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Maintenance Practices for Plant and Equipment

• satyendra
• January 17, 2014
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• Breakdown maintenance, CBM, Corrective maintenance, Improvement maintenance, Mean time between failure, predictive maintenance, preventive maintenance, RCM, TPM,

Maintenance Practices for Plant and Equipment

The management of an operating plant is interested in the smooth functioning of the plant equipment and production processes which are used for the conversion of inputs to the product outputs. The regular use of the plant, equipments, and facility results in their wear and tear, resulting into their failures. Hence, regular maintenance of the plant, equipments, and facility improves their functionality and enhance the efficiency of the production process. The maintenance activities in the plant are performed by way of inspection, repair, lubrication, and replacement of worn-out equipment parts.

Nothing lasts forever and all the equipment in the plant has associated with it some pre-defined life expectancy or operational life. Maintenance is the work of keeping the plant, equipment, and facility in good condition for operation. It is the action taken to prevent plant and equipment from failing and to repair normal degradation experienced during the operation and to keep it fit for operation. Some organizations do not spend the necessary resources to maintain equipment in proper working order. Instead, they wait for equipment failure to occur and then take whatever actions are necessary to repair or replace the equipment. However, it is to be noted that if there is failure in carrying out the required maintenance activities recommended by the equipment manufacturer, the life of the operating equipment gets shortened.

Maintenance is a set of activities which is necessary to keep the plant, equipment, and facility in good operating conditions. It can be defined as a routine and recurring activity of keeping a particular plant, equipment, or facility at their normal operating condition so that they can deliver their expected performance without causing any loss of time on account of accidental damage or breakdown. Once equipment is designed, fabricated and installed, the operational availability of it depends on meeting of its maintenance requirement.

Maintenance is carried out following detection of an anomaly in the plant, equipment, and facility and is aimed at the restoration to their normal operating conditions. This approach is based on the firm belief that the costs sustained for downtime and repair in case of fault are lower than the investment needed for a planned maintenance programme for keeping healthy the plant equipment and facility. This strategy can be cost-effective until catastrophic faults occur.

Adequate maintenance of plant and equipment is necessary to ensure that the plant, equipment and facility is working reliably and effectively. Maintenance can be part of a planned programme or can be required to be carried out at short notice after a breakdown. It is carried out to prevent the problems of the plant, equipment, and facility and to correct the fault. It always involves non-routine activities and can expose those involved and others as well to a range of risks.

An effective maintenance programme can result into more reliable plant and equipment. Fewer breakdowns mean less dangerous contact with equipment is needed. It also results into cost benefits because of better productivity and efficiency.

The idea of maintenance is very old and was introduced along with inception of the equipment. In the early days, an equipment was used as long as it worked. When it stopped working, it was either repaired / serviced or discarded. Maintenance was considered to be an area which did not need attention. However, with the greater focus on safety, environment, energy efficiency, and profitability, maintenance has now become an area where there is big attention is given. Maintenance in the past was thought in terms of breakdown and preventive maintenance. Starting from the late eighties and early nineties, there have been major developments in the maintenance activities.

Maintenance of plant, equipment, and facility is carried out (i) to prevent problems arising, (ii) to put faults right, and (iii) to ensure the same is working effectively. Maintenance can be part of a planned programme or can be carried out at short notice after a breakdown. Maintenance always involves non-routine activities and can expose those involved (and others) to a range of risks. The high cost of the present-day equipment and processes needs that the plant, equipments and facilities are to be properly maintained / serviced during their entire life cycle for maximizing their availability. The development of mechanization and automation of production systems and associated equipment, with the accompanying development of auxiliary services and safety requirements, has increased the importance of maintenance in an operating plant. Maintenance function also involves looking after the safety aspects of certain equipment where the failure of component can cause an accident. For example, a poorly maintained pressure vessel such as steam boiler can cause a serious accident.

