How to Adjust the Compensator on a Parker PVP or PAVC Pump

On a Parker PVP or PAVC, deadhead the pump with a gauge in the outlet port, free the lock on the pressure compensator adjusting screw, and turn the screw clockwise to raise pressure and counterclockwise to lower it, a little at a time, until the gauge reads your setting. Stay inside the factory range: on a PVP that is the pressure range code in the model number (up to 248 bar, 3,600 psi), and on a PAVC the standard compensator runs 28-207 bar (400-3,000 psi), or 41-207 bar on the PAVC100.

The rest of this page covers which screw is which on each control, how much one turn moves the pressure, the factory differential and load-sense settings, and the faults that make a Parker compensator look broken when it is not. Every number comes from Parker's catalog HY28-2662-CD/US and the PVP and PAVC service bulletins.

Searching "PVP compensator" turns up gun parts. This page is about the Parker PVP and PAVC variable displacement piston pumps from Parker's hydraulic pump division, not muzzle brakes. If you are not sure which pump you have, start with how to identify a Parker pump.

Which control does my Parker PVP or PAVC have?

The control is a letter field near the end of the model code. No letter ("omit") means the standard pressure compensator. Read the full code off the nameplate; our PVP page and PAVC page break down the rest of it, and the Parker Hannifin brand page and Parker piston pump guide cover the rest of the line.

Code	PVP	PAVC
Omit	Pressure compensated	Standard pressure compensated
M / ME	Remote pressure. M may be remotely controlled; ME requires an external pilot	Remote pressure, same M / ME meaning
A	Pressure and flow (load sensing)	Pressure and flow (load sensing)
H	Pressure compensated and power (horsepower, really a torque limiter)	Pressure and power (torque) limiting
C	Pressure, flow and power	Pressure, flow and power (torque) limiting
HLM / HLA	Hi/Lo power control, PVP41 and PVP48 only	Not offered
S / SE, AM, CM, HM	Not offered	Servo pressure and volume (needs a proportional pressure control, amplifier and sequence valve), and remote versions of A, C and H

Parker lists the PVP60 through PVP140 as phased out and refers them to the P1/PD series. Everything below covers the PVP16, 23, 33, 41 and 48 and the PAVC33, 38, 65 and 100.

Which screw is the compensator on a Parker PVP?

Standard compensator (omit): one pressure adjustment on the compensator body. That is the only pressure screw on the pump. A second adjuster, if fitted, is the maximum volume stop (option 2), which changes flow, not pressure.
Remote compensator (M, ME): a different compensator body with a maximum pressure adjustment and a remote port for the remote pressure valve. Parker's drawings show the differential adjustment only on the A and C controls.
Load sense (A): the same layout as the remote compensator, with an integral orifice and a solid spool. The maximum pressure adjustment caps pressure and the differential adjustment sets the margin. The sense line goes to the uppermost port on the compensator only.
Power control (H, C): a separate horsepower control block mounted on the pump housing and plumbed to the remote compensator by steel tubing. Its screw is the power (torque) adjustment, not a pressure setting.

On a left-hand (CCW) PVP the compensator sits on the opposite side of the pump, so do not go by a photo of a right-hand unit. And if you replace the pressure adjustment assembly on a PVP41 or PVP48, Parker's service bulletin says the compensator must be locked out at the pump's maximum operating pressure.

Which screw is which on a PAVC?

The PAVC uses field-changeable cartridge controls. Parker's control drawings label the adjusters on each one: a pressure compensator adjustment and a differential adjustment on every control, plus a power (torque) adjustment on H and C. The differential is adjustable only on pumps with differential option 4; on the standard (omit) option it is set with shims.

How much does one turn change the pressure?

These are Parker's approximate adjustment sensitivities from the dimension drawings in HY28-2662-CD/US. They are also the quickest way to tell two screws apart: give one a small, known move with the gauge on and see how far the reading shifts.

