YDK DUAL PLATE WAFER CHECK VALVE | MODEL: KDC-16

In water supply and drainage, fire protection (PCCC), and HVAC piping systems with limited installation space, the YDK dual plate check valve, Model KDC-16, is a top-tier solution. With its ultra-compact, lightweight wafer-type design, the valve uses two half-moon-shaped discs combined with fast-response springs. It closes instantly when the flow stops, effectively preventing backflow and eliminating water hammer to protect the pump.

Construction of the YDK dual plate check valve, Model KDC-16

This valve has a fairly simple mechanical construction, consisting of 5 main parts:

1. Body: Made of cast iron, in a wafer design clamped between two pipe flanges. The short face-to-face length minimizes weight and saves installation space.
2. Disc: Made of stainless steel 304, cast as a double disc in the shape of two butterfly wings. It withstands mechanical impact well and offers high corrosion resistance in humid environments.
3. Stem (hinge pin): Made of stainless steel 420, acting as a hinge that fixes the rotation direction so that the two discs open and close smoothly.
4. Spring: Made of stainless steel, providing the compressive force that automatically closes the two discs as soon as the flow pressure drops to zero.
5. Seal ring: Made of rubber, molded directly into the bore of the valve body, ensuring absolute tightness when the two discs are closed.

Dimension table of the YDK dual plate check valve, Model KDC-16

The table below provides the length, diameter, and disc radius data for sizes DN50 to DN700, to help engineers with quantity takeoff and shop drawings:

Note: The specifications of YDK products in the catalogue may be changed by the manufacturer without prior notice.

Technical notes for installing the YDK dual plate check valve

To keep the YDK dual plate check valve, Model KDC-16, running smoothly, extend the service life of the CF8 stainless steel discs, and minimize repairs and replacements, please observe the following points:

1. Orientation of the valve stem (spring shaft)

The dual plate check valve has two half-moon discs that open and close around a single stainless steel pin in the middle. If installed incorrectly (stem horizontal on a horizontal pipe), gravity will always pull the lower disc downward while the upper disc is pressed back against its stop. As a result, the sagging lower disc wears the rubber sealing groove unevenly, the valve soon starts to leak, and it does not open through its full stroke.

Correct installation:

• Horizontal pipelines: The valve body must be rotated so that the stem is vertical, perpendicular to the ground (pointing only in the 12 o’clock – 6 o’clock direction).
• Vertical pipelines: Install only when the flow runs from BOTTOM TO TOP (so that gravity and the force of the water help both discs open and close evenly). Never install on a pipeline with downward flow.

2. Disc opening and pipe bore clearance 

Unlike gate valves or ordinary butterfly valves, whose discs sit entirely within the body, the discs of a dual plate check valve protrude beyond the body thickness by a distance equal to the radius R (see the dimension table) when fully open.

Installation risk: If you use pipe with a wall that is too thick (or plastic/composite pipe with an inside diameter smaller than the D2 value), the two discs will jam against the inner edge of the pipe bore or the flange when they swing open. The valve then cannot open 100%, which obstructs the flow and creates a tearing stress on the discs.

Solution: Before tightening the flanges, the engineer should manually swing both discs fully open to check whether they rub against the edge of the connecting pipe bore.

3. Wafer clamping bolt tightening procedure

The YDK KDC-16 dual plate check valve has no bolt holes of its own. It is “clamped” between two pipeline flanges. The body is made of cast iron, so uneven clamping force can easily crack the body or cause leakage at the edge of the rubber seal.

Correct bolt tightening procedure:

• Center the valve exactly between the two flanges (stud bolts can be used for positioning).
• Tighten the bolts in a diagonal (star) pattern: top bolt → bottom bolt → left bolt → right bolt.
• Tighten gradually in 3–4 passes, increasing the torque each time. Never fully tighten one side first, as this will misalign the flanges.

 The staff of An Phu Thanh are always ready to advise on industrial valve installation solutions and water and fire protection supplies suited to each of your projects.

If you need more information about the YDK dual plate check valve, Model KDC-16, or would like a special quotation, please contact An Phu Thanh via Hotline/Zalo: 0946 729 913. We are always honored to serve you.