The organizational management is required to devise optimal maintenance strategy, which ensures that operational disruptions because of failure or breakdown of the plant, equipment, and facility is minimized. The objectives of maintenance include (i) to keep the plant, equipment, and facility in good working condition at the lowest possible cost, (ii) to maximize the quantity of time the plant, equipment, and facility is available for use and for the purpose for which they are needed, (iii) to ensure the use of the plant, equipment, and facility is carried out at their optimum capacity without any interruption, (iv) to ensure the availability of the plant, equipment, and facility perform their functions at the optimum level, (v) to avoid loss of production, (vi) to avoid unplanned repair which can take place because of the wear and tear that normally happens in a neglected equipment, (vii) to improve product quality, and the productivity of the of the plant, equipment, and facility, (viii) to improve the operational reliability of the plant, equipment, and facility, (ix) to minimize overall operational cost of production through reduction of scraps and wastages which can be because of the malfunctioning of the plant, equipment, and facility, and (x) to preserve the value of the assets by reducing the rate by which they deteriorate.

Lack of maintenance of the maintenance can lead to the breakdown of the plant, equipment, and facility which results into (i) loss in production time, (ii) rescheduling of the production activity, (iii) scrapping of the in-process material because of the breakdown, (iv) missing of the production targets, and (v) resulting into idling of the preceding and succeeding equipment and facilities. In the event of frequent breakdowns even a need can arise for the sub-contracting of some of the maintenance work.

The benefits of maintenance are (i) improved safety, (ii) increased reliability, which is, less disruption of normal activities of operations, and which results in increased production outputs, (iii) higher product quality, (iv) lower operating cost, (v) longer life span through regular care, cleaning and lubrication of facilities, and (vi) well maintained plant, equipment, and facility produces positive impact on customers and visitors to the plant.

The nature of the maintenance function affects the life of equipment. It is well known that the optimum maintenance prolongs the life of the equipment. On the other hand, carelessness in maintenance leads to reduced life of the equipment and in some cases an early failure as well. Further, proper maintenance helps to achieve the production targets. If the availability of the equipment in good working condition is high, the reliability of the production is also high. Another important effect of the maintenance function is the working environment. If the equipment is in good working condition, the operator feels comfortable to use it otherwise there is a tendency to let the equipment deteriorate further.

The objectives of maintenance are to be formulated within the framework of the overall organizational set up so that finally the goals of the organization are accomplished. The maintenance practices of the organization are to ensure that (i) the plant, equipment, and facility are always in an optimum working condition at the lowest possible cost, (ii) the time schedule for the maintenance activities is not compromised and simultaneously it meets the requirements of plant operations, (iii) the performance of the plant, equipment, and facility is dependable and reliable after its maintenance, (iv) the performance of the plant, equipment and facility through its maintenance is to ensure nil / minimum breakdowns, (v) the maintenance cost is required to be controlled within reasonable limits, (vi) the maintenance activity is to ensure that the life of the plant, equipment and facility is prolonged and avoid their replacement, (vii) the maintenance activity is to strike a balance between the availability of the plant, equipment and facility and the overall running costs, (viii) the maintenance activity is to ensure that the required standard of performance and safety of personnel and the plant, equipment and facility are not sacrificed after the maintenance.

Maintenance means to hold, keep, sustain, or preserve plant, equipment, and facility to an acceptable standard. Also, maintenance is a combination of technical and administrative activities to keep a plant, equipment, or facility in its functional state. A plant, equipment, or facility with poor maintenance results in its poor functioning which can likely to result in the loss of production and the production of lower quality products during the production process. It involves reliability of the plant, equipment, and facility to perform to a standard level of quality assurance. Poor maintenance of production facilities can result in poor end-product quality and lower customer dissatisfaction, lost production runs, cost inefficiencies, and sometimes, unavailability of the facility for future use. Unfortunately, several organizations lack good maintenance practices which results in frequent breakdown and stoppages and also rapid deterioration of the plant, equipment, and facility and consequent loss of their functional value and maximization of their useful life.

Additionally, hazards can occur when plant, equipment, or facility becomes unreliable and develops faults. Maintenance allows these faults to be diagnosed early to manage any risks. However, maintenance needs to be correctly planned and carried out. Unsafe maintenance can cause accidents and serious injuries either during the maintenance or to those using the badly maintained or inadequately maintained / repaired equipment

Maintenance is one of the major activities in a manufacturing plant and plays an important role in achieving the productivity of plant, equipment, and facility. Maintenance is also related with profitability through equipment output and its running cost. Timely maintenance assists the performance level and availability of the plant, equipment, and facility to the optimum level and hence helps in achieving the output targets for the product.  Normally the maintenance activities are looked after by a separate department.

