Core Differences Between Vacuum Butterfly Valves and Common Butterfly Valves
In industrial pipeline systems, butterfly valves serve as essential shut-off and control devices, with various types developed to meet different operational requirements. Among them, vacuum butterfly valves and common butterfly valves exhibit significant differences in design principles, application scenarios, and performance parameters. A precise understanding of their technical characteristics is crucial for engineering selection.
1. Application Scenarios: Pressure Environment Determines Functional Positioning
1.1 Vacuum Butterfly Valves: Core Components for Negative Pressure Systems
Designed specifically for vacuum environments, vacuum butterfly valves are suitable for working conditions with pressures below atmospheric pressure (0.1MPa). They are widely used in semiconductor manufacturing, vacuum coating, pharmaceutical vacuum drying, aerospace simulated vacuum chambers, and other fields. These scenarios require the valve to operate stably under negative pressure to prevent external air from infiltrating the system and ensure the vacuum level is maintained. For example, in semiconductor wafer manufacturing, the cleanliness and pressure stability of the vacuum environment directly affect chip yield, making the precise control of vacuum butterfly valves a critical factor.
1.2 Common Butterfly Valves: Universal Choices for Atmospheric and Low-Pressure Systems
Common butterfly valves are mainly applied in pipeline systems under atmospheric pressure (0.1MPa) or low pressure (≤1.6MPa), covering water supply and drainage projects, HVAC systems, chemical material transportation, and other scenarios. Their design goal is to achieve medium on-off control and flow regulation in conventional pressure environments, such as the opening/closing control of urban tap water pipelines or flow regulation in central air conditioning cooling water systems. Since they do not need to handle negative pressure conditions, common butterfly valves are more suitable for daily life and general industrial applications.
2. Sealing Structure: Technical Upgrades from Basic Sealing to Vacuum-Grade Sealing
2.1 Vacuum Butterfly Valves: Multiple Sealing Designs to Ensure Airtightness
Vacuum butterfly valves adopt high-grade sealing solutions, commonly featuring double-eccentric or triple-eccentric designs to reduce leakage through precise fitting between the disc and seat. Their sealing materials often include PTFE, metal bellows, or rubber-clad metal sheets, which can withstand pressure fluctuations from -0.1MPa to positive 0.2MPa. Some high-end products are equipped with dual-sealing structures, setting independent sealing components at the disc and stem to ensure a leakage rate below 1×10⁻⁶ mbar·L/s under vacuum conditions, meeting the vacuum-grade sealing standard (GB/T 6070-2007 Vacuum Technology – Valves – Leak Rate Test Methods).
2.2 Common Butterfly Valves: Single-Eccentric or Midline Structures for Basic Sealing
Common butterfly valves mostly use midline (disc center coinciding with pipeline center) or single-eccentric designs, with relatively simple sealing structures that mainly rely on elastic materials like rubber or EPDM for sealing. Their sealing performance meets general industrial standards (e.g., leakage class specified in GB/T 13927-2008 Industrial Valves – Pressure Tests), but under negative pressure, the disc is prone to deformation or seal failure, leading to air backflow. For example, in the aeration pipelines of wastewater treatment plants, common butterfly valves’ sealing performance is sufficient for air transportation under atmospheric pressure but unsuitable for vacuum degassing processes.
3. Structural Design: Mechanical Optimization for Different Pressure Conditions
3.1 Vacuum Butterfly Valves: Reinforced Structures to Handle Negative Pressure Loads
Vacuum butterfly valves feature thickened valve bodies and stems, typically made of high-strength materials such as stainless steel (304/316) or aluminum alloy (LF21), with some 低温 (low-temperature) applications using titanium alloy or Hastelloy. The disc structure is mostly streamlined and solid to reduce deformation risks under negative pressure, while guide devices ensure precise disc positioning during opening/closing. For instance, in vacuum freeze-drying machines, valves need to withstand -0.09MPa pressure, and the reinforced valve body structure prevents deformation or jamming caused by internal-external pressure differences.
3.2 Common Butterfly Valves: Lightweight Design for Cost-Effectiveness
Common butterfly valves prioritize lightweight design and low cost, with valve bodies commonly made of cast iron (HT200), carbon steel (WCB), or ductile iron (QT400). The discs often use hollow or truss structures to reduce weight. Due to low working pressure, their support structures and connection methods (mostly flange connections) do not require special reinforcement. For example, a DN100 common butterfly valve is typically 30%-50% lighter than an equivalent vacuum butterfly valve. This design gives it a cost advantage in municipal engineering and other large-scale applications but limits its use in high-pressure or negative pressure environments.
