CONSTRUCTION TIPS ON PRESSURE PARTS ERECTION FOR A THERMAL POWER PLANT.

Colour Coding of filler wire

Specification                                   Brand Name            Colour Code

RT ½ Mo (ER 80s-D2)                      TGSM                        Green

RT 1 Cr ½ Mo (ER 80s –B2)           TGS 1CM             Silver grey/white

RT2 ¼ Cr 1 Mo (ER90s –B3)          TGS 2CM             Brown /Red

RT 9 Cr 1 Mo ¼ V                            TGS9Cb                     -

RT 347 (ER 347)                               TGS -347             Blue

Low and extra low Hydrogen Electrodes    

As per IIW (Indian Institute of welding) classification of Hydrogen

Content classify electrodes is given below.

High   : greater than 15 ml /100gm

Medium: 10-15 ml /100gm

Low: 5-10 ml /100 gm

Extra low: less than 5 ml /100 gm

Baking, Storage and Handling

The electrodes have tendency to pick up moisture when exposed

to atmosphere and the amount depends on the time, relative humidity

and also the type of coating on the electrode. The recommendation

of baking electrodes are given below.

AWS Classification              Baking temperature & Time   Holding temp

E-7018                                 250-300 & 2 hrs                        100 deg C

E-7018 -1                            250-300 & 2 hrs                        100 deg C          

E-7018- A1                         250-300 & 2 hrs                        100 deg C

E -8018 –B2                       250-300 & 2 hrs                        100 deg C

E-9018- B3                         250-300 & 2 hrs                        100 deg C

E-8018- B2L                      250-300 & 2 hrs                         100 deg C

E-9018 –B3L                      250-300 & 2 hrs                        100 deg C

E309 & E347                      250-300 & 1 hr                          100 deg C     

** - After issue the electrode from site store to welder the temperature

Portable oven should be around 65 to 70 deg C during actual use by welder.

This is not applicable to E309, E347 and E 6013.

Selection of electrodes for non –pressure parts work

Material P1 + P1

A. For butt welds, up to 6mm inclusive:  E6013

                                      

                                       > 6mm            :  E7018

B. For fillet welds up to 8mm inclusive    :  E6013

                                      

                                    > 8mm                   :  E7018

Carbon Steel + P1                                     : E6013 or E7018

Carbon steel + Carbon Steel                     : E8018 –B2

Note: E6013 can be used for all non load carrying welds of all thickness

of IS2062 plates 20mm thickness and 8mm fillets. For structural material

like Ceiling Girders thickness of material is > 63 mm needs preheating (120

Degree C) and stress relieving (600-700 degree C) depends on material.

Common Knowledge required by construction supervisors engaged in boiler work

Weight Calculation for tubes:-

W = (D-1.1425t) x 1.1425t x 0.024466 Kg/M

           

            W= Weight of the tube in kg/M

            D = Specified outside diameter in mm

            t = Specific thickness

Weight Calculation For pipes:-

W = (D-t) t x 0.02466 kg/M

         

           W- Weight of pipes in Kg/M

            D- Specified outside diameter

            t - Specified thickness

Weight Calculation for ID controlled pipes/tubes

  

W = (Dot) t x 0.02466 kg/M

           

            W- Weight of pipes in Kg/M

            D- Specified outside diameter

            t - Specified thickness

 Temperature Measurement

For measuring the stress relieving temperature we generally use

Thermocouples. The thermoelectric voltage in a thermocouple depends

 on the temperature difference between two junctions and is used and

is used for the purpose of temperature measurement when one of the

temperature is known. At project site we use Chromel – Alumel thermocouple

popularly known as “ K “type.

Colour Code of thermocouple is yellow (+) and Red (-) over all Brown.

(Polarity +/- should be known otherwise it will give erroneous reading)

Thermocouple extension wire Yellow (+) and Red (-) overall yellow.

