 ´ For Pipe Diameter up to 12 ´ to 24´ For Pipe Diameter up to > ´`

-

1 thermocouple 2 thermocouple 3 thermocouple

One spare thermocouple shall be positioned beside thermocouple specified above, to be utilized in the event of thermocouple failure to avoid interruption in recording in case of failure of the other thermocouple. 11.12 The following are Code Requirement for band width distances for thermocouple placement: The width of the band shall be 3 times the wall thickness of the thickest part being joined. For nozzle and attachment welds, the width of the ba nd shall extend beyond the nozzle weld on each side at least 2 times the header thickness.



12.0


Page Rev Date

7 of 8 00

EXTENSION LEADS

While in use, extension leads shall positioned off the floor s uch that they are not damage by being subjected to direct weight or abuse.

13.0

TEMPERATURE RECORDING

Recorders

shall be calibrated every 6 months and current calibration sticker shall be maintained on the recorder. Frequency of calibration may be extended to 12 months with the approval of Client Inspection if the documented c alibration checks for that particular recorder demonstrate acceptable Accuracy for a suitable period. Calibration certificate shall be available for review. An automatic temperature recording shall be made of all PWHT operations utilizing a multipoint recorder. Heating and cooling records shall include all temperatures in excess of 600ÛF (326 C). The attachment ³B´ data stamp shall be applied to the back of the chart upon completion of the PWHT cycle. If a PWHT operation is a second or succeeding PWHT , it shall be indicated as such on the PWHT record. Multipoint chart recorder shall clearly differentiate / identify each channel / point by use of different colored inks or automatic stamping

14.0

PWHT OF DISSIMILAR P_NUMBER WELDS

PWHT of welded joi nts between dissimilar P -number welds having different post heat requirements shall be specified for the material requiring higher PWHT temperature .

15.0

NON-PRESSURE TO PRESSURE RETAINING PARTS

When non-pressure retaining materials are welded to pressu re retaining materials, the maximum temperature shall be the temperature specified for the pressure retaining parts as per attachment -A

16.0

SAFETY

All the heating elements shall be thoroughly examined before use in order to ensure that the element wire is not exposed. Twist lock connection shall also be examined to ensure that the insulation is sound and that a good electrical joint is made. All cable connections shall be properly insulated. The component surface shall be free of contaminants. Technicians performing the PWHT shall be experienced in PWHT operation and conversant with Electrical characteristics in resistance or induction heating. Care should be taken to protect themselves and others working in the area.




Page Rev Date

8 of 8 00

17.0

INSPECTION

17.1

SOMI QC Inspector shall be responsible for inspect5ion of all attributes defined in this section.

17.2

That special instructions / vendor manuals have been complied with.

17.3

That the joint has been properly prepared in accordance with this procedure.

17.4

That thermocouple have been attached in accordance with this procedure.

17.5

The thermocouple placement is in accordance with section 11.0

17.6

That the chart recorder is properly calibrated.

17.7

SOMI QC Inspector shall also review the information o n the face of the PWHT chart. If the all information is correct, ha shall sign and date the PWHT chart in the area of the information placed on the chart.

17.8

Upon completion of the PWHT operation, SOM I QC Inspector shall verify that all temporary attachments have been removed.

17.9

In

process monitoring of all PWHT operations shall be performed by SOM I QC Inspector. Acceptance by the Welding Inspector of individual PWHT operations shall be sign off on the Attachment B stamp on the back of each chart.

17.10 After completion of PWHT operation, SOM I QC Welding Inspector shall submit the PWHT Chart TPSA / SA for their monitoring and approval.

18.0

DOCUMENTATION

Documentation of PWHT shall consist of the PWHT chart, from the recorder. When the PWHT operation is completed successfully, the PWHT chart along with PWHT Report shall be submitted for Client for their review ad approval.

MS POST WELD HEAT TREATMENT

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