Yamada 771093 Diaphragm, PTFE for NDP-5
The Yamada 771093 is the genuine PTFE diaphragm for NDP-5 Series pumps including NDP-5FPT. It is the part that actually moves the fluid: compressed air pushes one diaphragm out while the center rod pulls the other in, so one chamber discharges while the other fills, and the pump alternates between them for as long as air is supplied.
Failures come from flexing, from chemical attack, or from being run dry against a closed valve. Flex fatigue shows as cracking in the convolution where the material bends; chemical attack shows as swelling, softening or a chalky surface; heat shows as hardening and loss of flexibility. Whatever the cause, the fix is the same, and it is worth working out which one it was, because the answer decides whether the replacement should be the same material.
Key Features
- Genuine Yamada replacement diaphragm
- Material: PTFE
- Fits NDP-5 Series pumps including NDP-5FPT
- Two per pump - always replace diaphragms in pairs
- Restores full stroke volume and flow
- Molded to the factory profile for correct flex life
Applications
- NDP-5 Series pumps including NDP-5FPT
- Scheduled diaphragm changes on transfer and dosing duty
- Restoring lost flow and slow cycling
- Repairing a pump venting product from the muffler
- Converting a pump to a different elastomer for a fluid change
- Marine, industrial, chemical and washdown service
Specifications
- Brand: Yamada
- Manufacturer: Yamada America
- Manufacturer Part Number: 771093
- Part Type: Diaphragm
- Material: PTFE
- Fits: NDP-5 Series pumps including NDP-5FPT
- Quantity Used: Two per pump
- Series Port Size: 1/4 in on the NDP-5 Series
- Condition: New
Frequently Asked Questions
Q: How tight should the diaphragm plates be?
Tight enough to seal, following the factory torque figures and tightening opposite bolts in sequence rather than working around the circle. Overtightening pinches the bead and starts a crack at exactly the point that flexes most.
Q: What shortens diaphragm life most?
Running against a closed discharge, air pressure above the pump rating, and cavitation from a starved suction line. All three make the diaphragm work harder than it was designed to on every stroke.
Q: Do I need to change the center disks at the same time?
Inspect them. The disks clamp the diaphragm and any burr, dishing or corrosion on them is transferred straight into the new diaphragm as a stress point, so a marked disk is worth replacing while the pump is open.
Q: Why replace both diaphragms when only one failed?
The second one has seen exactly the same number of cycles and the same fluid, so it is close behind. Beyond that, two diaphragms of different age and stiffness load the center rod unevenly and shorten the life of the new one.
Not sure this is the right part? Send us a Picture of the Pump Plate on your pump and the CLR Marine team will confirm the correct diaphragm.
CLRMarine
