CONSTRUCTION PLAN FOR MATERIAL OF PRESSURE PART INSUPER CRITICAL BOILER

Following Pressure Part items are required at the beginning of starting of pre-assembly

Works. If we assume start of erection of Boiler structure is Zero date. Then these 

 materials are required at site from 5^th month of structural erection. It has been observed

 that  Ceiling Girder  with Welded beams and Rolled beams erection gets completed

within six month. Completion of C.G erection is the starting date of Pressure Part erection. 

Super Heater Final spaced inlet header

Super Heater Platen inlet header

Super Heater Final spaced outlet header

Super Heater Platen outlet header

Super Heater final spaced assembly – Terminal Tube.

Super Heater Vertical Platen – Terminal Tube

Super Heater final spaced assembly – Terminal Tube

Super Heater Vertical Platen Coil -Terminal Tube

Re Heater vertical platen inlet header

Low Temperature Re Heater outlet header

Re Heater Vertical Platen outlet header

Re Heater Vertical Platen Inlet & Outlet - Terminal tubes ( L & R)

Low Temperature Re Heater Outlet terminal tubes

Following items will be required sequentially on Pre-assembly bed. This will help

to maintain pace for Pressure Part erection. Material required 2^nd month onwards

are given below.

Furnace upper Rear outlet Header

Furnace front wall and side wall interim header.

Furnace spiral upper front & rear wall panels.                                                                                       

Furnace upper spiral wall panels - L & R.

Furnace screen tube and hanger tube

SH front wall outlet header.

SH Radiant wall roof panel + attachments.

SH rear roof panels left & right

Furnace vertical wall panels rear

LTRH upper coil and LTRH intermediate Coil

Furnace rear wall interim header

Furnace upper wall

SH extended side wall

LTRH inlet header

Economiser outlet header

Economiser coil assembly- outlet terminal tubes

Economiser coil assembly –upper ( L & R )

Economiser interim plain tube       (L &  R )

Furnace front ,Rear and side header.

Furnace Bottom supports

Economiser inlet header

Economiser coil assembly lower – inlet terminal tubes.(L&R)

Above materials are required at site from 2^nd month to 7^th month so that pre-assembly

works can be completed.

In India for a sub critical Boiler ( 500 MW) takes 09 to 11 months for readiness of drainable

Hydraulic test from start of Pressure Part erection. For other developed countires Hydraulic

test is being done for non- drainble and drainable portion. There are advantages and dis advantages

for both the system. The same will be elaborated afterwards. Materials requirement for super

critical boiler is based on 12 month cycle for drainable Hydraulic test.

To achieve this we need to start preparing pre-assembly bed from 5th month of structural erection.

At least four beds are required outside the boiler cavity and two number bed inside cavity. The

bed area should be  near to the actual space of erection with the facility of transporting 18 M 

panels ,coils , headers etc . Four numbers hydra cranes , one number 18 MT crawler crane , one

number 50 MT crawler crane to be deployed for the job at both the places. If it is possible a

temporary rail line can be laid to transport the material from  outside bed to boiler cavity area.

Therefore a proper layout plan to be prepared before start of pressure part erection. There will

be lot of space problem and conflict with other works . Few photographs are being attached .

We have not been able to establish railway line but we have achieved to create nuber of beds

for pre-assembly outside boiler .

This pre-assembly bed is inside cavity. otherwise it is impossible to transport the same from outside.


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CONSTRUCTION QUALITY LIMITS FOR BOILER PRESSURE PART IN THERMALPOWER PLANT

1. Bow in headres -for membrane panels                                           1mm/M (min) / 8mm (Max)  

2. Bow in headers - for other   panels                                                 1mm/M ( min) /10 mm (Max)

3. Headers scarfing line -for membrane panels                                    2mm (Max)

4. Headers scarfing line -for other panels                                            4mm (Max)

5. Membrane Panel width                                                                 + 2mm to -5 mm

6. Diagonal difference of Panel (D1-D2)                                            10mm (Max)

7. Verticality of Downcomer lines                                                      1mm/M , 5 mm (Max)

8. Bow in seperator /collector tanks                                                    1mm/M, 10 mm (Max).

9. Headers -elevation and spacing                                                        + / -  3 mm.

10. Furnace alignment ( Front and back Pass) width & depth              + 10 mm or -15mm

11. --------------- Do------------------------ Diagonal difference                20 mm (Max)

