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Increasing efficiency and prolonging plant life through effective maintenance

Maintenance of plant and equipment is often pushed backwards to make way for further production, this is especially true in an industry where the production time is long, therefore any interruption to the process involves significant planning. However neglecting plant and equipment can lead to more significant loss of production time through either plant not operating efficiently or in the worst cast plant not operating at all. Proper maintenance should be cost effective and contribute to the plants profitability, most preventative maintenance procedures can be implemented with very little cost implications.

Plant and equipment that has operated for years without any significant problems can fail, and in some cases it will fail in quite a dramatic fashion.

The root cause of premature failure of plant and equipment and excessive downtime has generally been the lack of effective maintenance procedures, and lack of effective systems to ensure that all documentation, software and other items relating to the plant and equipment are in place. With the increasing use of automated equipment in the Investment Casting industry, it is all too easy to allow the plant to continue operating without any problems. In effect this equipment is almost forgotten, as it just keeps operating without any input for years on end as the foundry’s casting production capacity and quality are pushed to their limits. Problems only start to occur years later as wear and tear start to take effect causing breakdowns and downtime to clog production, and it is only then that the importance of this part of the process becomes apparent.
We all know the importance of ensuring when buying a used car that it has a full service history, this implies that the car is less likely to fail and will require less maintenance. But why is this ethos not applied to plant and equipment.

Lack of maintenance or lack of effective systems can cause over a week’s loss of production whilst new components are found for plant that has been installed years before, and in some cases where the original equipment manufacturers are no longer around and other suppliers must be found. Downtime for plant and equipment is normally seen as a bed graph effect for the operational time of plant and equipment. This effect plots downtime of the plant and equipment against the age of the equipment. What will be seen is an increased downtime just after the installation of the plant and equipment; this is due to small teething problems and plant optimisation.
As operators and maintenance staff become more familiar with the equipment the graph will then reach a lower level at which it will remain for many years, as the plant reaches the end of it’s lifetime the downtime will again increase, forming a graph with a bed shape. The importance of effective maintenance is to increase the time at which the graph stays at the lower level, postponing the end of the graph. Most manufacturers will specify maintenance procedures and schedules when they install the plant and equipment, and failure to carryout these procedures will bring the end of the graph forward causing premature failure of the plant.

Basics of effective preventative maintenance

One of the most effective and cheapest preventative maintenance procedures is plant cleanliness. The materials used in Investment Casting are naturally abrasive, so even a thin layer of dust on shell room conveyors and other moving equipment has the capability of turning into a grinding paste, causing unseen damage to the conveyor plant and bearings contained within equipment. As the conveyor chains and bearings are enclosed the damage being caused is almost invisible, until the day that the wear becomes all too apparent with the failure of that part of the plant. Excessive dirt on equipment can also hide the true cause of a failure. Putting regular cleaning schedules into place can reduce the chances of this happening and will not impact upon production time as most plants could be cleaned safely during natural downtimes in the process.
The operators of the plant form the primary source of information for preventative maintenance. Maintenance personnel may only spend a small portion of their time in the plant and do not have the full familiarity with the plant and it’s operation. The operators however are working at all times with the plant, their senses (visual, audio, olfactory, touch) form the first defence in keeping the plant operational. The first phase of any preventative maintenance routine is inspection, operational staff with the correct training and procedures in place can carry this out. Risk assessment for the activities should always be done as in cases where access to electrical panels or the internal workings of a piece of equipment is required then the routine inspection should only be done by suitably qualified personnel.

Ideally inspection should commence from the first day the plant has been installed, as it is necessary to establish a base line from which all other measurements are made. In the event that a preventative maintenance system is to be implemented after the plant and equipment has been operational for some time, it would be advisable to have the equipment fully serviced prior to commencing, otherwise the system will only maintain the current efficiency of the plant rather than it’s full capability.  Records of these observations should be kept as this then provides the bridge, when operational and maintenance staff change through the years, the knowledge accumulated by the previous staff will not be lost. This again forms an extremely low cost method of implementing a maintenance procedure, as these observations of the plant and equipment are made as part of the daily routine of the operational staff.
A reporting procedure for unusual occurrences such as a squeaking noise coming from a specific part of the plant, high reading on a manometer, dust gathering below a joint/belt housing or a loose part, should be put into place. Then the correct maintenance personnel can carry out the second phase of the preventative maintenance procedure and repair the equipment before it fails.

Records of the preventative maintenance measures and repairs that have taken place form the next defence in ensuring operational efficiency and reducing downtime. Correct analysis of these records can determine the root causes of problems (which are often missed as the symptom is treated) and help to determine any reoccurring problems that may be due to any of the following:
Incorrect levelling or adjustment

• Excessive wear on specific parts of the plant (may also be due to the above)
• Incorrectly specified plant
• Operator error

Allowing programs to be put into place for specific targeted preventative maintenance or extra training to take place.

Effective implementation of a simple preventative maintenance system such as described above should result in:

• Increased production time
• Reduced scrap due to correctly adjusted equipment
• Increased efficiency in the utilisation of personnel
• Reduced emergency repairs

Predictive maintenance programs can be put into place once preventative maintenance has established the requirements. In Investment Casting shell room facilities, control of the temperature and humidity are key, by correctly recording the differential pressure across a filter on an air handling unit, it can be predicted as to when the filter will require cleaning or replacing. It has also been demonstrated that this period is also effected by the cleanliness of the shell room, the filter will require less maintenance if there is less dust.

Compiling a fault finding book can assist in future analysis of problems experienced and due to the complexity of the systems controlling any one part of the plant, can assist in identifying the errant equipment quickly and without the requirement to immediately refer to maintenance personnel. An example of this is a fault that appears with the humidity controller on an air conditioning plant. This could be due to with a fault with a:

• Humidifier
• Air conditioning plant,
• PLC output
• Water supply to the humidifier