What are the common fault causes and treatment methods of manual reversing valve?


Manual reversing valve is a kind of direction control valve with two or more flow forms and two or more oil areas. It is a valve to realize the communication, interception, steering, pressure unloading and sequence motion control of hydraulic oil flow. It can be divided into manual direction valve, electromagnetic direction valve, electro-hydraulic direction valve and so on.

When the manual reversing valve is operated, the driving shaft is rotated by the driving mechanism outside the valve, and the valve is started with the swing arm, so that the working fluid leads to the lower outlet of the valve from the left inlet, and sometimes the lower outlet is switched from the right inlet to the lower outlet, so as to achieve the purpose of circulating switching flow.

Manual reversing valve This switch valve is widely used in petroleum, chemical production, often used in synthetic ammonia, natural gas manufacturing system. In addition, the steering valve can be used as a valve construction and is commonly used if a smaller flow rate is available. When working, as long as the handwheel is turned, the flow of the working fluid can be changed through the valve.

What are the common fault causes and treatment methods of manual reversing valve?

1. The leakage

External leakage is a common fault of manual directional valve, and the main reasons are as follows:

(1) The connection screw is loose. When the screw is not tight enough, or when the machine is running, the vibration will cause the screw to loosen. Just tighten it with the right tool.

(2) The sealing ring or sealing ring fails. Seal ring failure can take many forms. Such as appearance cracked; Flatness of local variation; Corrosion damage; Elasticity goes down and so on. The exclusion method is to replace the new seal ring.

(3) the oil pressure of the manual reversing valve is too high. External leakage may also occur if the hydraulic pressure is too high. In this case, you can read the pressure from the pressure gauge to determine whether the pressure is too high. If it is higher than the system pressure, the pressure is too high. Elimination method: Adjust system pressure through pressure valve.

(4) The installation surface is rough. External leakage may occur if the installation surface roughness does not meet the requirements. Elimination method: grinding the mounting surface to meet product requirements. Usually, the installation surface roughness value of the valve is below 0.8m.

Based on the above four reasons, the priority order of inspection is to first look at the pressure gauge, check whether the end cover is loose, and finally open the valve, check the sealing ring, and measure the roughness of the installation surface. This order reflects the principle of going from easy to hard and from the outside to the inside.

 

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2. The spool cannot be moved

The main fault of manual reversing valve is that the spool cannot be moved. The reasons are as follows:

(1) The gap between the valve core and the valve hole is not suitable. If the diameter of the spool is less than 20mm, the normal spacing is between 0.008mm and 0.015mm. If the diameter of the spool is greater than 20mm, the normal spacing is between 0.015mm and 0.025mm. The SPACING IS TOO LARGE, THE MANUAL DIRECTIONAL VALVE IS TILTED IN THE VALVE, AND THE VALVE IS BLOCKED. In this case, the valve may need to be refilled, or a plating process may be used. The gap is too small, the friction resistance increases, the valve core does not move when the need to polish the valve core.

(2) spool deformation. Spool deformation has three main causes.

The oil temperature is too high to prevent thermal deformation of the valve core. At this point, find out why the oil temperature rises and reduce the oil temperature.

If the spool is bent out of shape by external forces, the spool must be modified or replaced. After the valve surface is scratched and the valve inner hole is scratched, open the directional valve, carefully clean, sand and repair the valve.

(3) Other reasons. The manual connecting rod of the manual reversing valve is worn or faulty, the oil pollution card stops the spool, the spring elasticity does not match, the oil viscosity is too large, etc. If the manual rod is worn or broken, it needs to be replaced or repaired. When the oil contamination card is blocked or the oil viscosity is too high, the valve should be carefully cleaned or the oil should be replaced. If the spring elasticity is inconsistent, the spring must be replaced.

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