Independent Protection Layers & Conditional Modifiers

IPLs and Conditional Modifiers can be added to Initiating Events for the following SIL Determination methods:

  • LOPA
  • Risk Matrix

IPLs and Conditional Modifiers can also be managed for all Initiating Events on all Hazards via the IPLs Manager.

IPL Types

An Independent Protection Layer (IPL) is normally a preventative safeguard which reduces the frequency of the hazardous event. SIL Comp provides the following IPL Types:

  • General
  • BPCS
  • Alarms
  • SIF
  • Human Factors
  • Mechanical
  • Custom – Define your own IPL if not covered by any of the above

Conditional Modifier Types

Conditional Modifiers reduce the consequences of the specified hazard following the event, however are not engineered. Certain Modifiers are only applied to consequence Categories. For example occupancy only applies to safety.

Select from the following when adding Conditional Modifiers:

  • Vulnerability
  • Occupancy
  • Probability of Ignition
  • Custom – Define your own Conditional Modifier if not covered by any of the above

Adding IPLs

Adding IPLs & Modifiers - ProSET®
Adding IPLs & Modifiers – ProSET®

There are three methods of adding an IPL or Conditional Modifier to an Initiating Event:

  • Default IPLs – A list of preconfigured defaults. The defaults are provided as a guide and can be modified in each use depending on the study
  • New – Configure a new IPL or Conditional Modifier
  • Existing – Re-use an existing IPL or Conditional Modifier that has already been defined during the study

Adding a New IPL or Conditional Modifier

To add a new IPL or Conditional Modifier, click ‘Add IPLs / Modifiers’ and select the ‘New’ radio button.

When adding an IPL the factor will be applied to all Consequences (i.e. safety, environmental etc.) that are selected for that Hazard.

Conditional Modifier Factor
Conditional Modifier Factor

When adding Conditional Modifiers different factors can be applied for the different consequence category types (ie. Safety, Financial, etc). Tick the checkbox (Apply) for the Consequence Categories the Factor applies to.

Certain Conditional Modifiers can only be applied to specific Consequence Categories. The table below outlines which Conditional Modifiers should be applicable to which consequences. This is how the default Risk Profile is configured, but can be edited in the Risk Profile Configuration.

Safety Environmental Financial Reputation
Vulnerability Y Y Y Y
Occupancy Y N N N
Probability of Ignition Y N Y Y
Custom Y Y Y Y

Tip – Use the Used Text Function to use previous text used in that field within any Hazards in the project.

Use an Existing IPL or Conditional Modifier

Managing IPLs & Conditional Modifiers - ProSET®
Managing IPLs & Conditional Modifiers – ProSET®

The same IPLs and Conditional Modifiers are often used again and again within a study. To help with this SIL Comp also allows you to re-use an existing IPL or Conditional Modifier that has already been defined during the study. This speeds up the study and simplifies the process, allowing you to make any corrections in one place instead of each individual instance.

To add a new IPL or Conditional Modifier from an Existing one, click ‘Add IPLs / Modifiers’ and select the ‘Existing‘ radio button.

Note – When an existing IPL or Conditional Modifier is selected the data will appear in the fields at the top of the window. The user can then select ‘New’ and the data will remain. This is a quick way to pre-populate the fields for a new IPL or Conditional Modifier that is very similar to one that already exists.

Applying IPLs or Conditional Modifiers to multiple Initiating Events

When adding a new or existing IPL or Conditional Modifier it is possible to add them to other Initiating Events associated with the same Hazard. Just check the relevant Initiating Events in the ‘Additional Initiating Events’section of the ‘Add IPL / Modifier’ window.

Editing IPLs and Conditional Modifiers

There are two ways to edit an existing IPL or Conditional Modifier:

Edit

Edit IPL or Conditional Modifier
Edit IPL or Conditional Modifier

Edit should be used when the existing IPL or Conditional Modifier has been used in several instances across a project and the edit applies to all instances. Using this feature will change the IPL or Conditional Modifier in every instance that it is used.

To Edit right click on the required IPL or Conditional Modifier.

Warning: Editing the IPL or Conditional Modifier whilst selecting this option will affect this IPL or Conditional Modifier in all other instances where it has been used.

Use As New

If the existing IPL or Conditional Modifier has been used in several instances but needs to be changed only for one specific instance, select Use As New. Using this feature will create a new IPL or Conditional Modifier using the same data, allowing you to edit it without affecting the other instances where the original IPL/Conditional Modifier is used.

To Use As New right click on the required IPL or Conditional Modifier in the “Manage Event IPLs / Modifiers” screen and select “Use As New”. You can now edit the IPL or Modifier without affecting the original.