5 Residual risks
Failure of the protective equipment
If the purge gas supply and the monitoring for maintaining the protective
measures in the purging device fail simultaneously, the explosion protection
in an explosive atmosphere is no longer ensured and there is a risk of explo‐
sion.
Overload
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.
Grounding and discharge currents
Variable-speed drive systems cause unavoidable discharge currents. If the
protective conductor in the motor cable and the second separate protective
conductor at the motor housing have not been connected as specified or
have been interrupted by corrosion and other defects during their service life,
the discharge current flows as leakage current over conducting housing
parts, resulting in the risks of sparking at transfer points and explosions, if ex‐
plosive materials are present. For this reason, check the proper condition of
the two protective conductor connections at regular intervals.
Discharge currents with risk of sparking! Ex‐
plosion hazard!
Do not remove or modify any ground connectors at the motor.
It is ensured ex works that all metallically conductive parts at the motor are
interconnected by ground connectors.
Material aging
The time of action and penetration of explosive materials depend on the ap‐
plication. It depends, for example, on the aging degree of the seals, on the
mechanical attachment of the motor, the properties of the explosive materials
and the average temperature occurring during the operating time as a result
of the load cycles.
Shaft sealing ring
Radial shaft sealing rings are friction seals. They are therefore subject to
wear. Due to pressurization (Ex-px), signs of wear can lead to increased
leakage loss. If the leakage loss has reached the value set at the control de‐
vice, the system is switched off inevitably by the control device. Before the
maximum allowed leakage loss is reached, the shaft sealing ring should
therefore be replaced by Bosch Rexroth or another authorized body. Also ob‐
serve the notes in chapter "Maintenance" on page 59.
DOK-MOTOR*-IDYN*A*EXPD-IB05-EN-P Bosch Rexroth AG 23/69
Rexroth MAD and MAF Motors in EX px d Design acc. to ATEX Directive 2014/34/EU
Residual risks
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