On a fixed-displacement pump (a gear pump, a fixed vane pump or a fixed piston pump) there is nothing on the pump to adjust: system pressure is set by the relief valve. On a pressure-compensated variable pump, the compensator screw on the pump sets working pressure, and the relief valve is set above the compensator as a safety backstop, never below it.
Get that order backwards and the relief valve dumps full pump flow over its seat every time the system reaches pressure. The oil gets hot, the compensator never gets a chance to de-stroke the pump, and it looks like a pump fault. This page sorts out which kind of pump you have, the order to set things in, and the factory adjustment ranges for the brands we work on, with links to the detailed procedure for each.
Work with a gauge, never by counting turns. Every compensator in the table below can be screwed past its published range. Rexroth says it in so many words in the A10VSO data sheet: the setting range at the valve is higher than the permissible range. A gauge at the pump outlet is the only way to know where you are.
Is my pump fixed or variable displacement?
Check the model code and look at the pump. A pressure-compensated pump has a control block bolted to it with at least one adjusting screw and locknut, and the model code carries a control field (C, CM, DR, DFR, A, M, P-1NN and so on). A gear pump or a fixed vane pump has no such block. If you are not sure what you are looking at, start with identifying a pump with no tag.
| Pump type | What sets maximum pressure | What you adjust |
|---|---|---|
| Gear pump, fixed vane pump, fixed piston pump | The system relief valve | The relief valve only. The pump just makes flow. |
| Pressure-compensated variable pump (piston or vane) | The compensator on the pump | The compensator, with the relief valve set above it |
| Load-sensing variable pump | The compensator (maximum pressure), while the load-sense spool sets the margin above load pressure | Compensator and load-sense differential, relief above both |
| Remote pressure control | A small pilot relief piped to the remote port, capped by the maximum setting on the pump | The remote valve for working pressure, the pump screw for the cap |
| Power (torque or horsepower) limiter | Factory set to a horsepower at a given speed and pressure | Leave it alone unless you have the factory setting data |
Dump-truck and log-splitter pumps are usually fixed gear pumps, so the adjustment is wherever the relief is plumbed: in the directional valve, in a separate relief, or in the valve section of a dump pump. Setting that valve is covered in our relief valve guide. Zero-turn mowers and other hydrostatic drives are a different animal altogether; see hydrostatic transmission troubleshooting.
Relief valve or compensator: which one sets the pressure?
On a compensated pump, the compensator does the work. When outlet pressure reaches the setting, the control spool moves the swashplate (or the cam ring on a vane pump) toward zero stroke, and the pump holds that pressure while making only the flow the circuit uses. The relief valve sits above it and should only crack on a spike.
Set the relief below the compensator and the relief becomes the pressure control. The factory literature lists exactly the symptoms you would expect:
- Danfoss, Series 45 J frame service manual: a relief set below the pressure compensator setting causes low output flow and heat, and the external relief must be above the PC setting for the pump to work properly.
- Denison, PV/PVT service information: under heating of fluid, the causes listed are a relief valve set too low compared to the compensator, and a compensator set too high compared to the relief.
- Our Vickers compensator page and A10VSO compensator page both list "adjustment does nothing" as the first sign that the relief is set below the compensator.
Do not leave the relief out either. Rexroth's A10VSO data sheet says pressure controllers are not protection against overpressure and a relief valve is to be provided. Denison recommends system relief valves in all cases, Kawasaki puts a safety relief warning on its K3VL regulator pages, and Parker calls a relief recommended on the PVP and PAVC, and mandatory on a PAVC fitted with a minimum volume stop.
How far above the compensator should the relief valve be set?
There is no single factory number for every pump. Where a manufacturer does give a margin, here it is. Where the table says no figure, we did not find one in the manuals on file, so use the machine builder's setting or the service manual for your unit.
| Source | What it says |
|---|---|
| Danfoss Series 45 J frame service manual (fan drive setting guidelines) | System relief valves should have at least 15 bar (about 218 psi) separation from the PC setting, so the pump control and the relief do not "talk" to each other. |
| Bosch Racine SV/TV pump controls | In its two-pressure circuit example, the main-line relief is a "peak clipper" set 150 psi above maximum operating pressure. |
| Parker PVP load-sense setup sheet | Maximum pressure compensator set 200 psi higher than any remote pressure control. |
| Oilgear PVWJ "P-1NN" and "P-LNN" bulletins 947633, 947634, 947635 | Pump compensator at least 200 psi (13.8 bar) above the remote compensator module setting, to stop the two interacting. |
| Vickers, Rexroth, Denison, Kawasaki, Parker PAVC | Relief above the compensator (or a relief required), no numeric margin in the documents we have. |
The Parker and Oilgear figures are the gap between two pressure controls on the pump circuit, not a relief valve figure, but the reasoning is the same: two controls set too close together fight each other.
