The A21H/Y Type Safety Valve is a typicalspring-loaded, micro-lift, closed-type safety valvewidely used in medium- and low-pressure industrial systems. As a refined version within the A21 series, the A21H/Y combinesmetal sealing (H type)with optimized structural reliability, making it suitable for non-corrosive gases and liquids under stable operating conditions.
This valve is designed forpressure protection in pipelines and pressure vessels, automatically releasing excess pressure when system limits are exceeded and resealing once normal conditions are restored.
Compared with other models such as A28 series, the A21H/Y adopts alow-lift structure, which means it opens proportionally rather than fully, allowing for more controlled pressure relief. This makes it especially suitable for systems requiringprecision protection and minimal medium loss.
Typical specifications include:
Nominal size:DN15–DN50
Pressure rating:PN16–PN40 (or higher depending on design)
Applicable temperature:≤200°C
Applicable media:Air, ammonia, petroleum gas, water, and other non-corrosive fluids
The A21H/Y safety valve operates on adirect spring-loaded mechanism, similar to most conventional safety valves, but with amicro-opening (low lift) characteristicthat distinguishes it from full-lift designs.
Under normal operating pressure, the valve disc is tightly pressed against the seat by spring force. When system pressure exceeds the preset value:
The spring force is overcome
The valve disc lifts slightly (micro opening)
Excess pressure is gradually released
The valve reseats once pressure returns to safe levels
This controlled discharge behavior ensurespressure stability and system efficiency, especially in sensitive equipment.
Low Lift (Micro Opening) Design
Provides gradual pressure release instead of sudden discharge, improving system stability.
Closed-Type Structure
Prevents medium leakage into the environment, suitable for gas systems and controlled processes.
Spring Direct Acting Mechanism
Ensures accurate and repeatable pressure response.
Threaded Connection (Common)
Easy to install and maintain in compact systems.
Metal-to-Metal Sealing (H Type)
Enhances durability and resistance to wear under repeated operation.
These features make the A21HY particularly suitable for applications wheretight sealing and precise pressure controlare required.
Chinese manufacturers have established highly standardized production systems for A21HY safety valves, combiningprecision machining, strict quality control, and scalable production capacity.
The valve body is typically made from:
Carbon steel (WCB)for general industrial use
Stainless steel (304/316)for improved corrosion resistance
Internal components such as valve seats and discs often use:
Alloy steel
Hard-facing materials for enhanced sealing performance
Material selection is based onmedium characteristics, pressure class, and temperature conditions.
Advanced CNC machining ensures:
High dimensional accuracy
Smooth sealing surfaces
Consistent interchangeability
Critical sealing surfaces undergo:
Grinding and lapping
Optionalhard alloy overlayfor extended service life
The spring is the core component that determines valve performance. Manufacturers perform:
Elastic coefficient testing
Fatigue life testing
Precise pressure calibration
Each valve is preset to a specified opening pressure before delivery, ensuringreliable and repeatable operation.
Before shipment, every A21HY safety valve undergoes strict inspection, including:
Set pressure verification
Sealing performance test
Opening and reseating test
Manufacturing and testing typically comply with standards such as:
GB/T 12243 (spring safety valves)
GB/T 12241 (general safety valve requirements)
These processes ensure that each valve meets international safety and quality requirements.
The A21H/Y safety valve is widely used in industries requiringprecise pressure control and safe operation.
Used in:
Gas pipelines
Storage tanks
Process equipment
Its closed structure ensures that hazardous gases are not released directly into the environment.
Common applications include:
Air compressors
Gas separation units
Industrial gas pipelines
The valve ensures safe operation by preventing pressure buildup beyond design limits.
Installed on:
Steam systems
Low-pressure boilers
Auxiliary equipment
It protects equipment by automatically discharging excess pressure.
Applicable for:
Mechanical manufacturing systems
Energy and power plants
Chemical processing units
Its versatility makes it a standard safety component across industries.
With stricter industrial safety regulations worldwide, demand for reliable safety valves like A21HY continues to grow. Industries are placing greater emphasis on:
Equipment safety
Environmental protection
Operational stability
China has become a major global supplier of A21HY safety valves due to:
Mature manufacturing ecosystem
Competitive pricing
Strong customization capabilities
Many manufacturers offer:
OEM/ODM services
Flexible production volumes
Fast delivery cycles
Modern industrial systems require:
Accurate pressure control
Long service life
Minimal leakage
This drives continuous improvements in:
Sealing technology
Material performance
Testing standards
To meet global market requirements, manufacturers increasingly comply with:
ISO quality systems
CE certification
API standards (for export markets)
This enhances the global competitiveness of Chinese safety valve suppliers.
Choosing the right A21HY valve is critical for system safety and efficiency.
1. Set Pressure
Must match system design pressure and safety requirements.
2. Medium Type
Ensure compatibility with gas, liquid, or steam.
3. Material Selection
Carbon steel for general use
Stainless steel for corrosive environments
4. Connection Type
Threaded or flanged depending on installation conditions.
5. Certification Requirements
Important for export or regulated industries.
Install vertically for accurate operation
Avoid back pressure at the outlet
Ensure unobstructed discharge path
Regularly inspect sealing surfaces
Test opening pressure periodically
Replace worn springs or seals promptly
Proper maintenance ensures long-term reliability and reduces system risk.
The A21H/Y Type Safety Valve is a reliable and precise pressure protection solution widely used across industrial sectors. Itslow-lift design, closed structure, and durable sealing systemmake it ideal for applications requiring controlled pressure release and environmental safety.
With advanced manufacturing capabilities, strict quality standards, and strong customization services,Chinese manufacturershave become leading suppliers of A21HY safety valves in the global market.
As industries continue to prioritize safety, efficiency, and compliance, the A21HY safety valve will remain an essential component in modern pressure systems, delivering dependable performance and long-term value.
