1. Sealing structure and principle
Wedge gate valve
The gate sealing surface is wedge-shaped (at an angle with the center line of the gate), and the positive pressure of the wedge surface is increased by the thrust of the valve stem to achieve forced sealing, which is especially suitable for low-pressure media.
The elastic gate and double gate design can compensate for deformation caused by temperature changes and avoid jamming.
Parallel gate valve
The sealing surface is parallel to the center line of the gate. The single gate relies on the medium pressure to push the floating gate or valve seat to seal, and the double gate is sealed by the spring/opening mechanism.
The gate and the valve seat are always in close contact during the opening and closing process, and have bidirectional sealing capabilities.
2. Applicable scenarios
Wedge gate valve
High-pressure and high-temperature working conditions (such as the oil and gas industry), with typical pressure levels covering 150-2500 pounds.
The flow direction of the medium is not restricted, and the sealing reliability is required.
Parallel gate valve
It is mainly used for pipelines such as crude oil and natural gas, and the design with diversion holes facilitates pipe cleaning operations.
Suitable for low temperature and low pressure environment (≤120℃), and systems with high flow regulation requirements.
3. Performance characteristics comparison
Sealing strength
The wedge gate valve has more stable sealing performance under high pressure and better anti-scouring ability than the parallel type.
The parallel gate valve has poor sealing performance under low pressure environment and needs to rely on compensation mechanism to maintain a closed state.
Fluid resistance
The wedge gate valve flow channel is not designed with full diameter, and the fluid resistance is large.
The parallel gate valve has small flow resistance and is suitable for long-distance transmission pipelines.
Maintenance difficulty
The wedge gate plate has high machining accuracy requirements, especially the elastic gate plate needs to be regularly checked for deformation compensation ability.
The parallel gate valve has a simple structure and is easy to repair, but the double gate spring assembly is easily corroded by the medium and fails.
4. Structural characteristics Valve plate type
The wedge type is divided into three types: single gate plate, elastic gate plate, and double gate plate. The sealing effect is optimized by the wedge angle.
The parallel type is mostly a floating valve plate or a double gate plate structure with a spring.
External differences
Parallel gate valves have longer stem guards (with dust protection function), with a larger overall height but shorter structural length.
Wedge gate valve bodies are usually more compact and have no exposed guard design.
5. Typical design standards
Wedge gate valve: GB/T12234, API 600
Parallel gate valve: GB/T23300, API 6D
The structural differences between the two types of valves are due to different sealing principles and adaptability to working conditions. The actual selection requires a comprehensive evaluation based on the medium characteristics, system pressure and maintenance conditions.