Insane Hydraulics
Bold and audacious blog about fluid power
Here's a good example of why one might want to go through the hassle of ordering the o-rings by size instead of getting a proper seal kit. This is the Rexroth A6VM55EZ4/63W-VAB020HB hydraulic motor that I overhauled this week. In this picture, you can see the seals that it will require next to the standard Rexroth seal kit for A6VM55../63, part number R902002302:
I marked the seven seals that I would use from this kit with a red marker - the shaft seal, four o-rings, and two seal nuts. Below is the solenoid core of the EZ control - note that the kit does not even include the o-ring (21.82 x 3.53) for the plastic cap - the ones that it does include serve for EP core caps, but not for this one:
Also note that I will need to replace all of the metric plugs damaged by corrosion, and they are never included in these kits.
So - now you have a choice - you can either get the original four o-rings plus the shaft seal for a hundred and fifty bucks, or you can get them and the required plugs for less than fifty (even considering the fact that the BAFSL1SF shaft seals in FKM are not cheap).
I absolutely understand the commercial reasoning behind using an original seal kit in such situations, but I do like to have options to choose from, and getting seals by size is a valid one, IMHO. Also - before you say anything about the "special seal nuts" - after you work with Rexroth units for a while, I promise that you will not have a shortage of these bad boys:
And now - the lists:
| Qty | Type | Size | Obs. |
| 1 | BAFSL 1SF FKM | 45x62x7/5 | Shaft seal, R909831179 |
| 1 | O-RING NBR70 | 132.94x3.53 | Case seal, R909085366 |
| 2 | Seal Nut | M10 | R909152426 |
| 2 | O-RING FKM90 | 5.28x1.78 | High-pressure checks (old design), R909830726 |
| 6 | O-RING FKM90 | 7.65x1.78 | Control, R909085577 |
| 3 | O-RING FKM90 | 9.25x1.78 | High-pressure checks, piggyback flushing valve, R909086487 |
| 1 | O-RING FKM70 | 29.87x1.78 | Control (spring side), R909157562 |
| 1 | Seal Nut | M6 | R909152425 |
| 1 | O-RING FKM90 | 17.12x2.62 | Flushing relief valve plug, R909087938 |
| 3 | O-RING FKM90 | 15.54x2.62 | Flushing spool plugs, +..., R909087891 |
| 1 | O-RING FKM90 | 26.57x3.53 | Servo-cylinder plug, R909151882 |
| 1 | O-RING FKM90 | 20.29x2.62 | PC plug, R909152686 |
| 2 | PROFILE SEAL. RING | DCCS10150-14-FKM | Solenoid cores, R902602257 |
| 2 | O-RING NBR70 | 19.0x2.5 | Coil caps, R902602578 |
| 1 | Seal Nut | M6x0.5 | PC adjusting screw, R909157764 |
| 1 | O-RING FKM90 | 18.72x2.62 | Servo cylinder plug (some versions), R909154235 |
| 1 | O-RING FKM90 | 17.17x1.78 | Plug seal |
| 2 | O-RING FKM90 | 18.77x1.78 | Square coil, R902600646 |
| 2 | Backup ring | 12x9.4x1.4 | High-pressure checks, BG1300094-PT00, R902602322 |
| 1 | O-RING FKM90 | 26.64x2.62 | Control plug, R909157273 |
| 2 | O-RING FKM90 | 8.0x2.2 | High-pressure checks, R902602781 |
| 1 | O-RING FKM90 | 17.3x2.2 | Piggyback flushing valve, R909830862 |
| 2 | O-RING FKM90 | 15.3x2.2 | Piggyback flushing valve, R909830860 |
| 1 | O-RING NBR70 | 21.82x3.53 | EZ control solenoid cap (not included in the kit) |
| Front Bearing | Tail Bearing |
| NTN 4T-T7FC055HSTPX1 | FAG 33110 |