DUCTING , INSULATION AND OTHER ITEMS LIKE MOVS, DAMPERS , OIL UNIT ETC FOR BOILER PART _I

One of the major job in Boiler Erection is ducting of Air and Flue Gas. Around 20% of

Boiler weight comes from ducting and dampers ( excluding support structures). In our

country ducts are fabricated at site and erected. Duct plates manufactured from 6mm to

8 mm steel plates. It requires considerable space to store and to fabricate. Because of its

volume it is not easier to transport. Therefore it is advisable to create a space very near

to boiler for fabrication of Ducting. Ducting job can be subdivided into following groups.


- Prefabrication of ducting to be carried out in two to three places.

- Erection of Ducting inside Boiler area that wind box , FD discharge , Flue gas etc. up to

  Boiler Outlet Flange ( BOF)

- Boiler Outlet Flange to ESP inlet Funnel

- ESP Outlet Funnel to  Chimney through ID Fan.


Out of the above erection of duct inside Boiler is most challenging. It requires pre planning

to execute in a sequence otherwise erection in assembled condition is not possible . A few

areas ducts were erected piece by piece because of its size. There are approach problem in

Boiler . Ducting erection starts with pressure part erection with 03 months lag. During that

time prefabrication starts. Therefore pre fabrication area near boiler to be used for boiler

ducting and to be followed in a sequence  . FD , PA fan ducting to be taken up later as

that place will not be available for erection. Priorities to be given ducting which are

coming at height .

Boiler Outlet flange to ESP inlet ducting is extremely crucial because it comes late. It

will have fixed duration it varies from 60days to 90 days . It is advisable to start

erection from the centre line of the boiler move sideways to extreme end . This will

reduce the requirement of higher capacity of crane. If it starts from end higher capacity

crane more than 250MT class will required.  Please note that area involves lot of

interface with other work like ..CHP gallery , Ash handling structure, Cable and pipe

line structures , civil work of ash trench, Mill rejects Silo. etc. It has also interface

with suction chamber erection of FD and PA. All these need to be coordinated to

erect these ducts.

ESP outlet funnel to ID fan inlet and ID Fan outlet to Chimney does not have any

interface with other work and can be started at the earliest if foundations and material

are available. These ducts specially after ID fan are very big ducts and need to be

fabricated near erection point. Only point to be taken into account is completion of

Chimney outer shell otherwise debris from the top may disturb this erection.

A few photographs are attached herewith.

Above picture shows duct fabrication is going on by side of the ESP .

Duct erection inside boiler area is under progress.

Plan view of ducting from BOF to chimney.

PA fan discharge ducting../

to be continued.


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