PWHT Procedure A2

BD1253AA-BHAG-Q-PRO-0012 REVA2 Page 1 of 16

RAJASTHAN NORTHERN AREA DEVELOPMENT PROJECT

BHAGYAM FIELD DEVELOPMENT

MECHANICAL WORKS FOR WELL PAD

WORK PROCEDURE FOR PREHEATING & POST WELD HEAT TREATMENT (PWHT)

BD1253AA-BHAG-Q-PRO-0012

A2 21-07-11 Issued For Review SS Perumal Anwar Baig Nitin Makwana

A1 07-06-11 Issued For Review SS Perumal Anwar Baig Nitin Makwana

Rev Date Purpose of Issue Prepared By Checked By Approved By

WORK PROCEDURE FOR PRE-HEATING & POST WELD HEAT TREATMENT (PWHT)

TABLE OF CONTENTS

DESCRIPTION PAGE NO

1. Purpose 3

2. Scope 3

3. Reference Document 3

4. Definitions 3

5. Health and Safety 4

6. Method 4

7. Heat Treatment Cycle 5

8. Thermocouple Position 6

9. Arrangement Heating Element 6

10. Thermocouple 7

11. Thermocouple Extension Cable 7

12. Thermal Insulation 8

13. Temperature Recorder 9

14. Temperature Control System 10

15. Hardness Testing 10

16. Documentation 11

17. Job Safety Analysis 12



1. Purpose

This procedure intends to give guidelines for carrying out localized post

weld heat treatment of circumferential welds of process / pressure piping.

2. Scope

This procedure in general, conforms to recommendations of code

ANSI-B-31.3 for piping. This procedure is limited to the Heat Treatment

performed with Electric Power only. (I.e. Resistance Heaters: - either in

form of coils or "finger" elements.)

3. Reference Documents

ASME B31.3 “ Process Piping”

Drawing References.

Project Quality Control Plan.

Specification for piping fabrication & erecton.

4. Definitions

AEL Artson Engineering Ltd.

CEIL Cairn Energy India Pvt. Ltd.

HSE Health Safety and Environment

P&ID Piping & Instrument Drawing

PWHT Post Weld Heat Treatment

NDT Non Destructive Test



5. Health and Safety

As per HSE plan, the following systems to be followed;

All relevant elements of HSE Plan “BD1253AA-BHAG-R-PLN-0001” shall be

followed

Emergency and response Plan “BD1253AA-BHAG-R-PLN-0003” shall be

followed in case of any emergency

Project Security Plan “BD1253AA-BHAG-R-PLN-0004”

Daily pep talk shall be conducted prior to proceed for the work.

6. Method

Pre-heat shall be atleast sufficient to dry surface to be welded, but not

less than 10°C.

The minimum Pre-heat temperature shall be specified as in WPS.

The Pre-heat temperature shall be as per the ASME B31.3. Table

330.1.1.

If any loss or intterruptions of continuous Pre-heat then liquid penetrtrent

examination shall be done for incomplete weld joint.

Temperature indicating thermocouples or calibrated pyrometer shall be

used to measure Pre-heat and interpass temperature.

Heating Elements, of Ni-Cr (80% + 20%) wire of suitable gauge (Ranging

from 8 G to 20 G), insulated with porcelain beads, having various outputs (in

kw) depending on the requirement, either in the from of coils or finger, shall

be arranged around and on the weld portion and heated electrically at 240



Volt supply.

In case of high thickness & big diameter vessels, the heating

elements shall have to be provided also from the inside to achieve uniform

heating.

Heating element are covered initially with mineral wool and finally

wrapped with ceramic pad/blanket to shield the heat.

The electric power is to be supplied from 3 phase 4 wire system i.e. 3 x

240 V. with Neutral. Each control panel is having maximum current carrying

capacity of 63 Amp. per phase. The power to the heating elements is controlled

by timer as well as by on/off switch, manually.

The work piece is to be firmly supported and adequately earthed

electrically, before commencing the "HEATING" operation

7. Heat Treatment Cycle

The typical details of HT cycle for carbon steel & Aloy steel in general is as under.

Heating from Ambient to 300°C: unrestricted

Heating from

300°C to 650°C for carbon steel: 150 0 C (150 0 C/Hour Max.)

