One code, two displacement tables
A VQ double names its two sections with the same displacement codes the VQ single uses, but each end is looked up in a different table: the shaft-end code from one, the cover-end code from the other. The same code can therefore stand for two different displacements inside one string, which is the most common misreading of this family.
A VQ double pump carries two cartridge sections on one shaft inside a single housing: one inlet and two independent outlets, so two circuits run from one drive at their own flow — and, on the largest frames, at their own pressure. Both sections sit on the same shaft, the shaft-end section first and the cover-end section behind it.
The frame number is read as two pairs of digits: the first pair is the shaft-end section and the second pair the cover-end section. 2520VQ is a 25VQ section at the shaft end with a 20VQ section at the cover end. The six frames are 2520VQ, 3520VQ, 3525VQ, 4520VQ, 4525VQ and 4535VQ.
The VQ code is shorter than the V code: 11 positions instead of 13, because the port modifier is carried inside the port letter and both displacements are read on one common scale of code positions. A version with built-in flow control or priority valves adds three more positions, for 14 in total.
The 11 positions at a glance
| # | Position | What it sets |
|---|---|---|
| 1 | Seals | F3 for phosphate-ester and other fire-resistant fluids; omitted for mineral oil |
| 2 | Series | 2520VQ · 3520VQ · 3525VQ · 4520VQ · 4525VQ · 4535VQ |
| 3 | Pilot | S = SAE pilot to ISO 3019/1 (SAE J744); omitted for the standard pilot |
| 4 | Shaft-end displacement | Code from the shaft-end table |
| 5 | Port connections | A · AM · C · E · F |
| 6 | Cover-end displacement | Code from the cover-end table |
| 7 | Mounting and shaft seal | S = flange mount with a double shaft seal; omitted = flange mount with a single seal |
| 8 | Shaft type | Code from the shaft table |
| 9 | Outlet position | Two letters, one per outlet, read from the cover end |
| 10 | Design | 20 on the current code page |
| 11 | Rotation | L = left hand (counter-clockwise); omitted = right hand, read from the shaft end |
An omitted position is not a gap in the number: each position is dropped when its standard value applies, and the positions that follow do not shift.
The two displacement codes: positions 4 and 6
Position 4 is read on the shaft-end section and position 6 on the cover-end section. The two codes come from two different tables, and a code does not mean the same displacement in both: 12 is 40.2 cm³/r at the shaft end of a 2520VQ, but 39.5 cm³/r at the cover end of a 20VQ section.
| Shaft-end section | Codes and displacement (cm³/r) | Cover-end section | Codes and displacement (cm³/r) |
|---|---|---|---|
| 2520VQ (25VQ) | 12 = 40.2 · 14 = 45.4 · 17 = 55.2 · 21 = 67.5 | 20VQ (on 2520VQ, 3520VQ, 4520VQ) | 5 = 18.0 · 8 = 27.4 · 11 = 36.4 · 12 = 39.5 · 14 = 45.9 |
| 35 series (on 3520VQ, 3525VQ) | 25 = 81.6 · 30 = 97.7 · 35 = 112.8 · 38 = 121.6 | 25VQ (on 3525VQ, 4525VQ) | 12 = 40.2 · 14 = 45.4 · 17 = 55.2 · 21 = 67.5 |
| 45 series (on 4520VQ, 4525VQ, 4535VQ) | 42 = 138.7 · 50 = 162.3 · 60 = 193.4 | 35VQ (on 4535VQ only) | 25 = 81.6 · 30 = 97.7 · 35 = 112.8 · 38 = 121.6 |
Which table applies to the cover end is fixed by the frame: a 3520VQ always carries a 20VQ cover section, a 4525VQ a 25VQ one, and only the 4535VQ reaches the 35VQ cover section. A code that exists in one table may not exist in the other.
