A Vickers S20 or S21 steering booster code reads left to right: S for steering booster, 20 or 21 for the valve body, a spool letter (A, B or C for 5, 13 or 20 gpm), then the cylinder bore in eighths of an inch (12, 16, 22 or 26). So S20B26 is a standard-body booster with the 13 gpm spool and a 3-1/4 inch bore, and it takes seal kit 922625 at the valve end (923443 in Viton) and 922629 at the rod end.
Everything on this page comes from the Vickers service parts drawings M-2601-S through M-2605-S, the SC cylinder sheets M-2606-S through M-2609-S and the overhaul manual M-2600-S, all for the -11 design. Read the code off the nameplate, find your bore in the family table, and you have both kits.
What an S20 is. The S20 and S21 are integral linkage power steering units: an SV control valve bolted to an SC steering cylinder, with ball studs at the control end and the rod end. They were built for linkage-type power steering on trucks and other wheeled vehicles. The valve and the cylinder are sold as separate model families too, as the SV20 valve and the SC12, SC16, SC22 and SC26 cylinders.
How do you read a Vickers S20 model code?
Take this example, built from the M-2604-S breakdown: S20B26-4CBZBY15B-11-R05. Here is each position in order. The options are from the 26 bore drawing; the 12, 16 and 22 bore drawings differ in a few housing and mounting options, so check yours.
| Position | Example | What it means | Factory options |
|---|---|---|---|
| Steering booster | S | Integral linkage steering unit | S |
| Maximum valve capacity | 20 | Standard valve body | 20 = 20 gpm; 21 = 21 gpm with side ports |
| Spool type | B | Open center, 13 gpm | A = 5 gpm; B = 13 gpm; C = 20 gpm (all open center) |
| Cylinder bore | 26 | 3-1/4 inch bore | In 1/8 inch steps: 12 = 1-1/2 in, 16 = 2 in, 22 = 2-3/4 in, 26 = 3-1/4 in |
| Centering spring load | 4 | 100 lb | N = none; 1 = 10 lb; 2 = 25 lb; 3 = 50 lb; 4 = 100 lb; 5 = 150 lb |
| Control ball stud housing | C | 1.375-12 UNF straight female thread | B = 4-bolt flange; C = 1.375-12 UNF thread; A = 1.125-12 UNF thread on some smaller bores (not offered on the 26 bore) |
| Control ball stud | B | Short taper shank | N = no ball stud; A = long taper shank; B = short taper shank |
| Control ball stud position | Z | 90 degrees clockwise from the hydraulic connections | W = opposite the connections; X = 90 degrees counterclockwise; Y = in line; Z = 90 degrees clockwise |
| Control end mounting | B | Horizontal ball stud assembly, nylon seat | N = no attachments; A = steel seat; B = nylon seat |
| Control end mounting position | Y | In line with the connections | N = no position; W, X, Y, Z as above |
| Stroke | 15 | 15-3/32 inch | Two digits in inches, each plus 3/32 inch (10 = 10-3/32 in); range depends on bore, see the family table |
| Rod end mounting | B | Horizontal ball stud assembly, nylon seat | N = no attachments; A = steel seat; B = nylon seat |
| Design | -11 | 11 design | -11 (the -10 design is no longer serviced) |
| Integral relief (optional) | R05 | Relief valve set at 500 psi | R05 = 500 psi; R07 = 750 psi; R10 = 1,000 psi; R12 = 1,250 psi; omitted = no relief |
A real plate we saw read S20B26-4??ZBY15B-11, with two characters worn off. That is still enough to order seals, because the kits key on the body (20 or 21), the bore and the design, not on springs, studs or stroke. The worn characters only matter if you need a ball stud or housing kit.
Pressure limits. The overhaul manual M-2600-S rates these units for up to 2,000 psi, checked at full pump volume, and restricts S2**22 and SC22 models with the steel seat rod end mounting to 1,000 psi. The integral relief settings run from 500 to 1,250 psi.
