PWHT Procedure A2
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Transcript of 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
BD1253AA-BHAG-Q-PRO-0012 REVA2 Page 2 of 15
WORK PROCEDURE FOR PRE-HEATING & POST WELD HEAT TREATMENT (PWHT)
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
BD1253AA-BHAG-Q-PRO-0012 REVA2 Page 3 of 15
WORK PROCEDURE FOR PRE-HEATING & POST WELD HEAT TREATMENT (PWHT)
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
BD1253AA-BHAG-Q-PRO-0012 REVA2 Page 4 of 15
WORK PROCEDURE FOR PRE-HEATING & POST WELD HEAT TREATMENT (PWHT)
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
BD1253AA-BHAG-Q-PRO-0012 REVA2 Page 5 of 15
WORK PROCEDURE FOR PRE-HEATING & POST WELD HEAT TREATMENT (PWHT)
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.
BD1253AA-BHAG-Q-PRO-0012 REVA2 Page 6 of 15
WORK PROCEDURE FOR PRE-HEATING & POST WELD HEAT TREATMENT (PWHT)
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.
BD1253AA-BHAG-Q-PRO-0012 REVA2 Page 7 of 15
WORK PROCEDURE FOR PRE-HEATING & POST WELD HEAT TREATMENT (PWHT)
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
BD1253AA-BHAG-Q-PRO-0012 REVA2 Page 8 of 15
WORK PROCEDURE FOR PRE-HEATING & POST WELD HEAT TREATMENT (PWHT)
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
BD1253AA-BHAG-Q-PRO-0012 REVA2 Page 9 of 15
WORK PROCEDURE FOR PRE-HEATING & POST WELD HEAT TREATMENT (PWHT)
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
BD1253AA-BHAG-Q-PRO-0012 REVA2 Page 10 of 15
WORK PROCEDURE FOR PRE-HEATING & POST WELD HEAT TREATMENT (PWHT)
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.
BD1253AA-BHAG-Q-PRO-0012 REVA2 Page 11 of 15
WORK PROCEDURE FOR PRE-HEATING & POST WELD HEAT TREATMENT (PWHT)
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.
BD1253AA-BHAG-Q-PRO-0012 REVA2 Page 12 of 15
WORK PROCEDURE FOR PRE-HEATING & POST WELD HEAT TREATMENT (PWHT)
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.
BD1253AA-BHAG-Q-PRO-0012 REVA2 Page 13 of 15
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
WORK PROCEDURE FOR PRE-HEATING & POST WELD HEAT TREATMENT (PWHT)
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
BD1253AA-BHAG-Q-PRO-0012 REVA2 Page 14 of 15
WORK PROCEDURE FOR PRE-HEATING & POST WELD HEAT TREATMENT (PWHT)
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
BD1253AA-BHAG-Q-PRO-0012 REVA2 Page 15 of 15
WORK PROCEDURE FOR PRE-HEATING & POST WELD HEAT TREATMENT (PWHT)
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.
BD1253AA-BHAG-Q-PRO-0012 REVA2 Page 16 of 15