Anyone an expert on seal application engineering?

[bob in CT]

I am asking because I am going to re-bush and re-seal a steering box.
If you look at the seal cross references, there are two seals that fit for the steering shaft. (385703R92)
First is # 8677 with an HM14 style lip http://www.skfextranet.com/Catalogs/457010/sealdetail.asp?s=8677
Next is # 8660 with a CRWA5 lip. http://www.skfextranet.com/Catalogs/457010/sealdetail.asp?s=8660
I am not sure which is the better choice. Note that there is a speedi-sleeve available 99087

Next is the steering worm shaft seal 370510R91

We have a choice between nitrile #11067 http://www.skfextranet.com/Catalogs/457010/sealdetail.asp?s=11067 and Polyacrylate #11066. I think nitrile may be better for us. http://www.skf.com/caribbean/products/seals/industrial-seals/power-transmission-seals/principles/seal-materials/sealing-lip-materials/nitrile-rubber/index.html There is a speedi-sleeve for this too (99112), but it may be tricky to install as it would have to be installed after the shaft is in the bushing. Both of these seals have a CRW1 lip, different from the other two. There is probably a way to get the specific lip and material that would be best, but I don't have the background to make that determination.

[Jim Becker]

I think in general nitrile is the better choice for most tractor seals, not sure it matters much nitrile vs. polyacrylate. Polyacrylate has advantages with EP lubes combined with higher temperatures, a combination we probably will never see. The last time I changed out steering gear seals, I got them both from NAPA. They currently cross 385703R91 to NOS 8660. That is probably what I used. It was a double lip seal. The second lip should help keep water from getting past the seal when it runs down the shaft. I don't think I have ever seen enough wear on that shaft to need a wear sleeve.

[bob in CT]

I think in general nitrile is the better choice for most tractor seals, not sure it matters much nitrile vs. polyacrylate. Polyacrylate has advantages with EP lubes combined with higher temperatures, a combination we probably will never see. The last time I changed out steering gear seals, I got them both from NAPA. They currently cross 385703R91 to NOS 8660. That is probably what I used. It was a double lip seal. The second lip should help keep water from getting past the seal when it runs down the shaft. I don't think I have ever seen enough wear on that shaft to need a wear sleeve.

The steering pin seems to take a beating, especially if the steering box gets filled with water, but that is the hardest one to sleeve because of the bushing.

FYI, the part numbers I used all came from ATIS, a page I use frequently.

[Criswell]

The HM14 style lip (non-spring loaded) is not meant to be used for lube oil retention. The following comes from SKF's own literature:

Non-Spring Loaded Seals
These seal designs are typically used for grease retention or dirt exclusion in slower shaft speed applications. The seals illustrated in fig. 3a, HM14 and HM21, are SKF’s standard designs. Agricultural equipment and quarry conveyor systems are
typical uses. They can also be used as light-duty rod wipers. Other designs include FF, G, HD, HMA and TL. The heavy-duty TL seal is designed for severe conditions such as disc harrows. For maximum dirt exclusion, they should be installed with the lip facing outward. Non-spring loaded seals are not intended for lube oil retention. Non-spring loaded seals, especially the HM design, are generally less expensive than spring-loaded versions, and generally cost much less than the assembled seals they replace.

Here is their information on the CRWA5 lip style (spring loaded):

Spring-Loaded Seals
These seal designs are typically used to retain oil and/or exclude dirt in higher shaft speed applications (fig. 3b). SKF’s standard designs include: single lip, dual-lips, and single and double shell designs. The dual-lip design features a non-interference auxiliary lip for added exclusion protection without the heat build-up associated by traditional dual-lip designs. Typical applications include gearboxes, speed reducers, transmissions, motors and drive systems. CRW5 and CRWA5 types are designed for high pressure applications, up to 90 psi (.62 MPa). For maximum dirt exclusion, they should be installed with the lip facing outward. While this works well with grease, be aware of potentially high levels of oil leakage. The large diameter seal HDW1 type is designed for severe conditions. Spring-loaded seals provide longer, more consistent service life in radial applications than non-spring loaded designs, and better sealability over a wide range of conditions. They also perform exceptionally well in applications where there is shaft run-out and shaft-to-bore misalignment.

So not only is the 8677 seal the wrong dimension (thinner than original), it is also the wrong lip style for the application, grease versus oil. I think that the last line from the description for the HM14 lip style is very telling as to why it may have been chosen, non-spring loaded seals, especially the HM design, are generally less expensive than spring-loaded versions, and generally cost much less than the assembled seals they replace.

[bob in CT]

Thinner than original does not mean much in this case. The original rawhide seals are a completely different animal.

[bob in CT]

I think the CRWA5 lip seal is fine for the steering shaft, as they is not sealing oil but is does have to exclude dirt- plus it crosses over for the original part number as Jim pointed out.