KROHNE UFM 500 ATEX EN - Manual (Page 8)

7
5. SERVICE
5.1 Replacement of electronics unit or mains fuse(s)
IMPORTANT !
The following instructions must be followed carefully, if the flameproof UFM 500 K-EEx
signal converter housing has to be opened respectively closed again !
Before opening:
♦
Make absolutely sure that there is no explosion hazard !
♦
Gas-free certificate !
♦
Make sure that all connecting cables are safely isolated from the mains and low-
voltage circuits!
♦
Allow the prescribed waiting time to elapse before opening the housing:
20 minutes for temperature class T6
11 minutes for temperature class T5
When the instructions above are strictly followed, the cover of the electronics compartment
may be removed. First unscrew the hexagon socket head cap screw of the interlocking
device by a hollow-head screw wrench size 3, until the cover can rotate freely. Unscrew the
cover with the special plastic wrench (black) that is supplied with the apparatus.
After opening:
♦
The brass grounding strip at the back of the electronics unit must be securely screwed to
the housing (back-end of electronics compartment) by screw C (see Figure 5 below). The
electronics unit is screwed into the electronics compartment by two screws B. Before
screws B and C can be accessed, the display unit must be removed via screws A.
♦
Before the cover is screwed back into the housing, the screw-thread must be clean and
well-greased with an acid and resin-free grease , e.g. silicone grease.
♦
Screw the cover into the housing. Screw the hexagon socket head cap screw of the
interlocking device tight.
Figure 5: Display unit (left) / Electronics unit after removal of display unit (right).
A
A
C
B
B
Display unit
Flat cable of
display unit
Brass earth strip