MISC. PICTURES ,INSULATION WORK AND ERECTION PLAN OF BOILER

In my last two or three dispatches we have discussed miscellaneous items

erected in a steam generation and there strategies to be adopted. I am enclosing

some pictures to bring clarity about earlier topics.

The above two works are for ducts .One is getting erected in position and

other is getting assembled with subsequent duct on bed before erection.

We will now discuss about insulation work in boiler . In 500MW or

660 MW boiler around 4000 MT + insulation work to be executed.

Insulation work in India is not getting much importance compare to

main Boiler work. This job is extremely labour oriented and requires

experienced manpower to execute them. Insulation work in boiler

can be divided into three categories  e.g.  1) Castable  2 ) Pourable

3) Wool mattress . beside that there are work of iron parts and overall

sheathing.

In general boiler insulation work starts after conductance of Hydraulic

test ( preferably drainable) . If we conduct non drainable Hydraulic test

then it is mandatory to light up the boiler within 21 days to 30 days other

wise wet preservation is required for non drainable portion. This will open

a new area which is not a part of this topic. It has been observed that after

successful Hydro Test a unit takes 03 to 05 months  time for Light Up and

majority of the insulation to be completed. This becomes a very big problem

for erectors to race against time . Therefore a few steps to be taken to work

on parallel path .

- Most of the time it is found that leakage do occurs from water wall panel

while making gas cut on fins for fixing lifting lugs. This can be altogether

avoided by use of specially designed fixture or gas cutting to be done in

front of responsible supervisor.

- Regular inspection to be done during fin welding . Tube may get

punchered during striking an arc. All welding joints of pressure parts

are subjected to various NDE and inspected by various persons . Therefore

failure of High pressure joints are very minimal. But fin welding which

is to be done in Kilo meters without any major inspection needs to be

improved to pass through the hydraulic test in one go.

- Welding of insulation hooks is another area where mistake may happen.

Welding hooks to welded either on fins or on tubes. There are two school

of thought on this. If it is to be welded on tubes then 100% welding to be

completed before Hydro test . But if it is to be welded on fins then same

are to be done before Hydro test but risk are less.

- Duct insulation work can be done once kerosene test of duct is over . A

portion of both side can be kept open for final welding between two ducts.

This will help to achieve boiler light up and sub sequent activities.

A typical data of insulation used in 660MW Super critical Boiler.

s/n       area           temp C     thickness             sheathing          density

01. Furnace wall   439       310 mm  Al.sheathing 1.6mm       150kg/m3

02. Pent house      482       360 mm          do                            -do-

03. Separator        427       250                  do       1.2mm         150kg/m3

04. Flue gas Duct  343       210                  do       0.914mm    100kg/m3

05. ID duct            138         40                 do            do              do

06. Hot air Duct     321       140                do             do             do

07.  Cold air Duct  acoustic 200                do            do              do.

08. Misc. items                      50                do            do              do.

-Insulation Material as IS 8183 group 3&4 lightly resin bonded Mineral

 rock wool.

- Any surface more than 60 deg.C temp will be insulated.

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