What is the typical temperature range for the motor of a pump?

Corresponding requirements are specified in GB15703-1995 for the basic technical requirements of flameproof motors.

I have listed below the relevant sections of GB15703-1995 regarding the basic technical requirements for flameproof motors for reference: 3.1 Categories, grades, and temperature groups of flameproof motors 3.1.1 Flameproof motors are divided into Class I and Class II a. Class I: Motors for use in coal mines； 　　b. Class II: Motors for industrial use. 　　3.1.2 The classification of flameproof motors: For Class II flameproof motors, they are divided into three grades, A, B, and C, based on the maximum test safety clearance suitable for explosive gas mixtures. 　　3.1.3 The temperature groups for explosion-proof motors are classified based on the maximum allowable surface temperature of the motor. 　　a. When dust may accumulate on the surface of Class I motors, the maximum allowable surface temperature is 150℃ ； When dust will not accumulate or measures can be taken to prevent its accumulation, a maximum surface temperature of 450°C is permitted. 　　b. Class II motors are divided into six groups, T1 to T6, according to their maximum surface temperature; the allowable maximum surface temperatures for each group are shown in Table 1. 　　Table 1 　　 　　3.2 Enclosure protection rating (see GB4942.1) 　　3.2.1 The protection rating of the motor’s main enclosure shall be no lower than IP44, while that of the junction box shall be no lower than IP54. 　　3.2.2 For the external fan cooling motor, the protection rating of the ventilation openings shall be no less than IP20 at the air intake side and no less than IP10 at the air outlet side. 　　3.2.3 The protection rating at the air intake side of the fan shall be no lower than IP10. 　　3.2.4 Vertical motors must be capable of preventing foreign objects from falling vertically into the ventilation openings. 　　4 Environmental Conditions Unless otherwise specified by the user, the motor shall be designed for the following altitudes, ambient temperatures, and relative humidities. 　　4.1 The altitude shall not exceed 1000 m. 　　4.2 Ambient air temperature: minimum of –20°C, with a maximum that does not exceed 40°C depending on the season; in coal mines, it shall not exceed 35°C. 　　If the motor is specified for use at an altitude of over 1,000 m or in an environment where the maximum air temperature is above or below 40°C, the provisions of GB755 shall be followed. 　　4.3 Relative humidity of ambient air: the average highest relative humidity in the wettest month is 90%, and the average lowest temperature in that month is no higher than 25℃ ； The maximum relative humidity in coal mines shall not exceed 95% (at a temperature of 25°C).

For increased-safety and flameproof motors, if an alarm is set for the stator temperature at 135 degrees, then a surface temperature of around 120 to 130 degrees or lower is generally no problem.

The surface temperature of the motor is generally not monitored by end users. The simplest way to check it is by touching it with your hand; as long as the temperature isn’t too hot to touch, it’s fine. If it is too hot, the machine should be stopped immediately, otherwise it may get damaged. There are instructions available for gear oil pumps at www.hnppump.com