Common Reliability Element Locally Available Properties

Locally available properties are special attributes of some elements in GoldSim. Locally available properties are similar to element outputs in that they have a data type (e.g., value, condition), order (e.g., scalar, vector) and dimensions (i.e., units). However, they do not appear as outputs of the element to which they belong. Rather, they are only visible in browsers (the main browser, or the Insert Link browser within their parent element).

Note: Locally available properties are only shown in the main browser if you choose to Show element subitems (accessed via the browser context menu by right-clicking in the browser).

Locally available properties derive their name from the fact that they may only be available, or they may take on different values (i.e., be over-ridden), in “local” parts of your model (e.g., within a particular element, or within a particular input field for an element).

The Function and Action components provide five outputs in the form of locally available properties:

Status. This is the current value of the main output of the reliability element.

OpTime. A value indicating the cumulative time that the element has been operating since the start of the simulation or its last Replacement event.

OpTimeSincePM. A value indicating the cumulative time that the element has been operating since the start of the simulation or its last Replacement event, or since the last time the component has completed a PM: Preventive Maintenance (failure mode) event.

TotalTime. A value indicating the time since the start of the simulation or the last replacement of the component.

Failed. This is a vector of ten items. Each item in the vector corresponds to a failure mode defined for the element (GoldSim allows up to 10 failure modes). For example, ~Failed[1] corresponds to the first failure mode. Each item is set to True if its corresponding failure mode has occurred (and it is reset to False if the mode is repaired).

These five outputs can only be referenced within the reliability element itself (i.e., within a property dialog of the element, or if it is a system, within the system) by adding the ~ prefix. For example, if you wanted to reference the Status of the element inside a reliability element dialog (e.g., to define a failure mode), you would have to reference "~Status".

Note: The locally available properties Status and Failed are also outputs of the element. If you want to reference the Status outside of the element, you should use the element name (the Status is the element’s primary output). If you want to reference this variable inside the element, you should use "~Status". Similarly, if you want to reference the Failed vector outside of the element, you should use “elementID.Failed”. If you want to reference this variable inside the element, you should use "~Failed".

Note: The most common example of the use of a local variable can be seen by looking at an element’s Operating Requirements. When you add a failure mode to an element, GoldSim automatically adds the failure mode as an Internal Requirement in the element’s Requirements tree. It actually does this by inserting a “Not” condition: Not ~Failed[n], where n is the failure mode. ~Failed[n] is a local variable.

If a component is defined as a system, its locally available properties are available inside the system (but not within the dialogs of child reliability elements inside the system). For example, if you created an Expression element inside a reliability element defined as a system, and defined it as "~Status", this would return the Status of the parent component. However, if you referenced "~Status" inside the dialog of a child reliability element inside the system, it would return the Status of the child (since the child's local property would override the parent's local property).

In addition to the use of the ~Failed variable in an element’s Internal Requirements, other examples of where it could be useful to reference locally available properties within a reliability element include the following:

1. In the case of non-fatal failure modes (in which you have manually removed the Not ~Fail[n] condition for that mode from the Internal Requirements), you may want to specify that the failure, while not fatal, reduces the capacity or performance of some internal component of the system by referencing Failed[n] in an ancillary calculation (e.g., throughput).

2. You may want to trigger a preventive maintenance "failure mode" based on the value of OpTimeSincePM or TotalTime.

3. You may want to accelerate or decelerate a failure mode based on the Status of the element or based on the value of OpTime or TotalTime.

Three other locally available properties (FMCV, FM_Failed, and FM_TimeToFail) are available from within input fields for certain failure mode input parameters. The former is discussed elsewhere while describing FMCVs. The latter two are discussed with regard to simulating preventive maintenance as a failure mode.