Block and connection types
Every block type and connection type a reliability block diagram recognises, what to write for each, how each is drawn under the Custom and IEC 61078:2016 profiles, and the rules for the input and output.
Block types
| Node type | Write it as | Under Custom | Under IEC 61078:2016 |
|---|---|---|---|
| Input terminal | Input, Input Terminal, Start, Source, In | Small white circle, label beneath | Small filled dot, label beneath |
| Component | Component, Block, Unit, Reliability Block, Elementary Block, Item, Element, Equipment | Blue rectangle | Square-cornered rectangle |
| Subsystem | Subsystem, Sub System, System, Composite Block, Assembly | Purple rounded rectangle | Rectangle with a heavier border |
| Standby component | Standby Component, Standby, Backup | Green dashed rectangle | Ordinary rectangle |
| Switch | Switch, Selector | Amber diamond | Amber diamond. The standard has no switch symbol. |
| Series junction | Series Junction, Series | Small dark dot | Small filled dot |
| Parallel junction | Parallel Junction, Parallel, Split, Merge | Small blue dot | Small filled dot |
| m-out-of-n block | Voting, Vote, Voting Block, M out of N, K out of N, M/N, K/N, MooN, Majority Vote, Redundancy, Voting Junction, M out of N Junction | Blue circle | White circle |
| NOT gate | NOT, NOT Gate, Invert, Inverter, Complement | NOT gate symbol | NOT gate symbol |
| Priority AND gate | PAND, Priority AND, Priority AND Gate | Priority AND symbol | Priority AND symbol |
| Sequential gate | SEQ, Sequential, Sequential Gate, Sequence Gate | Amber circle | White circle |
| Transfer in, Transfer out | Transfer In, TIN; Transfer Out, TOUT | Transfer triangle | Transfer triangle |
| Repeated block | Repeated, Repeated Block, Direct State, Shared Block, Common Block | Blue block with a double border | Block with a double border |
| Inverted repeated block | Inverted, Inverted State, Inverted Block, Negated Block | Red dashed block with a double border | Dashed block with a double border |
| External element | External, External Element, CCF, Common Cause Failure, Maintenance Team, Event | Purple rounded rectangle | Rounded rectangle |
| Output terminal | Output, Output Terminal, End, Sink, Out | Small green circle, label beneath | Small filled dot, label beneath |
Matching ignores case, spaces, underscores, hyphens and full stops, so M-out-of-N Junction and m out of n junction both read as an m-out-of-n block. Wording that matches nothing can be mapped under Node type values on the Data Mapping tab.
Only three types carry rules of their own: the input and the output, and the m-out-of-n block, whose numbers are checked. NOT, Priority AND, Sequential, transfer, repeated and inverted blocks are drawn with the symbols IEC 61078:2016 gives them, with no further checks.
Connection types
| Relationship type | Write it as | Use it for | Under Custom | Under IEC 61078:2016 |
|---|---|---|---|---|
| Series path | Series Path, Series, Next | The ordinary connection. The default for a blank cell. | Grey arrow | Plain line |
| Parallel path | Parallel Path, Parallel, Branch | A connection into one of several paths. | Blue arrow | Plain line |
| Standby path | Standby Path, Standby, Backup | A connection to a standby block. | Green dashed arrow | Plain line |
| Bypass | Bypass, Alternate | A connection that goes around blocks. | Amber dashed arrow | Plain line |
| Dependency | Dependency, Depends On | A block or external element affecting another block. | Purple dotted arrow | Dashed line with an arrow |
Connection types change how a connection is drawn, not how the diagram is checked, with one exception: dependencies are left out of the check for cycles, so a dependency may point back to a block earlier in the diagram. To show a common cause failure, add an External Element row for it with one Dependency row for each block it affects.
The input and the output
- Use one Input and one Output. A second is a warning, such as Input occurs 2 times.
- Nothing may lead into the input, and nothing may follow the output.
- With no Input or Output type, the block with nothing before it and the block with nothing after it are taken as the ends.
- There must be a path from the input to the output.