Herrenknecht company production of EPB shield machine, used in tunnel construction of Shenzhen Metro Line 1. In the field construction, two shield machines all appear the phenomenon that the hydraulic oil temperature is too high (the alarm temperature of each device of the hydraulic system of the shield machine is 60 degrees Celsius).

Check the working load of the shield machine, the cutter torque is only 1900 kN / M (the maximum set torque is 4350 kN / M); the screw conveyor is only 120 kN / M (the maximum set torque is 239 kN / m). Because the shield machine load is very small, and the hydraulic equipment return oil is smooth, so it can be ruled out because the shield machine load is too large and hydraulic device return oil circuit is not smooth, resulting in hydraulic system oil temperature is too high. But because the oil temperature of the hydraulic tank is too high, it can be inferred that the oil temperature of the whole hydraulic system of the shield machine is too high, which may be caused by the problem of the cooling device of the hydraulic oil. Because the hydraulic tank oil is cooled by cooling water, as shown in Figure 1, so when the shield machine inlet low pressure, high water temperature, water filter, filter plug, hydraulic tank oil level is insufficient, and the cooling water loop and hydraulic oil cooler is not smooth, will lead to the hydraulic oil temperature is too high alarm. Itemized examination and analysis are as follows.

1. check the inlet pressure

If the machine inlet pressure is low, the lack of the shield machine caused by water flow, cooler water pressure, water flow through the small cooler, slow velocity, the hydraulic oil is not effectively cooling, will lead to high temperature of hydraulic oil. The water table to check the pressure of shield machine (see Figure 2), the pressure value is 0.5 MPa, which shows that the pressure is normal.

2. check the inlet temperature

If the inlet temperature of the shield machine is high, the water temperature of the cooler is also high, and the hydraulic oil can not be effectively cooled, which will lead to a high hydraulic oil temperature. The inlet temperature of shield machine is greatly affected by the environment. When the ambient temperature is high, the inlet temperature is high, but the inlet temperature is not more than 30 degrees to normal range. The water temperature check in Figure 2 of the shield machine, that water temperature is normal.

Fig 1 cooling diagram of hydraulic oil

1. pump 2. hydraulic oil filter 3. hydraulic table 4. water outlet inlet pipe 5.

Fig. 2 Schematic diagram of water cycle

1. water filter 2. water pressure gauge 3. water temperature meter

3. check the filter screen

Remove the top cover of the filter, remove the strainer, and know that the strainer is clean (cleaned in advance).

4. check the oil level of the hydraulic oil tank

Observe the oil level of the hydraulic oil tank, check the oil level is normal, and the fuel tank is full of oil.

5. check the cooling circuit of hydraulic oil

Remove the filter core of the hydraulic oil filter and find the filter core clean. Check the oil supply pressure of the hydraulic pump, and result in normal pressure. By touching the cooler inlet and outlet pipe with hand, it is found that the inlet pipe is hot and the outlet pipe is hotter. It can be seen that the hydraulic oil has not been cooled well in the cooler, indicating that the cooler is faulty. Remove the hydraulic oil cooler, check the inlet and outlet of the cooler, and find that the small hole in the inlet and outlet of the cooler is blocked by dirt and rust. Use cleaning agent and high pressure water to clean the water holes in the cooler, and dredge each small hole with wire, until the cooler channel is completely unblocked. The cleaning cooler is reinstalled and tested, the temperature of the hydraulic oil is normal, and the oil temperature alarm phenomenon disappears, indicating that the fault has been eliminated.

Because my unit is easy to rust, water pipes, rust contains many impurities in tap water, the water without treatment by water pump is supplied directly into the shield, even after the water filter, but because the water filter mesh is larger, can filter out impurities of larger diameter, and other impurities and dirt and scale formation easy to plug the hole inside the water cooler, hydraulic oil cooler flow is not smooth, not the normal cooling, which leads to high oil temperature alarm.

In order to solve this problem, we improved the water supply device, that is, a sedimentation tank was added (dotted part in Figure 2). The reservoir water, first in sedimentation tank and precipitation softening treatment, and then to the water in the reservoir, the reservoir sedimentation and the original clean dirt, corrosion inhibitor in B reservoir, the supply of the shield machine clean water. After the improvement, the two shield machines did not appear the alarm that the oil temperature of the hydraulic system was too high due to the blockage of the inner channel small hole of the cooler.