Automatic oil temperature control device of the ho

Oil temperature automatic control device of large hydraulic pump station

Abstract This paper introduces an oil temperature control method for large hydraulic pump station, which can automatically control four temperature points

key words large hydraulic pump station oil temperature control four point temperature control method

when the hydraulic system is working, its pressure loss, volume loss and mechanical loss will be converted into heat energy to increase the oil temperature, especially when the high-power closed circuit hydraulic system is working for a long time, the oil temperature rise is more serious. The working temperature of the oil will affect the service life of the hydraulic oil and hydraulic components. The change of the oil temperature will cause the viscosity change of the oil, resulting in the instability of the movement speed of the mechanical system. Therefore, it is necessary to control the oil temperature within a certain range

generally, the oil temperature is controlled by the yield limit obtained in the electronic experiment of Jinan new era Gold Testing Instrument Co., Ltd б B and strength limit б S two-point control method, that is, the change of oil temperature is controlled within an allowable range (even if t lower limit

the composition of the temperature control system of the hydraulic pump station is shown in Figure 1. The actual temperature T of the oil is measured by the temperature sensor, and the measured signal is input to the thermostat, which has four outputs

Figure 1 composition diagram of temperature control system of hydraulic pump station

set T1 (25 ~ 30 ℃) as the lowest limit value of oil temperature. When the oil temperature is lower than T1 value, the oil viscosity is too high, and the hydraulic pump cannot be started; T2 (40 ~ 45 ℃) is the lower limit of working temperature; T3 (45 ~ 50 ℃) is the upper limit of the working temperature; T4 (55 ~ 60 ℃) is the maximum allowable limit value of oil temperature. The control temperature of T1 ~ T4 points is adjustable, and its value can be set arbitrarily according to actual needs. For example, the difference between T1 and T2 can be made, otherwise the test result will be less inaccurate, and even T1 = T2. When the actual temperature T reaches which temperature point, the thermostat will send a control signal in which way

oil temperature control circuit is shown in Figure 2. When the machine is just started or the oil temperature is too low (t ＜ T1), the thermostat sends a T1 signal to close TP1, turn on the heater and heat the oil. When the oil temperature T reaches T1, the T1 signal of the thermostat disappears, TP1 is disconnected, and the heating is stopped. When the oil temperature reaches T2, the temperature controller sends a T2 signal to turn on TP2, preparing for a corresponding reduction of 2% in the order quantity of the water pump electric single screw extruder that turns on the cooler. At this time, TP 1 is disconnected

Figure 2 oil temperature control circuit

when the plasticity decreases and the oil temperature T reaches T3 (upper limit of working temperature), the thermostat sends a T3 signal to turn on TP3 (TP2 is closed at this time), and the cooler works to cool the oil. J2 is self-locking and controls the water pump motor at the same time (see Figure 3)

Figure 3 working diagram of cooling water pump

when the temperature drops to T2, that is, t ≤ T2, T2 and T3 signals disappear, TP2 and TP3 are disconnected, and the cooling water pump stops working, which makes the oil temperature fluctuate between T2 and T3

if the oil temperature is too high and the cooling efficiency is not enough for some reason, so that the oil temperature T reaches the T4 temperature, the thermostat will send a T4 signal to make TP4 close and connect J3, make J4 work through J3, and J4 will control the unloading control unit to work, forcibly unload the whole hydraulic system, reduce the pressure of the whole system and stop working, so as to achieve the purpose of protecting the system. At the same time, the alarm bell DL gives an alarm sound and the unloading indicator light is on. J3 can also force the cooler to work when the cooler is not working but the system suddenly has high temperature, so as to accelerate the cooling speed of oil

the cooling and heating of the oil temperature control device can be controlled manually and automatically, which can be switched by SD knob

for hydraulic components, constant oil temperature is the most ideal, but thermostatic control has too much heat loss and high cost. In large hydraulic systems, due to long pipelines and large heat loss, thermostatic control cannot be achieved and is unnecessary. In this scheme, the temperature measurement point is selected in the oil tank. For a single loop system with only one working point, it is better to select the temperature measurement point at the working point, and its working temperature can be controlled within a very small range

the above temperature control devices have been used in a large hydraulic pump station designed for a unit, using plate heat exchangers and submersible pumps with high cooling efficiency. Practice has proved that the working temperature range can be controlled within 5 ℃. This equipment has been used for more than two years, and its performance is stable and reliable

compared with single-chip microcomputer and PLC control methods, this relay logic control circuit has the advantages of low cost, simple and convenient installation, debugging and maintenance for a single fixed equipment used for a long time, and is more acceptable to user units