Industry Knowledge: Spring Low-lift Safety Valve with External Thread & Test Lever (DN25 PN16)

1. Product Definition & Core Positioning

The DN25 external thread safety valve with hand lever belongs to spring-loaded low-lift safety valves, a core overpressure protection component for small-bore pressure-bearing equipment. Unlike flanged safety valves for large pipelines, this compact threaded model is designed for miniature pressure vessels, air compressors, small boilers and lab pressure equipment. Its core function is to automatically release excess medium once internal pressure exceeds the preset threshold, preventing equipment burst, pipeline rupture and industrial safety accidents.

2. Key Structural Design & Industry Advantages

(1) External Thread Connection

Most medium-to-large safety valves adopt flanged connection, which requires matching flanges, gaskets and more installation space. External NPT/BSP thread design directly screws into equipment threaded ports, cutting installation accessories and space occupation by over 40%. This design fills the demand gap of compact equipment with narrow mounting cavities, widely adopted by OEMs of small air tanks and hydraulic stations.

(2) Manual Test Lever Structure

This is a mandatory optimized design for medium-risk pressure equipment per national and international pressure vessel codes. Maintenance teams can lift the lever manually during routine inspection to verify valve flexibility without disassembly. For fully enclosed safety valves without levers, operators cannot check if the valve disc gets stuck by scale or rust, which may lead to complete failure during sudden overpressure. The lever structure effectively reduces hidden dangers in non-stop production lines.

(3) Low-lift Pressure Relief Mechanism

Low-lift safety valves feature a small opening stroke (only 1/4 of the nominal diameter) when popping open. Compared with full-lift safety valves for large boilers, they discharge medium gently instead of instant massive ejection. This characteristic suits systems requiring mild pressure regulation: compressed air pipelines, low-temperature heat transfer oil loops and water circulation equipment, reducing unnecessary medium waste while maintaining stable pressure control.

(4) WCB Carbon Steel Integrated Cast Body

WCB carbon steel is the mainstream casting material for general industrial safety valves. It balances cost, pressure resistance and medium compatibility, applicable to air, water and non-corrosive oil within -20℃~180℃. One-piece casting eliminates assembly leakage points, and anti-rust coating on the top bonnet extends service life in humid workshops and outdoor environments.

3. Core Technical Parameters Standard Explanation

DN25: Nominal diameter 25mm, the mainstream small caliber for auxiliary supporting equipment

PN16: Rated working pressure 1.6MPa, covering most light industrial low-pressure fluid systems

Popping pressure tolerance: ±5% of set pressure, the unified inspection standard for qualified safety valves

Sealing standard: Zero leakage after resealing under rated working pressure after pressure relief

4. Standard Production & Inspection Specifications

All safety valves are special pressure safety accessories with strict access thresholds. Every finished unit must complete three core factory tests before delivery:

1. Hydrostatic shell test: Test the pressure resistance of the valve body to eliminate casting pores and cracks;
2. Popping pressure calibration: Adjust spring preload to ensure the valve opens at the exact preset pressure;
3. Sealing durability test: Tens of thousands of opening-closing cycles to verify long-term tight resealing performance.

Only valves passing all tests can be equipped with factory inspection certificates, meeting equipment acceptance requirements of machinery manufacturing, HVAC, food processing and other industries.

5. Main Application Industry Scenarios

1. Pneumatic supporting: Small air storage tanks, screw air compressors, pneumatic power stations;
2. Thermal equipment: Mini vertical boilers, small heat-conducting oil heating machines;
3. Laboratory & light industry: Pressure reaction kettles, small water treatment pressure vessels;
4. Hydraulic systems: Low-pressure hydraulic stations, small hydraulic buffer tanks.

6. Industry Selection & Maintenance Tips

Selection Notes

1. Match caliber and pressure rating with equipment design parameters, do not select a valve with lower PN rating than system working pressure;
2. For equipment requiring regular safety inspection, prioritize models with manual test levers;
3. Corrosive medium systems need stainless steel safety valves instead of WCB carbon steel versions.

Daily Maintenance Rules

1. Conduct lever test once every 1–3 months to prevent valve jamming;
2. Clean internal scale and impurities every half year for water medium pipelines;
3. Replace aging springs and sealing gaskets after two years of continuous operation to guarantee protection performance.

7. Market Development Trend

In recent years, small-sized threaded safety valves have seen rising market demand driven by the rapid growth of small automated equipment and lab instrument industries. End clients now prioritize compact installation, convenient maintenance and complete inspection documents, pushing manufacturers like SND to upgrade small-bore safety valve series with lever structures, standardized calibration and ready stock supply, replacing outdated fully enclosed threaded safety valves in the market.