Inside BOP-Kelly check valve is a constant-open type blowout prevention device used in drilling tools. It automatically closes when a kick occurs, preventing underground fluids from surging up through the water hole in the drill string. During well control operations, if the hose or high-pressure manifold is damaged, it can be safely replaced while the valve remains closed.
The upper check valve uses a left-hand thread, while the lower one uses a right-hand thread. Despite this difference, both have identical ball valve structures, ensuring consistent performance and reliability.
**Application**
The Kelly check valve must have a rated working pressure that matches the BOP's rated pressure. Its internal diameter (ID) should be equal to or larger than the Kelly rod’s ID. The maximum working pressure and test pressure must be conducted according to the specifications listed in the table below. A sealing test is considered qualified if there is no leakage after holding pressure for 3 minutes. The operating temperature range for the check valve is up to 82°C, and the check wrench should remain in an available or usable position at all times.
**Features**
The upper check valve consists of several key components, including the valve body, upper/lower seats, ball body, rotary block, retainer, spring, and non-metallic seals. The valve body is made from ASTM 4140 forging, and after heat treatment, its mechanical properties meet the requirements of API Spec 7.
The valve seat and ball body are constructed from heat-resistant stainless steel, offering excellent resistance to abrasion and corrosion. This ensures long-lasting performance even under harsh conditions.
The valve provides a single-direction seal. When closed, the ball body quickly moves toward the back-seat due to the combined effect of well pressure and pre-load spring force, creating a tight seal. To enhance sealing performance, a PTFE non-metallic ring is added to the back-seat, reducing the contact pressure between the ball and the seat. This design improves the overall reliability of the valve.
Additionally, the surface of the valve body is stamped with visible indicators showing “open†or “close,†allowing users to easily identify the current status of the check valve.
**Parts List**
| Item | Component | Qty | Material |
|------|-----------------|-----|------------|
| 1 | Handle | 1 | 1045 |
| 2 | Rotary Block | 1 | 4130 |
| 3 | O-Ring | 1 | NBR |
| 4 | Body | 1 | 4130 |
| 5 | Spring | 8 | 1566 |
| 6 | Lower Seat | 1 | 410 |
| 7 | Ball | 1 | 410 |
| 8 | Lower Retainer | 1 | 410 |
| 9 | O-Ring | 1 | NBR |
| 10 | Upper Seat | 1 | 410 |
| 11 | Upper Retainer | 1 | 4130 |
| 12 | Retainer | 1 | 410 |
| 13 | Circlip | 1 | 1566 |
This detailed design and construction ensure that the Inside BOP-Kelly check valve performs reliably in critical drilling operations, providing essential protection against uncontrolled fluid flow.
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