Maintenance, being an important function in any production system, has far reaching effects on the system. If the right practice of maintenance is not established for a particular environment, it can lead to serious problem of either over maintenance or under maintenance. The selection of a particular maintenance policy is also governed by the past history of the equipment. Cost effective maintenance helps in enhancing productivity. Hence, a close coordination between the operation and the maintenance personnel is needed to decide on the extent of the maintenance work. Further, the maintenance personnel need to have the required knowledge and skills for maintaining of the equipment.

Maintenance activity consists of taking the decisions and actions regarding the upkeep of the plant, equipment, and facility. These are inclusive, but not limited to (i) actions focused on maintaining and analyzing the data related to the health of the plant, equipment, and facility, (ii) planning of adequate and necessary inventory of spare parts, lubricants, fast moving consumables, and storage items including standardization of spares and consumables, (iii) actions focused on scheduling, procedures, work / system control and optimization, and (iv) performance of routine, preventive, predictive, scheduled, and unscheduled actions aimed at preventing equipment failure as well as achieving the goal of increasing efficiency, reliability and safety.

The maintenance function of a modern industry faces a number of challenges attributable to the rapid growth of technology resulting in current technology becoming obsolete. Such a challenge has enhanced because of (i) automatic controls, (ii) computerized processes, (iii) use of information and communications technology (ICT), (iv) advent of new advanced diagnostic tools and rapid repair systems, (v) advance store management techniques to incorporate modular technologies, and requirements of keeping both outdated and modern machines in service. The effective management of maintenance aspects under such challenging circumstances is frequently a difficult job.

Further, besides the rectification of the faults in the equipment, the maintenance activities include (i) up-gradation of the existing plants and equipments and training maintenance personnel to attain the required technical skills, (ii) effective maintenance of the old equipment for higher availability, (iii) cost optimization of all maintenance functions, (iv) improvement of maintenance activities in the areas of tribology and terotechnology, (v) reconditioning of used / unserviceable spare parts, (vi) development of indigenous sources for parts for import substitution, (vii) setting up of an effective maintenance information management systems (MIMS), (viii) effective utilization of the maintenance personnel, and (ix) carrying out in-house research and development activities for effecting improvements in maintenance practices.

There are several types of maintenance practices which are being followed. These include planned maintenance, routine or reactive maintenance, preventive maintenance, predictive maintenance and reliability centered maintenance. Some types of maintenance practices are shown in Fig 1. These maintenance practices are explained below.

Fig 1 Types of maintenance practices

Planned maintenance is that maintenance which is organized and carried out with fore-thought, control, and the use of records to a pre-determined plan.

Breakdown maintenance is also known as reactive maintenance or run-to failure maintenance. It basically consists of running the equipment till it breakdown. No actions are taken or efforts are made to maintain the equipment till the failure of the equipment. In this type of maintenance strategy, the maintenance action is taken up when the equipment breaks down completely and needs repair to resume operation. Sometimes breakdown maintenance is the default maintenance strategy, relying on reactive maintenance. The breakdown maintenance strategy is preferable where repair of the equipment is simple and easier, and where preventive maintenance carried out in stopping or disrupting normal production runs is very costly.

Under the breakdown maintenance strategy approach, there is no expenditure on maintenance manpower nor on cost of spares and consumables till there is a breakdown of the equipment. However, a large expenditure is needed when there is a breakdown in the equipment both in terms of manpower costs and capital costs. This approach can result into secondary equipment or process damage from equipment failure. Also, longer shutdown is needed for repair which affects the production. Unplanned shutdown of the equipment because of the failure disturbs the production planning. All these affect the supply of the products to the customers. With this type of maintenance approach, the life of the equipment gets shortened resulting in more frequent replacement. Further since the equipment is run to failure, a large material inventory of repair parts is needed to be maintained.

Preventive maintenance is defined as ‘actions performed on a time or machine run based schedule which detect, preclude, or mitigate degradation of a component or equipment with the aim of sustaining or extending its useful life through controlling degradation to an acceptable level’. Preventive maintenance is carried out at pre-determined intervals or corresponding to prescribed criteria and intended to reduce the probability of failure or the performance degradation of an item. The maintenance cycles are planned according to the need and the incidence of operating faults is reduced.

