Series Groups [Image: seriesGroup.png]

A series group represents a collection of items in which all items must function in

order for the series group to function. The reliability of a series grouping is based

on the premise that if any one of the items fail, the entire group fails. The figure

below shows four components in a series grouping.

[Image: series.png]

The reliability of the series group is the product of the reliabilities of each

individual item, with overall reliability decreasing with increasing number of items in

the group.

Series Group Mathematical Expression

Expressed mathematically for the Exponential Distribution Type:

[Image: seriesexpeq.png]

Where n is the total number of items in a group, i is the item

counter, λ is the failure rate and t is time.

Expressed mathematically for the Weibull Distribution Type:

[Image: seriesweibeq.png]

Where β is the Weibull slope and η is the Weibull

characteristic life.

Series Grouping Equation Example

An example for the reliability of a 3 item series group is as follows:

[Image: series_group_eqn.png]

Creating a Series Group

To create a Series RBD Group in the RBD editor:

1. Right-click an the item in the Project explorer or System Model
2. Select 'RBD Model' Note: The RBD editor will show all items under the currently

selected item.

3. In the RBD editor, select items (hold SHIFT and left-click) to include in the Series group
4. Right-clicking the RBD diagram and selecting "Group → Series Group" from the right-click menu Note: An alternative method is to select the series icon

[Image: seriesGroup.png]

from the icon menu to create

the series group.

5. Verify that all selected items have been included in the series group

[Image: createseries.gif]

The items in a series group can be rearranged (as well as included or omitted from

the group)in any order by left-clicking and dragging each individual item.

Note: Rearranging the items in the series group does not affect the group

reliability.

[Image: seriesmove.gif]