Or to 7200C for Alloy steel: Wall thickness in inches

Soaking Period: One hour per inch of Wall thickness (one hour

minimum



Rate of cooling to 300°C: 170°C (170°C/Hour)

Wall thickness in inches

300°C to Ambient: To Cool in still Air.

8. Arrangement of Heating Elements

Normally three sets of heating elements shall be wound round the

joint. One on each side of the weld and the third at the center of the weld.

Similar configuration to be adopted, if Heating elements are required to be

placed from inside.

The Heating element shall be held in position by Asbestos

string.

The Heating element are to be arranged in nos. of zones to

effect even heating of the entire desired portion.

The width of the Heating Elements, on either side of the weld,

shall be minimum distance.

9. Thermocouples

All Thermocouples shall be of the nickel-chromium/nickel-

aluminum type, con-forming to BS 4937, part 4. Type K All

Thermocouples/Thermocouple wire shall be supplied with a valid

certificate of conformance.

Thermocouples shall be attached by means of the direct wire

discharge method in order to avoid errors introduced by direct heating

sources. The conductor wires shall be fixed to the work piece no further

than 5 mm. apart.



To enhance the mechanical strength of the Thermocouple hot-

Junction, chloride-free high temperature cement shall be applied to the

hot junction.

The Thermocouple to thermocouple extension cable junction shall

be kept clear from the heated zone

10. Thermocouple Position

All thermo couples positions and numbers/colour, shall be

distinguished on temperature recording chart.

The following Thermo couple location shall be considered as

guide only

Sl.No Size No of Thermocouples Thermocouple Position

1 Up to & including 50 mm one 360(top)

2 Above 50mm to 300mm two 60/360

3 Above 300mm to 500mm three 120/240/360

NOTE: The specific requirements of Heat Treatment Cycle as well as

Thermocouple placement for a particular job, however, are to be obtained

from the inspection Authorities concerned, prior to commencement of job.

11. Thermocouple Extension Cable

Copper-Constantan compensating cables shall be used.



The Copper Lead (+Ve) shall be connected to the nickel

chromium conductor (non-magnetic), and the Constantan lead (-Ve) to the

nickel aluminum conductor (magnetic).

Care shall be taken to ensure that the compensating cable is not

subject to

a. direct or indirect heating

b. Electrical interference

c. Mechanical damage.

12. Thermal Insulation

The insulation consists of mineral wool wrapped around Heating

Element and then covered with a layer of ceramic blanket on entire

length of heating zone.

The insulation shall extend a minimum distance of 300 mm

beyond the outer-most edges of the heated band

The number of layers applied and extent is dependent on

wall thickness, pipe diameter, gradient requirements and site

conditions , in all cases , a minimum of two layers shall be applied. The

overall width of insulation shall be minimum 10 times JRT(R=radius &

T=Thickness)

Where ever possible, pipes/vessels open ends shall be blanked

off before heat treatment commences.

The insulation shall be bound with black annealed iron wire



The total insulation covering will be such to provide minimum

heat loss.

Temperature crayons shall be used to ensure that the

temperature do not exceed 300°C at any nearest point beyond

insulation covering.

13. Temperature Recorders

The records shall be of six point type, suitable for 0 – 1000

C/1200° C having continuous recording chart and chopper bar with colour dots,

with scanning period of 20 seconds/dot. Accuracy 1%. only 1 no. Chart to be used

for each weld joint preferably. Position of Thermocouples to be shown on a

sketch and identified on chart recording.

With these recorders, a continuous graph chart of all the

thermocouples is obtained, providing information of temperature differences

and trends during the heat treatment cycle. The charts also provide proof of

the heat treatment cycle on completion.

The chart speed shall be adjusted to 20 mm. per hour, and

the time interval between cycles for any particular thermocouple will be

approximately 2 minutes.

Each recording instrument will give information and immediate

indication of a thermocouple open circuit condition.

Each temperature recording instrument shall be checked,

calibrated before commencement of a heat treatment contract and



thereafter at intervals not exceeding one month.

Calibration certificates shall be available for review and such

calibrations can be witnessed by client if required.

During a heat treatment cycle, the recorder shall be securely

locked.

14. Temperature Control System

The temperature control system shall guarantee a post weld

heat treatment within the limits of the specification.