With preventive maintenance the equipment life is extended and its reliability is increased by simply spending the necessary resources to conduct the maintenance activities intended by the equipment designer. Though the preventive maintenance is not the optimum maintenance method, yet it has got several advantages over that of a purely breakdown maintenance method.

By performing the preventive maintenance as the equipment designer has envisioned, the equipment life can be extended to the design values. Preventive maintenance helps equipment to run more efficiently. While equipment failures are not prevented by preventive maintenance but the numbers of failures are decreased because of it. Minimizing of failures means savings in maintenance and capital costs. Preventive maintenance provides flexibility for the adjustment of maintenance periodicity. It results into increased component / equipment life cycle. The estimated cost savings over breakdown maintenance method is estimated to be in the range of around 15 %.

Opportunity maintenance is a set of maintenance activities which are performed on an equipment or a facility when an unplanned opportunity exists during the period of performing planned maintenance activities to other equipments or facilities. This maintenance is used in multi component systems. When an equipment or system is taken down for maintenance of one or few worn out component, the opportunity is utilized for maintaining or changing other wear out components, even though they are not failed. It is actually not a specific maintenance system, but it is a system of utilizing an opportunity which can come up any time.

Corrective maintenance is the maintaining action for correcting or restoring a failed unit. It is the maintenance which is carried out following detection and aimed at restoring normal operating conditions. This approach is based on the firm belief that the costs sustained for downtime and repair in case of fault are lower than the investment needed for a maintenance programme. However, this strategy is only good until catastrophic faults occur and all savings are gone.

Corrective maintenance has a very vast scope for small actions such as adjustment, minor repairs to redesign of equipments. It is normally carried out in four steps namely (i) collecting the data, information, and analysis, (ii) identifying the causes, (iii) finding out the best possible solution to eliminate likely causes, and (iv) implementing the solutions.

Emergency maintenance is carried out as fast as possible in order to bring a failed equipment or facility to a safe and operationally efficient condition.

Routine maintenance includes those maintenance activities which are repetitive and periodic in nature such as lubrication, cleaning, and small adjustment.

Running maintenance includes those maintenance activities which are carried out while the equipment is running and it represents those activities which are performed before the actual preventive maintenance activities take place.

Window maintenance is a set of activities which is carried out when an equipment is not needed for a definite period of time.

Shutdown preventive maintenance is a set of preventive maintenance activities which is carried out when the production line is in total stoppage situation.

Remedial maintenance is a set of activities which are performed to eliminate the source of failure without interrupting the continuity of the production process.

Deferred maintenance is a set of corrective maintenance activities which are not immediately initiated after the occurrence of a failure but are delayed in such a way which does not affect the production process.

Shutdown corrective maintenance is a set of corrective maintenance activities which are performed when the production line is in total stoppage situation.

Design-out maintenance is a set of activities which are used to eliminate the cause of maintenance, simplify maintenance tasks, or raise equipment performance from the maintenance point of view by redesigning those equipments and facilities which are vulnerable to frequent occurrence of failure and their long-term repair or replacement cost is very expensive.

Engineering services include construction and construction modification, removal and installation, and rearrangement of facilities.

Shutdown improvement maintenance is a set of improvement maintenance activities which are performed while the production line is in a complete stoppage situation.

Predictive maintenance can be defined as ‘measurements that detect the onset of a degradation mechanism, thereby allowing casual stressors to be eliminated or controlled prior to any significant deterioration in the component / equipment physical state’. Predictive maintenance is a set of activities which detect changes in the physical condition of equipment (signs of failure) in order to carry out the appropriate maintenance work for maximizing the service life of equipment without increasing the risk of failure. It is classified into two kinds according to the methods of detecting the signs of failure namely (i) condition-based predictive maintenance, and (ii) statistical-based predictive maintenance. Main predictive maintenance technologies are thermography, oil or lubricant analysis, ultrasonic or ultrasound analysis, vibration analysis, motor analysis, and performance trending etc. Some of these are shown in Fig 2.

Fig 2 Technologies for predictive maintenance

Measurement results in predictive maintenance indicate current and future functional capability of the equipment. Some people classify predictive maintenance as a type of preventive maintenance. However, basically predictive maintenance differs from preventive maintenance need on the actual condition of the equipment rather than on some preset schedule. The main difference between preventive maintenance and predictive maintenance is that predictive maintenance uses monitoring the condition of the equipments to determine the actual mean time to failure whereas preventive maintenance depends on industrial average life statistics. Further, predictive maintenance is used to define needed maintenance task based on quantified material / equipment condition, which is the fundamental difference between predictive maintenance and the preventive maintenance.

