Oil/grease seal fitting direction

Hi folks. I'm getting on, and things have a nasty habit of changing. My >50-year-old 'knowledge' about oil seals may now be out of date. What direction should the lip of an oil seal face, in this case, in an agricultural vehicle's wheel hub?

The hub will eventually fill with grease, if regular greasing instruction is obeyed. My belief is that the seal should therefore allow passage of material (grease) to the outside of the hub, whilst preventing muck getting in. (The seal is primarily a 'muck-keeper-outer', rather than a 'grease-keeper-inner). Therefore, the lip should 'face' the outside, with the 'smooth' side of the seal facing in. This is the opposite direction to, for example, a crankshaft oilseal. But my knowledge may be OK for ancient, single-lip seals, or even leather seals, and now we are supplied with double-lip seals, so have fitting instructions changed (for this type of application)?

Edited By Kiwi Bloke on 02/03/2023 01:37:58

I have never seen a seal fitted otherwise than with the garter spring and lip facing toward the oil or grease in the bearing. (But I have never worked on ag equipment) But if the workshop manual for your machine says otherwise, follow that.

That includes double lip seals, which usually face the same way as a single lip seal.

Normally it is not recommended to pump a bearing so full of grease that it comes out the seal. The recommendation is they need air space inside the bearing for the grease to flow around in there. One or two squirts a year should be enough. If it is packed full the grease can overheat and deteriorate. Again, if the factory workshop manual or owners manual says otherwise, follow that.

If the machine is so old that it came with leather seals, which always puked eveywhere, then it probably had instructions to keep up the grease supply regularly. But if replacing the leather with modern double lip seals you probably don't need to top up the grease regularly. Like wheel bearings in a car, they pretty much will run for life without fresh grease as long as none is leaking out.

Edited By Hopper on 02/03/2023 02:35:00

Hopper, thanks for a quick reply. My belief is that it was common practice to fit hub bearing seals with the lip & spring on the air side of the hub, even if there was no facility to feed the hub with grease. This is certainly the case for Massey-Ferguson 165 tractor front hubs, as printed in the manual. In that application, the hubs are supposed to be fed liberal quantities of grease regularly, presumably to flush out any muck that gets past the single-lip rubber seal. I'm pretty sure I've fitted seals in various cars this way round, but it was a long time ago...

I'm aware of the dangers of over-packing anti-friction bearings, but I suppose that in such low speed applications, it's acceptable to drown them in grease. I agree that a single charge should be good for years, so I suppose the provision of grease nipples is for 'muck-flushing-out', rather than lubrication. The application in question is for the wheels of a gang mower, the hubs carrying grease nipples, and for which the manual is hopeless, so no help there...

I'll bet that a lot of similar stuff comes out of the factory - or the repair shop - with seals fitted the 'conventional' way round (my tractor's were the wrong way round) - but is it 'correct'? Does it really matter? It would be nice to know...

Might be one of those perennial arguments with its adherents either way, bit like oils!

I am having lunch tomorrow with an old farmer originally from the South Island so I will ask him which way he did it. He is one of those guys who can fix anything with a bit of No.8 wire after working all his life on the land.

But when you think of it, if the hub has grease nipples and the seals were installed lip-side in, if you pumped the hub full of grease and kept pumping, it would/could push the seal right out of the hub from the hydraulic pressure. Installed lip-side out, the seal would let the grease flow out, and stop the dust from coming in. And as you say, low speed operation may be ok with the bearing chock full of grease.

Yes, exactly my thoughts. Beware the farmer with No. 8 wire. He's almost as dangerous as his mate with a stick welder. They both think they can fix anything, and to hell with doing it the 'right' way!

With 25 years of repairing plant machinery I have never encountered a seal that has not been fitted with the lip facing inwards. That is to say the flat side with all the information on it faces out

Clearly not many Morris Minor rear axles involved with agri-machinery. Lots get it wrong when changing bearings on these old cars.

My experience follows NDIY's Never seen a sedal fitted witht he garter spring exposed.

