Changes

==Control and measurement system==

==Control and measurement system==

The ''blowout preventers (BOPs)'' (38 in [[:file:Land rig example drawing.png|Figure 1]]) are the major component of the control system on a rig, and they are the last line of defence against a blowout. The BOPs are bolted to the wellhead and are not removed until the well is completed and production equipment is installed. BOPs usually have at least four sections:

The ''[http://www.glossary.oilfield.slb.com/en/Terms/b/blowout_preventer.aspx blowout preventers] (BOPs)'' (38 in [[:file:Land rig example drawing.png|Figure 1]]) are the major component of the control system on a rig, and they are the last line of defence against a blowout. The BOPs are bolted to the wellhead and are not removed until the well is completed and production equipment is installed. BOPs usually have at least four sections:

* ''[[Annular]]s'' are large, hard rubber slips that fit around any sized pipe. The size flexibility, however, is at the expense of the pressure rating.

* ''[[Annular]]s'' are large, hard rubber slips that fit around any sized pipe. The size flexibility, however, is at the expense of the pressure rating.