12. Fire ball angle -Permissible limit                                                    + /-  1 degree

13. Pitch of  water wall screen tubes & Back Pass front wall tubes      + /- 3mm

14. Pitch of Screen Tubes                                                                      +/- 10mm

15.  LTRH Coil and Pitch between centre line of side wall end to coil assembly  + /- 10mm

16. LTRH- Pitch coils                                                                            + /- 10 mm.

17. LTRH Coil and Pitch between centre line of front /rear wall to coils end +/- 20 mm.

18. Spacing between RH hanger  tubes                                                  + /- 3mm.

19. Platen  Super heaters coil and pitch between centre line of side
      water wall and end coil assembly.                                                    + / - 25 mm.

20. Platen Super heaters - Pitch of coils                                                 + /- 25 mm.

21.  Final Super heaters -  coil and pitch between centre line of side
      water wall and end coil assembly.                                                     +/- 10 mm.

22. Final Super Heaters - Pitch of coils                                                  + /- 10 mm.

23. Economiser- coil and pitch between centre line of side
      backpass  wall and end coil assembly.                                               +/- 10 mm.

24. Economiser- pitch of coils                                                                 +/- 10 mm.

25. Economiser -clearance between centre line of back pass front/
      rear wall and coil ends.                                                                       +/- 20 mm.

26. Re -heaters - coil and pitch between centre line of side water wall
      and coil assembly.                                                                               +/- 10 mm.

27. Re-heaters - Pitch of coils                                                                   + / - 10 mm.


In sub critical boiler where drum erection is involved instead of seperator an collector

following field quality checks are made.

1. Drum suspension U rod twist between limbs                                           10 mm max.

2. Disposition of Drum axis centre line of ceiling Girder                             1mm/M max +/- 5 mm

3. Spacing of washer plate w.r.t. longitudinal axis and drum axis                 1mm/M max +/- 3mm

4.Diagonal difference between washer plate locations                                   max 5 mm.

5.Elevation of Drum                                                                                       +/- 5mm

6. Elevation of drum -cummulative                                                                 max 8mm

7. Spacing of Drum axis w.r.t to centre line of ceiling girders.                      1mm/M max +/- 5 mm

8. Axial shifting of drum w.r.t longitudinal axis                                            5 mm max

9. Verticality of drum suspension U rod                                                        10 mm max.

Beisdes above checks for pressure parts there are certain checks to be carried out and

recorded like above. It is to be noted that all Pressure parts item vessels , pipes and tubes

etc .are coming under the perview of Boiler directorate and their acceptance is must and

binding to all. Therefore all the records are to be maintained accordingly.


- Inspection authority's stamp to be checked in every material and if possible take the copy

  of the stamp . Also match with the paper certificate.

- All the pressure part items like vessel , pipes , coils ,panels etc are to be cleaned from outside

  and inside. Sponge ball test to be carried with compressed specially for coils , panels etc .

- For major items like drum , vessel etc level marking to be done accurately for future reference.

  For sub critical Boiler all the reference of headers start from drum positioning.

- Alignment of headers , coils ,panels are to recorded.

 Platen super heater coils and Final super heater coils are visible through water wall panel

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THERMAL POWER PROJECT PR. PARTS RE-HEATER ,SEPERATOR ETC

                                                                  Re heater System:

The re-heater system of Once Through Super Critical designs consists of generally two stages of

reheating sections. One is positioned in the 2nd Pass of the two pass designs. Generally, in Sub-

critical designs, we have horizontal banks of low temperature super heaters in the second pass above

economisers. The low temperature re heaters are placed in 4 banks in the designs of this project. The

LTRH coil inlet header is positioned inside the flue gas path and is supported by separate set of hanger

tubes, which are taken from the rear wall inlet header for this purpose.  The headers (inlet & outlet) are

with short stubs. The coils are made in four banks and are hanger tube supported designs.

