4.5
Residual risks
The existing residual risks are to be observed by the user, when the installa‐
tion is designed.
Explosion hazard!
WARNING
Due to the risks mentioned herein, the motors are not approved for use in
areas, in which an explosive atmosphere or explosive materials
●
permanently occur or occur over a longer period or
●
may occur in case of frequent device malfunctions or typical error states
.
Overloading
When the motor is overloaded, including cases where errors in the mechani‐
cal or electrical equipment of the machine cause such overloading, high tem‐
peratures may occur that result in explosion hazards.
An operation in explosive dust-atmosphere can built a layer on the motor dur‐
ing a residence time, which does no longer ensure a sufficient motor cooling
chapter 10.12 "Motor cooling" on page 137
Grounding and discharge currents
Variable-speed drive systems cause unavoidable discharge currents. If the
grounding connector in the motor cable and the second separate grounding
connector on the motor housing are not connected as specified or are inter‐
rupted due to corrosion or other defects during their lifetime, the discharge
current flows as leakage current over conducting housing parts, resulting in
the risks of sparking at transfer points and, if explosive materials are present,
explosions.
Material aging
The time of action and penetration of explosive materials depend on the ap‐
plication. It depends on the ageing degree of the seals, on the mechanical at‐
tachment of the motor, the properties of the explosive materials and the aver‐
age temperature occurring during the operating time as a result of the load
cycles.
Impermeability
Due to unavoidable temperature fluctuations as well as due to the deteriora‐
tion of gaskets, the housing is not leak proof. Hence, explosive gases that oc‐
cur within the equipment during a fault can penetrate into the motor. The de‐
sign and checking of the impermeability are carried out according to the de‐
gree of protection IP 65 (EN 60034-5:2001). The maximum temperature of
parts within the motor can reach 155 °C during normal operation at maximum
ambient temperature.
Temperature monitoring
The failure of the single-channel temperature monitor in the device system
may occur, as the result of an error, and might not be detected, even if the
motor is operated within the normal temperature range and load cycle.
DOK-MOTOR*-MSK*EXGIIK3-PR09-EN-P
Bosch Rexroth AG
29/175
Synchronous Servomotors MSK For Potentially Explosive Areas
Explosion protection for MSK motors
