Inside the BOP-Kelly check valve, a constant-open type blowout protection device used in drilling tools, it automatically closes when a kick occurs to prevent underground fluids from surging up through the water hole in the drill column. During well control operations, if the hose or high-pressure manifold is damaged, the valve can be safely replaced while remaining closed. The upper check uses a left-hand thread, while the lower part uses a right-hand thread, and both have identical ball valve structures.
**Application**
The rated working pressure of the Kelly check valve must match that of the BOP. The internal diameter (ID) of the check valve should be larger than or equal to the ID of the Kelly rod. Maximum working pressure and test pressure should be conducted according to the requirements listed in the table below. A sealing test is considered qualified if no leakage occurs after holding pressure for 3 minutes. The operating temperature range for the check valve is up to 82°C, and the check wrench must remain in an available and usable position.
**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 its mechanical properties after heat treatment meet the requirements of API Spec 7. The valve seat and ball body are constructed from heat-resistant stainless steel, providing excellent wear and corrosion resistance.
The valve operates as a single-direction seal. When closed, the ball body moves quickly toward the back-seat due to the combined effect of well fluid pressure and pre-load spring pressure, creating a tight seal. To enhance performance, a PTFE non-metallic ring is added to the back-seat sealing face, reducing contact pressure between the ball and seat for improved reliability.
The surface of the valve body is clearly marked with visible indicators showing whether the valve is in the "open" or "closed" position, making it easy to identify the status of the check valve at a glance.
**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 ensures reliable performance under harsh drilling conditions, making the BOP-Kelly check valve a critical component in maintaining well control and safety.
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