2.4.2 Potential hazards
The ignition hazard assessment for the roots pumps in the ATEX series was performed in accordance
with the harmonized standard ISO 80079-36 (Non-electrical equipment for explosive atmospheres - Ba-
sic method and requirements). This assessment includes the identification of hazards described as fol-
lows which will not occur if the system is operated properly with the respective safety measures.
Potential
hazard
Occurrence due to
Safety measures
Hot surfaces
Heating up of compo-
nents due to compression
work and friction
When used as intended, all surface temperatures are be-
low the measuring gas temperature in the exhaust chan-
nel.
Induction of eddy cur-
rents when the magnetic
coupling slips through
● Note the information to avoid this in the operating in-
structions.
Hot gases
Compression of the re-
quired gases
● Measure the gas temperature in the exhaust channel
using the supplied thermometer and evaluate the
temperatures.
● Note the information in the operating instructions of
the thermometer.
Mechanical
sparks
Contact of the pistons in
the suction chamber
The air gaps for the maximum gas temperature are de-
signed taking into account a safety factor.
Electrical
sparks
Electric motor
The use of an explosion-proof electric motor is prescri-
bed.
● Observe the marking on the motor rating plate.
Static elec-
tricity
Vacuum pump not earth-
ed
● Integrate the vacuum pump in the equipotential
bonding at the installation location.
Chemical re-
action
Between the process gas
and lubricant or between
the process gas and
components that are part
of the housing
● Evaluate the process and avoid hazardous process
conditions.
Zone en-
trainment
due to leaky vacuum
pump
The vacuum pump underwent a final inspection with heli-
um leak test within the framework of a production control
(leakage rate < 1 × 10
-6
Pa m
3
/s).
Tbl. 5:
Potential hazards
2.4.3 Safety measures
► Observe and implement the following safety measures for safe operation of the roots pump in ac-
cordance with the respective device category:
Place
Measures/safety equipment
Category 2
Category 3
Speci-
fica-
tion
We
rec-
om-
mend
Speci-
fica-
tion
We
rec-
om-
mend
Magnetic
coupling
First switch on the roots pump when the back-
ing pump can accept the required amount of
gas
x
x
You must observe the volume flow ratio of
≤ 10:1 between the roots pump and backing
pump
x
x
Only use the motors specified by Pfeiffer Vac-
uum.
x
x
Limitation of the motor torque by:
● frequency converter that limits the permis-
sible torque
or
● soft starter and continuous monitoring of
the power consumption
x
x
Safety
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