Question 1

What is a Check Valve and why is it necessary?

Accepted Answer

A Check Valve allows fluid to flow in one direction and automatically closes when flow stops or reverses. This prevents backflow that can damage pumps, contaminate clean media, cause water hammer or lead to pipe collapse under vacuum. Xiangzheng Check Valves use either a swinging disc, a spring-loaded poppet or a dual-plate design to achieve quick closure with minimal pressure loss.

Question 2

How do I choose the right Check Valve for my system?

Accepted Answer

Start by identifying the fluid type, temperature, pressure class and required flow rate. Then select the body material and seal material based on chemical compatibility, and consider available installation space and connection type. For low-pressure systems a spring-loaded Check Valve with low cracking pressure may be ideal; for high-flow pipelines a swing or dual-plate Check Valve offers lower pressure drop. Xiangzheng technical engineers can review your process data and recommend a model from the standard range or propose a custom design.

Question 3

How do I prevent water hammer with a Check Valve?

Accepted Answer

Water hammer occurs when a Check Valve closes too slowly or too quickly. To prevent it, use a spring-loaded or dual-plate Check Valve with a short closing stroke and a spring force matched to system flow characteristics. Install the valve as close as possible to the pump discharge or the source of reverse flow, avoid oversizing the valve which can cause disc flutter, and for long pipelines consider a nozzle or dashpot-assisted Check Valve to achieve controlled closure. Xiangzheng can provide dynamic analysis to determine the correct closure time for your specific pipeline.

Question 4

What materials are available for corrosive media?

Accepted Answer

Xiangzheng offers Check Valves in stainless steel 316, duplex stainless steel, Alloy 20, Hastelloy C276, Monel 400, Inconel 625 and titanium. Seal materials include PTFE, RPTFE, PEEK, Devlon and metal-to-metal combinations. For strong acids such as sulfuric or hydrochloric acid, Alloy 20 or Hastelloy bodies with PTFE seals provide excellent resistance; for seawater and chloride environments, duplex stainless steel or titanium with RPTFE seals is recommended. Always provide the full chemical composition, concentration and temperature to ensure correct material selection.

Question 5

What is the difference between a swing Check Valve and a spring Check Valve?

Accepted Answer

A swing Check Valve uses a hinged disc that swings open with forward flow and swings closed by gravity or reverse flow. It offers low pressure drop and suits large pipe sizes but requires sufficient flow velocity to fully open and may chatter under low flow. A spring Check Valve uses a spring-loaded poppet or disc that opens when pressure overcomes spring force and closes automatically when flow stops. It provides faster, more controlled closure and can be installed in any orientation, making it better for preventing water hammer and for applications with pulsating flow.

Question 6

How often should a Check Valve be inspected?

Accepted Answer

Inspection frequency depends on operating conditions. For clean, non-corrosive fluids at moderate temperatures an annual visual inspection and functional test are usually sufficient; for abrasive, corrosive or high-cycle applications inspect the valve every six months. During inspection, remove the cover or access plate and check the disc, hinge pin, spring and seat for wear, corrosion or fouling, and replace any component showing deep pitting, deformation or loss of sealing contact. For critical services, consider installing a pressure gauge or acoustic sensor to monitor reverse flow and detect early leakage.

China Reliable Check Valves Manufacturer

ANSI Standard CS Swing Check Valve