The catalogue says 210 bar. The pump is rated at about 206 because the manufacturer published 210 kgf/cm². On antiwear water glycol, the same Yuken pump is rated at 160 kgf/cm², about 157 bar.
Three numbers, one pump, and none of them is wrong. Each is a rating at a different set of conditions, and the conditions are the specification.
That gap is what vane pump derating measures. A catalogue rating is not a property of the pump. It is a measurement taken at stated reference conditions, and if you change the fluid, the speed, the temperature, or the duty cycle, the rating changes.
This article gives you the method: five factors, a worksheet, two worked examples from published Parker and Yuken data, the cold-start rule most buyers never see, and an honest answer when derating says the pump is wrong. Family fundamentals are in our complete guide to hydraulic vane pumps; the pressure ceiling is in the high-pressure vane pump guide.
Scope: industrial hydraulic vane pumps, not rotary-vane transfer pumps, vacuum pumps, or electronic control derating.
What Is Vane Pump Derating?
Vane pump derating is the reduction of a pump’s catalogue pressure and speed ratings to match its actual operating conditions: fluid type, viscosity, temperature, rotational speed, displacement, and duty cycle. A catalogue rating is valid only at the reference conditions stated in the manufacturer’s data sheet.
Derating is a translation, not a discount. It is arithmetic with published inputs, and it produces a number you can defend in a specification meeting.
Sizing asks which pump to buy. Derating asks whether the pump you chose can sustain the duty you have. Our vane pump sizing method handles the first; this article handles the second.
The mechanism connects both. Fluid, speed, and temperature change vane tip loading, cam ring deflection, and internal leakage, which change what the pump can hold. Our guide to why vane pumps have a pressure limit traces that chain.
Running a duty close to the catalogue number? Send us the duty data, and we will return the permissible continuous pressure at your fluid, speed, and temperature.
Why a Catalogue Rating Is Not a Machine Rating
Parker states it plainly in its industrial vane pump catalogue: “The use of fluids other than petroleum-based antiwear R&O fluids requires that the maximum ratings of the pumps will be reduced.”
One frame proves it. The Parker T7A B13 displaces 12.8 ml/rev and runs down to 600 rpm. On HF-0 or HF-2 antiwear petroleum, it carries 275 bar continuous and 300 bar intermittent at up to 3,600 rpm. On HF-1, HF-4, or HF-5, it drops to 210 bar and 1,800 rpm. On HF-3, the water-in-oil emulsion falls to 140 bar.
Same cartridge, three ratings, 135 bar apart. The fluid and the speed allowance did the work.
Yuken’s PV2R2-47 shows the same effect and a unit trap. The catalogue rates it 210 kgf/cm² on specially specified petroleum, about 206 bar, not 210 bar. The ladder runs 175 kgf/cm² on antiwear petroleum (about 172 bar), 140 on R&O (137 bar), 160 on antiwear water glycol (157 bar), and 70 on water glycol or water-in-oil (69 bar).
A buyer who reads “210” as “210 bar” is 4 bar over the rating before any fluid correction. The stack runs one way: series, frame, displacement, fluid, speed, temperature, duty, then permissible continuous pressure. Our high-pressure vane pump series guide maps the frame tables.
The Five Factors That Derate a Vane Pump
The factors interact, but they do not multiply. Multiplying is how buyers reach 120 bar for a pump genuinely rated 190 bar.
Apply each factor as a constraint from its own published table and take the lowest result. Contamination and inlet pressure are validity conditions, not multipliers: a pump on dirty oil at a starved inlet is outside its rating, whatever the arithmetic says.
1. Fluid Type and Viscosity: The Largest Correction
Fluid class is the biggest lever most plants have. The Parker T7A B13 table is the clearest published example:
| Fluid class | Continuous | Intermittent | Maximum speed |
|---|---|---|---|
| HF-0 / HF-2 antiwear petroleum | 275 bar | 300 bar | 3,600 rpm |
| HF-1 / HF-4 / HF-5 | 210 bar | 240 bar | 1,800 rpm |
| HF-3 water-in-oil emulsion | 140 bar | 175 bar | 1,800 rpm |
Frame T7A B13, 12.8 ml/rev, minimum speed 600 rpm. Source: Parker HY29-0001/UK.
Read the ratios, not just the bar figures, because ratios transfer between frames more reliably. Against HF-0/HF-2, the HF-1/HF-4/HF-5 band is roughly 0.76 times the continuous rating and 0.8 times the intermittent one. HF-3 is roughly 0.51 times continuous and 0.58 times intermittent: water-in-oil is far harsher than water-glycol, and treating them as equivalent overstates this pump by about 70 bar.
