Created on:2022-02-19 09:54

Selection and troubleshooting of oil filter with blockage indication device

Selection and troubleshooting of oil filter with blockage indication device

1. Introduction

The function of the oil filter is to filter out the impurities in the hydraulic oil and ensure the normal operation of the hydraulic system. In order to ensure that the oil filter can work normally and play its role, and enable users to observe the working performance in time when the oil filter is blocked, at present, most oil filters are equipped with blocking indication devices. When the pressure drop of the oil filter reaches the rated pressure drop of the filter element, that is, the oil filter is blocked. The blocking indication device can display the blockage of the filter element or send an alarm signal, so that the operator can replace or clean the filter element in time.

2. Type of oil filter with blockage indication device

(1) Annunciator buzzer alarm device. The transmitter and the buzzer are connected in series on a 12V or 24V DC power supply. When the filter element is gradually blocked and the pressure difference between the inlet and outlet of oil reaches the set value, the transmitter will send a signal to connect the electric buzzer, that is, send an audible signal through the electric buzzer to give an alarm.

(2) Transmitter signal lamp alarm device. The transmitter and signal lamp are connected in series on the DC power supply with voltage of 12V or 24V. When the filter element is gradually blocked and the differential pressure at the inlet and outlet reaches the set value (generally 0.35Mpa), the transmitter will send a signal to turn on the signal lamp, that is, send a light through the signal lamp to give an alarm.

(3) Slide valve type blockage indicator. The inlet and outlet pressure oil ports of the oil filter are respectively connected with the left and right ends of the slide valve. When the passing capacity of the filter element is good, the pointer on the slide valve is in the left end position under the action of the spring. With the gradual blockage of the filter element, the differential pressure at both ends of the slide valve gradually increases and the pointer gradually moves to the right, indicating the blockage of the filter element, The operator can determine whether the filter element should be cleaned or replaced according to the above instructions.

Because the structure of the transmitter signal lamp alarm device is relatively simple, easy to implement and cheap, and the signal lamp can be installed on the instrument panel, the operator can detect it in time when sending the alarm signal, so it has been widely used in the hydraulic system of construction machinery.

3. Selection of oil filter with blockage indication device

In practical application, when selecting the oil filter with blockage indication device, in addition to the filtration accuracy and system pressure, the following aspects should also be considered.

(1)       Effective filtering area of filter element. According to the calculation formula of the effective filtering area of the filter element, it can be seen that the effective filtering area of the filter element is inversely proportional to the differential pressure △ P, so the filter element is required to have a certain effective filtering area. Generally, the rated flow of the oil filter should be 1.5 ~ 2 times of the rated flow of the system.

(2)       The filter element with small pressure loss shall be selected as far as possible. The oil filter with blockage indicator sends a signal when the differential pressure at both ends is 0.35Mpa, so the filter element with small pressure loss should be selected as far as possible, so that the oil filter with blockage indicator can have a certain margin of pressure loss.

4. Troubleshooting of oil filter with blockage indicator

The oil filter with blockage indication device has the problem of signal indication as soon as the device is connected in use. This indicates that the pressure difference at both ends of the filter element has exceeded 0.35Mpa, and troubleshooting is required.

(1) The setting of blockage indication device is unreasonable. For the steering system with full hydraulic steering gear, it is required to set a 30 µ m oil return filter on the oil return road to ensure that the return oil of full hydraulic steering gear has a back pressure of 0.2 ~ 0.3MPa, so as to prevent the oil from flowing back to the oil tank during manual steering. Due to the large pressure loss of the oil filter itself, the blockage indication device should not be set on the oil filter.

(2) Too dirty. Replace the hydraulic oil in the hydraulic system and clean the hydraulic system to meet the specified cleanliness level requirements.

(3) If the selected hydraulic oil has too high viscosity or starts at low temperature, resulting in too large pressure loss, replace the hydraulic oil with low viscosity or take heating measures.

(4) The filtering area of the selected filter element is small, so that the differential pressure △ P at both ends of the filter element increases exponentially, and the pressure loss is too large. The oil filter with large filtering area should be replaced.

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