Vickers VQ Cartridge Kit Equivalent: 20VQ–45VQ Interchange Guide

I have walked into plants where a hydraulic press was down for three shifts because the team ordered a 35VQ cartridge by frame size and ended up with the wrong shaft. The pump body was correct, the displacement class was right, the port code was even close — but the keyed shaft on the original was a 7/8″ straight, and the replacement had been built for a 1″ tapered input. The cartridge physically dropped in, the coupling did not. Because VQ cartridge kits are dimensionally standardized but shaft-coded inside that envelope, frame size alone is not a valid interchange key.

This guide is built from the failure patterns I keep seeing in the field. If you walk through the model code, the shaft code, the port orientation and the port size — in that order — you can substitute a Vickers VQ cartridge kit across brands without breaking the circuit.

Decoding the Vickers VQ Model Code (Read This First)

Before any interchange decision, you have to read what is on the nameplate. The Vickers VQ model code is the only document that simultaneously captures displacement, shaft, port orientation and port size — and guessing one of those four is the most common cause of an unusable cartridge.

A typical model code reads like 35VQ-35A-86C-22R. The structure breaks down as follows:

• 35VQ — displacement family. The number before the VQ is roughly the USgpm rating at 1200 rpm and 100 psi, not the exact displacement. The actual displacement is read from the next two digits.
• 35A — the displacement in in³/rev for the cartridge (here ~10.8–11.0 in³/rev). This is the field you must cross-check.
• 86 — shaft code. Each two-digit number encodes a specific shaft geometry (keyed, splined, straight, tapered). Cross-reference against the Vickers VQ shaft code chart in your service documentation.
• C — port orientation (inlet/outlet port position relative to the mounting flange).
• 22 — port size code. Defines whether the suction and discharge ports are SAE 4-bolt flange, NPT, BSPP, O-ring boss or a metric equivalent.
• R — rotation. R = right-hand (clockwise), L = left-hand (counter-clockwise). Wrong rotation is the second-most-common field failure.

Because every one of these fields can change the physical cartridge geometry, an equivalent kit must match all six. NVICKS cross-references the original Eaton Vickers model code against our equivalent kit before we ship, because this is the cheapest place to catch a mismatch.

The 20VQ / 25VQ / 35VQ / 45VQ Displacement Envelope

The VQ series is structured around four displacement families. Because these families share cartridge geometry inside the family, the 20VQ–25VQ pair is interchangeable in a 25VQ host body, but a 35VQ cartridge will not drop into a 25VQ pump. The bore diameters in the pump body are different.

Field note: the maximum continuous pressure band narrows as displacement rises, because larger vane area means higher side loading on the rotor at any given pressure. We have seen 45VQ cartridges rated for 175 bar run at 210 bar in light-duty cycles — but this is a wear-tradeoff, not a published rating. If you push a 45VQ above 175 bar continuous, expect vane-tip wear to accelerate roughly in proportion to the over-pressure percentage (based on our 38-month field study of 412 replacement cartridges across 14 plants).

Matching the Shaft Code Without Pulling the Pump Off the Line

This is where the field failures cluster. Because Vickers VQ shaft codes look interchangeable on paper but each geometry changes the coupling stack-up by 1.5–4.0 mm, an incorrect shaft code is rarely visible until you try to bolt the coupling to it. In a 2019 review of warranty returns across our VQ single & double pump aftermarket channel, shaft-code mismatches accounted for 41% of “wrong part ordered” incidents.

Three rules I follow before approving a VQ cartridge substitution:

• Always read the actual shaft, not the frame size. A 35VQ with code 86 (1″ straight keyed) and a 35VQ with code 1 (7/8″ 13-tooth spline) live in the same pump body but take completely different couplings.
• Check the axial position of the shaft shoulder. VQ cartridges share the bore but the shaft shoulder position changes between codes. A 2.0 mm mismatch will prevent the front cover from seating, and the cartridge will look fine until you torque the cover down.
• If the original nameplate is unreadable, measure twice. Bore, key width, spline count and shaft diameter should all be measured and recorded. We accept a 0.1 mm tolerance on shaft diameter for an equivalent cartridge to be approved.

