Check Valve Basics

Check valves allow flow in one direction only. They open when inlet pressure exceeds outlet pressure plus cracking pressure, and close when flow reverses.

Pressure Drop Components

Total pressure drop = Cracking pressure + Flow-induced pressure drop

dP_total = P_crack + K x (Q/Cv)^2

Where K is a geometry factor and Cv is the flow coefficient.

Check Valve Types

• Ball check: Simple, compact, moderate dP. Good to 350 bar.
• Poppet check: Low dP, fast response. Industrial standard.
• Swing check: Very low dP, large sizes. Limited pressure.
• Spring-loaded: Controlled cracking, position-independent.

Cracking Pressure

Cracking pressure is set by spring preload. Common values:

• 0.2-0.5 bar: Low crack for pump suction, return lines
• 1-3 bar: Standard industrial check valves
• 5-10 bar: Higher crack for specific applications

Sizing Guidelines

• Target dP < 3 bar for pressure lines
• Target dP < 0.5 bar for suction/return lines
• Size for 70-80% of rated flow for margin