There are several advantages of predictive maintenance. A well-planned predictive maintenance programme can eliminate catastrophic equipment failures since it is based on the pre-emptive corrective action. The inventory of spares can be reduced and the equipment reliability can be increased. Since there is decrease in the equipment and process down time, operation of the equipment or the process can be optimized. Estimated cost saving from a properly functioning predictive maintenance method can provide a saving of around 10 % over preventive maintenance method and a saving of around 35 % over breakdown maintenance method.

The drawback of predictive maintenance is that it depends heavily on information and the correct interpretation of the information. Also, predictive maintenance needs expansive diagnostic equipments and personnel handing predictive maintenance need specialized training in these diagnostic equipments. Further predictive maintenance to be effective needs firm commitment from the all departments and the management of the organization. This is necessary since the savings potential is not readily visible to the management.

Risk based maintenance is the maintenance carried out by integrating analysis, measurement, and periodic test activities to standard preventive maintenance. For this maintenance, data is viewed in the context of the environmental, operation, and process condition of the equipment. It is aimed to perform the equipment condition and risk assessment for defining the appropriate maintenance programme. All equipment displaying abnormal values are refurbished or replaced hence extending the useful life and ensuring high levels of reliability, safety, and efficiency of the plant.

Condition based maintenance (CBM) sometimes called condition-based predictive maintenance depends on continuous or periodic condition monitoring equipment to detect the signs of failure. It is based on the equipment performance monitoring and the control of the corrective actions taken as a result. In this maintenance on-line detection of real time parameters of equipment is measured for automatic comparison with average values and performance. Maintenance is carried out when certain indicators give the signal that the equipment is deteriorating and the failure probability is increasing. This strategy, in the long term, allows reducing drastically the costs associated with maintenance.

CBM is in the class of preventive maintenance, allowing maintenance of the facility only when the opportunity is created to do so. The prompting factors which call for maintenance action are the measured values (condition data indicating a developing failure) which indicate that the equipment needs maintenance action. CBM leads to higher probability of preventing failures. As long as the failure is a gradual process with a detectable deterioration and the condition can be monitored then CBM can be a useful tool in ensuring smooth operations.

Statistical-based predictive maintenance depends on statistical data from the meticulous recording of the stoppages of the in-plant items and components in order to develop models for predicting failures.

Reliability centered maintenance (RCM) defined as ‘a process used to determine the maintenance requirements of any physical asset in its operating context’. Basically, RCM methodology deals with some key issues which are not dealt by other maintenance methodology. It recognizes that all equipments in a facility are not of equal importance to either the process or to the facility’s safety. It also recognizes that the equipment design differs and that some equipment have a higher probability to undergo failures from different degrading mechanisms than others.

RCM is used to identify the maintenance requirements of equipment. The RCM establishes the functional requirements and the desired performances standards of equipments and these are then related to design and inherent reliability parameters of the equipment. For each function, the associated functional failure is defined, and the failure modes and the consequences of the functional failures are analyzed. The consequences of each failure are established, which fall in one of the four categories (i) hidden, (ii) safety or environmental, (iii) operational, and (iv) which is not operational. Following the RCM logic, preemptive maintenance tasks which prevents these consequences are selected, provided the applicability and effectiveness criteria for preventive maintenance are satisfied.

RCM based maintenance programme recognizes that an organization does not have unlimited financial and personnel resources and that the use of both need to be prioritized and optimized. RCM is a systematic method to evaluate an organization’s equipment and resources so that they mate with each other well and result in a high-level reliability and cost effectiveness. RCM relies very much on predictive maintenance but also recognizes that maintenance activities on equipment which are inexpensive and unimportant to plant reliability can be left to a reactive maintenance method approach. Top performing manufacturing organization following RCM approach to maintenance utilizes all the three maintenance methods. The break up includes around 15 % to 30 % reactive maintenance, around 25 % to 45 % preventive maintenance, and around 25 % to 45 % predictive maintenance.