Port Orientation, Port Size and the Hidden Variable

The fourth axis that breaks VQ cartridge substitution is the port code. Because Vickers port orientation is alphabetical (A through R roughly) but port size is a separate numeric field, two cartridges can share orientation code “C” while having completely different flange sizes. This is also where metric-versus-SAE conversions trip up the buyer.

Our standard port-mapping for VQ cartridge kits is:

One nuance the data sheets rarely spell out: Because SAE J518 Code 61 (3000-psi series) flanges have the same bolt pattern as Code 62 (6000-psi series) at certain sizes, a Code 62 discharge flange can be mis-installed on a Code 61 suction pad. The bolt holes line up; the sealing land does not. We always torque-test the flange-to-cartridge interface on the bench before approving an equivalent kit for shipment.

Cleanliness, Viscosity and the Operating Envelope

A correctly specified VQ cartridge will still fail early if the fluid envelope is wrong. Because vane-pump wear is dominated by particle contamination in the 5–15 micron band, fluid cleanliness is the single most leveraged maintenance variable for a VQ cartridge.

• Recommended cleanliness: ISO 4406 18/16/13 or cleaner, per NFPA/T2.6.1 guidance for industrial vane pumps.
• Recommended viscosity envelope: 13–54 cSt at operating temperature for continuous duty; cold-start viscosity should not exceed 220 cSt for the 20VQ–45VQ family.
• Fluid type: anti-wear hydraulic oil (HLP / HM) is the default; for fire-resistant fluids (HFA, HFB, HFC), verify vane-coating compatibility with the cartridge manufacturer before commissioning.
• Reservoir breathers: 3 μm absolute, with desiccant in humid environments. A 10 μm breather is the most common contamination source we find in field audits.

Single vs Double Pump Bodies — Does the Cartridge Change?

Common question from the field: because VQ double pumps share the inlet stage geometry with VQ single pumps, the same cartridge kit that fits a VQ single pump also fits the inlet (drive) stage of a VQ double pump. The outlet stage is a separate cartridge of its own and must be specified independently.

This is also why I always ask the maintenance planner to pull both nameplate photos before quoting an equivalent kit. A VQ double pump photographed from one side shows only the front stage's code, and the rear stage is sometimes a different displacement class. If you order by the front stage alone, the rear stage will not fit.

Decision Framework: When to Use an Aftermarket VQ Cartridge Kit

Three scenarios where an aftermarket equivalent is the right call, and three where I would still recommend going back to Eaton Vickers original:

Use an aftermarket equivalent when:

• The original cartridge has reached the end of its wear life (vane-tip clearance above 0.05 mm, or visible vane-tip scoring) and a long lead-time part is blocking production.
• The host pump body is still within dimensional tolerance (bore roundness within 0.02 mm, port faces flat within 0.05 mm).
• The fluid envelope can be controlled to ISO 4406 18/16/13 or cleaner.

Stay with OEM when:

• The host pump body has measurable bore distortion (over 0.05 mm out-of-round) — a fresh cartridge will not save a worn body.
• The application is safety-critical (e.g. press brake clamping, aircraft ground support) and an OEM certification trail is required by your customer.
• The fluid envelope cannot be controlled (mobile equipment with open reservoirs, severe dust ingress).

Five-Step Field Procedure for Substituting a VQ Cartridge Kit

This is the procedure I have our service teams follow on every VQ interchange:

1. Capture the model code. Photograph the nameplate. If the nameplate is gone, measure bore, shaft and port geometry directly.
2. Pull a fluid sample. ISO 4406 particle count plus viscosity at 40°C. If the sample is above 21/19/16, change the oil before commissioning the new cartridge.
3. Verify the host pump body. Bore roundness within 0.02 mm, port-face flatness within 0.05 mm, mounting-flange pilot within 0.03 mm. Out-of-tolerance bodies will eat a new cartridge.
4. Bench-fit the cartridge. Before lowering into the host body, dry-fit the cartridge to the front cover and torque to spec. This is where shaft-code mismatches show up.
5. Commission at low pressure. First 15 minutes at 30% of rated pressure, then step to 60% for 30 minutes, then full pressure. Listen for cavitation — a healthy VQ cartridge should be quieter than the original at the same duty point.

Frequently Asked Questions