STRUCTURAL ERECTION CONTINUED FOR THERMAL POWER PLANT

We will be discussing about the bolting structures in Steam Generation .

Most of the structures erected for Boiler is either welded or bolted . Some of the company

 used both as per their design. For all the bolted structure HSFG bolts are used . HSFG

 stands for High strength Friction Grip bolts . The specification and use of such bolts are

 explained in IS 3757 - 1985 and IS 4000 - 1992. However we will give only the information

 required at site . 

-The most commonly used ordinary bolts are 4.8 grade   

- The most commonly used High strength is 8.8 Precision bolts.

- High strength bolts used in INDIA is 8.8S and 10.9 and 10.9S..

- The grade and manufactured name are embossed on the head of the bolt.

- Generally we use M16 , M20 and M24 of various length.

- As a thumb rule after tightening of the bolt at least 10mm length protruded outside nut.

- These bolts are used for column to column connection , bracing connection , gusset plate etc.

- The bolts are hand tighten at first. Then these bolts are tightened by electric or pneumatic

  torque wrench . The value can be obtained for IS codes mentioned above.

-  Finally calibrated manual torque wrench is being used to check the tightening in citu 

   by sampling method.

- There is also other method where HSFG bolts quantities are very less. The same is called

   half turn method . The same has been explained in the IS Code.

- Colour coding is used to identify bolts to be torque tightened , already torquing done 

  and after torquing checking is also completed. This will give us status of torquing at a

  glance. 

- HSFG bolts are much costlier than ordinary 4.8 and 8.8 precision bolts.

- Bolt once torque tightened can not be used  for the same purposes.

Above picture shows the erection of bracing in steam generation. Wherever HSFG bolts are used

are shown in the picture. Column bolting also can be seen in the picture.

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