Pump and adjustment	Approximate change per turn
PVP16, PVP23/33, PVP41/48 standard pressure compensator	37.9 bar (550 psi)
PVP remote and load-sense compensator (M, ME, A, H, C), maximum pressure screw	64.8 bar (940 psi)
PVP differential adjustment (A control, and C on the PVP16)	27.5 bar (400 psi)
PVP16 power control, option H	21.4 N·m (190 in-lb) of input torque
PVP23/33 power control, option H	22.5 N·m (200 in-lb) of input torque
PAVC33/38, PAVC65, PAVC100 pressure compensator	55 bar (800 psi)
PAVC33/38 and PAVC65 adjustable differential, option 4	13.8 bar (200 psi)
PAVC100 adjustable differential, option 4	28 bar (400 psi)
PAVC power (torque) control	PAVC33/38: 56 N·m (500 in-lb). PAVC65: 90 N·m (800 in-lb). PAVC100: 130 N·m (1,150 in-lb)

A quarter turn on a PAVC compensator is roughly 200 psi. That is a big step near the top of the range, so go an eighth of a turn at a time as you get close.

What are the factory pressure ranges for the PVP and PAVC?

PVP pressure range code

The PVP model code has a pressure range field right after the displacement. It is the same on the PVP16, PVP23/33 and PVP41/48.

Code	Compensator range
10	17-69 bar (250-1,000 psi)
20	17-138 bar (250-2,000 psi)
30	17-207 bar (250-3,000 psi)
36	17-248 bar (250-3,600 psi)

Parker notes that the minimum of each range applies only to the standard (omit) control. The PVP is rated 248 bar (3,600 psi) continuous and 310 bar (4,500 psi) peak. Stay inside the range your pump was built with. A pump coded 10 or 20 is not rated for 3,000 psi just because the screw will turn further.

PAVC setting range and factory defaults

Frame	Standard compensator range	Shipped at (unless ordered otherwise)
PAVC33 / PAVC38	28-207 bar (400-3,000 psi)	Maximum flow and 69 bar (1,000 psi). Power default 7.5 hp at 1,800 rpm and 1,000 psi on H and C, 20 hp at 1,800 rpm and 3,000 psi on HM and CM
PAVC65	28-207 bar (400-3,000 psi)	Maximum flow and 69 bar (1,000 psi). Power default 15 hp at 1,800 rpm and 1,000 psi on H and C, 40 hp at 1,800 rpm and 3,000 psi on HM and CM
PAVC100	41-207 bar (600-3,000 psi)	Maximum flow and 69 bar (1,000 psi). Power default 22.5 hp at 1,800 rpm and 1,000 psi on H and C, 60 hp at 1,800 rpm and 3,000 psi on HM and CM

Pumps with M, ME, AM, CM or HM controls (and S or SE on the PAVC33/38) leave the factory set to compensate at 207 bar (3,000 psi). The PAVC is rated 207 bar (3,000 psi) continuous. So two PAVCs straight from the factory can be set 2,000 psi apart depending on the control, and a used one could be set anywhere, which is one more reason to put a gauge on it before you touch anything.

What is the best compensator setting for a Parker PVP?

There is no single best number, and Parker does not publish one for the PVP. The right setting is the lowest pressure that does the work: set the compensator just above the highest pressure the machine really needs, keep the main relief above the compensator, and stay inside the pressure range code on the nameplate. Pressure the job does not use only turns into heat. On a load-sense PVP, set the differential only as high as it takes for the valve to get full flow; Parker's own note is that a higher differential just raises pressure and wastes horsepower. If you are replacing a pump, read the old setting with a gauge before it comes off the machine.

How do you set the pressure compensator on a PVP or PAVC?

