Yamada 643139 O-Ring, PTFE for NDP-50
The Yamada 643139 is the factory o-ring specified for NDP-50 Series pumps. It seals one of the joints inside the pump, and because it costs almost nothing next to the downtime a leak causes, it is the kind of part worth replacing on sight rather than on schedule.
Elastomer seals fail in a predictable way. Heat and time take the flexibility out of the rubber, the ring takes a permanent set in the shape of its groove, and it stops pushing back against the surfaces it is meant to seal. Chemical attack does the same job faster, swelling the ring until it will not fit the groove or hardening it until it cracks. Either way the first sign is usually a weep rather than a spray, so it pays to look at the joint faces whenever the pump is apart.
Key Features
- Genuine Yamada replacement o-ring
- Material: PTFE
- Fits NDP-50 Series pumps
- 4 per pump in the assemblies that use it
- Restores a positive seal at the joint without machining or adjustment
Applications
- NDP-50 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: 643139
- Part Type: O-Ring
- Material: PTFE
- Fits: NDP-50 Series pumps
- Quantity Used: 4 per pump
- Series Port Size: 2 in on the NDP-50 Series
- Condition: New
Frequently Asked Questions
Q: Does the durometer number matter?
Yes. Hardness sets how far the ring deflects under a given squeeze. A softer ring in a groove designed for a harder one extrudes into the gap and nibbles away at the edge; a harder one in a soft ring groove may not fill the groove at all.
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.
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.
CLRMarine
