The metal seat plug valve is a type of plug valve that uses metal materials as a sealing pair. Its core feature is that the seal is achieved through direct contact between the finely machined metal plug body and the valve body. This valve is mainly used in fluid control systems. It is opened and closed or adjusts the flow of the medium by rotating 90 degrees. It is suitable for occasions that require wear resistance or high temperature resistance but low sealing requirements. The following is a detailed explanation from the aspects of principle, characteristics, type and application.
- Working principle
The working principle of the metal seat plug valve is based on the plug body (usually cylindrical or conical) rotating with the valve stem. When the plug body channel port is aligned with the valve body channel port, the fluid passes through, and when it is misaligned, the fluid is blocked. Its sealing depends on the precise matching of the metal sealing surface: through low surface roughness (such as small Ra value) and accurate geometric tolerance, a sealing pressure is formed under pressure to prevent leakage. The operating torque is mainly derived from the metal contact friction, not the fluid pressure.
- Main features
The design of metal seat plug valve emphasizes durability, but there are specific advantages and disadvantages:
Advantages:
Simple and compact structure, fast opening and closing, and low fluid resistance, suitable for frequent operation occasions.
The metal sealing pair is resistant to high temperature and erosion, and is suitable for working conditions with suspended particles or crystalline media.
No dependence on soft materials, relatively simple maintenance, such as the tight-fitting type can adjust the seal by tightening the nut.
Disadvantages:
Poor sealing, easy to leak due to wear, usually limited to low pressure (≤1 MPa) and small diameter (≤100 mm) systems.
The opening and closing torque is large, requiring a large operating force; long-term use may require the addition of sealing grease or regular grinding and repair of the sealing surface.
- Common types
Based on structural differences, metal seat plug valves are mainly divided into two categories:
Tight-fitting plug valve: The valve body and the plug body are both metal, and the sealing is achieved by applying a pre-tightening force to the bottom nut, without packing; suitable for food or pharmaceutical industries, easy to disassemble and repair.
Packed conical plug valve: Add packing (such as graphite or metal fiber) between the valve body and the plug body to enhance the seal by compressing the packing; suitable for medium pressure (about 1.0 MPa), but the sealing load is limited, and sealing grease needs to be applied to reduce friction.
- Applications
Metal seat plug valves are often used in low-pressure industrial environments, such as:
Petrochemical industry, control the cut-off and diversion of particle-containing fluids (such as mud or crystallizing media).
Food or pharmaceutical industry, because austenitic stainless steel meets hygiene standards.
General industrial systems, as an alternative to shut-off valves, but high-pressure or high-precision sealing requirements need to be avoided.
In short, metal seat plug valves are based on metal sealing pairs and are suitable for low-pressure, small-caliber and wear-resistant working conditions, but their sealing limitations and maintenance requirements should be weighed when choosing.
