№ | Defect | Possible cause |
1 | The pump does not supply liquid to the system | Incorrect direction of rotation of the pump shaft |
There is not enough working fluid in the tank |
The suction line is clogged |
Air suction in the suction pipe |
Pump failure |
The viscosity of the liquid is high |
The overflow valve damper is clogged |
2 | The pump does not generate pressure in the system | The pump does not supply liquid to the system |
High wear of the pump (internal leakage is large) |
High external leakage along the shaft through the pump housing |
High internal leaks in the hydraulic system |
The safety valve spool or overflow valve is jammed and cannot be installed on the seat |
Reduced oil viscosity due to heating (usually above 50 C) |
3 | Noise and vibration in the system | High resistance in the suction line |
The filter throughput is low or it is clogged |
Air suction in the suction pipe |
The breather in the tank is clogged |
Valve vibration |
A sharp change in the flow section of pipelines |
Non-rigid fastening of pipelines |
4 | Unequal movement of working bodies | Air in the hydraulic system |
The pressure setting of the safety valve is close to the pressure required for the movement of the working units |
Low back pressure on the cylinder drain |
Mechanical jamming of the moving parts of the hydraulic cylinder. Uneven oil supply by the pump. Noise and knocking in the pump due to failure of one of the blades or plunger |
5 | A sharp decrease in speed when the load increases | Large internal or external leaks in hydraulic system elements |
The speed controller jams in the open position |
The safety and bypass valves are adjusted for low pressure |
6 | Gradual decrease in the speed of movement of the working body | Contamination of the working fluid |
Clogging of filters, throttles and other devices of the system. The obliteration (overgrowth) of cracks of the throttle |
The sealing surfaces of hydraulic units were worn out or the viscosity of the working fluid decreased |
7 | Increased pressure in the discharge line at idle | Increased pressure losses in the system due to the wrong choice of equipment, reduced cross-section of pipelines, as well as as a result of poor-quality installation |
The control channel of the distributor overflow valve is clogged |
Increased mechanical resistance to movement of working bodies |
8 | Increased heating of the oil in the system | Increased pressure losses in pipelines and hydraulic equipment. Low heat removal from the tank and pipelines |
The pump does not unload during pauses |
Malfunction of temperature control equipment |
9 | The check valve allows the liquid to flow when the flow direction changes | The valve does not fit the seat. Defect in the working edges of the valve or seat. The valve spring broke |
10 | The safety valve does not hold the pressure | The damper or valve seat is clogged. Loss of tightness in the remote discharge system |
The ball or seat is worn out |
A spring broke |
11 | There is no pressure behind the pressure reducing valve | The damper or valve seat is clogged |
The ball or seat is worn out |
A spring broke |
12 | There are large leaks through the drainage holes | Seals were worn out |
The working surfaces of mobile switchgears were worn out |
13 | The electrohydraulic control spool does not switch when the electromagnet is switched on | Jamming of the spool in the housing (the spool teaser). Spool jamming with dirty oil or a sagging return spring. Thick oil makes it difficult to move the spool |
The armors of the electromagnets do not move at full stroke |
The end of the pusher has splintered |
The drain hole in the spool is clogged |
14 | The electromagnets are humming and overheating | See paragraph 13 |
The recoil springs are too strong |
The supply voltage does not match the nominal value |
The armature of the electromagnet has been loosened |
15 | Breakage and cracks of oil pipelines with changes in sealing | Unacceptable deformations of flexible hoses |
Aging and wear of flexible hoses |
Resonant vibrations of pipelines |
Significant pressure peaks in the hydraulic system |
16 | The pressure reducing valve does not lower the pressure or does not lower enough | The control spring is compressed almost to the full fit of the coils. The valve spool is jammed. The oil discharge line after the ball into the tank is clogged. The control spring has settled. The damper hole of the spool is clogged. There is dirt between the ball and the seat or the ball is damaged |
17 | The feed rate of the power unit is low and falls under load (controlled by the flow regulator) | The throttle gap is clogged. The spring of the integrated pressure reducing valve is loose or the spool is stuck |
Increased leakage in the pump and hydraulic units |
High oil viscosity |
18 | The oil flow is not reversed by the inlet spool | Jamming of the spool in the housing due to dirty oil, clamping of the mounting bolts, flatness of the mounting surface, breakage of the return springs, lack of control pressure |
The pushrod of the control spool’s electromagnet was lost. The coil burned or the anchor broke |
19 | Oil and foam are ejected through the filling neck of the oil tank or the lid of the built-in drain filter | Excess oil in the tank. |
Air intake to the hydraulic system |
The filter is clogged or the filter cover seals are damaged. There is no retarding valve on the cylinder drain |