Port connections: position 5
One letter describes the inlet and both outlets together. Three of the five codes are restricted to particular frames, so the available choice follows the frame you have:
| Code | Available on | Inlet | Outlet 1 | Outlet 2 |
|---|---|---|---|---|
| A | all frames | SAE 4-bolt flange | SAE 4-bolt flange | SAE 4-bolt flange |
| AM | all frames | Metric 4-bolt flange | Metric 4-bolt flange | Metric 4-bolt flange |
| C | 2520VQ only | SAE 4-bolt flange | SAE straight thread | SAE straight thread |
| E | all but 4535VQ | SAE 4-bolt flange | SAE 4-bolt flange | SAE straight thread |
| F | 2520VQ only | SAE 4-bolt flange | SAE straight thread | SAE 4-bolt flange |
AM matches A except that the threads fastening the flanges are metric. The pump is drained internally to the inlet, so the inlet is a flange connection on every code.
Shaft seal and shaft: positions 7 and 8
Position 7 covers the mounting and the shaft seal together: S gives a flange mount with a double shaft seal, and leaving it out gives a flange mount with a single seal. Position 8 then names the shaft, and the choice depends on the pilot and on how many seals the pump carries:
| Build | Shaft codes |
|---|---|
| Standard pilot, single shaft seal | 1 straight keyed · 11 splined · 86 straight keyed, heavy duty |
| Standard pilot, double shaft seal | 123 splined (not available on the 45 frames) · 130 splined (45 frames only) |
| SAE pilot, single or double shaft seal | 203 straight keyed, heavy duty · 297 splined |
Two of the codes are tied to the largest frames: 123 is not offered on 4520VQ, 4525VQ and 4535VQ, and 130 is offered only there. The pages covering the valve version of the pump list the same two codes with a narrower restriction, so the build is confirmed position by position when an integral-valve pump is ordered.
Two outlet letters: position 9
Two outlets need two letters, and the second is read relative to the first. Both are measured from the cover end of the pump. The first letter places outlet 1 against the inlet:
| Letter | Outlet 1 position | Letter | Outlet 2 position, measured from outlet 1 |
|---|---|---|---|
| A | opposite the inlet | A | 135° counter-clockwise |
| B | 90° counter-clockwise from the inlet | B | 45° counter-clockwise |
| C | inline with the inlet | C | 45° clockwise |
| D | 90° clockwise from the inlet | D | 135° clockwise |
Sixteen pairs are possible on five of the six frames. The 4535VQ is the exception: its cover section is large enough that the second letter is read on the same four-step scale as the first — A opposite the inlet, B 90° counter-clockwise, C inline, D 90° clockwise — so on that frame the pair reads as two independent positions rather than a position and an offset.
Design and rotation: positions 10 and 11
Position 10 carries the design number of the build, printed as 20 on the current code page, and position 11 the direction of rotation seen from the shaft end: L for left hand, counter-clockwise, and nothing for right hand. The inlet and both outlets keep their positions when the rotation changes, but the internal parts are assembled differently, so rotation is fixed when the pump is built.
Pressure follows the section
The two sections are rated separately, and the frame number alone does not give the pressure of the pump. On the 45 frames the shaft-end section is rated 175 bar while the cover-end section keeps 210 bar, and on every frame the small 20VQ cover section loses pressure as its displacement code grows:
| Frame | Shaft-end section: codes and maximum pressure | Cover-end section: codes and maximum pressure | Maximum speed (r/min) |
|---|---|---|---|
| 2520VQ | 12 · 14 · 17 · 21 — 210 bar | 5 · 8 · 11 — 210 bar; 12 — 160 bar; 14 — 140 bar | 2500–2700 |
| 3520VQ | 25 · 30 · 35 · 38 — 210 bar | 5 · 8 · 11 — 210 bar; 12 — 160 bar; 14 — 140 bar | 2400–2500 |
| 3525VQ | 25 · 30 · 35 · 38 — 210 bar | 12 · 14 · 17 · 21 — 210 bar | 2400–2500 |
| 4520VQ | 42 · 50 · 60 — 175 bar | 5 · 8 · 11 — 210 bar; 12 — 160 bar; 14 — 140 bar | 2200 |
| 4525VQ | 42 · 50 · 60 — 175 bar | 12 · 14 · 17 · 21 — 210 bar | 2200 |
| 4535VQ | 42 · 50 · 60 — 175 bar | 25 · 30 · 35 · 38 — 210 bar | 2200 |
Two working limits apply to the whole pump. It drains internally to the inlet, so inlet pressure must stay at or below 1.4 bar (20 psi), and outlet pressure must always be higher than inlet pressure. Both are checked at the same time as the two section ratings.
