Working Principle And Material Selection Of Sanitary Stainless Steel Union Check Valve

A sanitary check valve with union ends should combine corrosion-resistant stainless steel, a smooth internal finish, compatible seals, and a removable connection. This combination prevents reverse flow while making inspection and seal replacement easier. For hygienic service, material grade, surface roughness, opening pressure, temperature, and union dimensions should be selected together.

Why Material and Surface Finish Matter

The valve body and wetted surfaces must suit the process fluid and cleaning conditions. SS304 fits many general applications, while SS316L is used where higher corrosion resistance is needed.

Surface roughness also affects cleanability. A hygienic check valve with damaged or uneven internal surfaces can retain product residue and make sanitation harder. The referenced design specifies an internal surface finish of Ra≤0.8.

Surface Design Points

🧼 Surface roughness: Lower roughness reduces locations where residue can remain.

🔍 Internal geometry: Smooth transitions around the seat and flow passage support easier cleaning.

🧽 Surface condition: Scratches, pits, and welding defects should be avoided on fluid-contact areas.

How Union Ends Improve Maintenance

A sanitary check valves configuration with union ends allows the valve to be separated from the piping without cutting the tube. This makes inspection, cleaning, and seal replacement easier.

The removable connection is useful near pumps, return lines, and process equipment where reverse-flow protection must remain accessible. Proper installation space should be reserved around each union.

Installation Checks

1. 🔩 Match the union connection with the piping standard.
2. 📐 Confirm the flow arrow and installation direction.
3. 🧩 Select seals according to the fluid and cleaning temperature.
4. 🔧 Keep enough clearance for union disassembly.

How the Check Mechanism Works

A sanitary check valve opens when upstream pressure overcomes the internal closing force. When flow stops or reverses, the valve closes and restricts backflow.

This function can protect pumps and downstream equipment from reverse flow. Opening pressure also affects pressure loss, so the selected valve should match the expected flow conditions.

The referenced configuration lists opening pressures of 0.3 bar for DN25, 0.2 bar for DN32/40, and 0.1 bar for DN50/100.

Seal Selection and Temperature

A sanitary check should use a seal compatible with both the process medium and cleaning cycle. The listed options include silicone, EPDM, Viton, and NBR.

For the EPDM configuration, the stated working temperature is -10°C to +120°C. The actual process temperature should remain within the selected seal specification.

Where This Configuration Fits

A check valve sanitary installation is suitable for process lines where cleanability, reverse-flow protection, and component access must be considered together. Typical applications include food, dairy, beverage, cosmetic, and pharmaceutical processing.

Before installation, the following conditions should be checked:

• Flow direction
• Pump operating point
• Pressure drop
• Cleaning temperature
• Seal compatibility
• Union clearance

Practical Selection Checklist

Before specifying sanitary check valves, the following points should be confirmed:

1. Stainless steel grade and corrosion resistance
2. Internal surface finish
3. Union size and connection standard
4. Seal material
5. Opening pressure
6. Operating temperature
7. Flow direction
8. Maintenance clearance

The design value of a union-end valve comes from combining hygienic stainless steel construction with a removable connection. Correct material selection, controlled surface finish, suitable sealing, and proper sizing allow reverse-flow protection without adding unnecessary maintenance work.

Sanitary Stainless Steel Check Valve With Union Ends

• Check valve can prevent the fluid from flowing back and ensures that it flows in only one direction.
• It can be used to prevent the less of prime of the pump and to avoid pipe-hammering.
• It is used in the food-processing, beverage, wine-making, oil-making, cosmetics, pharmaceutical and chemical industries.
• The valve opens when the pressure of the fluid exceeds the pressure exerted by the pump spring. 
• When the two pressures are equalized, the valve closes. A stronger counter-pressure allows the valve to close.

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