DUCTING

ERECTION METHODOLOGY FOR DUCTING

1.    ERECTION SEQUENCE OF DUCTING

The erection of ducting in a 600MW boiler, probably, leads to one of the most complicated sequences of erection. Primarily there are three different circuits of ducting. Secondary air ducting starts from FD fans and goes to burner (Wind Box) via APHs. Primary air ducting starts from PA fans and goes to mills via AHPs . A parallel path of cold air ducting, bypassing the APHs also goes to mills for tempering. The flue gas ducting starts from economizer zone goes up to Boiler House via APHs.

2.    Construction Scope

·        All approved drawings for constructions are to be provided by SEPCO.

·        Erection engineers, work men and tools for erection are to be provided by PECL.

·        Cranes of capacity less than 75MT and hydras are to be provided by PECL.

·        All safety measures during erection will be taken care by PECL.

·        Electrical power and water for construction to be provided by SEPCO.

3.    The major sequence of erection of Ducting are as:

Ø  Wind Box Duct

Ø  Secondary hot air duct

Ø  Flue gas duct

Ø  Secondary cold air duct ( FD fan to APH)

Ø  Primary hot air duct

Ø  Primary cold air duct

Ø  Secondary cold air duct (FD fan to coal Mill)

4.    Wind Box Duct

The wind box on left and right wall is to be installed in position only, raising the items wall by wall. This area can only be touched when burner blocks and water wall panels of this zone are fairly aligned

5.    Secondary Hot Air Duct.

Raise of supports in their respective location before erecting Secondary hot air duct.

The length of secondary air duct from hot air bus duct to wind box, on left and right of boiler, can even be pre-assembled and raised to approximate location during structural erection period. Later date raising is too difficult.

The hot secondary air bus duct, which runs the full width of boiler and is located below economizer hopper duct, is to be raised after eco. Hopper duct only. Sections of bus duct can be assembled on ground and can be raised by winches only.

Other accessories such as welding with kerosene test which make it ready.

After completion of welding, Insulation work is Parallel Initiated.

6.    Flue Gas Duct

Economizer hopper duct, of flue gas path, cannot be assembled on ground due to its huge size and weight. This section is to be raised wall by wall and shape is formed in position. However, the bottom ash collecting hoppers of this section can be pre-assembled before raising.

Considerable length of economizer bypass duct and flue gas duct from economizer hopper to all four APH can be pre-assembled on ground.

Raise of supports in their respective location after completion of Flue gas duct

Other accessories such as welding with kerosene test which make it ready

After completion of welding, Insulation work is Parallel Initiated

7.    Secondary Cold Air Duct ( FD Fan To APH)

Raise of supports in their respective location before erecting Secondary cold air duct.

Horizontal run of secondary cold air ducts, from respective FD fans to APH can be pre-assembled but have to be raised by crane only.

Other accessories such as welding with kerosene test which make it ready

After completion of welding, Insulation work is Parallel Initiated

8.    Primary Hot Air Duct.

Raise of supports in their respective location before erecting Primary hot air duct.

Horizontal and Vertical run of primary hot air ducts, from respective APH to coal mill can be pre-assembled but have to be raised by winch only.

Other accessories such as welding with kerosene test which make it ready

After completion of welding, Insulation work is Parallel Initiated.

9.    Primary Cold Air Duct.

Raise of supports in their respective location before erecting Primary cold air duct.

Horizontal run of Primary cold air ducts, from respective PA fans to APH can be pre-assembled but have to be raised by crane only.

Other accessories such as welding with kerosene test which make it ready

After completion of welding, Insulation work is Parallel Initiated.

10. Secondary Cold Air Duct (FD Fan To Coal Mill)

Raise of supports in their respective location before erecting Secondary cold air duct.

Horizontal and Vertical run of primary hot air ducts, from respective FD FAN  to coal mill can be pre-assembled but have to be raised by winch only.

Other accessories such as welding with kerosene test which make it ready

After completion of welding, Insulation work is Parallel Initiated.