Maintenance

Minus twenty five Celsius. Two o’clock in the morning in Serbian mountain. We are running (critically) low on the mill feed in the copper concentrator.Two hundred tonne truck broke down preventing any access to the beast of hydraulic shovel and also stopped few already loaded trucks.Diesel obtained from the black market clogged fuel pipes and fuel pump and started to turn into paraffin wax in the reservoir. I am standing with my men by the truck looking into the lifeless thing. There is no way to halt the concentrator’s operation, stop the pipeline towards the smelter and eventually shut down the smelter.Do not do at home what we’ve done! But we did it and the trucks were on their merry ways.

• There are as many definitions of the maintenance as people offering it.

• Maintenance costs as defined by plant accounting procedures, are a major portion of the total operating costs in most plants.

• Impact of the maintenance on the bottom-line profit is often ignored as “necessary evil”.

• With development of microprocessor based instrumentations (infrared monitoring and vibration devices) there is no justification for such approach anymore.

• Nothing lasts forever and equipment is designed for predetermined operational life and ideally, maintenance is performed to keep equipment and systems running efficiently for at least design life of the component(s).

MTTF

• The mean-time-to-failure (MTTF) or bathtub curve indicates that a new machine has a high probability of failure during the first few hours or weeks of operation (infant mortality period).

Reactive Maintenance (Run-to-failure Management)

Allow machinery to run to failure; Repair or replace damaged equipment when obvious problem

occurs; Cost: US$18 /hp/annum*

*John Piotrowski, Effective Predictive and Pro-Active Maintenance for Pumps, 2007; http://www.maintenanceworld.com/effective-predictive-and-pro-active-maintenance-for-pumps/

Preventive Maintenance (Time-Based Maintenance)

Schedule maintenance activities at predetermined time intervals; Repair or replace damaged equipment before obvious problem

occurs; Cost: US$13 /hp/annum*

*John Piotrowski, Effective Predictive and Pro-Active Maintenance for Pumps, 2007; http://www.maintenanceworld.com/effective-predictive-and-pro-active-maintenance-for-pumps/

Predictive Maintenance (Condition-Based Maintenance)

Schedule maintenance activities when mechanical or operational conditions warrant;

Repair or replace damaged equipment before obvious problem occurs;

• Cost: US$9 /hp/annum* *John Piotrowski, Effective Predictive and Pro-Active Maintenance for Pumps, 2007; http://www.maintenanceworld.com/effective-predictive-and-pro-active-maintenance-for-pumps/

Proactive MaintenanceProactive approach is close to my heart.Proactive maintenance improves maintenance through better design, installation, maintenance procedures, workmanship, and scheduling. The characteristics of proactive maintenance are: Using feedback and communications - changes in design or

procedures are rapidly made available to designers and managers. Employing a life-cycle view of maintenance and supporting

functions. Ensuring that nothing affecting maintenance occurs in isolation. Employing a continuous process of improvement. Optimizing and tailoring maintenance techniques and technologies

to each application.

Proactive Maintenance (cont.) Integrating functions that support maintenance into maintenance

program planning. Using root-cause failure analysis and predictive analysis to maximize

maintenance effectiveness. Adopting an ultimate goal of fixing the equipment permanently. Periodic evaluation of the technical content and performance

interval of maintenance tasks (PM and PT&I).Proactive maintenance employs the following basic techniques: Specifications for equipment Commissioning Precision rebuild Failed-part analysis

Root-cause failure analysis Reliability engineering Rebuild certification/verification Recurrence control

Age exploration and the relationship with replacement of obsolete Items

Reliability Cantered Maintenance (RCM)

Reliability-Centered Maintenance (RCM) integrates Preventive Maintenance (PM), Predictive Testing and Inspection (PT&I), Repair (also called reactive maintenance), and Proactive Maintenance. These principal maintenance strategies, rather than being applied independently, are optimally integrated to take advantage of their respective strengths, and maximize facility and equipment reliability while minimizing life-cycle costs. The goal: Reduce the Life-Cycle Cost (LCC) of a facility to a minimum while continuing to allow the facility to function as intended with required reliability and availability.

RCM (cont.)RCM breakdown:• <10% Reactive Maintenance• 25% to 35% Preventive Maintenance• 45% to 55% Predictive Maintenance

How to Initiate Reliability Cantered MaintenanceThe following is a list of some basic steps that will help to get moving down this path (NASA 2000).

How to Initiate RCM (cont.)1. Develop a Master equipment list identifying the equipment in your facility. 2. Prioritize the listed components based on importance or criticality to

operation, process, or mission – see text box highlighting priority scheme. 3. Assign components into logical groupings. 4. Determine the type and number of maintenance activities required and

periodicity using: a. Manufacturer technical manuals b. Machinery history c. Root cause analysis findings - Why did it fail? d. Good engineering judgment

5. Assess the size of maintenance staff. 6. Identify tasks that may be performed by operations maintenance personnel. 7. Analyze equipment failure modes and impacts on components and systems. 8. Identify effective maintenance tasks or mitigation strategies.

ReferencesNSA, RCM GUIDE RELIABILITY-CENTERED MAINTENANCE GUIDE, September 2008

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