Fault diagnosis of hydraulic cylinder

- Dec 26, 2017 -

The hydraulic cylinder is the actuator that the hydraulic energy can be converted into mechanical energy in the hydraulic system. The fault can be summarized as hydraulic cylinder misoperation, inability to push load and piston slipping or creeping. Due to the failure of the hydraulic cylinder caused by the phenomenon of equipment downtime is not uncommon, therefore, should pay attention to the hydraulic cylinder fault diagnosis and use of maintenance work.

Fault Diagnosis and treatment

1, wrong action or action failure

The reasons and treatment methods are as follows:

(1) The spool is jammed or the valve hole is blocked. When the flow valve or direction valve spool jammed or valve hole plugging, hydraulic cylinder prone to misoperation or action failure. At this time should check the oil pollution situation, check whether the dirty or colloid sediment is stuck to the spool or plug the valve hole, check the body wear, cleaning, replacement system filter, cleaning tank, replacement hydraulic media.

(2) The piston rod is jammed with the cylinder or the hydraulic cylinder. At this point, regardless of the operation, the hydraulic cylinder does not move or very little action. At this time should check the pistons and piston rod seals are too tight, whether to enter the dirty and colloidal sediments: piston rod and cylinder axis of the alignment, vulnerable parts and seals are ineffective, the load is too large.

(3) Hydraulic system control pressure is too low. The throttle resistance in the control pipeline may be too large, the flow valve is improperly adjusted, the control pressure is unsuitable, and the pressure source is disturbed. At this time should be checked to control the pressure source, to ensure that pressure regulation to the system's specified value.

(4) The hydraulic system enters the air. This is mainly due to leaks occurring in the system. At this time should check the hydraulic tank level, hydraulic pump oil side seals and fittings, oil suction coarse filter is too dirty. If so, the hydraulic oil should be added, handle seals and fittings, clean or replace the coarse filter.

(5) The hydraulic cylinder initial movement is slow. In the case of low temperature, the hydraulic oil viscosity is big, the fluidity is poor, causes the hydraulic cylinder to move slowly. The improvement method is, the replacement viscosity temperature performance better hydraulic oil, at low temperature can use the heater or the machine itself heating to upgrade the oil temperature at start-up, the system normal operating oil temperature should be kept in 40 ℃ or so.

2, work can not drive the load

The main performance is the piston rod stop position, the thrust is insufficient, the speed drops, the work instability and so on, the reason is:

(1) internal leakage of hydraulic cylinder. The internal leakage of the hydraulic cylinder includes the hydraulic cylinder seal, the piston rod and the seal cover seal and the piston seal are excessive wear and tear.

PISTON rod and seal seal leakage reason is that the sealing parts wrinkle, Squeeze, tear, wear, aging, metamorphism, deformation, etc., at this time should replace the new seals.

The main reason for the excessive wear of piston seals is that the speed control valve is improperly adjusted, resulting in excessive back pressure and improper installation of seals or hydraulic oil contamination. Secondly, there is a foreign body to enter the assembly and the quality of the sealing material is not good. The result is slow, powerless, serious damage to the piston and cylinder, there is a "pull cylinder" phenomenon. The treatment method is to adjust the speed control valve and to do the necessary operation and improvement against the installation instructions.

(2) leakage of hydraulic circuit. including valve and hydraulic pipe leakage. The overhaul method is to check and eliminate the leakage of the hydraulic connecting pipe by manipulating the reversing valve.


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