4. Pressure Range: Technical Boundaries Between Positive and Negative Pressure Systems
| Performance Parameter | Vacuum Butterfly Valve | Common Butterfly Valve |
|---|---|---|
| Operating Pressure Range | -0.1MPa to +0.2MPa | 0 to +1.6MPa (conventional type) |
| Maximum Negative Pressure | -0.1MPa (absolute vacuum) | -0.02MPa (ultimate negative pressure) |
| Pressure Test Standard | GB/T 6072-2017 Vacuum Valves | GB/T 13927 Pressure Test Standard |
As shown in the table, vacuum butterfly valves cover the full vacuum range (absolute pressure 0 to 0.1MPa), while common butterfly valves have a maximum working negative pressure of only -0.02MPa (approximately 80kPa vacuum degree), beyond which seal failure may occur. This difference fundamentally stems from their design objectives: vacuum butterfly valves focus on “preventing external leakage” (stopping atmospheric air from entering the system), while common butterfly valves prioritize “preventing internal leakage” (stopping medium from leaking to the outside).
5. Material Selection: Upgrades from General Materials to Special Alloys
5.1 Vacuum Butterfly Valves: Priority on Low-Temperature and Corrosion-Resistant Materials
Vacuum systems often involve low-temperature environments (e.g., freeze-vacuum drying) or corrosive media (e.g., sputtering gases in vacuum coating), so vacuum butterfly valves typically use low-temperature-resistant stainless steel (304L, 316L), aluminum alloy (LF21), or non-metallic materials (PEEK). For example, in liquid oxygen vacuum pipelines, valves must use austenitic stainless steel with cryogenic treatment to ensure no embrittlement at -196℃. In sealing materials, besides conventional rubber, vacuum butterfly valves often use metal bellows seals (suitable for ultra-high vacuum scenarios) to avoid organic material volatilization contaminating the vacuum system.
5.2 Common Butterfly Valves: Economy-Driven Material Selection
Material selection for common butterfly valves is guided by cost-effectiveness, with valve bodies commonly made of cast iron or carbon steel, suitable for conventional media like water, air, and neutral gases. In corrosive environments, corrosion resistance is improved via epoxy coating or rubber lining, but the overall material grade is lower than that of vacuum butterfly valves. For example, cast iron common butterfly valves suffice for hot water transportation in urban heating networks without requiring high-cost stainless steel.
6. Functional Extensions: From Basic Control to Vacuum System-Specific Designs
6.1 Special Functions of Vacuum Butterfly Valves
- Anti-Static Design: In scenarios like vacuum coating, static electricity may generate from medium flow, so vacuum butterfly valves are equipped with conductive pathways to prevent static accumulation;
- Quick Opening/Closing: Some vacuum butterfly valves use pneumatic or electric actuators to achieve full closure within 0.5 seconds, meeting emergency vacuum protection requirements;
- Clean Surface Treatment: Internal walls undergo electropolishing (Ra≤0.8μm) to avoid particle residue and comply with ISO 14644-1 cleanroom standards.
6.2 Functional Features of Common Butterfly Valves
- Low Torque Operation: Midline structure with elastic sealing reduces manual operation torque by over 40% compared to vacuum butterfly valves;
- Flow Regulation: Linear flow control is achieved via disc angle adjustment (0°-90°), suitable for pipeline systems requiring dynamic control;
- Cost-Effectiveness: Manufacturing costs are only 1/3 to 1/2 of equivalent vacuum butterfly valves, making them suitable for large-scale pipeline projects.
7. Selection Guidelines: Operational Requirements Determine Technical Solutions
In practical engineering, valve selection should follow these principles:
- Priority on Pressure Parameters: First confirm whether the system is negative pressure (vacuum butterfly valve) or atmospheric/positive pressure (common butterfly valve). Vacuum butterfly valves are mandatory when the absolute negative pressure exceeds -0.02MPa;
- Medium Characteristics Analysis: For corrosive, low-temperature, or high-cleanliness vacuum environments, select stainless steel + bellows-sealed vacuum butterfly valves; for neutral media in atmospheric systems, cast iron common butterfly valves are preferable;
- Standards Compliance: Vacuum systems must adhere to GB/T 6070 vacuum valve standards, while general industrial systems follow GB/T 12238 general butterfly valve standards;
- Cost-Benefit Balance: Under suitable conditions, common butterfly valves offer significant economic advantages, while the high sealing and structural strength of vacuum butterfly valves are necessary investments for negative pressure scenarios.
Although vacuum butterfly valves and common butterfly valves belong to the same valve family, their differences in pressure environments and functional requirements have created a complete technical divide in structural design and material application. Correctly understanding their core distinctions in sealing performance, pressure range, and material selection is key to ensuring the safe and efficient operation of industrial pipeline systems. With the development of high-end manufacturing fields like semiconductors and new energy, the technical requirements for vacuum butterfly valves will continue to rise, while common butterfly valves will maintain stable demand in infrastructure construction. Engineers must combine specific working conditions to find the optimal balance between performance indicators and cost control, achieving scientific and precise valve selection.