The gate valve in oil and gas is a valve that realizes full open/full closed control of fluid by vertical lifting of the gate. Its core function is to cut off or restore the flow of pipeline media. Combining industry characteristics and technical specifications, its key features are as follows:
1. Core functions and definitions
Full open/full closed control
The gate valve is completely sealed by the fit between the gate and the valve seat. It is only used to cut off or allow the flow of media and cannot adjust the flow.
Low flow resistance characteristics
The full-diameter structure and straight-through flow channel design make the fluid resistance close to that of a straight pipe, reducing the pumping energy consumption of high-pressure long-distance pipelines (such as oil and gas trunk lines).
2. Typical structures and classifications
- Design by valve stem
Rising stem gate valve: The valve stem is exposed, and the lifting and lowering are visible. It is suitable for scenarios that require frequent manual operation or opening monitoring (such as wellhead devices);
Non-rising stem gate valve: The valve stem is built-in, with a compact structure, suitable for high-pressure, large-flow and space-constrained industrial pipelines.
- By gate form
Parallel gate valve: The double gates are parallel and fitted, and the sealing surface can be self-compensated by the medium pressure after wear. It is suitable for crude oil pipelines containing impurities or particles;
Wedge gate valve: The single gate is wedge-shaped, relying on mechanical force to force sealing, and its high-pressure resistance is better than the parallel type. It is used in natural gas high-pressure gathering and transportation systems.
3. Industry application scenarios
Oil and gas production and processing
Control the flow of oil/gas into the Christmas tree in the wellhead device (such as the anti-leakage wellhead gate valve described in the patent, which prolongs its life by alternating double seals);
In fracturing operations, the lifting and releasing two-stage oil pipe switching valve is used to achieve pressure transfer to prevent sand jam or pressure loss.
Long-distance pipeline system
The main line cut-off valve chamber is equipped with a rising stem gate valve, which cooperates with the SCADA system to achieve remote emergency cutoff;
The pig sending and receiving station uses a full-bore gate valve to ensure that the pig passes unimpeded and isolates the operating section.
Storage and Terminal
LNG receiving stations use low-temperature gate valves to control the transportation of -162℃ liquefied natural gas;
Refinery atmospheric pressure reduction units use high-temperature resistant gate valves to isolate heavy oil pipelines.
4. Technical Standards and Performance Requirements
Sealing Reliability
API 6D standard requires that the leakage rate of metal-sealed gate valves under high pressure (such as Class 1500) is ≤100 ppm, and elastic-sealed gate valves must pass API 607 fire test.
Corrosion and Wear Resistance
WCC, F51 and other materials are selected for sulfur-containing oil and gas environments, and the valve seat is welded with Stellite alloy or tungsten carbide coating to resist H₂S corrosion and sand erosion.
Operational Safety
According to GB/T 19672, large-diameter gate valves must be equipped with gearboxes or pneumatic actuators, and the opening and closing torque is ≤250 N·m (DN300 working conditions).
5. Technical Advantages and Limitations
| Advantages | Limitaion |
|---|---|
| When fully open, the flow resistance approaches zero | The opening and closing time is long, not suitable for frequent operation |
| Bidirectional sealing without flow restriction | High temperature can easily cause thermal jamming of the gate and valve seat |
| Low maintenance cost | Large-diameter valves are bulky and limited in installation |