ATOS plunger pump output pressure abnormality problem

Brand

ATOS/Italian Atos

Application Areas

Chemical, Petroleum, Automotive & Parts, Electrical, General

ATOS Piston Pumps, ATOS Gear Pumps, ATOS Axial Piston Pumps, ATOS Vane Pumps, ATOS Cylinders, ATOS Relief Valves

ATOS Piston Pump Flow Problems

(1) Insufficient suction. Caused by excessive resistance in the suction line or insufficient replenishment. For example, excessive pump speed, low oil level in the tank, air leakage in the inlet pipe, or clogged oil filter.

(2) Excessive leakage. Caused by excessive pump clearance and poor sealing. For example, scratches on the distributor plate by metal fragments or iron filings, resulting in end-face oil leakage; poor fit of the check valve sealing surface in the variable mechanism; sand holes or scratches on the support surfaces of the pump body and distributor plate. The damaged part of the pump can be identified by checking for foreign matter mixed in the hydraulic oil within the pump body. (3) If the swashplate angle is too small, the pump's displacement will be low. This requires adjusting the variable piston to increase the swashplate angle.

Discharge is not zero in the neutral position.

The swashplate angle of a variable axial piston pump is zero when it is called the neutral position, at which point the pump's output flow should be zero. However, sometimes the neutral position deviates from the midpoint of the adjustment mechanism, and there is still flow output at the midpoint. This is because the controller is misaligned, loose, or damaged, requiring readjustment, tightening, or replacement. Insufficient pump angle holding force and wear on the swashplate trunnion can also cause this phenomenon.

ATOS piston pump output flow fluctuation.

ATOS piston pump output flow fluctuation is related to many factors. For variable pumps, it can be considered to be caused by poor control of the variable mechanism, such as foreign objects entering the variable mechanism, scratching, grinding, or damaging the control piston, causing unstable control piston movement. Insufficient amplifier energy or damaged parts, and poor damping efficiency of the control piston containing a spring, can all cause unstable control piston movement. Unstable flow is often accompanied by pressure fluctuations. These types of faults generally require disassembling the hydraulic pump, replacing damaged parts, increasing damping, improving spring stiffness, and adjusting control pressure.

(1) Low Output Pressure

When the pump is in self-priming mode, if there is air leakage in the inlet line or significant leakage in the hydraulic cylinder, check valve, or directional valve in the system, the pressure will not rise. This requires finding the leak, tightening, and replacing the seals to increase the pressure. If the relief valve is faulty or the adjusted pressure is too low, the system pressure will also not rise; the pressure should be readjusted or the relief valve repaired. If the hydraulic pump cylinder body and distributor plate deviate, causing significant leakage, the cylinder body may crack in severe cases; in this case, the mating surfaces should be re-ground or the hydraulic pump replaced.

(2) High Output Pressure

If the circuit load continues to increase, the pump pressure will also continue to increase, which is normal. If the load is constant and the pump pressure exceeds the required load value, the hydraulic components other than the pump, such as directional valves, pressure valves, transmission devices, and return lines, should be checked. If the maximum pressure is too high, the relief valve should be adjusted.

Vibration and Noise

Vibration and noise occur simultaneously. These not only harm machine operators but also pollute the environment.

(1) Mechanical Vibration and Noise

Noise is generated by misalignment or jamming of the pump shaft and motor shaft, damage to bearings and couplings of the rotating shaft, broken elastic pads, and loose assembly bolts. For pumps operating at high speeds or transmitting large amounts of energy, regular inspections are necessary to record the amplitude, frequency, and noise of each component. Resonance will occur if the pump's rotational frequency matches the natural frequency of the pressure valve; this can be eliminated by changing the pump's speed.

(2) Noise Generated by Fluid Flow in Pipelines

Noise is generated by factors such as a narrow inlet pipe, insufficient flow capacity or blockage of the inlet filter, air intake in the inlet pipe, excessively high oil level, insufficient oil suction due to low oil level, and liquid slugging in high-pressure pipelines. Therefore, proper design of the oil tank and correct selection of filters, oil pipes, and directional valves are essential.

Hydraulic Pump Overheating

There are two reasons for excessive heating of hydraulic pumps: one is heat generated by mechanical friction. Heat is generated by the friction between moving parts due to dry or semi-dry friction on the moving surfaces. The other is heat generated by fluid friction. High-pressure oil leaks into the low-pressure chamber through various gaps, resulting in a significant loss of hydraulic energy converted into heat. Therefore, correctly selecting the clearances between moving parts, the tank volume, and the cooler can prevent excessive pump overheating and oil temperature rise. Additionally, a clogged return oil filter causing excessive back pressure can also lead to high oil temperature and pump overheating.

Working Principle of the Italian ATOS Piston Pump

The Italian ATOS piston pump is an important component of a hydraulic system. It relies on the reciprocating motion of the piston within the cylinder to change the volume of the sealed working chamber, thus achieving oil suction and pressure. Piston pumps offer advantages such as high rated pressure, compact structure, high efficiency, and convenient flow adjustment, and are widely used in high-pressure, high-flow applications where flow regulation is required, such as hydraulic presses, construction machinery, and ships.

The Italian ATOS piston pump is a type of reciprocating pump, belonging to the category of volumetric pumps. Its piston is driven by the eccentric rotation of the pump shaft, resulting in reciprocating motion. Both its suction and discharge valves are one-way valves. When the plunger is pulled outward, the pressure in the working chamber decreases, the outlet valve closes, and when the pressure is lower than the inlet pressure, the inlet valve opens, allowing liquid to enter. When the plunger is pushed inward, the pressure in the working chamber increases, the inlet valve closes, and when the pressure is higher than the outlet pressure, the outlet valve opens, allowing liquid to exit. When the drive shaft drives the cylinder block to rotate, the swashplate pulls the plunger out of or pushes it back into the cylinder block, completing the oil suction and discharge process. The oil in the working chamber formed by the plunger and cylinder bore communicates with the pump's suction and discharge chambers through the distribution plate. The variable displacement mechanism is used to change the swashplate's tilt angle; by adjusting the swashplate's tilt angle, the pump's displacement can be changed.