Fit a gauge in the pump outlet. Not in the low-signal "B" port on a PAVC; Parker is specific about that. Use a gauge rated above your target, for example the 0-207 bar (0-3,000 psi) gauge Parker calls for on the PAVC differential check.
Check the relief valve. Parker recommends a relief in the main circuit on both pumps, and on a PAVC with a minimum volume stop it is mandatory. It must be set above the compensator, or the relief takes the flow and the compensator never controls. See relief valve or compensator for the order.
Start low. Parker's service bulletins say to start a new or serviced pump with the compensator at its minimum setting, then cycle the pump on and off stroke while raising it to the required setting. Full counterclockwise is minimum.
Warm the oil and deadhead the pump. Block the outlet downstream of the gauge, or run a cylinder to the end of its stroke, so the pump is at zero flow.
Free the lock on the adjusting screw (the jam nut, where fitted) and adjust clockwise. Small moves, letting the gauge settle each time. Use the per-turn figures above to judge the step size.
Stop at your setting, inside the range code. Never past the top of the range for your pump.
Lock and recheck. Hold the screw, re-tighten the lock, then cycle the pump off and back on stroke and confirm it comes back to the same reading.

Keep the drain lines open while you test. The PVP case drain must not see more than 0.7 bar (10 psi) back pressure, and the PAVC control drain not more than 7 bar (100 psi). Never cap a drain to "see what it does." Stay clear of hoses and fittings under pressure, keep the machine secured so nothing moves unexpectedly, and relieve pressure before you remove a gauge.

How do you check and set the PAVC differential?

Parker ships the standard pressure-compensated PAVC with a differential of about 10 bar (150 psi) on the PAVC33, 38 and 65, and 21 bar (300 psi) on the PAVC100, at 50% of maximum swash angle. Parker says it does not normally change over the life of the pump. If someone has been into the control, their check is:

Deadhead the pump (no flow) with a 0-207 bar (0-3,000 psi) gauge in the outlet, not the "B" port.
Back the pressure compensator adjustment all the way out, full counterclockwise.
Read the gauge. It should sit at 22-26 bar (325-375 psi) on a PAVC33, 38 or 65, and 34-40 bar (500-575 psi) on a PAVC100.
If it does not, turn the differential adjustment (option 4) or add or remove shims (omit option) until it does. Then reset the compensator to your working pressure.

How do you set up load sense on a Parker PVP?

This is the sequence from Parker's setup sheet for the "A" control on the PVP, in shop words:

Connect the load-sense line to the top port of the remote compensator only. If the pump was converted from another control, make sure the orifice plug Parker specifies (800599) is in that top port.
For the first setting, tee the sense line in upstream of the valve you are sensing across, or at the pump outlet.
Fit any remote or vent valve to a side port of the compensator, set remote valves to their maximum and close the vent valve. Back the maximum pressure compensator to its lowest setting (counterclockwise).
Block the pump outlet downstream of the sense tee and start the system.
With the pump deadheaded, set the maximum pressure compensator, then any remote valves to their working settings. Parker wants the maximum compensator 200 psi higher than any remote pressure control.
Shut down, move the sense line back downstream of the load-sense valve, restart, open the system to full flow, and set the flow control orifice if it is adjustable.

Parker's note on the differential: set too low and the pump will not reach the full flow the valve allows; set too high and pressure runs higher than it needs to, wasting horsepower as heat. Neither makes the pump erratic. The differential adjustment is how you find the sweet spot, and it also changes standby pressure. Parker does not publish a default PVP differential in the catalog, so measure what you have: outlet pressure minus sense-line pressure, with a function running at part flow below the compensator setting.

Low pressure standby on a PAVC

On a PAVC with load sense (A), you get low pressure standby by venting the "B" port through a simple on/off valve sized for 3.8-7.6 L/min (1-2 gpm). With the remote control (M), the pump holds roughly the "B" port pressure plus the differential, so a relief or proportional valve on the "B" port line sets working pressure. In the compensating mode the M control flows about 1.1 L/min (0.3 gpm) out of the "B" port on top of about 3.4 L/min (0.9 gpm) from the control drain. On a remote PVP, the remote relief valve must be able to pass 1.89 L/min (0.5 gpm).

