Vacuum Isolation Valve | Zero Leakage | DN10–DN100

The Vacuum Isolation Valve separates vacuum systems from atmospheric pressure or other sections, preventing air infiltration and maintaining vacuum integrity. Cast-forged with parallel dual-seal semi-forced bidirectional sealing achieves zero leakage via positioning and wedge quick-wedging. The bonnet packing chamber has a vacuum seal with self-expanding/compressing effect; all joints use high-strength expansion materials for complete atmospheric isolation. Alloy/carbide seats have low friction and automatic wear compensation for light operation and 10+ year life. Flange/welded, manual/electric, 25#/WCB/Cr-Mo, DN10–DN100, ≤425/550°C, water/steam/air. Per GB/T12234/12235/12221, JB/T78-79, GB/T9112-9124 - indispensable for power condensers, semiconductor chambers, chemical vacuum distillation, research.

1. Zero-Leakage Vacuum Sealing: Equipped with a dedicated vacuum sealing structure in the valve cover packing chamber, featuring expanded graphite packing with a self-expanding and compressing effect - under vacuum negative pressure, the atmospheric pressure differential actively compresses the packing tighter against the valve stem, enhancing rather than degrading the stem seal. All body-bonnet joint surfaces are sealed with high-strength expansion materials (expanded graphite or metal-reinforced gaskets) to completely isolate the vacuum system from the atmosphere, achieving excellent airtightness and zero leakage performance, effectively protecting the vacuum environment from air infiltration and contamination that would degrade vacuum level and process quality.

2. Durable & Wear-Resistant Construction: The main body adopts a high-quality casting and forging (cast-forged) composite structure, providing strong structural stability, pressure resistance, and a long service life of up to 10 years or more. The parallel dual-seal design ensures that the sealing surfaces have very small movement friction force during the positioning stroke, enabling light and smooth opening and closing. An automatic wear compensation mechanism maintains consistent sealing force as the sealing surfaces wear over time, reducing maintenance frequency, extending service intervals, and lowering the total cost of ownership over the valve's lifecycle.

3. Flexible Configuration & Customization: Available in two connection forms - flange (per JB/T78-79 and GB/T9112-9124 standards) and welding (butt weld) - and two drive modes - manual (handwheel) and electric (with local/remote control) - suitable for different pipeline sizes, installation scenarios, and operational automation needs. It can be fully customized according to specific working conditions, including high-temperature resistance configurations (up to 550°C), corrosion-resistant material options, special flange standards (ANSI, DIN, JIS), and larger nominal diameters beyond the standard DN10–DN100 range.

4. Easy Installation & Maintenance: The overall structure is simple and compact with a rational design that facilitates on-site installation, disassembly, and reassembly. Routine maintenance only requires simple visual inspection, periodic operation (valve exercising), and replacement of wearing parts (packing, gaskets) - no specialized tools or complex procedures are needed. This minimizes equipment downtime and reduces operational and maintenance costs for vacuum systems, which are particularly sensitive to unplanned shutdowns that could break vacuum and ruin production batches.

5. Wide Temperature & Media Adaptability: Suitable for working temperatures up to 425°C (standard model) or 550°C (high-temperature model, depending on configuration and material selection), compatible with working media such as water, steam, and air. It can adapt to harsh working environments combining high temperature and vacuum negative pressure, such as power plant condenser systems and high-temperature vacuum process lines. Cr-Mo steel body options are available for the most demanding high-temperature applications, while WCB and 25# carbon steel cover standard and moderate-temperature vacuum service.

6. Compliance with International & National Standards: Manufacture and acceptance technical conditions comply with GB/T12234 (steel gate valves) and GB/T12235 (steel globe valves), valve structural length complies with GB/T12221, and flange dimensions comply with JB/T78-79 and GB/T9112-9124. These standards ensure dimensional interchangeability, pressure-temperature rating consistency, and quality compatibility with global industrial equipment, facilitating easy integration into existing vacuum systems and new construction projects worldwide.

