8
2.2 ATEX SAFETY MEASURES
Pump
type
Risk
Liquid
Dry running of mechanical
seal
(overheated seal faces are an
ignition source)
Leakage
(inflammable liquid can come into the
atmosphere)
F
lo
o
d
e
d
su
ct
io
n
P
u
m
p
Non ignitable
liquid
Flushed mechanical seal
or flow monitoring to be
installed by the customer
No danger
Ignitable liquid
Flushed mechanical seal
or single seal with preventive
maintenance by the customer
The flashpoint of a combustible liquid is the lowest temperature at which sufficient vapor is created
above a combustible liquid so that it can ignite when mixed with air. However, be aware that the
temperature of certain spots on the pump (e.g. the mechanical seal or motor) could be warmer than
the temperature of the circulated liquid. Therefore, if the flashpoint of the liquid is above the
temperature the liquid is pumped but below 135°C, it should also be considered as ignitable when
considering the risk leakage.
Please be aware that if a mechanical seal runs dry, the temperature of the seal faces can rise above
400°C.
Pumps with flushed mechanical seal:
You have to make sure there is a continuous circulation of the flushing liquid and the motor
is stopped immediately in case of lack of flushing liquid. Otherwise the mechanical seal can
run dry and generate dangerous high temperatures. When a quench reservoir is applied, the
level of the flushing liquid in the quench reservoir must be guarded by an ATEX approved
level sensor. If the level becomes too high or too low, the pump must be stopped. The
temperature in the quench reservoir should be guarded by an ATEX approved temperature
sensor. The temperature of the flushing liquid should be kept below 60°C. If necessary an
external cooling system should be used to keep the flushing temperature under 60°C. It is
the responsibility of the end user to use a suitable flushing liquid for the mechanical seals.
The mix of the flushing liquid and the pumped liquid must not create any dangerous or
explosive gasses.
The pump should never run with closed valve.
Pumps with single mechanical seal:
You must monitor the flow (e.g. with an ATEX approved flow sensor on the inlet of the pump).
If there is no flow detected, you must stop the motor immediately.
Leakage of an ignitable liquid is a serious safety risk. The end-user has to evaluate the
consequences of the leak and adjust the check frequency for leak of the mechanical seal. In
case leak is detected, the pump must be stopped and the mechanical seal has to be replaced.
The mechanical seal has to be replaced preventively every 3000 operating hours.
The baseplate of the pump must be earthed in order to prevent a build-up of static
electricity.
The pump must not pump liquids warmer than 108°C.
The pump should not be started before compliance with all these safety measures.
