# Thread: How to calculate the number of fasteners and size of a fastener required?

1. ## How to calculate the number of fasteners and size of a fastener required?

Hi all,

I need a help to calculate number of fastener and size of fastener for this below mentioned case.

A circular plate (disc) is holding a seat and seat retainer as shown in below image. There is a pressure of 10N/mm^2 acting over the disc. The disc rotates 90 dgerees and the Torque required is 3000 N-m.

Capture.jpg

Dia of Disc = 178mm , Thickness of disc where seat is butted = 25 mm
Dia of Seat = 181 mm, Thickness of seat = 5mm
Dia of Seat Retainer = 175mm, Thickness of Seat Retainer = 8 mm

2. Your primary issue is the tendency of the pressure to act on the inner diameter of the seat ring to try and extrude it during the initial opening unseating and final closing reseating stages of the valve operation, so before going any further I need to know the seat ring material. Is it a flexible elastomer or a relatively rigid polymer?

On a side note, since this is relatively pressure balanced valve configuration, similar to that of a butterfly valve, I am surprised at the high operating torque unless it is due to friction in the shaft bearings.

3. Once you know the axial forces required - calculate the number of bolts and torque required.

See: Torque Engineering and Design