Escalation factors
Adding escalation factors and their controls to a bow-tie, the rules they are checked against, where they are drawn, and hiding them on a busy diagram.
What they are
An escalation factor is a condition that weakens a barrier, such as Instrument air failure weakening Relief valve in the example. An escalation-factor control manages that condition, such as Backup air receiver. Neither is a step on a path from threat to consequence. A factor can weaken a barrier on either side of the top event.
In an edge list
| Node ID | Connected Node ID | Node Type | Label | Relationship Type |
|---|---|---|---|---|
| EF-AIR | PB-PSV | Escalation Factor | Instrument air failure | Escalates |
| EFC-AIR | EF-AIR | Escalation Factor Control | Backup air receiver | Controlled by |
- The factor's row leads to the barrier it weakens.
- The control's row leads to the factor.
- Relationship Type can be left blank; the visual reads these connections as Escalates and Controlled by.
- A factor that weakens more than one barrier has a row for each. A barrier weakened by several factors is the Connected Node ID of each factor's row.
In a register
Put the factor in Escalation Factor, and its control in Escalation Control, on the row of the barrier it weakens. Both take that row's Status and Health, which describe the barrier.
Rules
| Rule | Severity | Message |
|---|---|---|
| A factor is connected to a barrier | Error | An escalation factor must degrade a barrier. Connect it to one with an Escalates relationship. |
| A control is connected to a factor | Error | This escalation control does not address any escalation factor. |
| A factor has a control | Warning | This escalation factor has no control. Barrier degradation is unmanaged unless that is deliberate. |
Where they are drawn
A factor is drawn in the barrier column, in the path of the barrier it weakens and after that path's barriers, with its control after it. The connector from factor to barrier is an amber dashed arrow, and from control to factor a grey dashed arrow.
In the Node Inspector and focus
| Selected | Relationships |
|---|---|
| A barrier | Escalation factors: the factors that weaken it. |
| An escalation factor | Degrades: the barrier it weakens. Controlled by: its controls. |
| An escalation-factor control | Addresses: its factor. |
Focus branch on a factor or a control keeps the barrier it weakens, that barrier's path, the top event and the hazard. Focus on a barrier keeps its factors and their controls. Controls are not counted in the summary strip.
Hiding escalation factors
On a busy diagram, set Diagram → Validation → Escalation branches to Collapse. Factors and controls are taken out of the diagram and the layout closes up the space. While they are hidden, their rules are not checked. Show brings them back.