STRUCTURAL WORK IN A THERMAL POWER STATION

Structural work comprises of Power House structure , Gallery , Miscellaneous building structures , pipe and cable rack structures etc. It has two parts one is Fabrication and other part is erection. In India   structural work ( civil) are executed at site unlike Boiler and other equipment . The approximate tonnage involved in structural work is given below .

- For a project 2x210 MW unit the structural steel required is                 13000 MT.

- For a project 2x500 MW unit the structural steel required is                 29000 MT.

- For a project 2x660 MW super critical unit structural steel required is  30000 MT.

Fabrication for the above tonnage is also done at site.

 

STRUCTURAL STEEL.

Some of the standard sections of structural steel are given below  for ready reference.

Angles : Designation                             Size ( lxbxt)                      weight in kg/M

              ISA 50x50x6                           50x50x6                                     4.9

              ISA 50x50x5                           50x50x5                                     4.1

              ISA 65x65x5                           65x65x5                                     4.9

              ISA 65x65x6                           65x65x6                                     5.8

              ISA 65x65x8                           65x65x8                                     7.7

              ISA 75x75x8                           75x75x8                                     8.9

              ISA 100x100x10                    100x100x10                               14.9

              ISA  130x130x10                   130x130x10                               19.7

              ISA  130x130x12                   130x130x12                               23.4    

 Beam    ISMB 100                               100 X50 ( HXB)                         8.9

              ISMB 125                               125 X 70                                    13.3

              ISMB 150                               150 X 75                                    15.0

              ISMB 175                               175 X 85                                    19.6

              ISMB 200                               200 X100                                   24.2

              ISMB 250                               250 X125                                   37.3

              ISMB 300                               300 X140                                   46.0

              ISMB 400                               400 X 140                                  61.5

              ISMB 500                               500 X 180                                  86.9

              ISMB 600                               600 X 210                                123.0  

Channel ISMC 75                                 75 X40                                       7.14

              ISMC 100                              100X50                                       9.56

              ISMC 125                              125X65                                      13.10

              ISMC 150                              150X75                                      16.80

              ISMC 200                              200X75                                      22.30

( these are few section mentioned above generally being used in thermal power structural fabrication.)

Besides standard machine cut plates are also used such as 6mm, 8mm , 10mm,12mm, 16mm ,20mm, 28mm ,32mm ,40mm, 50mm up to 63mm. ETC.

- Fabrication to be done as per fabrication drawing developed from the structural drawing. There are companies available in India who makes the fabrication drawings / detailed drawing. The fabrication drawing includes every detail requires for fabrication.

- Welding of structural items are done by electric arc process  as referred in the drawing. For resolving any disputes these documents may please be referred. 1. Drawing . 2. Welding Procedure defined (WPS) .3. Welding Manual . 4. NDE manual .5. Relevant IS codes like 817 , 7215, 12843 ,1852 , 2062 , 9595, 3502, 1239, 3589 etc 6. ASME sec IX  7.

- Submerged arc welding shall be used for welding longitudinal fillet welds.

- Longitudinal / transverse butt joints for fabrication of columns, framing beams and crane girders and

all other built-up members.

- Efforts should be made to position the job such a way so that down hand welding is possible.

-Only qualified welders are to be employed for welding procedures and positions.

- Fillet weld members should be close enough so  that gap is 0mm. In no case the gap should be more than 3mm. For example if the fillet gap is found to be 2 mm then fillet size of the joint should be increased by 2 mm.

        

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