Viscosity sets the window in which any pressure rating is valid. Parker publishes an optimum of about 30 cSt, full speed and pressure from 10 to 108 cSt, and a cold-start ceiling of 860 cSt. Eaton’s VMQ manual is tighter: 16 to 40 cSt optimum, full pressure to 54 cSt industrial, and 100 cSt mobile.
Non-petroleum fluids also raise the inlet requirement. Parker calls for minimum absolute inlet pressure multipliers of 1.25 for HF-3 and HF-4, 1.35 for HF-5, and 1.10 for ester or rapeseed base. A water-glycol conversion that ignores them cavitates before it reaches its derated pressure.
2. Vane Pump Speed Derating: Both Ends Matter
Maximum speed is fluid-dependent. The T7A B13 turns to 3,600 rpm on petroleum and 1,800 rpm on every non-petroleum class. Yuken’s PV2R catalogue is blunt: “If phosphate ester or water-containing fluids are used, the maximum speed is limited to 1200 r/min.”
Danfoss publishes its VMQ maximum speeds at 0 bar inlet, varying by frame from 2,600 to 3,000 rpm on frame 25 down to 2,200 rpm on frame 45. A speed limit without its inlet condition is incomplete.
The minimum matters too. Vane extension depends on centrifugal force, so below a floor speed the vanes stop sealing against the cam ring. Parker and Yuken publish 600 rpm for these frames, PV2R1 needs 750, and single-acting designs commonly require 600 to 900. Our single-acting vane pump design article covers why. Speed also raises the PV factor, the product of pressure and sliding velocity, so doubling speed roughly doubles the work at the vane tip.
3. Displacement and Frame Size: Bigger Is Not Safer
Within a frame, larger displacement usually means a lower rating. Yuken’s PV2R3-76, 94, and 116 sizes carry 160 kgf/cm² (about 157 bar), whereas smaller PV2R2 sizes reach 210. PV2R3-116 is limited to 0 kgf/cm² suction pressure above 1,700 rpm, effectively banning pressurized inlets at high speed.
Frames differ too. Parker’s T7A B13 holds 275 bar continuous, while the larger-frame T6C 025 to 031 holds 160 bar continuous and 210 bar intermittent at up to 2,500 rpm. Buying the bigger pump for margin can move you to a lower-pressure design.
Multi-section pumps add another cap: Parker’s multiple-pump table limits most combinations to about 2,200 rpm. Our guide to double and triple vane pumps explains how sections combine. The practical rule is never to quote a series headline for a specific pump. Quote the frame, the displacement code, the fluid, then the speed.
4. Vane Pump Temperature Derating: A Hard Limit, Not Just a Percentage
Hot oil is thinner oil. Thinner oil leaks past the vane tips and side plates faster, which is slip, and slip converts pressure energy into heat. The loop compounds. Our vane pump oil and filtration guidance covers the fluid side; the vane pump fault diagnosis matrix covers the symptoms once the loop has started.
Temperature is the input most often skipped in vane pump derating, and it enters the rating in two ways.
The first is a hard maximum. Parker publishes maximum fluid temperatures of +100 °C for HF-0, HF-1, and HF-2; +50 °C for HF-3 and HF-4; +70 °C for HF-5; and +65 °C for biodegradable ester or rapeseed. Standard seals are limited to -30 °C to +90 °C. Eaton publishes operating limits instead: 66 °C continuous and 74 °C intermittent industrial, 82 °C and 99 °C mobile. A fluid maximum and an operating maximum are not interchangeable.
The second is a smooth percentage rule. Vicks Hydraulic publishes a practice of reducing pressure by 10% for every 15 °C above 50 °C, which takes a 17.5 MPa pump to 15.75 MPa at 65 °C, 14 MPa at 80 °C, and 12.25 MPa at 95 °C. It is a usable approximation, and it is not a standard. No standard or test method is cited, so attribute it to the manufacturer.
The rule cannot override a hard limit. A water glycol pump at 60 °C is outside its +50 °C fluid maximum. Derating pressure by 7% does not make that valid; more cooling or a different fluid does.
Hafiz, a maintenance planner in Johor, learned the distinction in 2024. His team replaced a worn cartridge but left cooler cleaning on the deferred list. Pressure returned for five weeks. By week nine, the pump was 30 bar below setpoint because the fluid still ran at 68 °C against a 50 °C limit.
