Reliability HotWire

Reliability HotWire

Issue 137, July 2012

Tool Tips

*In the Weibull++ parametric RDA folio, what is the difference between the GRP and Eta/RF parameterization?

For repairable system analysis, the Weibull++ parametric RDA folio is based on the general renewal process (GRP) model, which uses the concept of virtual age to mathematically capture the effect of repairs on the subsequent rate of occurrence of failure (i.e., failure intensity). The rate of occurrence of failure over time is modeled by the power law function. This means that the GRP analysis method has three parameters, two of which are used to describe the power law function and a third for estimating the virtual age of a system.

In Version 8, the parametric RDA folio allows you to select how you want the parameters to be calculated. By default, the software calculates the beta, lambda and q parameters. However, if you want to publish the model and use it in BlockSim, then you need to express the power law parameter, lambda, in terms of the Weibull parameter, eta, and you need to express the virtual age parameter, q, in terms of the RF parameter (which users of BlockSim will recognize as the restoration factor of a maintenance action). To do this, select the check box in the Parameterization area shown next.

parametric RDA folio control panel

The relationship between the lambda (λ) and eta (η) parameters is described as:

parametric RDA folio control panel

The relationship between the q and RF parameters is described as:

parametric RDA folio control panel

To learn more about the GRP model and the mathematical concept behind virtual age, see

*In a Synthesis repository, how do I change the project owner for an existing project?

Each project in a Synthesis repository has a single project owner. The project owner for a particular project has full permissions within the project. This includes read/write access to all the project items, the ability to modify the properties of the project and its security settings, the ability to create/edit/delete project resources and the ability to delete the project.

By default, the project owner is the user who created the project. The project owner, or any user who has the "Manage all projects" permission in the repository, can assign a different user to be the owner for the project by selecting the project name in the project list and choosing Project > Security > Change Owner.

change owner icon

Users with the "Manage all projects" permission can also select multiple projects and assign one user to be the owner of those projects via the Manage Projects window. To access this window, choose Project > Management > Manage Projects.

manage projects icon