Every industry and built environments (hospitals / office space / hotels) operate a large number of production and service equipment & systems in their day-to-day functioning. The scope of the site maintenance team encompasses preventive and predictive maintenance of a large variety of equipment, machinery and systems. The normal KRAs of the maintenance team are:
- Maximise availability & serviceability of site equipment.
- Optimise usage of equipment and systems to ensure long service life and energy conservation.
- Ensure that the logistics arrangements for carrying out maintenance activities are available in time, every time.
This guideline document covers the ten steps on deciding on “What”, “Why”, “Where”, “When”, “Who” and “How” the maintenance jobs are to be done. All these and site-specific needs are to be identified while formulating the PM Schedules.
The aim of these guidelines is to help the Maintenance Managers and other staff to formulate effective Preventive and Predictive Maintenance Schedules for site-specific equipment, machinery and systems.
Step 1. Identifying the equipment, machinery and systems that form a natural group is the first step. For example, Air Compressors, Dryers, Accumulators and the Air system would form a natural group – a “Compressed Air System.”
Step 2. Breaking down the machinery, equipment and systems into manageable elements is the next step. In the above example, the Compressed Air System could be broken down into the following elements:
- Air Compressors (If more than one type of compressor is feeding the system, these have to be listed separately). Main equipment prime mover driven pumps, mounted filters etc are considered as part of the main machinery.
- Associated Pumps – mounted separately. This would cover items such as pumps for Pre-Lubricating oil, Standby Lubricating oil, inter-stage cooling water etc.
- Control System.
- Dryer with drier specific systems and equipment.
- Air system pipeline and other elements such as manifolds, valves, pressure relief valves, pressure gauges, sensors, down stream equipment etc.
- Power supply system as applicable.
- Prime mover for the compressor. If the prime mover is anything other than an electric motor, the specific systems for the prime mover are to be covered separately as the case may be. For example, a diesel engine driven air compressor, the diesel engine will have its own fuel / lubricating oil / cooling water / air intake / exhaust systems that are to be covered in the maintenance plan.
Step 3. The next step is to assess the level of automation in the operation, age of the equipment elements and systems, operating profile, criticality and basis of operation (During shift / Continuous / Periodic / Intermittent). These parameters would help us in arriving at the level of attention that we have to give to the system as a whole.
- Automation in Operation. Most of the latest commercial equipment comes with highly automated controls and data logging systems. This would mean that continuous manning of equipment is not required. A technician may need to check the system health physically once in a shift or so. For non-automated systems, a technician would have to manually record the operating parameters of the equipment periodically, whenever it is in operation.
- Age of Machinery Elements and Systems. Older equipment and systems need to be assessed for their current condition to assess essential maintenance to be carried out immediately, followed by regular maintenance. The equipment and system history has to be studied by looking at the log books, spares consumption pattern, record of cost of maintenance, average running parameters, consumables consumption pattern etc.
- Basis of Operation. The basis of operation could be as follows:
- Continuous. Equipment and systems for a manufacturing process or process support may be on continuous duty. Say a compressed air system in a glass manufacturing plant. This would mean high system availability requirement, planned redundancy of equipment and system elements to enable periodic maintenance of all the items.
- Shift Based. The equipment or system may be operating only when the shifts are operating. An example would be the air conditioning system in an office space. The system may be operated only during the general shift timings when the office is manned. This would reduce the total system usage, increase time available for periodic maintenance, reduce need for redundant equipment etc.
- Periodic. There may be certain equipment or systems that are activated periodically. Chemical dosing systems that are operated as per a fixed schedule would be an example.
- Intermittent. There are certain machinery that are operated intermittently. A captive power plant may be kept on standby and will come into operation only when there is a power failure. Capital expense budgets will be the driving force in this case. Essential equipment would get budgeted, but after deliberations. With power shortage, power cuts and failures, extensive and regular use of captive power plants becomes imperative. Thus, maintaining the limited equipment that is essential, in good condition, will become a key area.
- Equipment or System Operating Profile. The operating profile of an equipment would mean the load condition at which it normally operates and the normal environmental conditions. Some of the equipment may have un-loader and loader mechanism by which the equipment adjusts its operation according to load. Generators running in parallel could be set to share the load automatically. This will avoid overloading of one generator while the other may be running at low load. Normally all equipments have a continuous rating. This is the loading condition in which it may be operated continuously. Normally the loading is restricted to just below the continuous rating so that optimum loading with least risk of damage is maintained.
- Criticality. For an industry handling heavy loads within the premise, a heavy-duty EOT crane may be the critical equipment that could be a show stopper if it becomes non-operational. For a “Communication Room or Data Centre”, UPS and HVAC will be critical requirements. For a hospital, uninterrupted power supply will be critical. Such criticality will drive the decision on maintenance frequencies.
- Operating Conditions. The operating environments also vary from site to site. Humidity, temperature, dust, corrosive chemicals, grit and slurry etc may be the limiting parameters considered. For example, the service life of centrifugal pumps handling corrosive chemicals or slurry would be lesser than pumps handling DM water.
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