What are the S20 and S21 model families, and which kits fit them?
Every bore drawing lists a body for both the S20 and the S21, and the same three spools. That gives twelve S20 codes and twelve S21 codes. The valve end kit is common to all of them; the rod end kit changes with the bore.
| Bore | Diameter | S20 codes | S21 codes | Stroke codes | Valve end kit | Rod end kit | Drawing |
|---|---|---|---|---|---|---|---|
| 12 | 1-1/2 inch | S20A12, S20B12, S20C12 | S21A12, S21B12, S21C12 | 06 to 12 | 922625 or 923443 | 922626 | M-2601-S |
| 16 | 2 inch | S20A16, S20B16, S20C16 | S21A16, S21B16, S21C16 | 06 to 16 | 922625 or 923443 | 922627 | M-2602-S |
| 22 | 2-3/4 inch | S20A22, S20B22, S20C22 | S21A22, S21B22, S21C22 | 06 to 17 | 922625 or 923443 | 922628 | M-2603-S |
| 26 | 3-1/4 inch | S20A26, S20B26, S20C26 | S21A26, S21B26, S21C26 | 10 to 24 | 922625 or 923443 | 922629 | M-2604-S |
| Valve or cylinder only | Codes | Seal kit | Drawing |
|---|---|---|---|
| SV20 steering valve | SV20A, SV20B, SV20C | 922625 | M-2605-S |
| SC12 steering cylinder | SC12 | 922626 | M-2606-S |
| SC16 steering cylinder | SC16 | 922627 | M-2608-S |
| SC22 steering cylinder | SC22 | 922628 | M-2607-S |
| SC26 steering cylinder | SC26 | 922629 | M-2609-S |
Standard units only. These kits fit the standard Vickers unit. Units built for equipment makers may differ, so compare the full model code on your nameplate before you order, and send it to us if anything in it looks unusual.
Which seal kit fits my S20 or S21 steering booster?
A booster has two sealing points, and Vickers kits them separately.
- Valve end: 922625 seal kit for S20 steering boosters. It seals the valve section. Kit includes but is not limited to a 287694 back-up ring, 154012, 170255 and 154004 o-rings, three 215680 seals, and the 154006 o-ring used on relief models. It fits every S20 and S21 bore and the SV20 valve.
- Rod end, 26 bore: 922629 rod end seal kit for S20 26 boosters. Kit includes but is not limited to a 208137 seal, 222750 washer, 208136 wiper ring, 214279 scraper, a retainer and a retaining ring. The same parts are also serviced as part of the cylinder sub-assembly.
- Rod end, 12, 16 and 22 bore: 922626, 922627 and 922628. These are not listed on our site yet; request a quote and we reply with price, availability and lead time.
The common mistake is ordering one kit and expecting it to stop both leaks. A booster weeping at the rod wiper needs the rod end kit; one leaking around the control ball stud housing or the valve body needs the valve end kit. If it has been apart before, do both while it is on the bench. Our guide to choosing the right hydraulic seal kit covers the general checks.
Buna or Viton: 922625 or 923443?
Every bore drawing names 923443 as the F3 equivalent of 922625, which is the Vickers way of saying the same valve end seal set in Viton. Run Buna-N on ordinary petroleum oil. Pick Viton where oil temperature runs high or your fluid calls for it. Do not reach for Viton on phosphate ester fluid such as Skydrol; it is the wrong material there. The hydraulic seal materials guide and the seal material codes by brand explain the choices.
For the 26 bore rod end, M-2604-S lists only 922629, with no separate Viton kit, and the later SC26 sheet M-2609-S calls 922629 an F3 seal kit. If material matters for your fluid, ask before you order.
