Distillation Process Analyzer DPA-4.5
Safety
2.4.3 Measuring unit box (Ex d)
Figure 2.3: Measuring unit box Flame arresters (3)
prevent any flame propagation outwards via pipelines.
The cover is secured with a locking screw (1). To turn
the cover, socket wrenches can be inserted in the drill
holes (2)
The
measuring unit box (Ex d)
contains operating
equipment without its own ignition protection type and
therefore contains potential ignition sources. In addition,
the box contains failsafe and non-failsafe pipeline
systems for the product and auxiliary media. Non-failsafe
pipeline systems are always guided to the outside via
flame arresters.
The measuring unit box provides explosion protection
through the pressure-resistant enclosure ignition
protection (Ex d) along with the flame arresters and
cable ducts.
The box is designed in such a way that in the event of an
explosion in the interior, the pressure is maintained and
thereby prevents the spread of the explosion to the
explosive atmosphere surrounding the box.
Flame arresters prevent any flame propagation outwards
via the pipelines. In case of failsafe pipeline systems,
flame arresters are closed towards the outside.
If a flashback has been registered, the entire device
needs to be checked and all flame arresters replaced!
If the temperature on the surface of the flame arrester is
more than 60 C, explosion protection is compromised.
Temperature class
For distillation, the product is heated up to 600 °C in a
distillation flask in the Ex d box. At the end of a
distillation, the hot product is drained out of the
distillation flask and conveyed out of the Ex d box. The
product and any components it flows through outside the
Ex d box must not reach a temperature above T4. This
ensures that the product has cooled own to below T4
(135 °C) before being drained out of the distillation flask.
It must also be ensured that the flame arresters do not
heat up to more than 60 °C. Otherwise, explosion
protection is no longer guaranteed.
Cable ducts
Only cable ducts with metric threads M25 and M32 x 1.5
are permitted. All other thread types damage the threads
in the box. If the box has defective threads, it will not
offer explosion protection even with suitable cable ducts
and may not be used.
Electrical charges and
high temperatures
Even after the power supply is switched off, components
on the inside can still have electrical charges or high
temperatures which represent potential ignition sources.
•
Keep the cover of the measuring unit box shut during
operation and for up to 25 minutes after switching off
the power supply in order to allow electrical charges
to discharge and high temperatures to drop safely.
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