The RH steam is carried over to the second stage of re heater by means of two links which are end

connected and are criss-crossed before it reaches the inlet header of RH pendent section.

The Pendent section is positioned on the water wall arch tube zone. These are platen sections .The

coils are with 76.2 tube as wrapper and 63.5 as inner tube. The material of coils is SA213TP347H and

SA213 Super 304H. This is a new material for our use.The hot reheat steam from the pendent outlet

section goes to the finishing RH outlet header. The finishing RH outlet header is split header and is

made of SA335 P91 material. The header has end connections.

The hot reheat steam from the pendent outlet section goes to the finishing RH outlet header. The

finishing RH outlet header is split header and is made of SA335 P91 material. The header has end

connections.


Start up System:

The following are the critical components of start up system for which detailing is to be done afterwards.

a) Separator Vessel.

b) Collector Vessel or Storage Tank.

I. Separator Vessel:

 The separator vessel as the name suggested is instrumental in steam water separation on during the low

load operation. The steam water mixture at low load enters the vessels through the nozzles arranged

axially around vessel. The nozzles are arranged at an angle of 5° from the horizontal plane. This is to

facilitate to create swirl and centrifugal force to create better separation during the start up and low

load operations.

II. Collector Vessel:

The collector vessel as the name suggested is reservoir for the start up system. In this vessel, the water

enters through the nozzles arranged axially around vessel. The nozzles are arranged horizontally.

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THERMAL POWER PLANT PRESSURE PARTS REAR ROOF WITH HANGER TUBES ERECTION.

More photos of Pressure parts Pre -assembly are attached herewith with brief description.

Three numbers rear roof panel are getting pre-assembled here including fixture of hanger tubes.

Hanger tubes of nearly 18M long are to be fitted on the roof . This is typical erection procedure of

super critical boiler. Panels are welded at ground level and lifted up to 20 M and kept hanging

with the help of winch machine . If structures are available then temporary locking can be done.

Hanger tubes are placed from the bottom through its position temporary stopper arrangement is

welded on the tube to keep it in position. temporary structure were welded to avoid panel bending

due to its own weight and hanger tubes weight. Temporary ladder was placed from nearest platform

for easy approach.

After completion of jobs ( for 03 panels ) assembly look like above and it is ready for lifting .

After placed in position roof panel looks like above. Picture shows suspension are already hanged

and to be attached with the supports. Other pressure parts erection is also going on.



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THERMAL POWER PLANT PRESSURE PARTS PRE-ASSEMBLY PHOTOES.

We are discussing about super heaters of a super critical boiler. It is felt prudent to attach

a few pictures of different pressure part items in the write up. Number of major pre-assembly

has been carried out in pressure parts and the same is also attached herewith.

This was  pre-assembled  inside the boiler cavity after preparing a bed for its assembly. We

have used two 10 MT winches with multi sheave pulleys to place it in position. Two cranes

are also used to tail the assembly during erection . Otherwise there is every possible chance

that the panel will get bend on its own weight . The total weight will be around 60 MT.

Pre-assembly of different headers with loose tubes were done and kept ready. It can be seen few

tubes are left behind due to facilitate the erection hardware fitting and alignment afterwards. Also

in the picture spiral wall pre-assembly is going on.

Pre-assembled panel erected in position .



continued

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THERMAL POWER PLANT PRESSURE PARTS SUPERHEATERS.

                                                                         Super heater System:



The steam from riser comes to the separator vessels. The steam is taken to the radiant

super heater inlet header. The super heater links are 8 in numbers and are generally of the size

219.1 to 273.0. These are connected to the header by means of nozzle (forged) or by reduced

branch end tees. The selection is based on the header size and connecting nozzle size. From the

Radiant Roof inlet header, Roof tubes start and they cover for the furnace and extended pass.

