Yamada 771083 Diaphragm, PTFE for NDP-20
The Yamada 771083 is the genuine replacement PTFE diaphragm specified for NDP-20 Series pumps including NDP-20BST. Each stroke flexes it from one extreme to the other, and it does this several hundred times a minute at full flow, which is a great deal of work for one piece of molded elastomer.
A diaphragm gives warning before it goes if you know what to look for. Output drops, the pump runs faster for less flow, and product starts showing up at the muffler, which is the classic symptom of a split diaphragm venting pumped fluid into the air side. Replace both diaphragms together even when only one has failed. The surviving one has done the same hours, and a mismatched pair loads the center rod unevenly.
Key Features
- Genuine Yamada replacement diaphragm
- Material: PTFE
- Fits NDP-20 Series pumps including NDP-20BST
- 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-20 Series pumps including NDP-20BST
- 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: 771083
- Part Type: Diaphragm
- Material: PTFE
- Fits: NDP-20 Series pumps including NDP-20BST
- Quantity Used: Two per pump
- Series Port Size: 3/4 in on the NDP-20 Series
- Condition: New
Frequently Asked Questions
Q: Which diaphragm material should I choose?
It depends on the fluid, the temperature and how abrasive the product is. PTFE handles the widest chemical range but flexes less freely, Santoprene and Hytrel give long flex life, Buna-N suits oils and fuels, EPDM suits water and many chemicals, and Viton suits aggressive service.
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.
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
