Configuring Pressure Relief Devices
Pressure relief devices (PRDs) are used to relieve excess pressure build-up in a plant and they are the only pieces of RBI equipment that include RBI-specific properties.
General Properties
The General Properties tab contains information about the pressure relief device and is divided into three nodes: General, Financial and Demand.
IMPORTANT: If you change a measurement unit, you must also manually change the specified value, as the RBI software will not change the values.
General
The properties in this node determine the basic properties of the pressure relief device. Note the following:
The Maximum Allowed Working Pressure value must be greater than 101,325 pascals or the equivalent in other units.
The Failure on Demand Model Available field allows you to specify that there is a model available that describes the failure properties of the pressure relief device. You can then use the Reliability Model for PRD FOD field to assign a model, which may represent a fixed time or a distribution. You can choose an existing model or create a new one.
The Leakage Model Available field allows you to specify that there is a model available that describes the leakage properties of the pressure relief device. You can then use the Reliability Model for PRD POL field to assign a model, which may represent a fixed time or a distribution. You can choose an existing model or create a new one.
If no models are available, then you must answer other several other questions that RBI uses to generate the internal models that will be used in the RBI calculations. (These internal models are not resources and cannot be modified by the user.)
Use the Last Installation Date/Inspection Re-furbish Date to specify when the pressure relief device was installed or last refurbished. It must be before the current date.
Use the Plan Date to specify the date when the pressure relief device is scheduled to be maintained. It must be later than the current date.
Use the Regulatory Inspection Interval (yrs) to specify the maximum number of years allowed between the refurbishing of the pressure relief device.
Financial
The Financial properties are used to determine the monetary cost of failure. These calculations take into consideration or calculate the hole costs, material costs, plant downtime, cost of the equipment, the cost on the surrounding area and the personal injury costs.
Demand
The Demand properties are used to determine the properties that relate to the various overpressure demands to which the pressure relief device can be subjected. Note the following:
In the Overpressure Multiplier field, enter a value between 1 and 4, where 1 indicates the best case scenario and 4 indicates the worst case scenario (i.e., the component is expected to rupture).
If desired, you can use the Notes column, 
, to
record any notes about the information supplied. These notes appear only
in the RBI Properties tab and are not displayed in any reports. Double-click
inside the cell to open the Notes window. An icon in the cell indicates
that notes have been saved for that field.
Assigning Components
For each pressure relief device, you must assign the components that are being protected by the device. The possible component types that can be assigned are:
All component types for the Compressor, Pipe, Pump and Vessel-FinFan equipment types.
The HEXSS and HEXTS component types for the Heat Exchanger equipment.
Each assigned component must already have its properties defined in its parent piece of equipment before being used by the pressure relief device.
To assign a component to the PRD, while on the General Properties tab, choose System Hierarchy > Risk Based Inspection > PRD Components > Assign Components.
In the window that is displayed, select the applicable components. You can assign the same component to multiple pressure relief devices.
Results Properties
The displayed results include the following information:
The Area - Based Risk and Financial - Based Risk ($) fields display the risk at the next recommended inspection/refurbishment date.
The Target Date displays the date of the next recommended inspection/refurbishment.