Reading a reliability block diagram
How a reliability block diagram is laid out, the two notation profiles, showing reliability on blocks, the summary strip, the Node Inspector, focus, and splitting a large diagram with transfers.
How it is laid out
- The input is on the left, and each step is one column further right.
- Blocks in the same column follow Order, from the top.
- Parallel paths stay side by side between their split and their merge.
- Terminals and junctions are small dots with their labels beneath them.
Nodes cannot be dragged. Change the result with Order, orientation, density and spacing. Under Custom every orientation is available; under IEC 61078:2016 the diagram runs left to right or right to left.
Notation profiles
| Profile | How it draws | Settings it controls |
|---|---|---|
| Custom (default) | Coloured blocks, and arrowed connectors coloured by type. | None. |
| IEC 61078:2016 | Square-cornered blocks, small filled dots for terminals and junctions, and plain lines without arrowheads, except on dependencies. | Corner radius is fixed at square. Orientation is limited to left to right or right to left. Border width is limited to 1–4 px. |
Choose the profile under Diagram → Notation → Profile. Under IEC 61078:2016 a standby component is drawn as an ordinary block, because the standard shows standby through the structure, and a switch keeps its Custom diamond, because the standard has no switch symbol.
Showing reliability on the diagram
Reliability, availability and failure rate are not written on the blocks by default. Add them under Labels → Value annotations, which uses the column's Power BI format, so 0.998 with a percentage format reads as a percentage. The m/n of an m-out-of-n block is written beneath it without any setting.
Summary strip
Turn on Labels → Summary strip → Show summary. A reliability block diagram counts its components, subsystems and standby components by Status. For the example it shows 7 blocks: 5 Healthy, 1 Degraded and 1 Failed. Terminals, junctions, m-out-of-n blocks and the other types are not counted.
Node Inspector
The Analysis section lists the block's Reliability, Availability, Failure rate, Status and vote numbers. There is no Relationships section, except in two cases.
| Selected | Relationships |
|---|---|
| A block several connections lead into, such as an m-out-of-n block or a merge junction | Used in: the number of connections arriving, followed by the blocks they come from. Trip logic in the example reads Used in 3 branches. |
| A Transfer In or Transfer Out with a Linked Diagram ID | Developed in or Referenced from, with Open linked diagram. |
Focus branch
Focus branch keeps the selected block, every block before it and every block after it, and fades the rest. Focused on the duty pump in the example, only the standby pump fades.
Splitting a large diagram
Give each part its own Diagram ID
Every row of the main diagram carries one Diagram ID, and every row of the section developed separately carries another.
Replace the section with a Transfer In
On the main diagram, a Transfer In row where the section was, with its Linked Diagram ID set to the other diagram's Diagram ID.
Start the other diagram from a Transfer Out
Its Linked Diagram ID points back to the main diagram, and its rows lead on to that diagram's own Output.
Readers select the transfer and choose Open linked diagram in the Node Inspector.