How do you adjust hydraulic pump pressure safely?
- Identify the pump and its control. Read the full model code off the nameplate and find your control in the table further down. The range belongs to the control code, not just the series: a Vickers PVH with a CM control tops out at 2,000 psi, not 4,000.
- Put a gauge where the factory wants it. At the pump outlet, rated above the pump's maximum. Parker specifically says the outlet, not the low-signal "B" port on a PAVC. On a Danfoss Series 45, add a gauge on the case drain port, because the PC setting is referenced to case pressure.
- Warm the oil up. Cold oil reads high and settles differently. Set at normal operating temperature or you will be doing it twice.
- Write down the current settings. Deadhead the pump against a closed function and note where the gauge settles. If something goes wrong you want the original number.
- Start low. Parker's PVP and PAVC service bulletins say to bring a new or rebuilt pump up with the compensator at its minimum setting and cycle it on and off stroke while raising it. Denison's start-up list also says to reduce the compensator and relief settings first.
- Set the relief. To read a relief valve on a compensated pump, the compensator has to be high enough to let the relief crack. Bring the compensator up only as far as it takes, set the relief to its target, and keep it brief: full flow over a relief is all heat.
- Bring the compensator to the working setting, below the relief. Loosen the locknut while holding the screw, then adjust in small steps, a quarter turn at a time, letting the gauge settle. On every control in our table where the factory states a direction, clockwise raises pressure. Confirm it on the gauge with the first small move anyway.
- Lock it and check again. Tightening a locknut moves the screw more often than not. Re-run the pump to deadhead and confirm the reading held. Some controls are lockwired after setting (Vickers PVE19 and PVE21).
- Load-sense pumps: set the margin too. It is a separate screw, and the factories do not agree on the order: Rexroth and Parker set maximum pressure first, Danfoss sets the margin first. Follow the procedure for your pump; the load-sense section below has the numbers.
Never go past the factory range. The screw will turn further; that is not permission. Vickers states that a PVQ45C compensator shall not be set above 2,750 psi. Keep hands off hoses and fittings under pressure (escaping oil can penetrate skin), secure or block the machine so nothing moves while you work, and relieve pressure before you remove a gauge or a line.
Factory compensator ranges by brand
All figures are from the manufacturer documents listed in the last column. The adjustment screw on all of these is on the pump-mounted control, with a locknut, jam nut or set screw holding it. Follow the link for the full procedure where we have one.
| Pump | Control type | Adjustment screw | Factory range | Source |
|---|---|---|---|---|
| Vickers PVH57-PVH141 | C compensator / CM low-pressure compensator | Compensator on the pump, screw and locknut | C: 140-280 bar (2,000-4,000 psi). CM: 35-140 bar (500-2,000 psi) | Vickers PVH service data. Full detail: Vickers compensator adjustment |
| Vickers PVB (PVB45 data) | C / CM | Compensator on the pump | C: 250-3,000 psi. CM: 150-1,500 psi | Vickers PVB45 service data I-3297-S |
| Vickers PVQ (PVQ25, PVQ40/45 data) | C** / CM** (digits are the setting in tens of bar), C**V**B with load sense | Compensator on the pump | C**: 350-2,750 psi. CM**: 350-1,500 psi | Vickers PVQ25 and PVQ40/45 service data |
| Vickers PVE19 / PVE21 | C-10 pressure compensated | Compensator on the pump, lockwired after setting | PVE19: 250-3,000 psi. PVE21: 250-2,700 psi | Vickers M-2841-S (PDF) |
| Vickers PVE27 | Pressure compensator | Compensator on the pump | 25-250 bar | Vickers PVE27 service data |
| Rexroth A10VSO Series 31 | DR pressure controller; DFR/DFR1 adds a differential screw | Controller on the end cap. DR has one screw, DFR two | DR: 20-280 bar, factory standard 280 bar. DFR differential 14-22 bar, standard 14 bar | Rexroth RE 92711. Full detail: A10VSO compensator adjustment |
| Parker PVP16-PVP48 | Pressure compensated (omit), remote (M, ME), load sense (A), power (H, C) | Compensator on the pump. One screw on the standard control; maximum pressure plus differential on the load-sense control | Set by the pressure range code: 10 = 17-69 bar (250-1,000 psi), 20 = 17-138 bar, 30 = 17-207 bar, 36 = 17-248 bar (250-3,600 psi) | Parker catalog HY28-2662-CD/US. Full detail: Parker PVP and PAVC compensator adjustment |
| Parker PAVC33-PAVC100 | Pressure compensated (omit), load sense (A), remote (M, ME), power (H, C) | Cartridge control on the pump: pressure compensator and differential adjustments, plus power adjustment on H and C | Standard compensator: 28-207 bar (400-3,000 psi) on PAVC33, 38 and 65; 41-207 bar (600-3,000 psi) on PAVC100 | Parker catalog HY28-2662-CD/US (PAVC) |
