Page 157 - Well Control for Completions and Interventions

Well Control Surface Equipment 149

The minimum requirements for choke manifolds and the associated
kill and choke lines are set down in API 53. The main points are:
• All choke manifold components that may be exposed to well pressure
must have a working pressure rating equal to or greater than that of
the preventer stack in use.
• Choke manifolds, choke lines, and kill lines having a working pressure
of 3000 psi and above must use flanged, welded, clamped connections
on components subjected to well pressure.
• Where possible, the choke manifold should be situated in an easily
accessible location, preferably outside the rig substructure.
• A minimum of one remotely operated choke should be installed on
10,000, 15,000, and 20,000 psi rated working pressure manifolds.
• Choke manifolds should be configured to allow re-routing of flow (in
the event of eroded, plugged, or malfunctioning parts) without having
to interrupt flow control.
• The choke line must have a working pressure that is equal to, or
greater than the stack in use.
The choke line (which connects the BOP stack to the choke man-
ifold) and lines downstream of the choke should:
• be as straight as practicable; turns, if required, should be targeted.
• be firmly anchored to prevent excessive whip or vibration.
• have a bore of sufficient size to prevent excessive erosion or fluid
friction.
• The minimum recommended size of choke line for pressure up
to (and including) 5000 psi is 2 in. nominal diameter. Some
operating companies recommend using 3 in. lines for all pressure
ratings.
• The minimum recommended size of choke line for 10,000, 15,000,
and 20,000 psi equipment is 3 in. nominal diameter.
• For air or gas drilling operations the minimum recommended size for
the choke line is 4 in. nominal diameter.
• The kill line must have a working pressure equal to or greater than
the ram BOP in use.
• Two full bore manual valves plus a check valve, or a manual valve and
a hydraulically actuated valve between the BOP stack and the kill line
are recommended for systems with a rated working pressure more
than 5000 psi.
• The minimum recommended size for choke lines is 2 in. (Fig. 4.5).