100/180 mm PAPERLESS GRAPHIC RECORDER: USER GUIDE
User Guide
Page 113
HA028910
Issue 13 Sep 16
4.3.11 FUNCTION (Cont.)
FVALUE
To calculate the equivalent time at Sterilizing Temperature (for temperatures below, at and above Steriliz-
ing Temperature) both in dry (FH) and steam (FO) sterilizing environments, using the following equation:
Fval
t
!
Fval
t
"
1
#
T
$
10
ma
t
"
Target temp
Z
Where Fval
t
= F value at time t (minutes)
Fval
t-1
= F value last iteration
T = Internal recorder iteration interval (minutes)
ma
t
= Value of temperature measuring channel
Target temp = 121.1˚C for FO; 170˚C for FH
Z = Temperature interval representing a factor-of-10 reduction in killing effi ciency
= 10˚C for FO; = 20˚C for FH
User confi guration consists of entering the channel which is measuring temperature, the relevant steriliz-
ing temperature and temperature interval (Z-value) and a low cut-off value, if required.
Figure 4.3.11c shows the confi guration fi elds for measuring Fo, using channel 1 as the temperature input
channel, Fo values for target temperature (121.1˚C) and z-value (10˚C), and 75˚C as the low cut-off value,
below which killing credits are not to be counted.
Figure 4.3.11c Fo setup example
APPLICATION NOTE
To ensure that sterilizer loads which contain materials with differing thermal inertias are thoroughly steri-
lized, a typical sterilizer has up to 12 different measuring points within the load. To ensure accuracy, the
temperature sensors should be calibrated, and the channel adjustment facility used to compensate for
any inaccuracies found.
If each of the inputs is used to compute an F value, each of these values can then be used as an input to a
Group Minimum function, with a high absolute alarm set at the correct F value. The alarm output can be
used to sound a warning, or an associated relay can be linked into the autoclave control system to signify
the end of a sterilization cycle.
Function
fValue
F value of
Sterilizing Temp
121.1
Temperature interval
Low cut off
Channel 1
75
Maths Number
2) Math 2
Value
OFF
Reset now
10