(Thermocouple can only be connected by thermocouple extension wire not

by any other wire)

There are other types of thermocouple but in India “K” type is only used at

the project site. The temperature – milivolt curve is linear. The increase is

4.13 mv per 100 degree C. (approximately)

Radiography Source

In India for industrial radiography we use two type of source i.e Cobalt -60

and Iridium -192. Out of that use of Cobalt -60 is extremely unpopular

because it requires stringent safety precautions to be followed and it

affects the progress of work. Instead of cobalt -60 now a day’s all are

using ultrasonic machine to detect the fault. Ultrasonic machine requires

Test block (made of same material to be tested) to be made as per the

Specification of IIW.

Iridium -192 is having half life of 74.4 days. All our pipes and tubes are

Radio graphed by this source except pipe /structural thickness of > 60 mm.

In those cases only UT is performed. The Iridium source should be more

than 30 Curie strength. It will require less exposure time and time can be

saved. Exposure time is inversely proportional to the strength. In 500MW

/660 MW boiler around 10,000 to 12000 shots are taken.

For surface defects of welds two very simple tests are carried out (i) Magnetic

particle test (ii) Dye Penetration test. 

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COMMON KNOWLEDGE OF PRESSURE PART WELDING FOR BOILER IN THERMAL POWER PLANT

There are few basic information required to carry out the erection / construction of

pressure parts of boiler. These items are described briefly below for ready reference.


The welding of all pressure parts and high pressure piping shall be in accordance

 with the following requirements:

Qualification of Weld Procedures



All the welding procedures adopted  shall be qualified in accordance with the latest

applicable requirements of Section IX of ASME code before the work is begun.

Certified welding procedures for welding of pressure parts and piping's  should

contain the type of material, material thickness, the joint details, the pre-heat

temperature maintained, the post weld heat treatment given and the welding current

and the voltage used during qualifications of welding procedures.

Welder's Qualification                 


Only welders, qualified in accordance with the latest applicable requirements of

the Indian Boiler Regulations, shall be permitted to perform any welding work

on the pressure parts. In addition to such statutory qualification requirements,

the welders shall also perform a satisfactory pre-production qualification test to

be conducted at site in consultation with site welding engineer . The services of

an independent testing laboratory can be retained  to perform welder qualification

tests for welders.

All the welders carrying out welding at site, shall carry an identification badge,

which shall indicate the category and the grade of welding for which they have

been tested and authorised to carry out welding. All such badges shall be presented

on demand to the inspection authority.


All records of the welding procedures, the welder's qualification tests and

the welders' performance details for the work performed shall be maintained .

The names of all the welders who made each weld on the boiler pressure parts and

piping within the jurisdiction of the Indian Boiler Regulations shall be maintained .

The certified copies of any or all the above documents shall be submitted to

authority on demand. Marking of welded joints to be done as per norms.

HEAT TREATMENT


Pre-heating, post-heating and post - weld stress relief operations of all welds, shall be

performed in accordance with the requirements of applicable code. Local post weld

stress relieving heat - treatments shall be adopted only in cases where it is normally

impracticable to subject the entire assembly as such for stress relieving operations.

Heating may be by means of electric induction coils or electric resistance coils.

Oxyacetylene flame heating or exothermic chemical heating methods will not be

permitted. Complete recording of the temperatures through out the stress relieving

cycle of the material and the weld subjected to heat treatment shall be made by means

of a potentiometric recorder. Recorders other than those of potentiometric type shall

not be used for such temperature recording during stress relieving operations.


After setting up the weld joint for heat treatment operation, signatures shall be obtained

on the strips chart of the recorder prior to starting of heat treatment cycle. The right

hand corner of the strip chart at the starting point of the heat treatment cycle shall

contain details like the weld number, material, diameter and thickness, method of

heating adopted, prescribed ranges of heat treatment temperatures, date of heat treatment,

reference to item number of the Field welding Schedule.


