mjcook
Chemical
- Nov 27, 2002
- 9
The chemical plant I work in uses B-7 bolting for all piping flange assembly. Confusion has surfaced recently regarding what thread pitch we standardize on for bolting over 1" diameter. For 1-1/8" and 1-1/4" bolts we have a mix of 7 TPI and 8 TPI fasteners.
I consulted John Bickford's "An Introduction to the Design and Behavior of Bolted Joints", and it implies 8 TPI may be the standard in this type of application. The book says, "The 8-thread series is used on large-diameter fasteners and was originally intended for bolts used in gasketed joints containing high pressure. It's also widely used as a substitute for coarse series fasteners when the basic fastener diameter exceeds 1 in."
Many items we get that have tapped holes in them like valves and expansion joints, though, are tapped for coarse thread fasteners, or 7 TPI.
What do most of you use in your plants? Is there a standard in the chemical industry for these larger fasteners? I'd just like to get all the data and input I can before choosing a direction to head on this. Thanks.
I consulted John Bickford's "An Introduction to the Design and Behavior of Bolted Joints", and it implies 8 TPI may be the standard in this type of application. The book says, "The 8-thread series is used on large-diameter fasteners and was originally intended for bolts used in gasketed joints containing high pressure. It's also widely used as a substitute for coarse series fasteners when the basic fastener diameter exceeds 1 in."
Many items we get that have tapped holes in them like valves and expansion joints, though, are tapped for coarse thread fasteners, or 7 TPI.
What do most of you use in your plants? Is there a standard in the chemical industry for these larger fasteners? I'd just like to get all the data and input I can before choosing a direction to head on this. Thanks.
