In organization

Organization

An organization is a social group which distributes tasks for a collective goal. The word itself is derived from the Greek word organon, itself derived from the better-known word ergon - as we know `organ` - and it means a compartment for a particular job.There are a variety of legal types of...

al management

Management

Management in all business and organizational activities is the act of getting people together to accomplish desired goals and objectives using available resources efficiently and effectively...

, mean down time (MDT) is the average

Average

In mathematics, an average, or central tendency of a data set is a measure of the "middle" value of the data set. Average is one form of central tendency. Not all central tendencies should be considered definitions of average....

 time that a system is non-operational. This includes all time associated with repair, corrective

Corrective maintenance

Corrective maintenance can be defined as a maintenance task performed to identify, isolate, and rectify a fault so that the failed equipment, machine, or system can be restored to an operational condition within the tolerances or limits established for in-service operations...

 and preventive maintenance

Preventive maintenance

Preventive maintenance has the following meanings:#The care and servicing by personnel for the purpose of maintaining equipment and facilities in satisfactory operating condition by providing for systematic inspection, detection, and correction of incipient failures either before they occur or...

, self imposed downtime

Downtime

The term downtime is used to refer to periods when a system is unavailable.Downtime or outage duration refers to a period of time that a system fails to provide or perform its primary function...

, and any logistics

Logistics

Logistics is the management of the flow of goods between the point of origin and the point of destination in order to meet the requirements of customers or corporations. Logistics involves the integration of information, transportation, inventory, warehousing, material handling, and packaging, and...

 or administrative delays. The inclusion of delay times distinguishes mean down time from mean time to repair

Mean time to repair

Mean time to repair is a basic measure of the maintainability of repairable items. It represents the average time required to repair a failed component or device. Expressed mathematically, it is the total corrective maintenance time divided by the total number of corrective maintenance actions...

 (MTTR), which includes only downtime specifically attributable to repairs.

Mean Down Time key factors:

1. SYSTEM FAILURE
   1. Identification & Recovery Time. First, the fact that the system is down must be identified, and maintainers notified & brought to action
   2. Fault detection and isolation
      Fault detection and isolation
      Fault detection and isolation is a subfield of control engineering which concerns itself with monitoring a system, identifying when a fault has occurred, and pinpointing the type of fault and its location...
      
      . The problem must be identified and the faulty part identified.
   3. Parts Procurement. Replacement parts needed (if any) must be obtained
   4. System Repair. Faulty parts must be replaced or repaired.
2. SCHEDULED DOWNTIME
   1. Preventive Maintenance. Preventive maintenance checks are often intrusive and require the system to be down (unless prognostics
      Prognostics
      Prognostics is an engineering discipline focused on predicting the time at which a system or a component will no longer perform its intended function . This lack of performance is most often a failure beyond which the system can no longer be used to meet desired performance...
      
       are used), e.g., checking oil in a car engine.
   2. System Upgrade. System downtime is usually required to bring new features to the system.
   3. Calibration. Many forms of mechanical or electronic equipment require periodic intrusive calibration.
   4. Other administrative actions

There are three main ways of reducing MDT:

1. Make the system repairable
   Repairable
   Repairable is a military logistics term for a hardware component of a weapons system that can be designated for repair.Repairable components tend to be more expensive than non-repairable components, known as consumables. This is because for items that are inexpensive to procure, it is often more...
   
   . If an item is repairable, it will be used for a longer time, and the user will become more familiar with its operation. This will decrease the MDT because the user will be able to detect abnormal operation sooner, and the system will be repaired before the problem becomes too serious.
2. Let the user repair the system. By designing a system to be user-repairable, the MDT will be considerably decreased, as it will not have to be taken out of service for long periods of time while it is being repaired by the manufacturer (which of course includes time spent in transit to and from the manufacturer).
3. Provide the user with a repair support system. The closer critical spare parts are to the system, the faster it will be able to be repaired, as this eliminates the delay involved in ordering parts from the manufacturer and waiting to receive them. Also, the clarity of any instructions on how to repair an item will greatly contribute to the speed at which it is repaired.