Yamada 640029 O-Ring size 217, Buna-N for NDP-40 to NDP-80
The Yamada 640029 is the genuine replacement o-ring for NDP-40, NDP-50 and NDP-80 Series pumps. It is a static seal: it sits in a machined groove, gets squeezed when the joint is closed, and that squeeze is the only thing standing between the fluid or the compressed air inside the pump and the outside world.
Getting the material right matters as much as getting the size right. The elastomer has to be compatible with what the pump is moving, because a seal attacked by the fluid swells, softens and extrudes out of its groove, and an incompatible ring can fail within hours rather than months. Check what the pump is actually handling before ordering, not what it handled when it was installed.
Key Features
- Genuine Yamada replacement o-ring
- Material: Buna-N (NBR), 70 durometer
- Nominal size: size 217
- Fits NDP-40, NDP-50 and NDP-80 Series pumps
- Two per pump in the assemblies that use it
- Restores a positive seal at the joint without machining or adjustment
Applications
- NDP-40, NDP-50 and NDP-80 Series pumps
- Scheduled rebuilds and seal kit top-ups
- Chasing a weep at a joint face after reassembly
- Replacing a ring that has taken a compression set
- Service after a fluid change that attacked the old elastomer
- Marine, industrial and transfer duty
Specifications
- Brand: Yamada
- Manufacturer: Yamada America
- Manufacturer Part Number: 640029
- Part Type: O-Ring
- Material: Buna-N (NBR), 70 durometer
- Nominal Size: size 217
- Fits: NDP-40, NDP-50 and NDP-80 Series pumps
- Quantity Used: Two per pump
- Series Port Size: 2 in on the NDP-50 Series
- Condition: New
Frequently Asked Questions
Q: Should I replace all the O-rings at once?
If the pump is open, yes. They are inexpensive next to the labor of opening the pump, they have all seen the same hours and the same fluid, and replacing one of a set usually means coming back for the others.
Q: What makes an O-ring swell?
Fluid absorption. The elastomer takes up the liquid it is sealing, grows, and eventually will not fit the groove. A ring noticeably larger than the new one is telling you the material choice is wrong for that service.
Q: Is a sleeve O-ring different from a body O-ring?
Functionally it is the same static seal, but the ones on the air valve sleeve see constant reversing pressure and a lot of cycles, so they are usually the first to go and are worth replacing whenever the air valve is stripped.
Q: Can I reuse the old O-ring if it looks fine?
It is a false economy. A ring that has been compressed for months has taken a set in the shape of its groove and no longer springs back against the sealing faces. It will often pass a dry test and then weep once the pump is running under pressure.
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 o-ring.
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