1oo2D voting
1oo2D voting
(OP)
What does the "D" in 1oo2D refer to ? When is it appriate to attach a "D" to the voting description for two analog inputs to a PLC used as a logic solver in an SIS.
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RE: 1oo2D voting
xnuke
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RE: 1oo2D voting
http://www.honeywell.com.pl/pdf/automatyka_przemyslowa/sterowanie/Fsc2004d.pdf
jwilsonimp
RE: 1oo2D voting
The X refers to the voting that is applied. For example, the safety system might decide that the pressure exceeds the pressure limit if two pressure sensors (out of the three) reach this limit. Hence the safety system would be classified as 2oo3. If only one pressure sensor needs to exceed the pressure limit then the safety system would be classified as 1oo3.
Thus, the Y refers to how many times the safety functions is carried out. The X refers to how many different paths actually need to be working correctly.
Concerning the D in 1oo1D or 1oo2D this refers to the use of diagnostics as an independent shutdown path. A 1oo1D system basically has two outputs that can be used to independently shutdown the process.
There are a few different definitions going around in the industry. Some say it the D of Diagnostics, others say its the D of degraded mode. Of course both are a litte bit true as you need a lot of Diagnostics capabilities in order to be able to go into degraded mode.
But just a system with a lot of diagnostics does not get the D behind it. You actually need to do and be able to do something with that diagnostic information. This can only be achieved with an indepedent path.
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RE: 1oo2D voting