Hydraulic fuel tank function, volume and accessories detailed

There are fuel tanks in the hydraulic system, and the volume rises from a few tenths to tens of thousands of liters. When the hydraulic system is working, the oil volume in the system will always change (differential cylinder, thermal expansion, cold contraction, external leakage, etc.). The following will give you a detailed introduction to the function, volume and accessories of the hydraulic press tank.

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1. Function

1) Balance the pressure

When the hydraulic system is working, the oil volume in the system will always change (differential cylinder, thermal expansion, cold contraction, external leakage, etc.). If the system is completely closed, the pressure will drastically change. The oil tank holds the oil, directly or indirectly through the atmosphere (see figure), so that the system can keep the oil inlet and return pressure constant.

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1 A filter screen 2 a partition 3 an exhaust screen 4 a ventilation filter 5- hydraulic system A a suction port B an oil drain port C a primary oil port

In order to reduce the moisture and dust in the air into the oil, the tank is generally made of closed, and the inside and outside are connected only through the filter.

2) Facilitate the separation of air, water and solid impurities in the oil

If the hydraulic oil can have a certain residence time in the tank, and the flow slows down, the water and solid impurities in the oil will precipitate to the bottom of the tank because they are heavier than the oil, and the air bubble can float to the surface of the hydraulic oil and be separated.

3) Heat dissipation

The energy efficiency of the hydraulic system when working, that is, the output power of the hydraulic cylinder/the input power of the prime mover, is good but 70%, and the difference is even less than 20%, which means that if the prime mover input is 100kW, the loss of power may reach 30-80kW. Most of this is converted into heat, into the oil, if there is no heat dissipation, every 1kW power per hour will make the temperature of 1000kg of oil rise by 2°C,50kW is 100 °C. Therefore, in the hydraulic system, heat dissipation is necessary.

Because the heat dissipation effect depends on the heat dissipation area, the greater the heat dissipation area, the more heat dissipation, the surface area of the pipeline and Hydraulic Components is relatively small, after all, the tank has a large area, which can help heat dissipation.

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2. Volume

For these functions, the larger the volume of the tank, the better. But big, it will be more cumbersome, manufacturing costs are high.

Regarding the determination of the Fuel Tank volume, Chinese and foreign textbooks have recommended: multiply the flow rate per minute of the pump by a number, take 3-5 for fixed equipment, 1-2 for mobile equipment, and 0.5-1 for aircraft. In fact, this is also for inexperienced designers to refer to, rather than necessarily follow. In fact, think about it, the same hydraulic pressure, why mobile equipment and aircraft fuel tanks can be smaller? Higher principles for determining the volume of the tank can be understood, for example, by attaching a vacuum oil treatment device to help remove water and air from the oil; If the hydraulic system is more energy efficient, does not produce much heat, or if a cooler is attached to help dissipate heat, the tank does not need to be large.

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Third, accessories

1) The liquid level gauge is used to monitor the liquid level in the tank, often made into one with the oil thermometer, called the liquid level thermometer. Some also have a live signal switch: when the liquid level is below a dangerous height, which is not conducive to the work of the pump, an alarm signal is issued, or the pump is prohibited to start, which is often used in the unattended persistence test bench: once the liquid level is below a certain set height, it means a lot of oil leakage, immediately stop the test.

2) When the heat dissipation only depends on the fuel tank is not enough, the cooler is needed. General coolers will give nominal heat dissipation power. But this is only a reference value. The actual heat dissipation power also depends on the temperature difference between the oil and the cooling medium. The greater the temperature difference, the more heat is lost. Therefore, it is generally installed in the return oil pipeline, because it is usually the highest oil temperature and the most conducive to heat dissipation. The cooler is generally not pressure resistant, so the outlet is multiple straight through the fuel tank.

Heat dissipation is actually the electricity or fuel that drives the pump operation, which is money. Therefore, the best measure is to reduce the energy loss of the hydraulic system, that is, to reduce the generation of heat. In view of the hydraulic system when the oil temperature is best within a certain range, too low is not good. Therefore, the cooler should be equipped with a bypass valve, which only works when the oil temperature exceeds the upper limit.

The cooler is divided into two categories: air cooling and water cooling. Those with large heat dissipation requirements are generally cooled by water.

3) Heater: If the temperature of the oil is too low, the viscosity will be too high, which is not conducive to the normal operation of the system, especially the pump, at this time, heating is required. The most common is the electric heat pipe, which is installed in the tank near the position of the pump suction port.

Because the hydraulic system itself also generates heat after operation, it is very important to avoid overheating, especially mineral oil, which can lead to combustion. Therefore, the anti-overheating facilities must be very reliable, and usually two sets are used at the same time.