Organizations which desire to follow RCM methodology are to follow some basic steps which include (i) to develop a master equipment list identifying the equipment in the organization, (ii) to prioritize the listed equipments based on importance to the process, (iii) to assign equipments into logical groupings, (iv) to determine the type and number of maintenance activities needed using manufacturer technical manuals, equipment history, root cause analysis findings, and good engineering judgment, (v) to assess the size of the maintenance personnel, (vi) to identify the tasks which can be attended by the department maintenance personnel, (vii) to analyze equipment failures modes and effects, and (viii) to identify effective maintenance tasks or mitigation strategies.

The applicability requirements refer to the technical characteristics and effectiveness criteria for preventive maintenance tasks and the frequency at which these are to be carried out. Effectiveness criteria depend on the consequences of the failure which include probabilities of the multiple failures for hidden failure consequences, acceptable low risk of failure for safety consequences, and non-operational consequences. When the requirements for planned maintenance are not fulfilled, default tasks include failure finding (for hidden failure, possible redesign of equipment, procedures and training processes) and no-schedule maintenance.

The advent of predictive and condition-based maintenance resulted in major improvement to equipment life and consequently to the overall reliability of equipment. The wider appeal of strategies like ‘total productive maintenance’ (TPM), ‘world class manufacturing’ (WCM) and ‘six-sigma’ also saw an increased focus on plant maintenance. In addition to plant maintenance, reliability management also has gained prominence, wherein the focus has shifted to not just attending to plant and equipment, but to manage equipment as an inter-connected system under a larger umbrella of ‘asset management’. In the present environment, plant maintenance and reliability management go together and are thought of as not two separate streams but as one integrated method. This interest in plant maintenance and reliability management resulted in several tools, methods and strategies.

TPM is the maintenance which is carried out by all employees through small group activities. The concept of TPM started in Japan. The objectives of TPM are (i) to improve equipment effectiveness, (ii) to achieve autonomous maintenance, that is, to allow the operators using the equipment to be responsible and knowledgeable in undertaking some level of maintenance tasks, (iii) to plan maintenance, that is, having a schedule programme on maintenance task, (iv) to train all the employees in relevant maintenance skills and training to ensure that both maintenance and operating staff have all the skills to do their tasks, and (v) to achieve early equipment management which is geared towards ‘maintenance prevention’. Maintenance prevention involves identifying the course of failure and the ‘maintainability’ of the equipment. Tab 1 shows a 2×2 matrix model of the roles and responsibilities of maintenance and operational employees in TPM.

The failure rate distribution determines the reliability of an equipment over its usage period. A typical failure rate distribution is shown in Fig 3. There are three failure rate distributions namely (i) infant mortality period, (ii) useful life period, and (iii) wear-out period in determining the degree of reliability of the equipment. From Fig 3, reliability is the chance which the equipment can last this long of the useful life of the equipment. The reliability of the equipment is time dependent, and if the mortality rate and wear-out failures are relatively insignificant, then the items which fail during the useful life can be estimated to determine reliability.

Fig 3 Typical system failure rate distribution

It can be seen that if the time taken before failure, T is very short, then there is high reliability, that is, the probability that the equipment lasts through its useful life is high. However, if T is very long, then the equipment’s reliability is very low. Reliability for time T = e-T/MTBF where, e is exponential distribution and MTBF is the mean time between failures. Statistically, it has been found out that the failures which occur within the useful life of the equipment are relatively random and the time between failures follows the negative exponential distribution. Moving beyond the useful life to the wear-out period, it can be seen that assuming most of the failures occur during the wear-out period and the distribution of failures follows approximately the normal distribution.

An effective maintenance programme makes the plant, equipment, and facility more reliable. Fewer breakdowns mean less dangerous contact with the plant, equipment, and facility is needed, as well as have the cost benefits of better productivity and efficiency. Additionally, hazards can occur when the plant, equipment, and facility become unreliable and develops faults. Maintenance allows these faults to be diagnosed early to manage any risks. However, maintenance needs to be correctly planned and carried out. Unsafe maintenance has caused several fatalities and serious injuries either during the maintenance or to those using the badly maintained or wrongly maintained / repaired equipment.

For a productive organization, it is needed that the plant, equipment, and facility is maintained so that the same remains safe as well as the maintenance operation is carried out safely.