The Vacuum Isolation Valve operates on parallel dual-seal semi-forced bidirectional sealing for vacuum service. Stem drives gate in two stages: surfaces position, then wedge semi-forces dual seal for bidirectional sealing. This minimizes friction, ensuring sealing under vacuum. Bonnet uses expanded graphite that self-compresses under vacuum, enhancing stem seal. Joints use expansion materials to isolate vacuum from atmosphere. Alloy/carbide seats resist wear, auto-compensating. Open, disc retracts for flow; closed, bidirectional seal holds vacuum. For on-off isolation only.

Power Plants: Particularly suitable for steam turbine condenser systems and vacuum negative pressure pipelines in thermal power plants, playing a critical role in vacuum isolation and sealing to maintain the condenser vacuum level (typically 5–20 kPa absolute) that directly affects turbine efficiency and power generation output. The zero-leakage bidirectional seal prevents air infiltration into the condenser, which would reduce vacuum, increase turbine backpressure, and decrease plant thermal efficiency - ensuring stable and efficient operation of power generation equipment.

Semiconductor & Electronics: Used in vacuum chambers, thin-film coating (PVD/CVD) systems, etching equipment, and semiconductor manufacturing processes to maintain a clean, high-vacuum environment and prevent air contamination that would ruin wafer quality and device yield. The low-outgassing construction and zero-leakage sealing ensure that process vacuum levels (often 10⁻³ to 10⁻⁷ Pa) are maintained during chamber isolation, while the compact design fits cleanroom equipment layouts.

Chemical & Pharmaceutical Industry: Suitable for vacuum distillation, vacuum drying, vacuum filtration, and vacuum reaction processes in petrochemical plants, fine chemical facilities, and pharmaceutical factories, isolating corrosive or sensitive media and ensuring the safety, stability, and product quality of vacuum production processes. Corrosion-resistant configurations (stainless steel or special alloy internals) are available for harsh chemical environments, and the zero-leakage design prevents both air ingress and product egress.

Scientific Research: Applied in laboratory vacuum systems, particle accelerators, vacuum testing equipment, space simulation chambers, and materials research vacuum furnaces, providing reliable vacuum isolation for scientific experiments and research work where vacuum integrity is critical to experimental accuracy and reproducibility. The precise sealing and low-friction operation make it suitable for research environments requiring dependable vacuum control over long test durations.

Other Industries: Also used in food and beverage vacuum packaging lines, vacuum metallurgy (vacuum induction melting, vacuum degassing), vacuum heat treatment, vacuum impregnation, and other industrial fields, meeting the diverse vacuum isolation needs of different industries. The valve's robust construction and wide temperature range make it adaptable to both clean vacuum processes and industrial vacuum environments with particulates or high temperatures.

Every Vacuum Isolation Valve is manufactured and tested per GB/T12234/12235/12221, JB/T78-79, ISO 9001. Raw materials MTR-verified by heat number for all body materials. Castings/forgings 100% RT/UT inspected. Stem heat-treated, hardness verified. Seat overlay 100% inspected, hardness/PT verified. Graphite packing verified for compression. Dual-seal assembly verified for movement. Valves get dimensional check, shell/seat pressure tests, plus dedicated helium vacuum leak test for zero air infiltration. Joint seals verified. Electric actuators tested. Units ship with serialized MTR, test certs, 18-month warranty, BV/SGS third-party on request.

Q1: What is a vacuum isolation valve and how does it differ from a standard gate valve?

A: A vacuum isolation valve is a specialized valve designed specifically to separate (isolate) a vacuum system from atmospheric pressure or from another section of piping, preventing air infiltration into the vacuum side and maintaining the integrity of the vacuum environment. While it may look similar to a standard gate valve externally, it differs in several critical design aspects: (1) Vacuum-optimized sealing - the bonnet packing chamber incorporates a dedicated vacuum sealing structure with expanded graphite packing that has a self-expanding and compressing effect. Under vacuum, the pressure differential (atmosphere pushing inward) actually compresses the packing tighter against the stem, enhancing the seal - whereas a standard valve's packing relies on gland compression alone and can leak air inward under vacuum. (2) Parallel dual-seal semi-forced bidirectional sealing - the gate uses a two-stage "position then wedge" motion that minimizes sealing surface friction during travel and then applies wedging force to create a tight bidirectional metal-to-metal seal, ensuring zero leakage in both directions (critical because vacuum can be on either side of the valve). (3) High-strength expansion joint seals - all body-bonnet and flange joints use expansion materials (expanded graphite or metal-reinforced gaskets) specifically selected for vacuum-tightness, rather than standard compressed fiber gaskets that can leak under vacuum. (4) Automatic wear compensation - the sealing mechanism compensates for wear to maintain vacuum-tightness over a long service life. A standard gate valve is designed for positive-pressure fluid isolation and will typically leak air inward when used on vacuum service, making it unsuitable for vacuum isolation duty.

