Finding Common Downtime Problems
Let us start by identifying common problems associated with downtime in industrial environments. Then, we will concentrate on several solutions we have selected for implementation.
Downtime usually refers to periods when production machinery is down or stopped working. The term is commonly applied in industrial environments in relation to failures in production equipment. Some industrial facilities measure the downtime that incurred during a work shift, or during a 12- or 24-hour period. Another common practice is to identify each downtime event as having the following parameters:
Downtime can be caused by failure in mechanical equipment, sensors, motors, conveyors, etc., software (PLC, HMI, SCADA), interconnecting equipment (such as cables, facilities, routers, Wi-Fi, and so on.
- The failures can occur because of damage, breaks, procedural (improper use by humans), engineering settings, overload (overcurrent, overvoltage, lightning), environment (support systems like power and HVAC), scheduled downtime, other (none of the above but known), or unknown.
- The failures can be the responsibility of OEM (original equipment manufacturer), vendor/supplier, utility, government, contractor, customer, public individuals, act of nature, other (none of the above but known), or unknown.
Mean Down Time
In organizational management, mean down time (MDT) is the average time that a system is non-operational. This includes all downtime associated with repair, corrective and preventive maintenance, self-imposed downtime, and any logistic or administrative delays. The inclusion of delay times distinguishes mean down time from mean time to repair (MTTR), which includes only downtime specifically attributable to repairs.
Mean Down Time Key Factors
- Identification & Recovery Time. First, the fact that the system is down must be identified. The maintenance crew must be notified and brought to action.
- Fault Detection and Isolation. The problem must be identified and the faulty part identified.
- Parts Procurement. Replacement parts needed (if any) must be obtained.
- System Repair. Faulty parts must be replaced or repaired.
- Preventive Maintenance. Preventive maintenance checks are often intrusive.
- System Upgrade. System downtime is usually required to bring new features into the system.
- Calibration. Many forms of mechanical or electronic equipment require periodic intrusive calibration and resetting.
- Other administrative actions.
There are five main ways of reducing downtime:
- Design the system to fail less. Sometimes a simple fault can be fixed without shutting the system down. A more reliable system that doesn’t fail often reduces the downtime.
- Make the system or machinery repairable. If an item is repairable, it will be used for a longer time.
- Let the maintenance crew repair the machinery. By designing a system to be user-repairable, the downtime will be considerably decreased, as it will not have to be taken down for long periods of time.
- Provide the user with a repair support system. The closer in proximity critical spare parts are to the system, the faster it will be able to be repaired.
- The faster any fault is detected and identified the less downtime becomes and the greater the saving is going to be.