Simulation fields for Maintenance General

Simulation input Maintenance - tab General

The General tab is identical for each maintenance action, which is the reason why it is discussed in this section. For maintenance actions in the Input section, there is no explanation of the related fields in the General tab. Data that can be filled in for a serial system are described in "Maintenance". The fields below are discussed with respect to their role in simulation.

Maintenance Effect

For the maintenance effect, you can choose between the Downtime, No Effect, and Out of Service effects.

The consequence of selecting "Down" within the simulation will be that downtime will be passed on to the parent object for the duration of the failure-dependent maintenance. If you select "No Effect" or "Out of Service", no downtime will be passed on to the parent object. You could select this for a failure which is then resolved outside normal operational hours.

Maintenance Duration

Maintenance duration is the duration (lead-time) of the maintenance. The maintenance duration is one of the contributing factors to the duration of the downtime.

Distribution en Deviation

• Normal distribution = Average value and deviation

• Exponential distribution = Average value

• Weibull distribution = Average value, deviation and minimum life span

• Log-normal distribution = Average value and deviation

• Fixed = Average value

Maintenance Action

For Maintenance Action, you can choose between Replace Component, Replace Part, and Repair.

• Replace Component - Replacing the component means that all failure causes and failure conditions associated with that component will be 'reset'. The result is a new component.

• Replace Part - With this option, the entire part will be replaced. The result is a new part, with new dependent components. All MTTFs of all failure causes and failure conditions will be reset.

• Repair - This maintenance action only concerns fixing (repairing) the failure cause and failure condition associated with this maintenance action. Only the failure cause and failure condition MTTFs will be reset. For all other failure causes associated with the same component, the associated MTTFs will not be reset.

Condition Loss

This percentage expresses the extent (in per cent) to which the condition has been decreased after completion of the maintenance action. This is reflected in a decrease of the MTTFs of the relevant component.

Note: Condition Loss only has effect on a simulation when for the Maintenance Action Replace Component was chosen (for other values the field will be ignored).

Condition Loss offers the opportunity to model the situation that a component is replaced by a B-quality component with a shorter MTTF.

Example: A failure cause of 10 years with condition loss of 25% will first fail in year 11; subsequently it will fail after (10yrs - 25% = 7.5 yrs). Therefore, the next failure will be in year 18 (11 + 7.5). Simulation will use the same reduced MTTF in its calculation (7.5 yrs in this example).

Note: Although the field Condition Loss is also available in a UBM Action that is directly linked to an object, simulation will ignore the field in this situation.

The Preventive Maintenance strategy for the maintenance under simulation model is to set the interval unit in 'weeks/months/ year'. If you have set the interval unit in 'hours' and provided a value less than '168', the simulations might not respond. Therefore, before running the simulation with interval unit in 'hours', perform the following step:

• In the Validation rules tab of the System Options, select the check box for Preventive Maintenance frequency value is less than and set a value greater than 168. To know more how to set the validation rules, see the topic Set up Validation rules.