# As per IBR, the efficiency of double-riveted butt joint with the double cover strap of equal width should be -

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As per IBR, the efficiency of double-riveted butt joint with the double cover strap of equal width should be -

1. 63 to 70%
2. 70 to 83%
3. 80 to 90%
4. 85 to 95%

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Correct Answer - Option 2 : 70 to 83%

Explanation:

As per Indian boiler Regulation

• The thickness of the boiler shell should not be less than 7 mm.
• The efficiency of the joint should be as per the recommendation of the Indian Boiling Regulations, for the best joint the efficiency may be taken as 85%.
• the efficiency of a double-riveted butt joint with the double cover strap of equal width should be ​70 to 83%.

The minimum distance between two rows of rivets as specified by IBR is as follows

• For lap joint or butt joint when the number of rivets in each row is equal, the distance should not be less than
0.33p + 0.67d for zig-zag riveting
⋆  2d for chain riveting
• For joints where the number of rivets in the outer rows is half the number of rivets in inner rows and the inner rows are chin riveting, the distance between the outer rows and the next rows should be maximum of
0.33p + 0.67d and 2d
• For joints where the number of rivets in outer rows is half the number of rivets in inner rows and the inner rows are zig-zag riveting, the distance between the outer rows and the next rows should be
⋆  0.2p + 1.15d