THERMAL POWER PLANT BOILER PRESSURE PART DESCRIPTION

We have discussed about the spiral wall with different pictures and illustration . We will leave

spiral wall there and proceed further on pressure parts of Boiler.

                                                          Furnace Vertical Walls:

The vertical wall panels are after the steam or steam and water mixture (as the case may be) comes out 

of intermediate headers. The tube size is 38.1 tubes @ 50.8 mm spacing. All the panels are of Alloy 

Steel tubes and are fin welded construction. The vertical wall transfer the total load of spiral walls to 

the ceiling by the means of Finger Strap plate welded to the spiral walls on all four sides. The walls are 

separately supported from the ceiling and the outlet headers are supported separately. The bent tubes at 

the end of vertical panels have lug welded as in case of Roof Panels in 210 / 250 MW designs.

                                         Furnace Vertical Wall Outlet Headers:

The vertical walls deposit the steam or steam and water mixture in outlet headers. The headers on front 

and sides are offset from the centre line of walls. Hence, the total loads of the walls are not transported 

through the header except the rear wall header, when the header takes the total load. This is no separate 

header in once through boiler for screen and hanger because the screen and hangers are at the same 

location and are inline with the rear wall. Hence, the rear wall header takes the total load. In some   

cases , there are two tubes for load carrying. Headers are supported by ‘U’ Rods separately.

                                           Furnace Wall Rear Arch Panels:

In Once Through Designs, the rear arch tubes are sent as panels. There are generally 6 rows of tubes 

forming the screen and one of the tubes (the rear one) is the hanger tube. This tube size is made bigger 

for load carrying purposes. In our project  this tube is 57.2 x 12.7 – SA213 T23 to take care of load.

                                              Furnace Riser Pipes to Separator:

As against in Conventional designs, the risers are in very less in number but are of bigger sizes. The 

sizes vary from 219.1 to 323.9 based on the capacity. The number of risers is totally 16 in our 

project. The risers from each of the 4 outlet headers are connected to each separator vessel. In

case of subcrtical boiler of 500 MW capacity the quantity approximately 61 nos of lower size

and length.

                                                          Burner Panels:

Without any doubt, the Burner Panel is the MOST Complicated piece of item in Once Through Boiler 

Pressure Parts. The burner panels are made in the spiral wall area. The boilers are tangential fired 

designs and the burner panels are positioned at four corners in our conventional designs. The main 

difference between our conventional design and once through spiral wall designing that in our 

conventional designs, we have single opening in burner panel through which the total wind box is 

inserted. But, in once through spiral wall designs, the opening for each nozzle is made separately by 

arranging tubes. The sizes of tubes in burner panels are 41.3 x 7.4 – SA213 T22. 

                                                             SOFA Tube Panels:

The extra air is fed into the furnace to control the Nox emissions through openings called SOFA

(Separate Over Fire Air) openings. For our project, these are located on the all  side walls.

Conceptually, the SOFA Panel Arrangement is similar to Burner Panel. The height is smaller as

compared to Burner Panels. Thus we can now sketch the flow of steam or steam and water mixture in

the furnace system:-

Economizer outlet links to Evaporator Inlet Header
               |
Spiral Hopper Loose Tubes
               |
Spiral Hopper Wall Panels
               |
Spiral Hopper to Wall Transitions
               |
Spiral Walls (including Burner & SOFA Panels)
               |
Intermediate Headers (including Spiral to Vertical wall transitions)
              |
Vertical Wall Panels (including Rear Arch tubes)
             |
Furnace Outlet Headers
             |
Furnace risers

Above picture shows the pressuse parts items are hanging from welded beam through suspension

rods. Some of the link pipes are visible here . These links pipes are to be erected first after

erection od suspension as these pipes big in length and having bends at different place to

avoid fouling with other members ,rods etc.

Some of the water wall panel ( vertical ) erection and alignment under progress. 

SOFA panel . In my next dispatch we will give the picture of Burner panel and its crticality .

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