Should I adjust the horsepower control?

Only with the data. The H and C controls are set at the factory to the horsepower, rpm and compensator pressure on the order, and if none was given they get Parker's default. On a PVP, a power control set low enough can bring the pump to zero stroke before the maximum compensator ever opens, which looks exactly like a low compensator. On the PVP41 and PVP48 Hi/Lo control there are up to four adjustments that all change the curve together. If the horsepower setting is in question, check it on a test stand, not on the machine.

Why won't my Parker compensator adjust?

From Parker's PVP and PAVC service bulletins, grouped the way they list them:

Symptom	Causes Parker lists
Can only build a few hundred psi	Compensator backed all the way out. Remote or load-sense line vented. Control orifice or spool plugged. Wrong compensator spool (PVP). Pressure control dart lodged open. Torque control plug missing (PAVC)
Pump will not compensate (stays on stroke)	Differential spring over-compressed (spring guide dislocated). Control drain line blocked (PAVC). Pressure control stem vent hole plugged. Control spool travel hindered. Control orifice missing (PAVC). Saturation orifice missing in a load-sense circuit
Cannot build any pressure	Pump not primed. Misalignment, especially on PAVC pumps without the "9" dual bearing option. Open circuit: a pump makes flow, not pressure, and can only limit pressure when the system asks for more than the compensator setting
Will not prime	Parker says a pump should prime within 30 seconds; if not, stop. Check rotation, coupling engagement, reservoir level and suction leaks

If the control checks out and pressure still sags under load, the rotating group is worn. A case drain flow test will tell you, and hydraulic pump not building pressure walks through the rest of the circuit.

Frequently asked questions

Which way do I turn the compensator on a Parker PVP?

Clockwise raises the pressure and counterclockwise lowers it. Full counterclockwise is the minimum setting, which is where Parker has you start a new or rebuilt pump. Always adjust with a gauge in the outlet port.

What is the pressure range of a Parker PVP compensator?

It is set by the pressure range code in the model number: 10 is 250-1,000 psi, 20 is 250-2,000 psi, 30 is 250-3,000 psi and 36 is 250-3,600 psi (17-248 bar). The PVP is rated 3,600 psi continuous.

How much does one turn of the compensator change the pressure?

About 550 psi per turn on a PVP standard compensator, about 940 psi per turn on the maximum pressure screw of a PVP remote or load-sense compensator, and about 800 psi per turn on a PAVC. The PVP differential screw is about 400 psi per turn.

What is the PAVC standard compensator range?

28-207 bar (400-3,000 psi) on the PAVC33, 38 and 65, and 41-207 bar (600-3,000 psi) on the PAVC100. Unless ordered otherwise, Parker ships the standard control set to 1,000 psi.

What should the differential be on a PAVC?

About 150 psi (10 bar) on the PAVC33, 38 and 65, and 300 psi (21 bar) on the PAVC100. To check it, deadhead the pump with the compensator backed fully out: the outlet gauge should read 325-375 psi on the smaller frames and 500-575 psi on the PAVC100.

My Parker PVP only builds a few hundred psi. Is the compensator bad?

Not necessarily. Parker lists a compensator backed all the way out, a vented remote or load-sense line, a plugged control orifice or spool, the wrong compensator spool and a pressure control dart stuck open. Check those, and the relief valve setting, before replacing anything.

Do I need a relief valve with a PVP or PAVC?

Parker says a relief in the main circuit is not mandatory but is recommended on both, to handle shock loads and add protection. On a PAVC with a minimum volume stop it is mandatory. Set it above the compensator.

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 Parker compensator, spring or seal kit?

Send us the full PVP or PAVC model code from the nameplate, including the pressure range and control letters, 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 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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