| Denison PV6-PV29 / PVT6-PVT29 | C, F and L compensators; J and K torque limiters | Compensator valve mounted on the port block pad | Maximum compensator setting 4,000 psi (276 bar) on sizes 6-20, 3,500 psi (241 bar) on size 29. About 650 psi (44.8 bar) per turn | Denison PV/PVT service information S1-AM009-L |
| Oilgear PVWJ (all frames) | "P-1NN" and "P-LNN" pressure compensators | Pressure compensator adjustment screw with jam nut on the control. Clockwise increases | P-1NN: 750 psi (51.7 bar) up to the pump's maximum rated pressure. P-LNN: 250-1,500 psi (17.2-103.4 bar) | Oilgear bulletins 947633 (A frame), 947634 (B), 947635 (C) |
| Kawasaki K3VL | P0 pressure cut-off; L0/L1 load sense with pressure cut-off | Regulator on the pump: cut-off spool and differential pressure spool adjustments | Cut-off: 21-320 bar (300-4,600 psi), standard 320 bar. Load-sense differential: 10-21 bar (145-300 psi), standard 15 bar (218 psi). K3VL60 is rated 250 bar (3,625 psi) | Kawasaki K3VL technical brochure |
| Danfoss (Sauer) Series 45 J frame | PC pressure compensator, LS load sense | PC adjusting plug and LS adjusting plug, each locked by a set screw. Gauge port M1 | PC: 100-310 bar depending on displacement. About 42 bar (610 psi) per turn on PC, 17 bar (250 psi) per turn on LS. Clockwise increases | Danfoss Series 45 J frame service manual AX00000041en-US0203 |
| Racine PVQ-PNSO-06 (vane) | P pressure compensator (spring-loaded governor) | Pressure adjusting screw (clockwise raises) and volume adjusting screw (counterclockwise increases flow) | Spring letter in the code: B = 250 psi, C = 500 psi, E = 1,000 psi. 1,000 psi maximum outlet (A-35); the 1985 edition of 5.10-20 rates the 06 at 750 psi continuous, 1,000 psi intermittent | Racine bulletin 5.10-20 (PDF), engineering data A-35 |
Pump not on the list? We have not published a range we cannot source. Send us the model code and we will look it up in the factory literature.
Racine PVQ is a vane pump, not a Vickers PVQ
The two get mixed up all the time. Racine's PVQ-PNSO-06 is a variable-volume vane pump with a spring-loaded pressure compensating governor, as Racine called it. Its pressure is capped by the spring fitted, which is the letter after the size in the code: PVQ-PNSO-06ER-20 is a 1,000 psi spring, right-hand rotation. Racine's engineering data for the Q-Q double version lists compensating ranges of 100-250, 150-500 and 150-1,000 psi. Going above the spring's range means a different spring, not more turns. Racine's own service manual adds two points worth keeping: make the adjustment against a closed circuit, not through open-center valves, and set the pressure to the minimum the job actually needs. Racine's PVB, PVS and PVF are variable-volume vane pumps as well; the piston pumps in the Racine line are the C4, C5, C11, Model 20 and Model 80 radial piston pumps. The Vickers PVQ is an axial piston pump covered on our Vickers PVQ catalog page.
Load-sense pumps: margin and standby pressure
A load-sense pump has two adjustments. The compensator (or cut-off) caps maximum pressure. The differential, or margin, screw sets how far above the load pressure the pump runs, which also sets standby pressure when nothing is working. Too low and the functions are slow; too high and you waste power as heat. The full explanation is in load-sensing pumps explained.
| Pump | Differential (margin) data | Source |
|---|---|---|
| Rexroth A10VSO 31 DFR / DFR1 | 14-22 bar, standard 14 bar. Zero-stroke standby about 1-2 bar above the differential | RE 92711 |
| Kawasaki K3VL L0 / L1 | 10-21 bar (145-300 psi), standard 15 bar (218 psi). With the integrated unloading valve, standby is about 14 bar (200 psi) at the minimum differential | K3VL technical brochure |
| Parker PAVC | Shipped at about 10 bar (150 psi) on PAVC33, 38 and 65, and 21 bar (300 psi) on PAVC100, at 50% of maximum swash angle | Parker HY28-2662-CD/US |
| Parker PVP "A" control | Adjustable; about 27.5 bar (400 psi) per turn. No factory default published in the catalog | Parker HY28-2662-CD/US |
| Vickers PVQ C**V**B | The V digits are the differential: C21V11B is 207 bar compensator with an 11 bar load-sense differential on a PVQ25 | Vickers PVQ25 service data |
| Danfoss Series 45 J frame LS | About 17 bar (250 psi) per turn. The setting is in the model code | Danfoss Series 45 J frame service manual |
How Danfoss has you measure it, and it works on any brand: gauges on the pump outlet and on the load-sense line, run a function at about half pump flow with pressure below the compensator setting, and read the difference between the two gauges. That difference is the margin. Danfoss then deadheads the pump and sets the compensator; Rexroth and Parker set maximum pressure before the margin, so follow the order for your brand. Two gauges that disagree by a few psi will throw the reading off, so check them against each other on the same port first.