Which Vickers drawings cover the S20, SV20 and SC units?
| Drawing | Covers | Revision on file |
|---|---|---|
| M-2600-S | Overhaul manual: S20/21 integral steering units, SV valves and SC cylinders, -11 design | 11-1-86 |
| M-2601-S | S20*12 service parts, -11 design | 11-1-85 |
| M-2602-S | S20*16 service parts, -11 design | 11-1-85 |
| M-2603-S | S20*22 service parts, -11 design | 12-1-87 |
| M-2604-S | S20*26 service parts, -11 design | 11-1-85 |
| M-2605-S | SV valves service parts, -11 design | 6-1-80 |
| M-2606-S to M-2609-S | SC12, SC22, SC16 and SC26 steering cylinder service data | 11/01/85 |
If you are working through other Vickers equipment, the Vickers parts hub, how to identify a Vickers hydraulic pump and the Vickers pump model number decoder cover the pump side.
Frequently asked questions
What does S20B26 mean on a Vickers steering booster?
S20B26 is a Vickers S20 steering booster with the standard 20 gpm valve body, the B open-center spool for 13 gpm and a 26 cylinder bore, which is 3-1/4 inch (26 eighths). The characters after the dash give the centering spring, control ball stud housing and stud, mounting positions, stroke and rod end mounting, and -11 is the design.
What is the difference between an S20 and an S21 booster?
The S21 uses a valve body with auxiliary side ports, which the Vickers overhaul manual M-2600-S says are there to control a slave cylinder. Otherwise the S21 shares the S20 code and, per drawings M-2601-S through M-2604-S, the same valve end seal kit.
Which seal kit fits an S20B26?
Two kits. The valve end takes 922625 (Buna-N) or its F3 equivalent 923443 (Viton). The rod end of a 26 bore takes 922629. Both come from Vickers drawing M-2604-S. Units built for equipment makers may differ, so send us the full model code from the nameplate.
Which kit for the rod end?
It depends on the bore: 922626 for 12, 922627 for 16, 922628 for 22 and 922629 for 26, per drawings M-2601-S through M-2604-S. The same kits service the matching SC12, SC16, SC22 and SC26 steering cylinders.
Buna or Viton for an S20 valve end?
922625 is the standard Buna-N kit and 923443 is the factory F3 (Viton) equivalent. Viton suits high oil temperature, but it is not the right material for phosphate ester fluids such as Skydrol, so ask us first if you run one.
What does R05, R07, R10 or R12 at the end of the code mean?
It is the optional integral relief valve: R05 is 500 psi, R07 is 750 psi, R10 is 1,000 psi and R12 is 1,250 psi. No R code means no integral relief. Relief models use the 154006 o-ring that comes in the 922625 kit.
Do these kits fit a -10 design booster?
The kits are listed for the -11 design. The Vickers drawings say -10 design units are no longer serviced and give the parts to convert one to -11, including a 284309 sleeve, a 1864 cotter pin, a ball stud kit and a housing kit.
Is an SV20 the same valve?
The SV20 is the valve section on its own, built to run with a remote cylinder or bolted to an SC cylinder. Drawing M-2605-S lists the same 922625 valve end kit for the SV20A, SV20B and SV20C valves.
About the technical information on this page. Figures, procedures and part numbers here come from manufacturer service literature and are provided for reference only. They are only as accurate as the factory data, and the revision we have on file may not be the latest for your unit. Always confirm against the current manufacturer documentation for your exact model and follow safe work practices. RestoPower is not responsible for damage, injury or loss resulting from the use or misuse of this information, or from incorrect assembly, adjustment, installation or operation of any unit.
Not sure which kit your booster takes?
Send us the full model code from the nameplate, even if part of it is worn off, and we will match the valve end and rod end kits. We reply with price, availability and lead time. Parts bought from our catalog carry a 2-year warranty on in-stock parts, and in-stock parts ship within 24-72 hours.
Related reading
- Vickers 922625 seal kit for S20 steering boosters
- Vickers 922629 rod end seal kit for S20 26 steering boosters
- Vickers 923443 Viton seal kit for S20 steering boosters
- How to identify a hydraulic pump or motor with no tag
- Obsolete Vickers hydraulic valve replacements
- Hydraulic seal materials guide
- All RestoPower resources