How to select the ventilator for the hydraulic oil tank of the excavator

This article takes the excavator as an example to help you understand how to select the respirator.

(1) filtration grade

In the working state of a respirator, the air is often inhaled and discharged from the tank. In this way, the air of the pollutants such as dust and water in the working environment of the excavator is easily inhaled into the tank, resulting in the pollution of the hydraulic oil. Therefore, the respirator must have filter function to prevent the erosion of these pollutants. According to the Cetop RP 98 H standard, the filter grade of the respirator should match the fine filter grade of the hydraulic system in the ideal state. For example, the filtration grade of the filter core of the hydraulic system is 10 u m, and the air filtration grade corresponding to the ventilator for the tank should also be 10 mu m.

(2) ventilatory capacity

The measure of ventilatory capacity is nominal air flow. For a respirator without bypass valves, it is the maximum air flow rate when the pressure drop reaches P<300Pa. For the respirator with bypass valves, the maximum air flow rate is about when the pressure drops to P<1kPa.

The ventilation volume of the respirator must be far greater than the volume of oil in the tank, which is usually more than 1.5~2 times more than the main pump. In the case of serious air dust pollution, its value should be moderately expanded. When the excavator works, the hydraulic oil flowing through the main pump and the motor drain port will cause the volume change of the oil tank, causing the alternation of positive pressure and negative pressure in the closed fuel tank. On the one hand, this phenomenon will cause the vacuum pump which is more sensitive to the main pump to generate suction, resulting in system fever. On the other hand, it will also cause the flow and pressure of the control valve to be unstable, or even cause malfunction.

If the strength of the respirator is insufficient, the oil temperature of the tank will rise and the oil and gas will be formed in the tank. In the recovery of the excavator bucket, the bucket rod and the piston rod of the movable arm cylinder, if the oil flowing back to the tank is larger than the oil absorption of the pump, the respirator will be exhaled out of the oil and gas. Oil and gas adhered to the outer wall of the tank and then adsorbed to dust, will affect the whole appearance of the machine, and at the same time easily cause fire and other unsafe hidden dangers.

(3) whether there is bypass valve

According to the structure, the respirator can be divided into 2 kinds: the bypass valve and the bypass valve. A two-way one-way valve with a bypass valve is built, and the back pressure of a one-way valve should be overcome when the respirator is opened. Using a respirator with bypass valves can reduce the probability of impurities entering the hydraulic system in the atmosphere, improve the service life of air filters, and effectively control the inhalation of water in the air and the escape of oil and gas in the tank.

Most of the hydraulic pumps are sensitive to the vacuum of the oil sucking port. If the absolute pressure requirements of Rexroth hydraulic pumps suction port is not less than 0.08MPa, less than the pressure of the system will produce suction air, noise and rapid overheating. Therefore, when the main hydraulic pump has a clear requirement for the suction oil pressure, a respirator with a bypass valve should be preferred.

(4) maintenance cycle

The lifespan and maintenance cycle of the respirator are obviously different from the manufacturer, the material of the filter core and the working condition. The supplier demarcates the maintenance cycle of the respirator for 3~12 months, and the industry generally stipulates that 500h is replaced. It is generally recommended that respirator without plugging indicator should be replaced with filter cartridge replacement. If a pressure indicator with a blockage indicator reaches 300Pa, it should be replaced, otherwise it will cause suction of the pump.

As a result, we must have a deep understanding of the hydraulic tank of the excavator, so that it can not make a mistake when choosing.