Yamada 771700 Diaphragm, Buna-N for NDP-40
The Yamada 771700 is a factory Buna-N (NBR) diaphragm for NDP-40 Series pumps including NDP-40BAN and NDP-40BSN. It separates the air side of the pump from the wet side, and it is the only moving part in direct contact with both, which is why it is the component that sets the service life of the whole pump.
Material choice is what makes the difference between a diaphragm that lasts and one that does not. Buna-N suits oils, fuels, hydraulic fluid and general transfer, and it gives good flex life at moderate cost, but it is not the material for strong acids, ketones or hot water. Always match the elastomer to the fluid, the temperature and the abrasiveness of what is being pumped rather than simply ordering what came out.
Key Features
- Genuine Yamada replacement diaphragm
- Material: Buna-N (NBR)
- Fits NDP-40 Series pumps including NDP-40BAN and NDP-40BSN
- 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-40 Series pumps including NDP-40BAN and NDP-40BSN
- 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: 771700
- Part Type: Diaphragm
- Material: Buna-N (NBR)
- Fits: NDP-40 Series pumps including NDP-40BAN and NDP-40BSN
- Quantity Used: Two per pump
- Series Port Size: 1-1/2 in on the NDP-40 Series
- Condition: New
Frequently Asked Questions
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.
Q: Product is coming out of the muffler. What does that mean?
That is the signature of a split diaphragm. The fluid side has broken through into the air side and is being vented through the exhaust. Stop the pump, because the air motor is now getting product through it and the valve internals will suffer.
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.
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