The 14-position version: integral valves
A VQ double can be built with a valve block on the pump rather than in the circuit. That build inserts three positions into the code: the valve choice becomes position 4, and the flow and pressure settings sit at positions 11 and 12, after the outlet position:
| Position | What it sets | Values |
|---|---|---|
| 4 | Integral valve | F = integral flow control and relief valve · P = integral priority valve and relief valve |
| 11 | Controlled flow | 2 · 4 · 6 · 7 · 8 · 10 · 12 USgpm |
| 12 | Relief valve setting | C = 52 · D = 70 · E = 86 · F = 100 · G = 121 · H = 140 · J = 155 · K = 175 bar |
Because three positions are added, the design number moves to position 13 and rotation to position 14. A pump with a valve block also gains a tank port, which is why the port table for that build carries one more column than the table for a plain double. The full code of such a pump reads, for example, (F3) 2520VQ (S) F 12 E 11 (S) 297 CC 6 D 20 (L): valve F, 40.2 cm³/r at the shaft end, port code E, 36.4 cm³/r at the cover end, double shaft seal, splined shaft, outlets CC, controlled flow 6 USgpm, relief set at 70 bar, design 20, left-hand rotation.
Four stock codes, decoded
| Code | How it reads |
|---|---|
| 2520VQ12A5 11CB20 | 25VQ shaft-end section, 40.2 cm³/r; port code A, all three ports on 4-bolt flanges; 20VQ cover section, 18.0 cm³/r; single shaft seal; shaft 11, splined; outlet 1 inline with the inlet and outlet 2 at 45° counter-clockwise; design 20, right-hand rotation |
| 3525VQ25A17 11CC20 | 35 series shaft-end section, 81.6 cm³/r; port code A; 25VQ cover section, 55.2 cm³/r at 210 bar; splined shaft; both outlets inline with the inlet; design 20, right-hand rotation |
| 4520VQ42A5 1AA20 | 45 series shaft-end section, 138.7 cm³/r at 175 bar; port code A; 20VQ cover section, 18.0 cm³/r at 210 bar; shaft 1, straight keyed; outlet 1 opposite the inlet and outlet 2 at 135° counter-clockwise; design 20, right-hand rotation |
| 4535VQ50A38 11AA20 | 45 series shaft-end section, 162.3 cm³/r at 175 bar; 35VQ cover section, 121.6 cm³/r at 210 bar; port code A; splined shaft; on this frame both letters are read against the inlet, so AA puts outlet 1 opposite the inlet and outlet 2 opposite the inlet as well; design 20, right-hand rotation |
Common ordering mistakes
- Reading both displacement codes in one table. Position 4 and position 6 are read on different tables, and the same code means different displacements on each.
- Taking the pressure limit from the frame. The 45 frames run their shaft-end section at 175 bar while the cover-end section stays at 210 bar, and the small 20VQ cover section drops to 160 bar at code 12 and 140 bar at code 14.
- Reading the two outlet letters as two independent positions. On five of the six frames the second letter is an offset from the first; only the 4535VQ reads both letters against the inlet.
- Applying the port codes of another frame. Codes C and F exist only on the 2520VQ, and E is not offered on the 4535VQ.
- Counting the positions of a valve build. With an integral valve the code holds 14 positions, and the design number and rotation sit two places further along than on a plain double.
Ordering
Send the complete model code from the nameplate, or the combination you need — frame, both displacement codes, shaft and outlet position — and we confirm both sections, the shaft and the port configuration before the order is placed. Where the nameplate is unreadable, photographs of the pump and of the port end, together with the machine model, are usually sufficient.
Browse the V and VQ double vane pumps or the VQ double vane pumps.