5. Duty Cycle: Continuous, Intermittent, Peak
Continuous pressure holds indefinitely. Intermittent pressure is a higher figure allowed for a defined part of the cycle. Peak pressure is a momentary transient. The hydraulic vane pump guide defines all three; here the arithmetic matters more.
Parker’s rule is precise: a T7 or T67 unit “may be operated intermittently at pressures higher than the recommended continuous rating when the time-weighted average of pressure is less than or equal to the continuous duty pressure rating.” The constraint is the average over the cycle, not the peak, and cycles longer than 15 minutes need manufacturer guidance.
A Parker T7B B10 is rated 290 bar continuous and 320 bar intermittent on HF-0/HF-2. A ten-minute cycle runs 4 minutes at 320 bar, 1 minute at 35 bar, and 5 minutes at 160 bar. The time-weighted average is (4×320 + 1×35 + 5×160) ÷ 10, which equals 211.5 bar, well under 290 bar. The cycle is acceptable.
Other manufacturers publish different allowances. One Parker HD series document permits +15% intermittent pressure for up to 80% of a 15-minute cycle. Treat that as one manufacturer’s rule for one series. Peak pressure is a transient; keep it out of a continuous duty calculation.
A Step-by-Step Vane Pump Derating Worksheet
How to derate a vane pump: work the constraints in order and stop at the lowest number.
- Record the duty in the pump’s units: continuous and peak pressure, flow, speed, fluid class, viscosity, fluid temperature, duty cycle, inlet condition, contamination target.
- Get the frame-specific catalogue rating, not the series headline, with its reference fluid, speed, and temperature.
- Apply the fluid correction from the OEM table. If none exists, use roughly 0.76× for HF-1, HF-4, and HF-5, treat HF-3 as closer to 0.51×, and verify with the supplier.
- Check speed at both ends: the fluid-specific maximum and the vane-extension minimum.
- Check temperature against the fluid’s hard maximum and the viscosity window.
- Check the time-weighted average of the duty against the continuous rating.
- Check cold start and inlet pressure, applying the 50% pressure rule and the inlet multipliers.
- Take the lowest resulting pressure and record the limiting factor.
Worked Example 1: Parker T7A B13 on HF-4
Marta, the Brno plant’s reliability engineer, had her answer within an hour once the method was clear. Catalogue on HF-0/HF-2: 275 bar continuous, 3,600 rpm maximum. Duty: 1,500 rpm, HF-4, 45 °C, continuous, 245 bar required.
The fluid row moves the rating to 210 bar continuous and caps speed at 1,800 rpm. At 1,500 rpm, the pump is inside that cap and above the 600 rpm floor, so speed adds nothing. At 45 °C, it sits under the +50 °C maximum. Continuous duty means no intermittent credit.
Permissible continuous pressure: 210 bar. Required: 245 bar. The duty is not acceptable.
Return to HF-0 or HF-2 if fire safety permits, which restores 275 bar. Reduce the setpoint. Or move to a frame rated higher on water glycol. Adding a 10% margin to 210 bar is not one of the options.
Worked Example 2: Yuken PV2R2-47 on Antiwear Water Glycol
The catalogue gives 160 kgf/cm², about 157 bar, on antiwear water glycol, with a 1,200 rpm maximum on water-containing fluids and a 600 rpm minimum.
Duty: 1,200 rpm, 50 °C, 60% of the cycle at 140 bar and 40% at 30 bar. Speed sits exactly at the ceiling with no margin, so raising speed to shorten cycle time is closed off. The time-weighted average is 0.6×140 + 0.4×30, which equals 96 bar.
Permissible continuous pressure: 157 bar. The pressure margin is real; the limiting factor is speed. That is the output a worksheet gives you, and a series headline does not.
Vane Pump Cold Start: The 50% Rule
Cold oil is the most common way a correctly derated pump still fails. Eaton’s rule is specific: above 54 cSt in industrial conditions, “the outlet pressure should not exceed 50% of the maximum rating for the VMQ pump until the system has warmed up.” Above 100 cSt in mobile service, speed and pressure are both limited to 50%. The startup ceilings are 860 cSt industrial and 2,000 cSt mobile.
Dale, a maintenance supervisor in Edmonton, started a cold press at full pressure in January 2023 with ISO VG 68 oil at -18 °C. Viscosity was well above 54 cSt. The pump should have been held to half pressure. It lasted four days.
Put the cold-start limit in the startup procedure, not just the selection sheet.
