Subsea Choke
As a core component of the subsea Christmas tree, the subsea choke is installed in the production bore of the subsea Christmas tree and is used to control and regulate subsea wellhead pressure and flow rate. It is designed with retrievability, with all wear-prone or failure-prone parts integrated into a retrievable insert assembly. A dedicated running and retrieval tool is provided to facilitate retrieval and reinstallation of the replaceable insert assembly. All choking functions can be remotely controlled through a multiplex electro-hydraulic subsea control system, and the choke is also equipped with ROV override operation capability.
Structural Features
▶ The choke trim adopts a multi-hole cage and plunger design, providing a near-equal-percentage flow characteristic. Designs with different flow coefficients (Cv) can be provided according to actual operating conditions;▶ The choke stem is provided with pressure balance holes to reduce the operating force required during opening and closing of the stem and actuator;
▶ A straight-bore U-shaped metal seal is used between the insert assembly and the body. This metal seal can withstand reverse test pressure of up to 5000 psi after retrieval and redeployment;
▶ A relief valve is arranged at the intermediate position between the choke and the actuator to prevent excessive actuator pressure in the event of stem seal leakage;
▶ The choke body and the insert assembly are connected by a two-stage clamp-type connector. The clamp-type connector adopts a bidirectional helical screw mechanism and provides visual indication of locked/unlocked status;
▶ The step-type hydraulic actuator can increase the choke valve by one incremental step through a single pulse operation, or by a predetermined number of incremental steps through a series of separate pulse operations;
▶ The actuator is also equipped with a mechanical override mechanism, independent of the hydraulic step-type main operating mechanism, and capable of operating the choke valve in either direction. Mechanical failure of the main operating mechanism does not prevent operation of the mechanical override mechanism;
▶ The choke trim position is remotely indicated by a position monitoring system. A linear variable differential transformer (LVDT) provides a 4–20 mA position signal interfacing with the subsea electronic control system in the subsea control module, and the linear displacement accuracy of the LVDT reaches ±0.2 mm;
▶ An external visual position indicator is arranged at the top of the actuator. This indicator is clearly visible to the ROV and is provided with a fixed linear scale.
Note: Other models can be custom designed.
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Keywords
- Product Introduction
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Choke Valve Technical Parameters
Category Technical Parameters Nominal size 4 1/16 in (103.2 mm) Rated working pressure 10,000 psi (69.0 MPa) Temperature level PU (-29℃～+121℃) Product specification level PSL3G Material grade HH Performance requirement level PR2F Trim style Plug and Multi-Hole Cage Leakage class ANSI/FC 70-02 CLASS IV Maximum Cv 20 Drive method Stepper hydraulic drive and ROV override Clamp connector ROV interface API RP 17H Standard Class 4 Interface Rated water depth 1500 meters Inlet connection API 6A 4 1/16″-10000psi 6BX BX155 Outlet connection API 6A 4 1/16″-10000psi 6BX BX155 Actuator Technical Parameters
Category Technical Parameters Hydraulic drive rated working pressure 5000 psi (34.5 MPa) Temperature range -5℃ to +66℃ Performance Rrequirement Level PR2F ROV Manual override drive interface API RP 17H Standard Class 4 Interface Number of turns for ROV manual override switch 9 Stepper hydraulic drive step count 90 Cleanliness Level NAS 1638 LEVEL 6 LVDT position sensing 4-20mA Retrieval style ROV-assisted recoverable Pressure compensator type Bladder Rated water depth 1500 meters
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