Yamada 711939 Center Rod for NDP-40 and NDP-50
The Yamada 711939 is the genuine center rod for NDP-40 and NDP-50 Series pumps with PTFE diaphragms. It is the shaft that ties the two diaphragms together: as compressed air pushes one out, the rod pulls the other in, so the pump discharges from one chamber while it fills the other.
The rod wears where it passes through the bearing and the packing. A scored or undersize rod will not seal against the V-packing any more, which shows up as air escaping into the wet side of the center block, or as a pump that stalls mid stroke because it is losing air past the rod. Run a fingernail along the bearing area: any ridge you can feel is enough to cut the packing.
Key Features
- Genuine Yamada replacement center rod
- Fits NDP-40 and NDP-50 Series pumps with PTFE diaphragms
- One per pump
- Ties both diaphragm assemblies into one reciprocating unit
- Ground bearing surface for correct sealing against the packing
- Direct replacement, no modification required
Applications
- NDP-40 and NDP-50 Series pumps with PTFE diaphragms
- Air motor and center block overhauls
- Replacing a scored, pitted or bent rod
- Service after product contamination of the air side
- Rebuilds following a diaphragm failure
- Marine, industrial and transfer duty
Specifications
- Brand: Yamada
- Manufacturer: Yamada America
- Manufacturer Part Number: 711939
- Part Type: Center Rod
- Fits: NDP-40 and NDP-50 Series pumps with PTFE diaphragms
- Quantity Used: One per pump
- Series Port Size: 2 in on the NDP-50 Series
- Condition: New
Frequently Asked Questions
Q: How do I know the center rod needs replacing?
Look and feel along the section that runs in the bearing. Scoring, pitting or a ridge at the end of the stroke means the packing cannot seal against it and the rod should be replaced rather than re-packed.
Q: The pump stalls part way through a stroke. Is the rod the cause?
It can be. A worn rod lets air leak past the packing so the air motor never builds enough pressure to complete the stroke. Check the air valve and pilot valve too, since they produce the same symptom.
Q: Does the rod need lubrication on assembly?
Yes. Yamada specifies grease on the rod where it passes through the bearing. Assembling dry accelerates wear on both the bearing and the packing.
Q: Can I reuse the old packing with a new rod?
No. The packing has bedded to the old rod profile and will leak against a new one. Fit new packing and, if it is worn, a new throat bearing at the same time.
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 center rod.
CLRMarine