Organizational management has to ensure that the plant, equipment, and facility (from hand tools and ladders to electrical power tools and larger plant) being used, is maintained in a safe and healthy condition. Hazards can occur (i) when tools break during use, (ii) equipment starts up unexpectedly, and (iii) there is contact with materials which are normally enclosed within the plant, equipment, and facility i.e., caused by leaks / breakage / ejection etc. Further, failing to correctly plan and communicate clear instructions and information before starting maintenance can lead to confusion and can cause accidents. This can be a particular problem if maintenance is carried out during normal production work or where there are contractors who are unfamiliar with the site.

Extra care is also needed if maintenance involves (i) working at height or when doing work which needs access to unusual parts of the plant, equipment, and facility, and (ii) when entering vessels or confined spaces where there can be toxic materials or a lack of air. In such a case, establishing a planned maintenance programme can be a useful step towards reducing risk, as well as having a reporting procedure for employees who can notice problems while working on the plant, equipment, and facility.

Some items of the plant, equipment, and facility can have safety-critical features where deterioration causes a risk. In such a case, arrangements are to in place to make sure that the necessary inspections take place. Further, other steps which are to be considered before the start of maintenance work are (i) to decide if the maintenance work is to be done by specialists who are prepared or competent, (ii) to plan the work carefully before it is started, ideally using the manufacturer’s maintenance instructions, and produce a safe system of work to avoid unforeseen delays and reduce the risks, (iii) to make sure maintenance personnel are competent and have appropriate clothing and tools, and (iv) to try and use downtime for maintenance. The difficulties in coordinating maintenance and production work is avoided if maintenance work is performed before start-up or during shutdown periods.

For maintenance in safe working areas, it is to be ensured that safe access and a safe place of work is provided. Also, there is not only just focus on the safety of maintenance personnel, but the necessary precautions to ensure the safety of others who can be affected by the maintenance work, is taken care, e.g., for other employees or contractors working nearby. Further, signs and barriers are set up, and people at key points are positioned if they are needed to keep other people out.

For a safe maintenance of plant, equipment, and facility, it is necessary that the plant, equipment, and facility is made safe before maintenance starts. For safe isolation, it is necessary to ensure moving plant has stopped and electrical and other power supplies has isolated. Majority of maintenance work is to be carried out with the power off. If the work is near uninsulated, overhead electrical conductors, e.g., close to overhead travelling cranes, then the power is cut / power off first. The power equipment is to be locked off if there is a chance that the power can be accidentally switched back on. Also, the plant and pipelines containing pressured fluid, gas, steam, or hazardous material are to be isolated by locking off the isolating valves.

Other factors which are required to be considered are (i) to release any stored energy, such as compressed air or hydraulic pressure which can cause the equipment to move or cycle, (ii) to support parts of plant which can fall, e.g., the blades of down-stroking bale cutters and guillotines with blocks are to be supported, (iii) to allow components, which operate at high temperatures time, to cool, (iv) to place mobile plant in neutral gear, and apply the brake and choke the wheels, (v) to safely clean out vessels containing flammable solids, liquids, gases or dusts, and to check them before hot work is carried out to prevent explosions and to take the help and advice of specialist to do this safely. (vi) to avoid entering tanks and vessels where possible since this can be very high-risk work, and if needed, to get specialist help to ensure adequate precautions are taken, and (vii) to clean and check vessels containing toxic materials before the start of the work.

‘Dos’ and ‘Don’ts’ of maintenance of plant, equipment, and facilities

The ‘Dos’ includes (i) to ensure maintenance is carried out by a competent person (someone who has the necessary skills, knowledge and experience to carry out the work safely, (ii) to maintain plant, equipment, and facility regularly by using the manufacturer’s maintenance instructions as a guide, particularly if there are safety-critical features, (iii) to have a procedure which allows employees to report damaged or faulty equipment, (iv) to provide the proper tools for the maintenance personnel, (v) to schedule maintenance to minimize the risk to other employees and the maintenance personnel wherever possible, and (vi) to make sure maintenance is done safely, and the equipments and moving parts are isolated or locked and that flammable / explosive /toxic materials are dealt with properly.

The ‘Don’t’ include (i) ignorance of maintenance, (ii) ignorance of the reports of damaged or unsafe equipment, and (iii) use of faulty or damaged equipment and tools.