2.8.9 Fly ash branch feed valves and segregation valves.

2.8.9   Fly ash branch feed valves and segregation valves.

 

                        One number fly ash feed valve under each fly ash collection chute,  i.e. ESP and flue gas duct collecting hoppers and one no. fly ash branch segregation valve for each branch pipe  for vacuum system shall be provided.

 

                        The valve shall be totally enclosed type and shall be designed for no air leakage.

 

                        (a)        Branch segregation valves shall be used in fly ash extraction and transport piping to isolate the pipe line sections as also to isolate extraction/transportation equipment (if necessary) from the conveying (extraction and transportation) piping.

 

                        (b)        Fly ash feed valve shall be provided under each fly ash collection chute/hopper.

 

                        The valve shall be totally enclosed type and shall be designed for no air leakage.

 

                        The type of the valves shall be swing type or slide plate type for vacuum system and plate type/butterfly/dome/cone type in case of pressure system.

 

                        The valve shall be solenoid operated pneumatic actuated type consist­ing of a double acting air cylinder, a 4-way solenoid control valve with manual override facility.

 

                        Valves shall be provided with suitably located rodding port/access plug/panel if applicable.

 

                        The material of construction for valves on vacuum/pressure system shall be

 

Body	Alloy Cast iron, with hardness of 250 BHN (Min.)
Plate/Disc	3 mm thick stainless steel with 300-350 BHN hardness for fly ash segregation valve and 10 mm thick SS with 300-350 BHN hardness for fly ash feed valves.
Seat	Replaceable type Alloy C.I. or SS smooth finished with minimum 250 BHN hardness.
	Material of construction for valves on Pressure system
Plate/Disc/Dome/Cone	Minimum 10mm thk. S.S/Alloy   C.I.-300-350 BHN.
Seat (wherever applicable)	Replaceable type Alloy CI or SS smooth finished. Hardened to 250 BHN (min.)

Vacuum Breaker

 

                        Vacuum breaker shall be employed to open automatically at the end of fly ash handling operation, to prevent any residual vacuum prevailing in the ash trans­port  pipeline.

 

                        The vacuum breaker shall be mounted on the pneumatic ash transport line.

 

                        The vacuum breaker shall be of slide plate type with a pneumatic cylinder and piston assembly with solenoid valve. The body shall be made of Alloy Cast Iron with a hardness of 250 BHN (min.) and the plate be min. 3 mm thick SS of 300 – 350 BHN Hardness.

 

Advertisement