Alarm Rationalisation and Priority Worksheet
Rationalise alarms with a simple priority matrix: consequence severity and allowable response time set the priority. The sheet checks the priority distribution against the common 80, 15, 5 % guideline.
Download
- Calculator sheet with a worked example
- How to Use sheet with steps
- 84 built in formulas, no macros
- Yellow input cells, grey results
- Calculation sign off block
- Excel, Google Sheets and LibreOffice
Worked Example
These are the results of the example already filled in the workbook. Replace the yellow cells with your own data.
Alarms
| Alarm tag | Description | Severity | Time to respond | Score | Priority | Operator action | Keep? | Set point | Remarks |
|---|---|---|---|---|---|---|---|---|---|
| PAHH 1101 | Steam header very high pressure | Severe | Under 5 min | 6 | High | Keep | |||
| LAL 2101 | Drum level low | Severe | 5 to 15 min | 5 | High | Keep | |||
| TAH 3105 | Bearing temperature high | Major | 5 to 15 min | 4 | Medium | Keep | |||
| FAL 4102 | Cooling water flow low | Major | 15 to 30 min | 3 | Low | Keep | |||
| PAL 5101 | Instrument air pressure low | Major | Under 5 min | 5 | High | Keep | |||
| AAH 6101 | Effluent pH high | Minor | 15 to 30 min | 2 | Low | Keep | |||
| LAH 7101 | Day tank level high | Minor | 5 to 15 min | 3 | Low | Keep |
About this Calculator
Too many alarms, or too many high priority ones, hide the important ones. Rationalisation gives each alarm a purpose, an action and a justified priority.
Basis: Example priority matrix (edit to your alarm philosophy): High when severity and urgency together score 5 or more, Medium at 4, Low otherwise. Distribution guidance about 80 % low, 15 % medium, 5 % high (ISA 18.2 / EEMUA 191).
How to use
- List alarms from the DCS.
- For each, agree the worst consequence without operator action and the time available.
- Priority is calculated; adjust the matrix to your philosophy if needed.
- Record the operator action and decide keep, remove or change.
- Compare the distribution with the guideline.
Formulas used
- Score = severity rank (1 to 3) + urgency rank (1 to 3).
- High ≥ 5, Medium = 4, Low ≤ 3.
- Distribution = count per priority ÷ total.
Related tools
Frequently Asked Questions
What distribution is recommended?
About 80 % low, 15 % medium and 5 % high is common guidance.
What is an alarm without action?
A nuisance; convert it to an event or remove it.
Is the matrix standard?
No, each site defines its own in the alarm philosophy; this is an editable example.
Learn more on the blog
Types of alarms in DCS every instrumentation engineer should know
A practical guide on instrumentationblog.in that explains the engineering behind this workbook.
Read Full Article