Short Bolting Issues

John NewhouseMidCon - Arkoma

May 7, 2008Arkoma

API RP 54

6.4.10 - All pipe fittings, valves, and unions placed on or connected with blowout prevention equipment, well casing, casinghead, drill pipe, or tubing and exposed to well pressure shall have a working pressure rating equal to or greater than the maximum anticipated well surface pressure. The BOP stack and related riser connections should not be short bolted (not less than three threads showing) and should be checked for properly torqued bolts.

Recommended Practice for Occupational Safety for Oil and Gas Well Drilling and Servicing Operations

May 7, 2008Arkoma

Basis of Standard

• Bolt thread must protrude through entire nut for full strength to be realized

• Short bolting increases risk of failure by way of thread stripping

• First 1 or 2 pitches of the thread are typically partially formed because of a chamfer

• Extra three threads allows for only full-strength threads to be engaged with nut

• API’s recommendation of three threads is conservative− Allows sloppiness in makeup

May 7, 2008Arkoma

Effect of Chamfer

Chamfer reduces integrity of first thread

Full thread profile

Images: www.colorado.edu

May 7, 2008Arkoma

Bolts below the double rams on BOP Stack

Bonnet Bolts on the rams on BOP Stack

BOP

May 7, 2008Arkoma

1

2

3

Choke

May 7, 2008Arkoma

Choke

May 7, 2008Arkoma

API RP 54

May 7, 2008Arkoma

High Pressure Non-BOP

May 7, 2008Arkoma

High Pressure Non-BOP

May 7, 2008Arkoma

Low Pressure