FURNACE AND EVAPORATOR SYSTEM OF BOILER

In last dispatch we have discussed what are the major components constitutes the Furnace

/ Evaporator System. Today we will describe the system individually in brief.

Furnace wall inlet Headers. 

1. The headers form a ring header   pattern link in all conventional designs. The basic difference

is in the arrangements of  headers. Basic points which make the header unique are that the side

wall headers donot have any stubs as they have only the economiser water connection and the

other point is headers on front and rear do not extend up to the wall as it in subcritical utility

boilers. As the spiral wall construction begins at hopper iyself , the stub arrangement is

staggered both front and rear headers.

Spiral wall inlet tubes

The spiral hopper formation starts at the hopper inlet tubes. The pitching and arrangement

 is such that the required angle of spiral hopper and pitching of tubes is achieved at the 

loose tubes.

Furnace Hopper Spiral Walls

The water from the bottom inlet header enters the spiral hopper walls. The hopper walls are slanted to 

the hopper angle on front and rear and are vertical on sides. The hopper walls on front and rear have 

two inclination angles to accommodate the tubes and to facilitate the formation of helix. All the end 

connections are with loose tubes only and there is no spiral panel gang bending requirement. These 

loose tubes at all the four corners are welded at site. Furnace hopper side walls have the large access 

door opening (610 mm x 762 mm), which is given for taking equipments like scaffold door, etc. inside 

the furnace. The tubes are to be bent in multi plane to arrive at all openings.

Furnace Hopper to Vertical Transition

On the front and rear sides of the furnace hopper, the tube panels are at angle of 50° to the vertical. To

match the vertical spiral wall, these transition panels have a bend in the vertical plane. These bends are

provided by the number of loose tubes in the matching panels.

This is typical status of erection site at the beginning of pressure part erection. Any body can observe

that roof sheeting work is over. It will benefit the erection work during monsoon season, As you

know structural work starts from bottom but Pressure parts work starts from Top.  Therefore

suspension work , lifting of link pipes , roof panel , top headers etc can be lifted. Suspended

suspension and a few headers can be seen. It also observed that lot of horizontal buck stay has

been lifted and kept in position . There are two schools of thought regarding lifting of buck stay

one is buck stay to be lifted along with the wall panel because bigger length and avoid bending

during lifting and other school is buck stay to be lifted separately and attached after lifting of

panel. Both the theories have their advantage and disadvantage therefore it will be the decision

of erectors and material position that will guide. We have followed mixed rout of both the system.

It can be observed that all silencers are erected on the roof .

As described earlier transition header with spiral panel and vertical panel pre-assembled and

getting lifted.

Furnace wall vertical is taking it shape . Buck stays were attached now and helping in formation of

furnace.