TMR and 2oo3

TMR usually means 'Triple Modular Redundant', which usually means a control system with three, redundant control processors each making determinations about the control and protection of a process.

2oo3, or TOOT, usually means 'Two out of Three' ('2 out of 3').

When a TMR control system is used to control and protect a process, it's customary to "vote" the outputs (and in some cases the inputs, when individual redundant inputs are used to each of the three processors). In other words, two of the three processors must agree that a solenoid should be energized for it to be energized, or two of three processors must agree that a motor should not be running for it to be commanded off.

The voting of inputs and outputs can be implemented in many different ways, not just in software or hardware. Some control systems use both software- and hardware voting, and sometimes the voting is not obvious.

TOOT can be used on non-TMR control systems with special capabilities, but it would be difficult to imagine a TMR control system without some kind of two-out-of-three voting.
 
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TMR stands for Triple Modular Redundant (Redundancy). It is a modular hardware/software architecture that provides triple redundancy (three independent channels) voting logic, typically voted 2oo3 in the process industries, i.e. at least two out of three "true" votes are required for the voting logic to provide a "true" output. 2oo3 is a voting architecture that provide a compromise between the 1oo2 (safety) and 2oo2 (reliability - spurious trip protection) voting architectures. Some of the manufacturers of TMR systems are Triconex, ICS-Triplex, & GE.

For some additional information, please see:

http://www.md.kth.se/RTC/SC3S/papers/Storey-designforsafety.pdf

Bill Mostia
Sr. Consultant
SIS-Tech Solutions
 
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