1. Definition and core concept of DIB ball valve
DIB Ball Valve (Double Isolation and Bleed Ball Valve), i.e. Double Isolation with Bleed Ball Valve, is a special fixed ball valve for high safety fluid control. It achieves media isolation through double sealing vice in the closed state, and is equipped with a relief mechanism to release the pressure in the valve chamber to prevent accidents caused by abnormal pressure rise.
2. Core structure and working principle
Basic structure
Fixed ball design: the ball is rigidly supported by trunnions to ensure stable rotation under high pressure (different from floating ball valves);
Seat Configuration: Contains two independent sealing pairs (upstream and downstream seats), which achieve sealing through pressure excitation;
Drain port: the valve cavity is equipped with a drain valve for discharging any trapped medium or pressure between the two sealing pairs.
Working process
Closed state: the double sealing pair blocks the medium flow at the same time, and the upstream and downstream pressures are isolated independently;
Bleed operation: the pressure in the valve chamber is discharged through the bleed valve, allowing for testing of seal integrity or maintenance.
3. Main types and differences
| Type | Seat Configuration | Key Features |
|---|---|---|
| DIB-1 | One unidirectional sealing seat (SPE) + one bidirectional sealing seat (DPE) | - SPE seats seal in one direction only (dependent on media pressure); - DPE seats seal in both directions (independent of pressure direction); |
| DIB-2 | Two bi-directional sealing seats (DPE) | - Bi-directional independent sealing for greater safety; - SPE valve seat must be installed in the upstream, the middle chamber overpressure automatic pressure relief to the upstream |
4. Typical application scenarios
Hazardous media transport: cut-off of flammable, explosive or toxic fluids (e.g. LNG) in oil and gas pipelines to prevent leakage and contamination;
High-pressure system maintenance: offshore gas field pipe cleaner sender and receiver for triple seal isolation during maintenance;
Severe working conditions: handling high temperature and high pressure fluids in chemical plants, replacing traditional DBB ball valves to enhance safety.
5. Key strengths and limitations
Core Advantages
Ultra-high sealing: double isolation design to achieve zero leakage (leakage rate ≤ 10-⁶ m³/s), far more than single-sealed valves;
Safe pressure relief: automatic discharge when the middle chamber is overpressure (e.g. DIB-2 pressure relief to upstream), avoiding explosion or environmental pollution;
Convenient maintenance: online relief function supports sealing detection, reducing downtime.
Usage limitations
Installation direction sensitive: DIB-2 must ensure that the SPE valve seat is located upstream, otherwise the pressure relief will not be effective;
Higher cost: complex structure and higher price than standard ball or DBB valves.