Q2: What vacuum level can it achieve and how is zero leakage verified?

A: Our vacuum isolation valves are designed to maintain high vacuum integrity when properly installed and maintained, suitable for rough vacuum (atmospheric to ~1 Pa), medium vacuum (~1 Pa to 10⁻³ Pa), and in clean, properly configured systems can support high vacuum (down to ~10⁻⁵ Pa or better) - the ultimate achievable vacuum depends on the entire system's pump capacity, total leak rate, outgassing rates, and installation quality, not solely the valve. The valve itself is verified for zero leakage through several tests: (1) Hydrostatic shell test at 6.0–15.0 MPa (depending on model) verifies pressure-containing integrity. (2) Seat seal test at 4.4–11.0 MPa verifies bidirectional seating tightness under positive pressure. (3) Dedicated vacuum leak test - the most critical quality check for this valve type - performed using either helium mass spectrometry (helium leak detector, capable of detecting leak rates as low as 1×10⁻⁹ Pa·m³/s or better) or a bubble/immersion test under vacuum, to verify zero air infiltration across the seat, stem packing, and all joints when the valve is under vacuum negative pressure. (4) Each valve is serialized and ships with a vacuum test report. For critical high-vacuum applications (semiconductor, research), we recommend specifying helium mass spectrometry leak testing with a documented maximum leak rate (e.g., ≤1×10⁻⁶ Pa·m³/s) and selecting polished internal surfaces and low-outgassing materials to minimize virtual leaks and outgassing.

Q3: What are the differences between the NKJ61, NKZ44, and NKZ64 types?

A: We offer three primary vacuum isolation valve configurations, differing in valve type and connection/drive:

NKJ61 - Vacuum Isolating Stop Valve (Globe Valve Pattern): This is a globe/stop valve pattern (not a gate valve), where the disc moves perpendicular to the seat face in a linear motion to seal against a single seat. It provides excellent throttling capability (though vacuum isolation valves are generally used for on-off service) and very tight shutoff. The "61" designation typically indicates welded (butt-weld) connection with manual drive. It is preferred for smaller sizes (DN10–DN50) and applications requiring exceptionally tight shutoff or some flow regulation capability.

NKZ44 - Vacuum Isolating Gate Valve, Flanged Connection: This is a gate valve pattern with the parallel dual-seal semi-forced bidirectional sealing described above, with flange end connections (per JB/T78-79 / GB/T9112-9124) and manual handwheel drive. The "44" designation indicates flanged ends with manual drive. It is the most common configuration for general vacuum isolation service in sizes DN50–DN100+, offering unobstructed straight-through flow when open and bidirectional zero-leakage sealing when closed.

NKZ64 - Vacuum Isolating Gate Valve, Welded Connection: Same gate valve pattern and sealing technology as NKZ44, but with butt-weld end connections and electric drive (or manual depending on specific sub-model). The "64" designation indicates welded ends with electric drive. Welded connections provide the highest level of vacuum integrity (no flange gasket leak path) and are preferred for permanent high-vacuum installations, while electric drive enables remote/automated control. In summary: NKJ61 = globe/stop valve pattern (tightest shutoff, smaller sizes); NKZ44 = gate valve, flanged, manual; NKZ64 = gate valve, welded, electric. All use the same vacuum sealing technology and are suitable for vacuum isolation service. Selection depends on required size, connection type, drive method, and whether a gate or globe flow pattern is preferred.

Q4: Can it be used for high-temperature vacuum service, and what materials are available?

A: Yes - our vacuum isolation valves are available in configurations suitable for high-temperature vacuum service, with two standard temperature ratings:

Standard model: ≤425°C - with 25# (carbon steel) or WCB (cast carbon steel) body, suitable for general vacuum service, condenser systems, and moderate-temperature vacuum processes up to 425°C.

