This week you will be doing hardness and tension tests on fasteners. You will individually select a nut, bolt or washer, try to visually identify its grade, perform a hardness test, and check whether the hardness results agree with the grade markings. Each group will also select a bolt, identify its grade, perform hardness and tension tests, and see if the results agree. You will be expected to review ASTM F606 and follow it as best you can.
Video Lecture (12 minutes)
- Fastener Information
Designers spend 20% of their time
on elements, 80% on connections.
photo by Jeff Thomas, 2010
Design of wellhead and Christmas tree equipment is covered under API 6A "Specification for Wellhead and Christmas Tree Equipment." A 21 ¼ inch nominal 5000 psi rated flange under this specification has 24-2 inch bolts. The recommended torque for these bolts is 3083 ft-lb per bolt. Sometimes instead of torque, they will stretch the studs. Flange design is covered under ASME Section VIII mandatory Appendix 2. A properly functioning pair of flanges must meet three design conditions. First, the bolt load-24 2 inch bolts-must be enough to seat the gasket. At first blush this would appear not to be very large. However, the force to seat a gasket-spiral wound or ring type-can be enormous. The oil field is accustomed to using RTJ flanges because of the high pressures. This means the flanges must seat a metallic ring. The ring is always softer than the flange seat so that galling does not occur. Second, the seal must not leak under internal pressure. The internal pressure will try to part the flanges so the bolt load must be able to seat the gasket and resist the internal pressure. Third, the bolt load must resist any overturning moment. This moment is almost always caused by external loads from the piping. For a 5000 foot riser the loads due to vortex shedding, weight, and the movement from the ships can be enormous.
* from Building Construction Illustrated, 3rd Ed, by FDK Ching and C Adams, Wiley, 2001