Vacuum Flanges: Component Specs, Materials & Applications

Q: What is the difference between KF and ISO vacuum flanges?

KF (Quick Flange) flanges use a clamp and O-ring seal for quick assembly in small to medium sizes (up to DN 50), while ISO flanges use bolted connections with larger O-rings or metal gaskets for bigger systems (DN 63 to DN 500).

Q: How do you prevent leaks in vacuum flanges?

Ensure clean, undamaged sealing surfaces; use correct gasket material for the vacuum level and temperature; apply proper torque in a star pattern for bolted flanges; and perform leak testing with helium mass spectrometers.

Q: Can vacuum flanges be reused?

Metal gaskets (copper) are typically single-use, while elastomer O-rings can be reused if undamaged. Always inspect sealing surfaces and replace gaskets during maintenance to prevent leaks.

Component Specifications

Definition

Vacuum flanges are precision-engineered mechanical interfaces designed to connect vacuum chambers, pumps, valves, gauges, and other components while maintaining ultra-high vacuum (UHV) or high vacuum (HV) integrity. They feature precisely machined sealing surfaces, bolt patterns, and gasket grooves to prevent atmospheric leakage and contamination. In cold trap/condenser applications, they provide reliable connections between the trap body, inlet/outlet ports, and vacuum pumping systems.

Working Principle

Vacuum flanges create a hermetic seal by compressing a deformable gasket (such as elastomer O-rings, metal seals, or copper gaskets) between two precisely aligned flange faces using bolts or clamps. The compression force deforms the gasket to fill microscopic surface imperfections, preventing gas molecules from passing through. Different flange types (KF/QF, ISO, CF) use specific sealing mechanisms: elastomer O-rings for quick connections, metal gaskets with knife-edge seals for UHV applications, or copper gaskets with conflat designs for high-temperature environments.

Materials

Common materials include 304/316 stainless steel (for corrosion resistance and UHV compatibility), aluminum alloys (for lightweight applications), and occasionally brass or carbon steel. Sealing surfaces are often electropolished or precision-machined to Ra < 0.8 μm. Gasket materials vary: Viton or Buna-N elastomers for moderate vacuum, copper or aluminum for metal seals, and Helicoflex for combined metal-elastomer designs.

Technical Parameters

Parameter	Typical range	Notes & selection driver
Seal Type	Elastomer O-ring, Metal Gasket (Copper/Aluminum), Helicoflex
Size Range	DN 10 to DN 500 (or 1/2" to 20")
Flange Types	KF/QF (Quick Flange), ISO (Large Flange), CF (ConFlat)
Pressure Rating	10^-9 to 10^-3 mbar (UHV to rough vacuum)
Connection Method	Bolted, Clamped (KF), Screwed
Temperature Range	-20°C to 450°C (depending on gasket material)

Ranges are indicative industry figures for RFQ preparation, not a supplier commitment. Confirm every value and standard with the legal manufacturer before ordering.

Standards

ISO 1609, ISO 2861, DIN 28404, DIN 28403

Parent Products

This component is used in the following industrial products

Cold Trap/Condenser

A vacuum system component that condenses vapors and traps contaminants by cooling surfaces below their dew points.

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Engineering Analysis

Risks & Mitigation

Leakage due to improper installation
Gasket degradation at high temperatures
Corrosion in aggressive environments
Misalignment causing seal failure

FMEA Triads

Trigger: Insufficient bolt torque or uneven tightening
Failure: Leak development leading to loss of vacuum
Mitigation: Use torque wrenches and follow star-pattern tightening procedures; implement regular leak-check protocols

Trigger: Gasket material incompatible with process temperature or chemicals
Failure: Gasket degradation and catastrophic leak
Mitigation: Select gasket materials based on temperature range and chemical compatibility charts; use metal gaskets for extreme conditions

Trigger: Scratches or contamination on flange sealing surfaces
Failure: Micro-leaks that degrade vacuum performance
Mitigation: Implement clean handling procedures; use protective caps; polish or replace damaged flanges

Industrial Ecosystem

Compatible With

Typical Suppliers & Equivalents

Compliance & Inspection

Tolerance

Flatness within 0.05 mm per 100 mm, surface roughness Ra < 0.8 μm for metal seals

Test Method

Helium leak detection per ASTM E493, pressure decay testing, mass spectrometer leak detection

Procurement Evaluation Criteria

A practical evidence checklist for RFQ preparation and supplier evaluation.

Technical documentation

Request current drawings, revision history, and a signed specification sheet.

Manufacturing capability

Verify equipment lists, process limits, capacity, and representative production evidence.

Inspection readiness

Confirm test methods, calibrated equipment, sampling plans, and traceable reports.

Supplier transparency

Check the legal entity, factory address, ownership, certifications, and direct contacts.

CNFX does not score or rank suppliers. Buyers must verify all claims and documents with the legal manufacturer before ordering.

Manufacturers of Vacuum Flanges

1 company lists this product among what they make. Company figures are quoted from each company's own website; every card states where the relationship came from.

China Sanitary Valve

Zhejiang, CN

Founded 200251~100 staff5,000-10,000 square meters

ISO9001 ASME CE Test Report

Also makes: Sanitary Pressure Relief Valve, Sanitary Centrifugal Pump, Dairy Flow Control Diaphragm Valve and 9 more

Listed on the company's own website · profile compiled by CNFX from public sources

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Manufacturer listings support early research and capability understanding. They are not certification, ranking, or transaction guarantees.

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Frequently Asked Questions

What is the difference between KF and ISO vacuum flanges?