FIELD WELDING SCHEDULE

Field welding schedule should contain following information:


a) Drawing No (s)

b) Location of the weld

c) Size of the weld (outside diameter and thickness)

d) Type of joints

e) Material specifications

f) Size of fillet on backing ring, when the type of joint is with backing ring

g) Electrode/ filler metal specifications

h) Number of welds per unit

i) Quantity of filler metal per weld

j) Indication of required Non-destructive Examination (NDE) for each weld

k) Pre-heat temperatures for welding

l) Process of welding

m) Post-welding heat treatment temperature ranges, duration, entitled 'Qualification of Weld Procedures' .

Continued to part-III

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CONSTRUCTION PLAN FOR PRESSURE PARTS- SCHEDULE FOR 11MONTHS PART -IIn

Continued from last dispatch about erection plan for pressure Part of

super critical boilers

6^th month erection schedule

Furnace Rear wall Interim Header

Furnace  Rear wall  Intermediate Header

Furnace lower buck stays

Upper furnace key buck stays

Lower Furnace key buck stays

Low Temperature Re Heater inlet header Low Temperature Re Heater coils lower 7th month erection schedule Furnace Lower Spiral  Rear  wall panels Furnace guides Economiser outlet header ( after pre-assembly) Economiser outlet terminal tubes (after pre-assembly) Economiser miscellaneous items  supports, suspension etc 8th month erection schedule Circulation system for feed water Furnace loose tubes for connecting furnace corners , burner panel etc Pressure Parts attachment items Economiser coil upper assembly ( after pre- assembly Economiser intermediate plain tube ( after pre-assembly) Recirculation pump and its piping etc (coming under Trim piping group) 9th month erection schedule Furnace front ,rear and side (L & R) header lower after pre-assembly Furnace bottom support after pre-assembly Expansion movement attachment, seal boxes arrangement etc Super heater & Re heater spacer tubes Economiser inlet header ( after pre-assembly) Economiser coil assembly lower ,Economiser Feed pipe and link etc Economiser outlet link etc 10th and 11th month schedule LRSB ( long retractable soot blower) mounting on furnace wall de slagger mounting on furnace Temperature probe Root valves for vent and drains Boiler Recirculation Pump and piping Starting of trim piping line ( soot Blower piping) Attachment work like door ,peep hole etc ,Supports of economiser line etc Mixing vessel , CBD and IBD tank , piping , vent piping etc. Schedule mentioned above is tentative and hold good for matching supply . This can be  varied as per requirement of site as per availability of material. We have not mentioned the pre- fabrication of crown plates. This is a major activities and can be started with ceiling girder pre-assembly if material (alloy steel ) plates are  available. The pre-  fabrication involves welding , pre-heating and post heating also. For pressure parts erection we require 10 to 12  electrical winches  ( 2 nos 10 T , 4 to 6 nos 5T ,rest  can be 3T) with 10000 mtrs wire rope 12 mm 19mm will be required . The winches  are to be positioned side of the main column. The level of winches should be 1 M above the ground level so that winches remain unaffected due to accumulated water below. Large number of max puller ,chain pulley blocks will be required ( more than 100 numbers).  Welding of pressure parts start from zero dates of pressure parts at pre-assembly bed. We are not going to discuss about welding here as this is specialised subject but information required for construction will be shared. P.S If  you are looking to earn few legitimate extra money from the comfort of your home then please click on the link given below LINK 1 - PLEASE CLICK HERE  LINK 2 - PLEASE CLICK HERE

CONSTRUCTION PLAN OF PRESSURE PART ERECTION -SCHEDULE 11MONTH FOR BOILER

After receipt of sequential material and timely pre-assembly of Boiler Pressure Parts planning for 

erection of the pressure parts is to be taken up. For Pressure Part erection ( beside cranes )  Electrical 

winches , Max puller , chain pulley block etc are required . Capacity of the above equipment will be as 

per requirement of the system. We have planned our erection activities in such a way that hydraulic test 

(drain able) is achieved by 12^th month from start of pressure part erection.

