EIED

Process Engineering and Contracting Division

NATIONALPETROCHEMICAL

COMPANY

(NPC)

AMIR KABIR PETROCHEMICAL COMPANYAmir Kabir 6th Olefi n Plant

Guide

by:date:page:

Richard Lothar TeichmannJuly28, 2004

Post Weld Heat Treatment

no.: 01/2004

1 of 4

Scope

This guide shall defi ne minimum requirements to carry out a successful post weld heat treatment on prefabricated and fi eld erected piping within the 6th olefi n plant of Amir Kabir Petrochemical Company as per design code and project specifi cations. It may used to monitor and control contractors and subcontractors activities and documents. Defi nitions and Abbreviations

AKPC ... Amir Kabir Petrochemical CompanyContractor ... company erecting piping and/or performing pwhtSubcontractor ... company performing post weld heat treatment on behalf of contractorDesign Code ... ASME B31.3WPS ... welding procedure specifi cationPWHT ... post weld heat treatment, heat treatment carried out after welding in order to decrease residual welding stress and/or change the micro structureNDT ... non destructive testing Reference Standards and Specifi cations

ASME B31.3 ... Process PipingASME IX ... Qualifi cation Standard for Welding and Brazing Procedures, Welders, Brazers, and Welding and Brazing Operators00-ESS-PI-3001 ... Welding Specifi cation of Piping Systems

Subcontracting

Subcontractor should work under the order and responsibility of the contractor and should fully comply with the relevant requirements by design code and/or project specifi cations.Contractor who orders pwht should supply all relevant specifi cations and requirements concerning these work to the subcontractor.

Subcontractor should provide records and documentation of his work as specifi ed by the contractor and/or this guide.

as per cover letterdistribution

Guide

by:date:page:

Richard Lothar TeichmannJuly28, 2004

Post Weld Heat Treatment

no.: 01/2004

2 of 4

Personnel

Contractor and/or subcontractor should appoint a suffi cient number of competent personnel for the planning, performing and supervising of pwht according to specifi ed requirementscompetence should be proofed by experience and certifi cation.

Inspection and Testing

General

Contractor and/or subcontractor should have at his disposal a suffi cient number of competent personnel for planning and performing, inspection, testing and assessing of the pwht activities according to specifi ed requirements.

Non Destructive Testing

Final NDT should be carried out at the stage of PWHT if specifi ed in the design code and/or project specifi cation or otherwise after the fi nal PWHT.

Equipment for Post Weld Heat Treatment

Equipment and Measurement

All equipment used should be adequate for the application concerned and should match the following minimum requirements:

- Thermocouples ... should be from nickel-chromium/nickel-aluminium type BS4937, part 4, type K or equivalent.- Thermocouple extension cable ... copper-constantan compensating cables should be used. The copper lead (+ve) should be connected to the nickel-chromium conductor (non magnetic) and constant lead (-ve) to the nickel-aluminium conductor (magnetic).- Thermal recorder ... should be suitable for the type and number of thermocouples used and should be capable to obtain a continuos graph chart, providing information of temperature differences and trends during the PWHT cycle, the chart speed should be adjusted to 50mm per hour.- Temperature control system ... in case of automatic control, the relevant design code and/or project specifi cation should be programmed into the unit. Once initiated the program shall run until completion. ... manual control requires adjustment of temperature controllers in increments of 10°C max.- Electric power supply ... should be controlled by a percentage (time) energy regulator.

Facilities

- Heating elements ... electrical resistance, multi standard wire, element beads made from high grade sintered aluminium, termination by male camlocks, max. operating temperature 1050°C, rating 43amps/63volts.- Insulation ... ceramic fi bre mesh mats of min. density 96kg/m³ or Rockwool ofmin. density 30kg/m³.

Guide

by:date:page:

Richard Lothar TeichmannJuly28, 2004

Post Weld Heat Treatment

no.: 01/2004

3 of 4

Checking of Post Weld Heat Treatment Equipment

Calibration of Adjustment and Recording Devices

- Temperature control system and thermal recorder should be calibrated at least once per year (12 month cycle).- Thermocouples should be calibrated at least twice per year (6 month cycle).- Records should certify these calibrations.

New Equipment

New or refurbished equipment should pass a function test prior to use verifying correct function of the equipment. Records should certify these tests.

Maintenance

Contractor and/or subcontractor should have a maintenance program for PWHT equipment and facilities in place, should be proofed.

Post Weld Heat Treatment Activities

PWHT Specifi cation

Contractor and/or subcontractor should prepare a PWHT specifi cation specifi c to the project and items to be heat treated, approval required.

Work Instruction

PWHT specifi cation should be used for instruction purposes, alternatively a work instruction based on an existing PWHT specifi cation should be produced. Work instruction should not be subject to approval.

Number of Measuring Points

- For piping dia. less or equal 6” one thermocouple should be used.- For piping dia. 6” - 20” three thermocouples should be used symmetrically around the weld.- For piping dia. greater than 20” four thermocouples should be used symmetrically around the weld.

Practice

- Welds made on SA335 Gr. P91 material must cool down below 100°C prior commencing PWHT.- Prior to start PWHT piping should be checked to ensure that all restrains have been removed, so it’s free to expand and contract.- Piping should be properly supported to avoid sagging and distortion.- If valves are involved in PWHT internals may be removed as per manufactors instructions.- Piping should be protected from impingement of wind and inclement weather, ends should be blinded off to prevent the effect of draughts on the inside of piping.- Thermocouples shall be attached on bright metal using capacitor discharge welding unit as close as possible to the weld and should be covered with high temperature putty after welding.- Heating elements shall cover the area defi ned by design code and project specifi cation, no gaps allowed around the piping and should be fi xed with stainless or mild steel banding.

Guide

by:date:page:

Richard Lothar TeichmannJuly28, 2004

Post Weld Heat Treatment

no.: 01/2004

4 of 4

- Insulation shall be extended to min. 200mm distance beyond the outer edges of the heating band, thickness min. two layers of ceramic fi bres or Rockwool 6” min. and should be fi xed in a suitable manner.- Perform PWHT cycle as required by design code, project specifi cation and WPS. After starting the cycle the thermal recorder should be securely locked.

Heat Treatment Records

Records shall include, but not limited to, the following information and should be signed by competent personnel involved:

- Clear item identifi cation.- Material (grade, dimension ...).- Equipment used.- Cycle performed.- Thermal recorder chart.- Thermal recorder calibration certifi cate.- Thermocouple calibration certifi cate.

Non Conformities and Corrective Action

If PWHT does not conform to specifi ed requirements the weld or component should not be assessed. AKPC should be informed and a Non Conformance Report should be generated. The satisfactory result of any corrective action should be demonstrated. It should be considered that the corrective action does not have any adverse infl uence on the weld or component.

If you require any further clarifi cation in these matters, please do not hesitate to contact Linde LE QA/QC site staff.