High-temperature model: ≤550°C - with Cr-Mo (chromium-molybdenum) steel body and high-temperature internal components, suitable for high-temperature vacuum processes such as vacuum heat treatment, vacuum metallurgy, and high-temperature vacuum reactors up to 550°C. Available body materials include:

25# - Chinese grade carbon steel (forged), for general low/medium-temperature vacuum service.

WCB - ASTM A216 WCB cast carbon steel, the most common general-purpose material for vacuum valves up to 425°C.

Cr-Mo Steel - chromium-molybdenum alloy steel (e.g., WC6/WC9/F11/F22 equivalents), for high-temperature vacuum service up to 550°C, providing creep resistance and high-temperature strength. Sealing surface materials include Alloy Steel (H) - typically Stellite/CoCr or similar hardfacing - and Carbide (Y) - tungsten carbide or similar, both providing wear resistance and hard sealing for vacuum service. Valve stem materials include Cr stainless steel, 25Cr2MoV, and 12Cr1Mo1VA (high-temperature Cr-Mo-V steels). Packing is expanded graphite (suitable for high temperatures and vacuum). For temperatures above 550°C, or for corrosive vacuum media (acids, alkalis, reactive gases), we can customize with stainless steel (CF8/CF8M/304/316), duplex stainless, or special alloy (Hastelloy, Inconel) construction - please provide your specific temperature, pressure, and medium conditions for proper material recommendation. Note that at high temperatures, the bonnet/packing area may require an extended bonnet or cooling fin configuration to protect the graphite packing from excessive heat.

Q5: What maintenance does a vacuum isolation valve require?

A: Vacuum isolation valves are designed for long service life (10+ years) with minimal maintenance, but proper care is essential to maintain vacuum integrity - especially because even a tiny leak can significantly degrade system vacuum level. Recommended maintenance includes:

Periodic valve exercising: For valves in static (normally open or normally closed) service, operate the valve through a full open-close cycle at least once every 3–6 months. This prevents stem seizure, redistributes packing, clears seating surfaces of debris, and verifies free operation. For critical systems, schedule exercising during planned maintenance outages.

Packing inspection and adjustment: Monitor the stem packing area for any signs of air leakage (detected by vacuum gauge fluctuation or helium leak check). If leakage is detected, the packing gland can be gently re-torqued (follow manufacturer's torque procedure, typically in small increments) to restore compression. Expanded graphite packing has a long service life but may need replacement after 5–10 years or after significant thermal cycling. When replacing packing, use only vacuum-grade expanded graphite packing (not standard PTFE or fiber packing).

Seat and sealing surface inspection: During major overhauls (typically every 5–10 years, or as determined by vacuum performance monitoring), inspect the alloy/carbide sealing surfaces for wear, scoring, or corrosion. The automatic wear compensation mechanism extends the interval between seat maintenance, but surfaces may need re-lapping or re-hardfacing if damaged.

Joint and gasket inspection: Check flange and body-bonnet joint gaskets for signs of leakage during vacuum leak testing. Expansion graphite gaskets are reusable in many cases but should be replaced if damaged or if the joint has been disassembled.

Actuator maintenance: Electric actuators require periodic inspection of wiring, motor, gearbox lubrication, and limit switch calibration per the actuator manufacturer's manual. Manual handwheel valves require only occasional lubrication of the stem threads.

Vacuum leak testing: After any maintenance or disassembly, perform a vacuum leak test (helium mass spectrometry or bubble test) to verify zero leakage before returning the valve to service.

Storage: Spare valves should be stored in a clean, dry environment with flange protectors in place to prevent contamination of sealing surfaces. Always follow the plant's mechanical integrity program and the manufacturer's O&M manual for specific maintenance intervals and procedures.

Hot Tags: Vacuum Isolation Valve | Zero Leakage | DN10–DN100, China Vacuum Isolation Valve | Zero Leakage | DN10–DN100 manufacturers, suppliers, factory, seal gate, 50 mm gate valve, 28mm gate valve, gate valve dn80, handwheel gate valve, gate valve dn25