As the project designs are without super heater divisional panels, the SH Radiant Roofs are in

the form of fin welded panel in this portion. The second part of the roof is saw cut fin welded

loose tubes. These tubes go to the SH Radiant Roof outlet header. There are 8 Nos. of SH By

pass pipes which connect the SH Radiant Roof inlet and outlet headers. Steam from the SH

Radiant Roof outlet header is bifurcated into two items:- (1) One portion goes to side walls & (2)

The second goes to the extended wall inlet headers. The arrangement of headers is in the shape

of English letter ‘H’ in the plan view. The steam in the extended walls flows through the vertical

walls through the bottom panels to the extended side wall outlet header placed on the centre line

of unit. The basic difference between our conventional design of 210 / 250 MW and this unit is

that the steam flow is upward in our designs where as the steam flow is downward in this

design.


The steam from extended wall outlet header then flows to the set of two extra headers used in

the specific project design. In between the two headers, there are 18 Nos. of pipes size 168.3 x 47.0

thick Alloy Steel, which take load and also complete the steam circuit. From the bottom header

steam is taken to the 2nd Pass Bottom Front wall inlet header by 2 Nos. of links. The second

part of steam flows from the 2nd pass side walls to the outlet bottom headers. From the side wall

outlet headers, the steam in correct proportion flows to Front Wall Inlet Header and Rear Wall

Inlet Header. Also, the steam cooled Hanger tubes are taken from both of these headers (as

against our 500 MW designs, where there are taken only from the front wall header). The fin

welded panels are made of Alloy Steel tubes. The Radiant Roof tubes and extended panel tubes

are of SA213 T23 material. The steam flows through the front walls, SH Screen tubes and also

through the Economiser / LTRH coil hanger tubes and Economiser outlet header support tubes

and gets connected to the Back pass front wall outlet junction header and hanger tube outlet

header respectively. Similarly, the steam in the Back pass rear walls goes through the roof tube

and also through the hanger tubes of Economiser / LTRH coils and LTRH inlet header support

tubes and finally gets connected to the Back pass front wall junction header and the hanger

outlet header respectively. The hangers tubes include:-



i) Economiser coil hanger tubes.

ii) LTRH coil hanger tube (continuation of same economiser hanger tubes)

iii) Economiser outlet header support tubes.

iv) LTRH inlet header support tubes.



From the both hanger outlet header and front wall junction header links are taken and they join

together in the pent house before carrying the steam to the Platen super heater. Platen super heater in

the sole pendent section is in furnace radiant zone. The design of the project has 24 elements. The

platen SH is made of tube 44.5 and the main material used is  SA213 TP347H  and  SA213 T91.

The headers are Short Stub headers.

From the platen SH coils the steam goes through the Platen outlet header, which is, split type (two

headers separately positioned and connected by mechanical means), the steam is carried by two links to

the final SH section. The SH DESH is placed in these links. These links are crissis crossed .The

finishing super heater coils are put in the extended super heater pass. This arrangement is more or less

similar to the 210 / 250 MW designs. There are two vertical banks of coils. The connection between

them by criss crossing the tube above the roof, The finishing SH coils are of 44.5 tubes and mainly

SA213 TP347H material. All the terminal tubes are SA213 T91. The steam reaches the main steam

outlet header, which is split header with end outlets and goes to HP Turbine.

Platen super heater coils in erected conditions .

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THERMAL POWER PLANT PRESSURE PART ( BURNER PANEL ARRANGEMENT)

This picture shows the lifting of wind box duct before erection of pressure parts . Please

note this is only for super critical boiler and not required for any sub critical boiler up to

500 MW. It has been told that if we do not erect this duct now it will be extremely difficult

to erect the same after pressure part erections and that is true. I thought it is better to mention

the same here.

Burner panel in view . The same is generally erected after erection of vertical /spiral wall up to Burner

panel top. However like all sub critical boiler it is seen that one or two burner panel are getting delayed

due to various reasons . Here also all the burner panel was delayed and we can not wait further because

we have close the furnace . The wait of single burner panel is around 50 T . Now it has to be erected

on temporary supports and burner panel needs to be shifted horizontally to the position . The same

was done afterwards . However it is preferred to have Burner panel in time for erection. The reason for

delay has been explained  in the next photograph.

We are doing super critical boiler first time and the kind pressure parts arrangements to be done

around burner is enormous. This job involves huge pipe bending etc to make it a panel. Final

connection will be loose tube with walls. We are told Burner panel was delayed in manufacturing .


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