manutenzione pompe a pistoni - hpp

High-pressure piston pumps are the key elements of many technological systems: exceptionally powerful tools that require particular and frequent maintenance to operate at their best.


In this article, therefore, we will discover the most important tips for obtaining the greatest efficiency from high-pressure pumps and the tricks for keeping them at their best.

How high pressure piston pumps work

High pressure piston pumps allow you to pump large quantities of liquids and fluids, even with high viscosity, inside circuits and pipes. These are high-performance systems, capable, for example, of producing a high-power jet of water and of withstanding such stresses at high frequency of use.

For these reasons they are particularly used in the cleaning sector – for example as the “heart” of pressure washer machines – for washing very large surfaces, cisterns, tanks and production plants with pressurized water. Likewise, they are used in various industrial sectors – food production, zootechnics, chemistry and petrochemistry – thanks to the particular technologies that constitute them and which allow the flow rate and pressure of the pumped fluids to be set with great precision, depending on the required use.


Included in the category of alternative volumetric pumps, they are equipped with technical characteristics whereby the flow of the liquid takes place by virtue of the variations of one or more capacities which, alternatively, prime and send the liquid through the action of pistons.

Preliminary precautions

The most commonly encountered problems with high pressure pumps are due to lack of routine maintenance, as well as poor conditions of use of the pump which can cause cavitation, dry running, poor or incorrect filtration.

If frequent inspections and routine maintenance of the components are not carried out, on the other hand, excessive wear, damage and oil leaks can occur, with consequent loss of pressure and pulsations, breakage of the pistons and of the entire pump.

So let’s start by listing some precautions to take even before using the pump. First of all, only clean with fresh water at standard temperature, not exceeding 40° centigrade, must circulate inside the high-pressure pump. In fact, high temperatures significantly increase the risk of cavitation which can cause considerable damage to various parts of the pump.

Likewise, the pump must not operate at temperatures below 0°C. In areas and periods of the year at risk of freezing, therefore, it will be necessary to run the vacuum pump for a few seconds before using it, so that the water contained in the head is evacuated, then open the taps or caps provided in the suction to remove trapped water. Furthermore, in the presence of ice, do not rotate the pump shaft for any reason until the circuit has thawed, to avoid serious damage to the pump itself. Also, in low temperatures, let the vacuum pump run for a while to make the oil in the crankcase fluid.

Furthermore, if you want to circulate liquids of a different nature and viscosity from that of water in the pump, it is also strongly recommended to first contact the manufacturer and follow the particular instructions in this regard.

Lastly, each pump is equipped with a card which indicates its maximum flow rate, pressure and power: never exceed the maximum pressure and number of revolutions indicated, regardless of the power used.

Put the high pressure pump into operation

As for any machinery, before operating any high pressure piston pump it is advisable to check that there is no visible damages, for example to the gearbox and cylinder head. Furthermore, before starting the engine, ensure that the pump is supplied with an adequate flow of water and check that the oil level inside the pump crankcase is correct using the dipstick and the sight glass, and replace the oil if it has a whitish appearance due to emulsion with water.

Before the pump shaft starts to rotate, check that the pump is not subjected to any load, by fully opening the regulating valve, zeroing the air supply for pneumatic regulators, so that the water flows out freely when the pump starts.

If the unit is being started up for the first time after a long period, before putting it into operation check the oil level in the pump and motor, then inspect the pump valves for proper operation. On the other hand, in anticipation of long inactivity, drain the suction and delivery lines and then run the vacuum pump for a few seconds, so that the water present in the fluid end is evacuated.

Before each closure, however:

  • lower the pressure by acting on the regulation valve or on any unloading devices;
  • reduce, if possible, the number of revolutions of the pump;
  • stop the engine and only finally disconnect the booster pump – if provided for by the system – to prevent any dry running of the piston pump.

Revolutions and flow rate of the pump

The progressive adjustment of RPM of the pump is carried out by acting on the accelerator of the motor which feeds the pump: never exceed the maximum number of revolutions of the pump indicated by the manufacturer and reach it with progressive speed increments. If unusual noises from the pump or transmission occur when the engine speed is increased, reduce the engine speed immediately and try again. If the noises persist, stop the engine and check their origin.

On the other hand, once the piston diameter has been chosen, the pump flow rate can only be adjusted by varying the engine rpm: it is not recommended, as a method of flow rate regulation, to by-pass excessive quantities of water through the regulation valve, in order to preserve the performance of the latter for a long time; in fact, the pressurized water, passing through a bottleneck and expanding in a free vein (by-pass system), acquires a considerable speed and this causes wear phenomena on the parts in contact with the water.

Routine maintenance

A correct maintenance plan for a piston pump, as well as extending the life of the instrument, will allow you to always obtain maximum performance.

This plan can be divided into three levels of maintenance and control:

  1. The first level is the daily one and includes a general check by the operator on the connections and all the components, making sure they are in good condition and that there is no visible damage;
  2. The second level concerns the regular external and internal control of the valves, connections and components, with the possible replacement of the parts involved by the operators but only if qualified;
  3. The third level concerns the complete reconditioning of the pump and of the major components making up the system: this operation must be carried out according to the maintenance methods and schemes provided by the pump manufacturer and carried out by highly qualified personnel.

In addition to the pump itself, maintenance operations must also be carried out on other components closely connected to it.

Regarding maintenance of the pump, it is necessary to check that there are no leaks or broken seals, both when it works empty and when it is under pressure. Furthermore, at least weekly checks must be made on the condition of the pistons – checking that they are not scored or that they do not get too hot – and of the seals.

Very important are the cleaning and replacement of the filtering elements, for which the interval of interventions depends on various factors (more or less arduous operating conditions, degree of dirt in the water, etc.). However, it is a good rule to carry out maintenance before the pressure drop reaches values that are not compatible with the correct supply of the piston pump.

When you decide to intervene for filter maintenance, you must carry out the following operations:

  1. Close the inlet valve to the unit.
  2. Open the drain and drain any fluid remaining in the filter
  3. Open the filter
  4. Unscrew the filter element
  5. Where possible, clean the cartridge or replace it
  6. Check the condition of the gaskets and, if worn, replace them
  7. Thoroughly clean the seat of the gaskets
  8. Carefully close the filter making sure there are no air infiltrations
  9. After making sure the drain and vent are closed, open the water shutoff valves.

The importance of lubrication

When we talk about pistons, lubrication is one of the most important factor; therefore, particular operations must be carried out in this sense.


Every day or at least every other day, check the oil through the viewers on the pump casing and on the indicator in the tank of the lubrication unit, if installed, even with the pump running.

If you notice traces of emulsion, check the tightness of the pistons and oil seals in the sliding area. For pumps without a lubrication unit, check the oil level by checking the dipstick with the pump stopped.

Equally important is how often the oil should be changed.

For one use of the construction site pump:

  • The first oil change must be carried out after 50 hours of use
  • The second oil change after 200 hours;
  • From the third change onwards, every 200 hours.

For stationary use, on the other hand, the second and subsequent changes must be made at 500 hours, while for industrial use at 500 and 1000 hours.

Monthly, it is necessary to check all the fixing screws and bolts (pump, motor, base, joint and joint cover).

Finally, every three months, all the safety sensors must be checked and the conditions and tightening of all the hoses (water and oil), electric cables and air pipes must be checked. These checks must be carried out with the pump stopped and the power supply disconnected.