Non return valves (NRVs), also known as check valves or reflux valves, are flow control devices that allow fluids to flow in one direction while preventing backflow. They comprise a simple yet ingenious mechanism that opens automatically to allow forward flow and then closes automatically to prevent reverse flow.
How Non Return Valves Work
NRVs contain a moving part known as a closure element that opens to allow forward flow and then closes to prevent backflow. There are various types of NRVs with different closure mechanisms:
• Swing check valves feature a disc or clapper that pivots to open and close. When fluid is flowing forward, the disc swings fully open. But when flow reverses, the increased back pressure causes the disc to swing shut, sealing against its seat to prevent backflow.
• Lift check valves contain a round or rectangular closure element that rises to allow forward flow and then drops back down to seal against backflow. The closure element is lighter than the fluid and floats up as flow begins, uncovering the passageway. When flow stops, the element drops by gravity to close the valve inlet.
• Dual plate check valves utilize two overlapping closure plates that separate to permit forward flow but press together to prevent backflow. The plates act independently of each other based on upstream and downstream pressures.
• Diaphragm check valves contain flexible diaphragm that rises to allow forward flow but then seals against a port when backflow occurs. Deflecting in response to pressure differentials, the diaphragm provides an instant, positive seal against reverse flow.
Non return valve opens automatically in response to fluid pressure and close automatically in the absence of sufficient flow. No external power is required for operation – only the pressure generated by the flowing fluid.
Uses And Applications For Non Return Valves
Non return valve serve various purposes across many industries by preventing reverse flow that could otherwise contaminate, overwhelm or damage systems. Common applications include:
• Water distribution – check valves by China non return valve suppliers, prevent back siphonage into potable water supplies from reservoirs or equipment at lower elevations.
• Appliance draining – NRV drain cocks allow sinks, tubs and tanks to fully empty while preventing used water from flowing back in.
• Irrigation systems – non return valves ensure water continues to flow one-way through sprinkler systems towards emitters and drip lines.
• Pumping equipment – check valves from non return valve manufacturer stop pumped liquids or gases from flowing backward through idle pumps, conserving energy and prolonging equipment life.
• Process control – NRVs isolate equipment or provide one-way flow within industrial processes across sectors like pharmaceutical, chemical, mining, oil & gas, and power generation.
• Instrumentation – non return valves protect delicate instruments from damage caused by fluid reversal that could result from system shutdowns or pipe network variations.
Chinese Non Return Valve Suppliers
Chinese manufacturers have become a major source of cost-effective non return valves for the global market due to lower production costs and competitive product quality. Chinese suppliers offer:
• Standard NRVs for water, air, gas, oil and chemical applications made from metal alloys like bronze, cast iron, stainless steel and more.
• High-performance zero leak valves with EPDM or FKM rubber seals for pharmaceutical and food grade applications.
• Valves with multiple end connections like flanged, threaded and welded to simplify installation.
• Certifications to international standards such as ISO, API, ASTM, ASME and CE marking.
When choosing a Chinese NRV supplier, look for a reputable company with a proven track record, certifications, customization capabilities and support services like application engineering and rapid prototyping. With proper due diligence, Chinese non return valves can provide excellent value and performance for your specific flow control needs.