VERY occasionally, I've come acorss double seals fitted so that they oppose, but the outer seal was always garter spring inside, facing the garter spring on the inner seal

Howard

If the garter spring is outside then it should be stainless, viton seals normally have this spring. Double lip is always worth a try. Seals have moved on since the MF 165 was produced. Noel.

The old farmer (and ex-farm manager on some large corporate farms/stations) reckons he remembers those old tractors with grease nipples on the hubs. Says they always fitted the seals in the conventional manner: the lip and garter spring facing inwards towards the bearing to keep the grease in. Says they just packed the bearings and the hub half full of grease as with a car wheelbearing set up and it stayed in there for the life of the bearings. Reckons leave the grease nipples alone.

That coincides with my experience working on machinery in dirty, dusty and often wet conditions in the mining industry and coal fired power stations. Never seen a seal fitted with the lip and spring outwards. Same on off-road motorcycles that go axle-deep in mud and creek crossings etc. A gang mower does not seem like particularly arduous duty by comparison. Bit of dust and chaff flying around but nothing that will get in past a conventional seal. Not like it's operating under water or anything.

In the absence of any workshop manual to the contrary, I would fit your seals in the conventional manner, lip and spring inside toward the grease and bearing. Pack the bearings and half the cavity on assembly with grease and then leave the grease gun alone.

You could try an enquiry with one of the bearing manufacturers/distributors such as SKF etc. if in doubt. Or your local ag machinery dealer/mechanic shop.

Confuius, he say "The wider you open the window, the more the muck flies in." I'm beginning to wish I hadn't asked, or even thought about this. In the public library today, I riffled through a number of motor vehicle and tractor manuals. Lips to air-side is certainly stipulated in some cases, but only occasionally in hubs with no provision for in-service grease addition. So I'm fairly confident that my memory of fitting hub seals lip-to-air-side is correct - in some cases. And I would think that the seals were of a somewhat different pattern to today's common double-lip seals. Things change...

Thanks everyone for the thoughts and info. The garter springs on the new seals I have are almost certainly Zn-plated steel, and there's no realistic possibility of adding an additional trash shield to the air-side of the seal. I think the bearings will outlive me on a single charge of grease, kept in with the seals fitted lip-inwards, as seems commoner. I'll ignore the grease nipples...

Hi, when I was in maintenance, there were machines where the shafts were mounted in a barrel with greased bearings, and these often had the lip facing outward, this was to allow grease to escape when fresh grease was pumped in, but most of these had a seal containing a dust shield, much the same as what is fitted to ball bearings. Many other types of greased bearing housing just had a labyrinth sealing arrangement. It the housings contained oil, then the lip would be on the inside, and for some in very dirty and/or wet, or dusty environments, would often have a double lip seal, which had to be fitted the correct way round. Maintenance manuals should tell which way any seal should be fitted.

Regards Nick.

Yes there is always that factor when restoring old machinery for occasional use at our stage in life. I have motorbikes that do fewer miles in a decade than they typically did in a few months back in the day. They will certainly be still going when I am not!

With most greased bearings, the seal is mainly to keep contamination out rather than the grease in. I had trouble with overheating of the seal that I fitted to the R8 spindle on the museum's Tom Senior mill. This runs up to 3000rpm and the double lipped seal was exactly matched to the ground spindle nose. First I dispensed with the garter spring with slight improvement, then I had to completely remove the main lipped seal. That left the secondary lip on the other side of the seal which works perfectly on its own keeping dirt and swarf out, the grease has not leaked out at all.

Dear All,

I would go along with what everyone has said. I would just add that on a tank like a Centurion or Conqueror, the road wheel hubs are filled right up with grease AND the lips of the seal face outwards. This is entirely consistent with what has been posted. The intent here is to ensure that little or nothing, including water, can get IN because there is no space available. Regular greasing would tend to push any muck out.

John

Our (old) tractor’s front wheels were mounted with tapered roller bearings. Grease nipple one side, felt seal on the other side of the axle stub. They were greased, every day when in use, until some old grease was visible. That effectively kept the bearings running in clean lubricant. The rotational speed, even flat out in top gear, was pretty low, mind. With steel wheels, top gear flat out may have been 5mph. 🙂