First month of erection plan:

Collector vessel with internals, attachment and supports

Separator vessel with internals, attachment and supports

Furnace upper front wall header

Furnace upper sidewall header L & R

Super Heater Radiant Roof inlet header

Re hater header supports and suspension

All suspension for the above

2^nd month erection plan

Collector vessels with internals, attachment and supports

Furnace upper vertical wall

Furnace riser pipes /links

( If the riser comes in one piece then it will longer length and having twist and turn in its layout . It will be advisable to lift it at the earliest to avoid difficulties in erection. But if it comes in two or three 

pieces then it can be done afterwards also.)

Super heater final spaced inlet header after Pre-assembly at bed

Super heater back pass side wall inlet header L & R

Super heaters extended side wall inlet headers

Super heater final spaced outlet header

Super heater Radiant roof outlet header

All suspension and structural arrangement

Riser pipes ,desh link ,SH connecting pipes –saturated etc

Re heater vertical panel outlet header pre assemble with terminal tubes L&R

Re heater cross over links etc.

Re heater vertical platen inlet header after per-assembly with terminal tubes

3^rd month erection plan

Furnace upper rear screen / hanger Outlet header after Pre-assembly

Furnace vertical side wall panels L & R

Furnace side risers & Furnace rear riser

Furnace Front riser and Furnace screen tubes ( after Pre-assembly)

Furnace Hanger tubes (after pre-assembly)

Furnace corner tubes upper and lower

Furnace upper Buck stays

Super heater platen inlet header ( after pre-assembly)

Super heater platen outlet header ( after pre-assembly)

Super heater front outlet header ( after Pre-assembly)

Super heater vertical platen coil L & R (after pre-assembly)

Super heater steam cooled wall rear upper and inter panel L&R

Super heater steam cool rear wall panel lower L & R

Super heater cool side wall panel upper L & R

Super heater steam cool side wall upper left and inter left

Super heater steam cool side wall upper right and inter right

Super heater rear roof panels L & R  after pre-assembly

Super heater Radiant wall roof panel + attachment after pre-assembly

Low temperature Re-heater outlet header after pre-assembly

Low temperature Re-heater outlet terminal tubes after pre-assembly

4^th month erection plan

Furnace front wall interim header ( after pre-assembly)

Furnace side wall interim header ( after pre-assembly)

SOFA panel opening panel

Furnace upper spiral front wall Panel (pre-assembly)

Furnace upper spiral side wall panels - L&R

Furnace extended wall panels

Separator collector link pipes

Furnace Intermediate Header Supports front

Furnace Intermediate Header support -Rear

Furnace Spiral Wall supports Misc items

Furnace upper inter buck stays

Rear arch Buck stays

Upper back  pass buck stays

Back pass lower rear header

Super heater Back pass front wall inlet header

Super heater front wall outlet header

Super heater final spaced assembly L & R

Super heater upper and lower panels

Super heater steam cool side wall panels L & R

Low temperature Re heater pendent assembly

5^th month erection schedule

Burner Panels

Furnace Lower Spiral

Furnace Lower Spiral Front wall panels

Furnace vertical wall panels rear ( after ore-assembly)

Mixing Sphere

Furnace Intermediate Header Support  Sides L&R

Furnace wall  Supports front

Furnace wall   Supports Sides L & R

Furnace lower inter Buck stays

SH Extended Side wall outlet header (after pre-assembly)

SH vertical platen coil left & right.

Re Heater Vertical  Platen  Coil L & R

Low Temperature Re Heater coils upper (after pre-assembly)

Low Temperature Re Heater coils inter ( after Pre- assembly)

RH vertical platen coil assy left & RH vertical platen front coil assembly right.

( CONTINUED TO PART II)

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