New tools and technology for the offshore industry
Multi-function gate valve provides improved shear, seal capabilities
Well barrier philosophy is a critical component of all aspects of life
cycle well integrity management. During workover of a live subsea well
the intervention system typically includes an emergency disconnect
package and either a lower riser package (LRP) or well control package
(WCP). The safety barriers are located in the LRP/WCP. Industry
standards require two well barriers during all well activities where a
pressure differential exists that may cause uncontrolled outflow from
the wellbore to the external environment [ 1]. These barriers typically
comprise a safety head (SH) and production isolation valve (PIV).
Enovate Systems has developed En-Tegrity, a 73⁄8-in., 10,000-psi (689-
bar) shear and seal gate valve (SSV) with dual independent barriers for
use as a SH, PIV, and/or combined SH and PIV. The SSV has been qualified as a SH and is currently undergoing qualification as a PIV. The use of
a single valve as a SH/PIV facilitates a reduction in the number of valves
in the LRP with consequent savings in weight and stack height.
There are six key innovations that differentiate this technology from
conventional gate valves, namely:
• A reverse actuation method. To close the valve the gates are pulled
across the bore rather than pushed into it. This means that the hy-
draulic pressure is aligned with the bore pressure resulting in the
latter assisting closure and allowing the SSV to close on a flowing
well. Wellbore pressure assists closure.
• Superior shearing. The actuator system can deliver 1 million lbf
and is designed to shear all envisaged work strings and tubing
likely to pass through the wellhead during intervention operations
at lower pressures than conventional gate/ram valves. During
qualification testing En-Tegrity cut 3.5-in. S135 drill pipe at pressures of around 1,500 psi (103 bar) and 27⁄8-in. 90ksi coil tubing
at 500 psi ( 34. 5 bar). In deepwater applications the lower cutting
pressures required more efficient use of accumulation because of
the improved useable volume available.
• Improved sealing. Full metal-to-metal sealing provides better sealing capability than
conventional gate valves through having
separate shearing and sealing surfaces
means that during shearing operations the
sealing portion of the gate remains clear of
the shear area, minimizing the risk of damage to this surface.
• Bi-directional sealing. When closed, upper
and lower seal plates align with upper and
lower seats providing bi-directional sealing.
• Dual independent barriers from below. The
system is operated by two independent hydraulic actuators. Well isolation is achieved
even with only the upper gate functioning.
• Reduced maintenance. Conventional gate
valves require frequent maintenance to re-
place elastomer seals due to damage caused
by erosion and degradation from tempera-
ture exposure and corrosive chemicals. As the SSV does not have
any elastomers in the bore, maintenance intervals can be extended.
Over the last two years Enovate has performed a program to qualify
the En-Tegrity SSV as a SH, in accordance with the following standards:
• API 6A (ISO 10423), Annex F, PR2 for a temperature range of
- 18°C to +121°C (-0.4 to 250°F) [ 2]
• API 6A (ISO 10423), Annex I, Class II Flow Testing
• API 17D (ISO 13628-4), Annex L, Hyperbaric Testing to 3,000 m
( 9,842 ft) [ 3]
• Norsok D-002, Annex B Cutting. [ 4]
Further planned developments of the technology include extend-
ing the qualification of the 73⁄8-in. SSV as a PIV and development of an
18¾-in. preventer for use in place of a blind shear ram/casing shear ram
in BOPs. New requirements in the recently published BSEE Final Well
Control Rule for BOPs mean that existing BOP rams will have difficulty
demonstrating their ability to cut all pipe used
during well completion and drilling operations.
However, the shear and seal capability of the En-
Tegrity system is not impacted by the new rule. •
[ 1] NORSOK Standard D-010, Rev 3, August 2004
[ 2] API 6A, Specification for Wellhead and Christmas
Tree Equipment, 19th Ed, July 2004
[ 3] API 17D, Specification for Subsea wellhead and tree
equipment, 2nd Ed, September 2011.
[ 4] Norsok D-002, Well Intervention Equipment, Revi-
sion1, 2000 and Revision 2, June 2013
Michael O’Sullivan is Technology & Development Director
at Enovate Systems. He has 25 years of experience in the
subsea industry and is an acknowledged authority on riser
system technology. He has worked on many joint industry
initiatives to develop subsea technology and enhance system
reliability. He led the JIPs that developed the current API
standards for unbonded flexible pipe (API Spec 17J and
API RP 17B) and flexible pipe ancillary equipment (API
Spec 17L1 and API RP 17L2). He holds bachelor’s degrees
in Mechanical Engineering and Law, and a Master’s
degree in Aeronautics & Astronautics from MIT.
Sour service testing of the thermoplastic lip
seals and chevron-stack seals at Element using a
bespoke test fixture that replicates the elastomer
sealing arrangement in the valve.
PR2 qualification at - 18°C (-0.4°F). (All images courtesy Enovate Systems)