Sleeved Plug Valve

The sleeved plug valve is commonly used in applications involving highly toxic, strongly corrosive, and high-hazard media where leakage is strictly prohibited and valve materials must not contaminate the process medium. It is widely applied in nitric acid service and also has important applications in acetic acid, acetic anhydride, metallurgy, and other chemical industries.

The sleeved plug valve features a compact, economical, and flexible flow-handling system, with lower manufacturing costs compared to ball valves and gate valves. It provides a large sealing surface to ensure reliable sealing performance during operation.

A key advantage of this design is its self-cleaning capability. When the plug rotates, a 360° sealing lip effectively scrapes away deposits, dirt, and sticky residues. This prevents fluid accumulation, reduces the risk of process contamination, and helps avoid clogging within the valve.

The sleeved plug valve adopts a double gland flange structure. The valve body and bonnet do not include welded flanges, and the wall thickness complies with ASME B16.34 standards. Increased safety and corrosion allowances are provided to ensure extended service life.

The valve uses an integral sleeve design, with the sleeve tightly fitted to the inner wall of the valve body. Sleeve materials can be selected from multiple options, such as PTFE and RPTFE. Body-to-bonnet sealing may include O-rings, lip seals, or gaskets. Stem sealing options include O-rings, lip seals, and low-leakage packing, making the valve suitable for a wide range of chemical applications.

• External Leakage Control: The static seal between the valve body and bonnet adopts a graphite gasket, or a combination of graphite gasket with O-ring or lip seal. A jacketed gasket combined with lip seal may also be selected depending on service conditions. The dynamic stem sealing system uses a low-torque, low-emission packing set. The design meets ISO 15848-1 fugitive emission requirements.
• Plug (Spool) Surface Treatment: Advanced machining equipment and mature processing technology are used to ensure plug coaxiality within 0.02 mm. The plug surface is further processed using precision cold extrusion technology to achieve surface roughness below Ra 0.2 μm. Quality inspection using coordinate measuring systems (CMM) ensures compliance with drawing requirements and guarantees zero-leakage sealing performance.
• Seat Sealing: The valve chamber adopts a multi-groove and flange structure to securely fix the sealing bushing, ensuring stable performance under special operating conditions and preventing simultaneous rotation of the sleeve and plug during operation. Sealing bushing materials are typically high-performance PTFE or filled PTFE, offering high strength, low friction coefficient, low operating torque, reliable sealing performance, and long service life.
• Flow Channel: The flow passage adopts either a Venturi or full-bore design. The smooth internal geometry eliminates dead zones, reducing the risk of crystallization and blockage of the medium.
• 360° Sealing Raised Lip: The 360° sealing raised lip effectively prevents or reduces leakage of flammable media, limiting fire propagation risk. It also reduces the effective sealing contact area, achieving low operating torque while maintaining reliable sealing performance. Additionally, the groove structure accommodates thermal expansion of the sleeve caused by temperature variations.
• Sleeve Design: The sleeve is manufactured using a multi-stage hot pressing and forming process to ensure tight bonding with the valve body. The sealing edge of the body is designed to lock the sleeve in place, preventing displacement caused by thermal expansion or contraction during operation. This results in smooth, stable, and low-torque valve operation.
• API 6FA Fire-Safe Design: All gaskets and packing materials strictly control graphite purity to reduce burn loss and ensure sealing integrity under high-temperature fire conditions.
• Fire-Safe and Antistatic Design: A spring-loaded grounding pin ensures electrical continuity between the plug, stem, and valve body, preventing static discharge during operation.
• Anti Blow-Out Stem: The lower end of the stem is designed with an integral shoulder to provide blow-out protection.
• Dynamic Stem Seal: Fluororubber (FKM) O-rings provide excellent resistance to strong acids and alkalis, and are compatible with over a thousand chemical media. They can operate continuously at temperatures up to 260°C and provide excellent anti-explosion and anti-tear performance. Conventional V-type or RPTFE packing systems are used for high-pressure sealing and self-energizing performance to prevent leakage. Low-emission packing is API 622 certified. Valves equipped with such packing can pass helium emission testing and meet ISO 15848 Class B requirements. Upper and lower metal wire reinforced packing prevents extrusion under high pressure conditions.
• Double Gland Flange Adjustment System: The lower gland flange incorporates butterfly spring-loaded packing, while the upper gland flange includes a spring-loaded plug mechanism. This double gland system allows independent online adjustment of both plug and packing seals, ensuring reliable sealing and reduced operating torque.
• Thrust Bearing Under Gland Flange: A thrust bearing is installed beneath the gland flange to reduce operating torque and improve overall operational smoothness.
• Automatic Compensation Sealing System: Disc springs installed on the packing and plug adjustment bolts provide automatic compensation for pressure and temperature variations in the pipeline system. This ensures continuous sealing integrity for both packing and plug interfaces.
• Fixed Plug Structure: The fixed plug design prevents displacement or extrusion of the seat insert under high temperature and high pressure conditions. The plug remains aligned along the central axis, effectively eliminating leakage caused by seat displacement in large-diameter applications.