Common Derating Mistakes, and When the Answer Is a Different Pump
Six mistakes account for most of the failures this method prevents:
- Quoting the series headline. “T7, 320 bar” is a T7B frame rating on HF-0/HF-2 in intermittent duty, not a family continuous rating.
- Applying a temperature percentage past a hard limit. At 60 °C, water glycol is outside its fluid maximum.
- Treating intermittent as continuous. The rating is time-weighted, and cycles over 15 minutes need manufacturer guidance.
- Skipping cold start and inlet pressure. The 50% rule and the 1.25/1.35 multipliers are part of the rating.
- Slowing the pump to fix pressure. Lower speed means lower flow. Recheck the actuator cycle time.
- Assuming larger displacement is safer. Within a frame, it usually carries a lower rating.
Sometimes the calculation ends below the duty, and that is a successful calculation. It prevented a premature failure. The honest options, in order of usual payoff: change to HF-0/HF-2 if fire safety allows, reduce speed and recheck flow, select a smaller displacement or a higher-pressure frame, add cooling, or re-architect with a hi-lo pump or accumulator for peak demand.
Above roughly 300 bar continuous, vane stops being the right family.
If the constraint is cost rather than pressure, the gear pump vs vane pump comparison is the other honest alternative.
What to Ask a Supplier About Derating
A derating table is a purchasing document. Ask before the order:
- What is the frame-specific continuous rating at my fluid, speed, and temperature, rather than the series headline?
- Can you provide the full derating table: fluid correction, maximum speed, maximum fluid temperature, viscosity window?
- What is the cold-start procedure and the pressure limit until warm?
- Can you provide pressure-hold test records at rated continuous pressure?
- Does the warranty reference pressure, fluid, and duty, or only elapsed time?
Frequently Asked Questions
What is vane pump derating?
It is the reduction of catalogue pressure and speed ratings to match actual conditions: fluid, viscosity, temperature, speed, displacement, and duty cycle. The catalogue figure holds only at its stated reference conditions.
How much should I derate a vane pump for temperature?
Check the fluid’s hard maximum first: +50 °C for HF-3 and HF-4, +70 °C for HF-5, +100 °C for HF-0/1/2 on Parker data. Only within those limits, apply a rule such as 10% per 15 °C above 50 °C.
Does higher speed reduce a vane pump’s pressure rating?
Indirectly. Maximum speed is fluid-dependent, and the pV factor rises with sliding velocity, so tip wear increases even at unchanged pressure. Doubling speed roughly doubles the wear work.
What is the water glycol pressure rating for a vane pump?
Substantially. On a Parker T7A B13, HF-4 drops continuous pressure from 275 to 210 bar, about 0.76×; HF-3 falls to 140 bar, about 0.51×. Yuken’s PV2R2-47 falls from 210 kgf/cm² on specially specified petroleum to 160 on antiwear water glycol.
Can I run a vane pump above its continuous rating intermittently?
Only when the time-weighted average pressure over the cycle is at or below the continuous rating, and only if speed, fluid, viscosity, and contamination stay within limits. Cycles over 15 minutes need manufacturer guidance.
What is the minimum speed for a vane pump?
It depends on the design. Parker and Yuken publish 600 rpm for these frames, PV2R1 needs 750 rpm, and single-acting designs commonly require 600 to 900 rpm.
Do larger vane pumps have lower pressure ratings?
Often. Within a frame, larger displacement usually carries a lower rating: Yuken’s PV2R3-76, 94, and 116 are rated 160 kgf/cm², whereas smaller PV2R2 sizes reach 210.
What happens if a vane pump runs on oil that is too hot?
Viscosity falls, slip rises, and slip generates more heat, so the loop compounds until volumetric efficiency collapses. Past the fluid’s hard maximum, derating pressure does not restore a valid rating.
Conclusion
Vane pump derating starts from one fact: a catalogue rating is conditional, and the conditions are the specification. Five factors move it: fluid and viscosity, speed, displacement and frame, temperature, and duty cycle. Apply them as constraints in sequence, take the lowest result, and name the limiting factor. Then check cold start, because a pump correctly derated for steady state can still fail in its first ten minutes.
Sometimes the number you reach is below the duty. That is not a failed calculation; it is the calculation doing its job. Change the fluid, slow the drive, add cooling, or choose a different pump before the cam ring decides for you.
Have a duty that sits close to the catalogue figure? Request a derating review with your fluid, speed, temperature, and cycle data. We will return the permissible continuous pressure for the frame you are considering, and tell you plainly if a vane pump is the wrong answer.
