Hydraulic system tank design

In the hydraulic system, the hydraulic tank is mainly to store oil to meet the flow required by the normal operation of the hydraulic system; In addition, it also plays a role in heat dissipation, separation of bubbles in the oil, precipitation impurities and so on. These functions are achieved by auxiliary components in the tank, such as air filters, oil filters, coolers, etc. As a hydraulic system oil storage device, in the design of the tank, in addition to calculating its circulation volume, it is necessary to fully consider the complexity of the equipment construction conditions, how to adopt a reasonable structural form to ensure the structural strength of the tank itself, but also optimize the process, give full play to the role of the tank accessories, in order to adapt to the application scenario of large vibration and fast reversing of the equipment.

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This paper will introduce in detail how to determine the volume of the oil tank of the hydraulic system, how to meet the requirements of the structure, how to design the accessories of the oil tank and control the cleanliness of the oil tank.

1. Volume calculation and structural design of hydraulic tank

The volume calculation of the hydraulic tank needs to comprehensively consider the circulation volume of the pump, the motor and the cylinder volume difference to determine the volume of the tank. The hydraulic oil volume refers to the oil volume when the liquid level is on the upper scale line of the level meter.

The cycle volume of the Oil Pump V1= the displacement of the oil pump * the speed of the oil pump * the cycle time /60(the cycle time of the pumping equipment is generally 25s or 30s; The volume difference of the cylinders V2= the volume of all cylinders without rod-the volume of all cylinders with rod-cavities. Tank volume V0=(circulation volume V1 of oil pump + volume difference V2 of cylinder)*1.2

The determination of the oil absorption height in the hydraulic tank affects the oil absorption effect, and the inappropriate determination of the height will make the hydraulic pump oil absorption is not smooth, the pump is easy to suck, the noise is large, and it is easy to damage. In a certain type of pumping equipment, the oil suction height H mainly depends on the height of the oil port and the accumulated height of the internal diameter of the oil suction flange, on the basis of which an empirical height is added. The minimum amount of oil that the oil pump does not empty the tank is determined by the bottom area of the tank and the height of the non-empty tank.

2, hydraulic tank box structure design

For a long time, the tank structure type to the rectangular column as the main body, coupled with the partition, the two ends of the sealing plate composition, this type of main body is the steel plate flange butt welding, the sealing plate stamping, the requirements of high processing precision, the box flange and the sealing plate pressure R is not easy to match, due to the needs of processing and repair, the surface is often concave, poor appearance quality. A certain type of pumping equipment is made of small and small U-shaped plate group welding and then welded on the diaphragm and other accessories, low cutting accuracy, folding parts can be adjusted at will, shorten the production cycle. The strength can meet the requirements of construction conditions by optimizing the punching bar design of the U-shaped plates.

Taking a certain type of pumping equipment as an example, the comparison of Fuel Tank deformation before and after the hedge rib is as follows:

① When there is no reinforcement design, the strength analysis of the tank is carried out for the pressure holding 0.2MPa, and the maximum deformation is 62 mm, as shown in Figure 1.

② Optimize the punching mode design of the inner and outer plates according to the following steps:

1) Design objective: Minimize the maximum deformation of the plate.

2) Design variables: width and depth of plate reinforcement.

3) Optimization method: Optistruct software is topography optimization function.

The optimized design results of the outer plate are shown in Figure 2: the right cloud image shows the position and depth of the reinforcement.

The optimal design results of the inner plate are shown in Figure 3: the right cloud image shows the position and depth of the reinforcement.

After the impact optimization design of the new fuel tank, the strength analysis of the 0.2MPa holding pressure shows that the maximum deformation of the outer plate is 18.5mm and the maximum deformation of the inner plate is 28.6mm.

③ The layout of suction and return pipe in the fuel tank.

By optimizing the impact width and thickness of the plate, the maximum deformation of the plate can be minimized to meet the strength requirements.

④ Arrangement of Hydraulic Oil Tank accessories.

In order to keep the oil clean, the tank should have a cover plate with a peripheral seal, and the cover plate is equipped with an air filter, and the oil injection and ventilation are generally completed by an air filter. In order to facilitate oil discharge and cleaning, the tank bottom is provided with a blowdown ball valve and oil discharge plug at the lowest place. The side of the fuel tank is provided with a cleaning hole to facilitate the cleaning of the inside of the fuel tank. Suction tubing and return tubing should be inserted below the lowest liquid level to prevent air bubbles caused by suction and return oil splash. The distance between the pipe mouth and the bottom and the wall of the box is generally not less than 3 times the diameter of the pipe. In the pumping condition, due to the large flow of the main pump, the return oil buffer plate should be set at the entrance of the tank to reduce the impact of the return oil flow.

3, hydraulic tank cleanliness control

Preparation before tank cleaning:

The internal surface phosphating layer is complete, no rust, and the outer surface is coated with anti-rust primer in accordance with the relevant provisions of the hydraulic tank, after passing the inspection, it can be transferred to the cleaning process. When cleaning the oil tank, do not use cotton yarn and paper scraps. When the relative humidity is greater than 70%, the oil tank should be heated and dried, and cleaned and assembled in time.

1. Cleaning the outer surface of the oil tank: remove and clean the paint of the cover plate and other sealing joints, clean the burr and flash of the threaded holes with a file, clean the welding slag with a pointed hammer, and then wipe the parts with the long fiber textiles with low particles, and blow with compressed air.

② Cleaning of the inner surface of the oil tank: After the oil tank is painted, use a vacuum cleaner to suck out dust, particles and other debris. Clean with 500 thinner and scrub clean. When the upper part of the tank is assembled, use the dough to glue away the small dust and particles on the inner surface. Dust and particles should not be felt when touched by hand.

③ Cleanliness test of the fuel tank: measuring by weighing method.

4. Conclusion

Considering the difference between the circulating volume of the oil pump and the volume of the cylinder, the welding process of the U-shaped plate after the optimized design of the punching bar is adopted, which not only reduces the difficulty of processing, but also improves the structural strength of the side plate of the oil tank, and the maximum deformation rate is reduced by 54%. In addition, the control method of cleanliness in the process of oil tank processing is put forward, which has positive significance for the normal operation of the subsequent hydraulic system.