Simulation fields for a Parallel System

Data that can be filled in for a parallel system are described in "Parallel System". The fields below are discussed with respect to their role in simulation.

Buffer time

The buffer time is the time required to pass the object's downtime on to the parent object.

Examples of the influence of buffer time

• If an object is down for a period of 1 hour, and the buffer time specified for this object is 4 hours, then the downtime is not passed on to the parent object.

• If an object is down for a period of 4 hours, and the buffer time specified for this object is 1 hour, then the downtime is passed on to the parent object, namely 3 hours.

  Note: Downtime can be caused by both failures and preventive maintenance

The object itself does go down, and will therefore be included in the downtime report; the buffer time only affecting the downtime of parent objects.

Redundancy model

In this field, you can select either of two options:.

• "Functional" redundancy type - By selecting this option, the window will display the "Min. Function Level %" parameter

• "N of M" redundancy type - By selecting this option, the window will display the "N of M" parameter

Min. Function level %

Here, you can specify a percentage of the functionality level. This value indicates the threshold that must be reached before the redundant system will go down.

Example

Assuming a redundant system consisting of 3 objects and a function level of 200%, this implies that the sum of the total function output of these 3 objects must be at least 200% before the redundant system will go down. Unlike the 'N of M' approach, this does not necessarily mean that at least 2 objects must remain operational. When all 3 objects are failing but from a function point of view have a function loss of 30%, this boils down to a total output = 3 * (100-30) = 210%. The bottom limit of 200% has not yet been reached then.

This approach only makes sense when a value of less than 100% for the function loss fields has been specified. For if this were not the case, objects will always score 100%. 200% Min. function level of 200% will then yield exactly the same results as N of M.

N of M

When selecting N of M, you enter a value which will indicate how many of the available objects of a redundant system must be available and operational before any downtime is passed on to the parent objects.

If a redundant system consists of 4 equal objects, and you enter the value 2 for the N of M field, then downtime will not be passed on to the parent object until the third object (because of a failure or preventive maintenance) goes down.

The number entered here is, therefore, the absolute minimal count of operational subsystems with respect to "normal" operation of a production line; if any more parts of the systems fail, the system fails and goes down.

Redundancy Type

There is only one option "Active" redundancy.

Assuming a redundant system with two objects, only one object will be operational. The second object is passive, and will only become operational when the first object goes down.

In the case of redundancy, both units of the parallel system contribute to the function of the object to which they belong. If an object goes down, this will not affect the parent object.

Start time

The start time is the time it takes before an object in a redundant system starts up (becomes operational) if the other object of a redundant system goes down. This parameter is relevant for systems with a redundancy, whereby the one object is active (operational) and the other is passive (not operational).