(I) Connection between Precision Oil Cooler and the Spindle and Hydraulic Systems:

Remarks:
1. The precision water cooler shall be stored in a well-ventilated, dust-free, active gases-free and sundries-free place.
2. During connecting the precision oil cooler and the machine tool equipment, it is suggested a filter added to the oil system, with the installation position shown above.
(II) Model Selecting Method:
1. Selection of Precision Oil Cooler for Cooling Spindle:
(1) Oil temperature: the temperature of the cooling oil for the spindle shall be controlled at 20~30 ℃ (environmental temperature: about 30℃).
(2) Oil pressure: the oil supply pressure needed is about 0.3~0.5MPa.
(3) Calculation of heating power of the spindle:
Pheat= Pmotor●η
Pheat---heating value of the spindle (kW)
Pmotor---power of the spindle motor (kW)
η---heat loss efficiency of the spindle
For common mechanical spindles, the heat loss η=5~8%; for high-speed electric spindles, the heat loss η=20~30%.
Example: if the spindle motor of some machine tool has the power of 22kW and the spindle is the common one, then the heating value of the spindle is:
Pheat=22x(5%~8%)=1.1~1.76kW
After looking up in the oil cooler curve diagram:
The refrigeration amount of MCO-20C is 1.9kW under the oil temperature of 30℃ and environmental temperature of 30℃, so this model meets the requirements. Under the oil supply pressure of 0.3MPa, the flow is 16L/min.
2. Selection of Precision Oil Cooler for the Hydraulic Pressure Station:
(1) Oil temperature: the oil temperature of the hydraulic pressure station is 30~50℃ (environmental temperature: 30℃).
(2) Oil pressure: the oil supply pressure required by the refrigeration circulation is about 0.3~0.5MPa.
(3) The heating power is calculated according to the oil pump power of the hydraulic pressure station:
Pheat= Pmotor●η1●η2●η3
Pheat---heating value (kW)
Pmotor---total power of motors in the hydraulic pressure station (kW)
η1---spindle efficiency, 70%~80%
η2---load-to-charge ratio of the motor, with the value determined by the operating mode
η3 ---heat loss efficiency, taking 70%~85%
For hydraulic pressure stations with the hydraulic pumps working continuously under HV, the η value shall take the upper one.
Example: if the oil pump power of some hydraulic pressure station is 9kW, with the working period of 20min and shutdown period (or LV standby) of 10min, then the heating value will be:
Pheat=Pmotor●η1●η2●η3 =9×80%×(20/30)×80%=3.84 kW
(4) The heating power is deduced from the rising rate of the oil temperature of the oil tank
Pheat=CP ●ρ●Vs●ΔT/t
Pheat: heating power (kW)
1kW=860kcal/h, 1 kcal/h =1.16×10-3 kW
CP: specific heat capacity at constant pressure (kJ/kg●℃); the specific heat capacity at constant pressure of the hydraulic oil is 1.9674 kJ/kg●℃.
ρ: specific gravity (density), kg/L; for the cooling oil, it is 0.876 kg/L
Vs: total oil volume (L)
ΔT: temperature rise (℃)
t: time (S)
Example: if the total oil volume of some hydraulic pressure station is 200L and under normal working for 10min, its oil temperature has been raised from 25℃ to 35℃, then the heating value of the hydraulic pressure station will be:
Pheat= CP ●ρ●Vs●ΔT/t = 1.9674 ×0.876×200×(35-25)/(60×10)=5.745 kW
The model selecting principle of coolers: the refrigeration amount of the precision oil cooler shall be 20~30% greater than the heating value.
Then, the oil cooler with the refrigeration amount of 7kW shall be selected.
(III) Calculation Method of Pipe Resistance
After the dimension of the oil pipeline has been decided, then the pipe resistance can be worked out according to the following formula:
Pipe resistance: △P=0.595×ν×Q×L/D4
(for common hydraulic oil and lubricating oil)
P: pipe resistance (MPa)
ν: kinematic viscosity of the oil (mm2/s), Q: flow (L/min)
L: pipeline length (m); D: inside diameter of the pipe (mm)