Why the Beveled Side Matters

Yamada center disks are beveled on the side that contacts the diaphragm. The bevel helps reduce the opportunity for abrasive particles to pack between the diaphragm and the center disk. The beveling also reduces the disks ability to cut the diaphragm’s surface during operation.

If the non-beveled side is installed against the diaphragm, the edge of the disk can concentrate wear at the diaphragm surface. In severe cases, the disk can begin to cut into the diaphragm. This type of wear can progress even faster when the pumped fluid contains suspended solids or abrasive particulates.

Air Side vs. Wetted Side

Correct orientation is not only about the shape of the disk. The material of the center disk also matters.

On many Yamada pump configurations, the air-side center disk is aluminum, while the wetted-side center disk is typically selected in a material compatible with the pump construction and the fluid being transferred. Reversing these components can expose the wrong material to the process fluid, increasing the potential for chemical attack or corrosion.

During reassembly, identify the air side and wetted side before tightening the diaphragm assembly. Do not assume the two center disks are interchangeable. There will also be a relevant torque value associated with the repair and that will vary based on pump size and diaphragm material selected see our Torque Values Page.

What to Check During a Wet-End Rebuild

• Confirm which center disk belongs on the air side and which belongs on the wetted side.
• Place the beveled face of the center disk against the diaphragm where specified for the pump assembly.
• Inspect the disk surfaces for damage, wear or sharp edges that could contact the diaphragm.
• Verify that the wetted-side material is appropriate for the pump model and process fluid.
• Follow the model-specific Yamada maintenance manual for assembly sequence and torque requirements before returning the pump to service. Some materials will require additional O-rings while some are built in, so check your reference materials.

A Small Detail That Can Prevent a Larger Failure

Incorrect center disk installation may look like a minor reassembly mistake, but the result can be premature diaphragm wear, fluid entering the air side of the pump and avoidable downtime.

Taking a few extra moments during a rebuild to confirm center disk orientation and material can help protect the new diaphragms and keep the pump operating as intended.

For additional maintenance information, see our Yamada AODD Pump Troubleshooting guide, browse Yamada Genuine Parts, or reference the Diaphragm, Ball, Center Disk & Center Rod Comparison Guide.

Need help identifying the correct components for your pump? Contact your Yamada representative.