Is it the setting or the pump?
If the pressure will not come up no matter how far you turn the screw, stop turning. Parker's service bulletins put it plainly: a pump produces flow, not pressure, and it can only limit pressure when the system wants more than the compensator setting. The usual suspects, in the order we check them:
- Relief valve set below the compensator, or a relief stuck open.
- Load-sense or remote line vented to tank, or a remote valve set low.
- Compensator backed all the way out, a plugged control orifice, or a sticking spool.
- Worn rotating group. Pressure that builds and then sags under load, or a pump that works cold and fails warm, is internal leakage. Measure it with a case drain flow test before you blame the control.
More on each of those in hydraulic pump not building pressure and why is my hydraulic pump overheating. If you have just rebuilt or replaced the pump, run through the start-up procedure before you set anything.
Frequently asked questions
Do you adjust hydraulic pressure at the pump or at the relief valve?
It depends on the pump. A gear pump or other fixed-displacement pump has no pressure adjustment, so you set the relief valve. A pressure-compensated variable pump is adjusted at the compensator screw on the pump, with the relief valve set above it as a backstop.
Should the relief valve be set higher than the compensator?
Yes, always. If the relief is lower, it dumps flow before the pump can de-stroke, which makes heat and makes the compensator look dead. Where factories give a margin it varies: Danfoss's Series 45 fan-drive guidelines ask for at least 15 bar between the PC setting and system reliefs, and Racine's SV/TV pump controls bulletin shows a peak-clipping relief 150 psi above maximum operating pressure.
Which way do you turn a compensator to increase pressure?
Clockwise, on every control in our table where the manufacturer states a direction, including Vickers, Rexroth, Parker, Oilgear, Danfoss Series 45 and Racine. Confirm it on the gauge with a small first move, and never set by counting turns.
How do I raise the pressure on a gear pump?
You raise the setting of the system relief valve, within the pump's rating and the rating of everything else in the circuit. The gear pump itself has nothing to adjust. If the pressure will not rise with the relief turned up, the pump or the relief is worn.
What is load-sense margin or standby pressure?
It is the differential pressure the pump holds above the load pressure, set by the differential screw. With no function working, it is roughly the standby pressure. Rexroth's A10VSO DFR standard is 14 bar, Kawasaki's K3VL standard is 15 bar (218 psi), and Parker ships the PAVC33, 38 and 65 at about 150 psi.
Why doesn't the pressure go up when I turn the compensator?
Usually because something else is limiting it: a relief valve set below the compensator, a vented load-sense or remote line, or a worn pump leaking internally. Check those before turning the screw further, and run a case drain flow test if pressure builds and then falls off under load.
Can I set the compensator above the published range?
No. The screw will usually turn further, but the published range is the limit for the pump and the spring fitted. Vickers states that a PVQ45C compensator shall not exceed 2,750 psi, and Rexroth warns that the A10VSO valve can be set above its permissible range. If you need more pressure, you need a different control or a different pump.
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.
Need a compensator, a spring or a whole control?
Send us the full model code from the nameplate, including the control field, and tell us what the pump is doing. We reply with price, availability and lead time. In-stock parts ship within 24-72 hours, and in-stock parts carry a 2-year warranty. If the pump itself is worn, the teardown evaluation is free and you get a firm, itemized quote before any billable work. Repairs are done in our shop or through the RestoPower repair network, we arrange getting the unit to the shop doing the work, and work done in our shop carries a 1-year repair warranty.
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Related reading
- Vickers pump compensator adjustment
- Rexroth A10VSO pressure compensator adjustment
- Parker PVP and PAVC compensator adjustment
- Troubleshooting and setting relief valves
- Load-sensing hydraulic pumps explained
- Hydraulic pump start-up procedure
- Case drain flow test
- Rexroth A10VSO and A10VO pump troubleshooting
- Brand catalogs: Vickers, Parker, Denison, Oilgear, Kawasaki, Racine, Sundstrand / Sauer-Danfoss
- Seal kits: Vickers piston, Parker, Rexroth, Denison, Oilgear, Kawasaki