The manual mode of operation shall require adjustment of

temperature controllers for heated zones within the heated band to ensure

temperature uniformity.

Adjustments shall be made in increments of 100 C or as

specifically required.

The heat shall be controlled by Timer or by 'ON/OFF' switch

manually.

Ultimate control is achieved by using Timer & manual control of

energy and by continuous inspection of Temperature Recorder chart.

Throughout the heat treatment cycle (restricted range) the

temperature differential between thermocouples registering peak temperatures

shall be within the limits± 20°C.

15. Hardness Testing



After PWHT, hardness of the weld joints and heat effected zone shall

be checked by hardness tests.

The hardness value shall be within 225.

16. Documentation

This procedure, any amendments and the heat treatment

specification are sanctioned by the customer prior to commencement of the

heat treatment.

The heat treatment chart shall have the following information:-

Technicians name.

Starting and Completion time with date.

Specification details.

Thermocouple locations.

Recorder identification number.

ISO, line and weld numbers as applicable.

The soak (hold) period shall clearly mark on the heat treatment

chart. The thickness to be used in applying the heat treatment requirements

shall be that of the thicker component measured at the joint.

Charts shall be reviewed and approved by Q.C. Department, prior

to submission to authorities concerned.



For OC purpose. Chart shall be signed by QC Supervisor with

time and date at the commencement and completion of heat treatment in

order to provide valid proof of chart recording.



NAME OF THE PROJECT : RAJASTHAN NORTHERN AREA DEVELOPMENT PROJECT ACTIVITY/IDENTITY OF TASK : Job Safety Analysis for PWHT

AREA AND LOCATION : All Well Pads.

PLANT & MACHINERY, EQUIPMENT INVOLVED : Thermocouples, Current regulators, Insulation materials etc.

PPE’s REQUIRED : Safety Helmet, Safety Glasses, Safety Shoes, Rubber Hand Gloves, Coverall.


Sl. No.

Name Position Signature Date

1 Approved By Mr. Mukeshwar Tiwary Sr. RCM

2. Checked By Mr. Nitin Makwana RCM

3. Prepared By Mr. Shohab Kardar HSE Manager


S.N

o

1

2.

Activity

Preparation for Post

Weld Heat Treatment.

Post Weld Heat

Treatment.

Hazards

1. Unauthorized Entry

2. Electricity Leakage.

1. Electrocution.

2. Injury (burn) to workers.

3. Insufficient Insulation.

4.No Asbestos shall be used,

Control Measures

1. Permit to work system shall be followed.

2. Barricade the testing area with proper sign

boards to restrict unauthorized entry.

3. Ensure isolation of the testing equipment or

line has been done.

4. Ensure all tools used for PWHT are having

calibration and test certificates.

5. Test piece is isolated and properly earthed.

6.Only 3 core double insulated cable shall be

used . No domestic wire shall be used

7. All cables shall be connected with proper

connector. No insulation tape shall be used.

8. Use separate earthing from pipe

1. Test piece shall be properly marked and kept

clear from other workers.

2. Ensure ELCB is used and shall be checked

Action Taken

Site Engineers/

Site Supervisor

Site Engineers/

Site Supervisor



3.

4.

Wind up and

housekeeping.

Heat Stress due to adverse weather conditions

use other insulation matetial

Example: Rockwool

1. Scattered material.

2. Slipping or tripping.

1.Heat stroke or unconsciousness.

2. Heat Rashes

before starting the test.

3. Insulation shall be checked before starting

the job.

4. Ensure the workers are wearing proper

PPEs.

5. Use dust mask & Hand Gloveswhile handling

insulation material.

6. Communicate burn hazard from hot surface

to employees in the tool box talk.

1. Ensure proper windup and housekeeping is

done at site. Area need to be free of scrap

insulation material.

2. All accessories (insulation materials used)

must being collected and kept separately if not

in use.

3. Barricading and other signage shall be

removed.

1. Wear Full Sleeves cotton coveralls.

Site Engineers/

Site Supervisor

Site Engineers/

Site Supervisor



3. Heat Exhaustion 2. Always wear Hard Hat and face covers.

3. Drink plenty of water and more frequently.

4. Make Schedule for rotation of workers if possible and work in groups.
