Description   

1. Executive Summary

Our Series HQ Slow-Closing Damper Check Valve is an engineered solution designed to prevent destructive water hammer in pump discharge and high-head fluid systems. Unlike standard check valves that close abruptly upon flow reversal, this valve features an external weighted lever and damping system that ensures a controlled, two-stage closing sequence. This critical functionality protects pipelines, pumps, and connected equipment from dangerous pressure surges (slam), significantly enhancing system safety, reliability, and longevity in water, wastewater, and industrial applications.

2. Key Features & Design Advantages

• Eliminates Water Hammer: The primary function. The controlled slow closure dramatically reduces pressure surge peaks, safeguarding the entire piping system from destructive shock waves.
• External Weight and Damping System: Features an adjustable external counterweight and an integrated oil damper (or hydraulic cylinder). This design allows for precise tuning of the closing speed to match specific system dynamics, independent of line pressure.
• Two-Stage Closing Action:

1.     Fast Initial Close: The valve disc closes rapidly under its own weight and spring assist (if applicable) for the first 80-85% of travel, preventing significant reverse flow.
2.     Slow Final Close: The final 15-20% of closure is hydraulically dampened and controlled by the weighted lever, gently seating the disc to complete the seal without slam.

• Superior Performance in High-Head Applications: Exceptionally effective in systems with high static heads and long pipe runs, where the risk of water hammer is most severe.
• Maintenance-Friendly Design: The external operating mechanism allows for inspection, adjustment, and maintenance without removing the valve from the pipeline.
• Robust Construction: Typically constructed from cast iron (ASTM A126), ductile iron (ASTM A536), or carbon steel (ASTM A216 WCB) to withstand high pressures and demanding environments.
• Multiple Disc Designs: Available with single disc (tilting-type) or double disc (wafer-type) configurations to suit different flow profiles and space constraints.

3. Technical Specifications

• Size Range: DN 50 to DN 1200 (NPS 2" to 48") 
• Pressure Class: PN 10/16, ANSI Class 125/150/250 
• Body Material: Cast Iron, Ductile Iron, Carbon Steel, Stainless Steel 
• Disc Material: Cast Iron + EPDM/NBR, Ductile Iron, Carbon Steel, Bronze, Stainless Steel 
• Seat Material: EPDM, NBR, Nitrile, Polyurethane, Metal 
• End Connections: Flanged (GB/T 9113, ANSI B16.5, EN 1092-1, AWWA C111)
• Standards Compliance: AWWA C508, ISO 9001, API 6D (General) 
• Damping System: Adjustable Oil Damper or Hydraulic Check Cylinder 

4. Operating Principle & Function

The valve's operation is a function of flow dynamics and the external mechanism:

1. Forward Flow: Under sufficient upstream pressure, the fluid force lifts the valve disc, opening the valve. The external weighted lever is simultaneously raised.
2. Flow Deceleration/Stoppage: As the pump shuts off or flow velocity decreases, the disc begins to close due to gravity.
3. Initial Fast Close: The disc descends quickly under its own weight, reaching the near-closed position.
4. Final Slow Close: The external weighted lever and damping mechanism engage for the final portion of the travel. The oil damper provides resistance, controlling the descent of the lever and disc to ensure a gentle, shock-free seal onto the seat.

5. Applications

This valve is critical in systems where pump shutdown or power failure could cause rapid flow reversal:

• Water & Wastewater Treatment: Pump discharge lines, high-head mains, and distribution systems.
• Power Plants: Circulating water systems, condenser cooling water lines.
• Industrial Plants: Cooling water networks, fire protection systems, raw water intake.
• Irrigation & Flood Control: Large-diameter pump stations and pipeline systems.
• Mining & Desalination Plants: High-capacity raw water and brine transfer lines.

6. Quality Assurance & Testing

Every Series HC-SC valve is validated to ensure performance and reliability:

• Hydrostatic Shell Test: Tested to 1.5 times the rated pressure per API 598 or AWWA C508.
• Seat Leakage Test: Tested to ensure bubble-tight sealing as per allowable rates in API 598.
• Functional Operation Test: The damping and closing mechanism is tested to verify proper slow-closing action.
• Material Certification: All materials are certified to meet relevant ASTM, EN, or AWWA standards.

7. Why Choose Our Slow-Closing Check Valve?

• System Protection: Actively prevents costly damage from water hammer, reducing downtime and maintenance costs.
• Engineered Performance: The adjustable closing feature allows for optimal performance tuning to your specific system requirements.
• Proven Reliability: Heavy-duty construction ensures long-term, maintenance-free operation in the most demanding environments.
• Expert Support: Our engineering team provides application analysis to ensure correct valve selection and adjustment for your system's inertia and head pressure.

Disclaimer: Specifications are subject to change without notice. Valve selection and adjustment are critical and must be based on a complete system analysis, including pump curves, pipeline profile, and fluid properties. Performance is dependent on correct installation, operation, and maintenance.