KROHNE UFM 500 ATEX EN - Manual (Page 4)

3
1.3 UFC 500-EEx signal converter
The UFC 500-EEx signal converter consists of a cylindrical housing made of die-casted
aluminum. It has of two separate compartments, divided from each other by an integrated
wall with casted flameproof terminal feed-through. The interconnecting part to the primary
head at the bottom of the housing contains a flameproof wire or coaxial cable feed-through.
The housing is closed on both ends by a cylindrical cover with M115x2-6g screw-thread and
O-ring sealing. The signal converter housing has an ingress protection degree in accordance
with the EN 60529 of at least IP 67. The two compartments are described in detail below.
1.3.1 Electronics compartment
The electronics compartment accommodates the UFC 500-EEx electronic unit. The
compartment is designed with type of protection flameproof enclosure "d" in accordance with
EN 50018. It is closed by a flameproof display cover with glass window, which is glued and
additionally mechanical supported by a screwed in back-up ring made of aluminum.
The UFC 500-EEx electronics unit is inserted into the electronics compartment with the help
of two sliding rubbers that position and fixate the unit at the front inside the housing. Two M4
screws mount the unit and a third M4 screw fixates the brass earth strip at the back-end of
the printed circuit board with integrated voltage/current limiting circuit (i.e. front-end PCB).
The three screws are screwed to the integrated wall in-between terminal and electronics
compartment. The integrated voltage/current limiting circuit provides the ultrasonic sensors
inside the primary head with type of protection intrinsic safety "ib" according to EN 50020.
The voltage/current limiting circuit has the following maximum values (i.e. entity parameters):
•
Maximum output voltage : U
o
= 8.72 V
•
Maximum output current : I
o
= 380 mA
•
Maximum allowed external capacitance : C
o
= 1.2 µF
•
Maximum allowed external inductance : L
o
= 0.17 mH
1.3.2 Terminal compartment
The terminal compartment accommodates seven M4 clamp terminals for connection of the
power supply and the signal output circuits (binary and current outputs). Figure 1 on the next
page shows the terminal arrangement. The terminals are separated from each other by
insulation plates (nine in total, from which one at each end of the row).
In the following section the electrical connection of the mains supply power and the signal
output circuits is described (this information only concerns the Ex-relevant subjects).
The terminal compartment (standard in type of protection increased safety "e") is standard
equipped with two metal cable glands.
As an option (must be explicitly ordered!) the terminal compartment can be provided as a
flameproof enclosure "d", in case the customer wants to use pre-certified "EEx d" cable
glands or conduits.
Note: EEx d certified cable glands are no part of the standard delivery, they must be provided
by the customer himself or ordered explicitly.
For flameproof conduit systems, the terminal compartment must have type of protection
flameproof enclosure "d" according to EN 50018. The conduits must be sealed by "EEx d"
approved (within the ATEX 100a directive) sealing devices (i.e. stopping box) directly at the
conduit entrances of the as flameproof enclosure performed terminal compartment.