Ex p Control unit
APEX
px
Safety
Rev. 0
01-37A2-7D0001_px_Manual_Exp-Control-Unit_20210923_0_en.docx
Page 17 of 96
Safety function
The safety function of the Ex p control unit is the purging with a defined quantity
of purging gas, the safe monitoring of the internal overpressure of the protected
equipment and the release for operation. The safe state means that in the event
of a drop in pressure or malfunction, the Ex p control unit switches to the safe
state = deactivation of the protected equipment.
The “safe state” is triggered by:
Falling below the minimum pressures within the Ex p equipment
Illogical pressure values within the Ex p equipment
Failure of the supply voltage
If the Ex p control unit does not deactivate or does not change to the safe state
on request or in the case of an error, a hazardous failure exists.
Safety parameters
THE FOLLOWING SAFETY PARAMETERS ARE WITHOUT OPTIONAL
SENSORS.
The optional sensors must be considered to determine the total
failure rate!
The safety parameters may be derived from the
documentation on the optional sensors used.
Safety parameters according to IEC/EN 61508 / DIN EN ISO 13849-:
SIL = 2
Performance Level: = d
PFH
sys
= (PFH_S+PFH_C) = 1.70E-08
HFT = 1
SFF
sys
= 92.85 %
MTTFd = 76 Yr
DC = 88.78 %
Device type B (complex equipment)
Interval of retests = 1 year
Category 3
