B10d: Beware of being trapped
3
1. Informations
For dry contact safety components, the average time of dangerous failure (MTTFd)
depends on the nature of the load being switched. Software can be used as an aid in
the development of the safety le. Under no circumstances does this software permit the
publication of the said le; instead, they should be considered more like "ISO 13849-1
calculators."
Be aware of the B10d value, which must be listed with the corresponding load. In most
cases, the manufacturers give a B10d for a low current, such as 10 mA; this is the case
for the reed switch, for example. In reality, this current is much higher. If the value of the
B10d is very high for 10 mA, it will be much lower at 100 mA and far too low at 1 A. In this
case, the MTTFd value will drop signicantly and the performance level of the installation
will be compromised. The results published by some software program should therefore
be taken lightly!
1.1 "Reed contact" technology
The usual notation is B10d at 20% of the rated current (In). If In = 50 mA, then B10d is
rated at 10 mA. This means that it is not possible to switch more than 10 mA with this
component. Some software will require the correction of this parameter.
Before choosing a component, check that the nature of the load to be switched corres-
ponds to 20% of In.
1.2 ACOTOM technology
The dry contacts of component X5 have an 8 A breaking capacity limited to 1/4 of its value
to avoid any risk of sticking by carbonization. The value of the B10d is clearly displayed
at 2 A with 2,000,000 cycles, which makes it possible to directly control power contactors.
SYTCOM software: https://www.comitronic-bti.fr/fr/sytcom
A calculator for ISO 13849-1
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