What is maintenance? What are the main historical developments in maintenance up to the present day?

 

 

Modern societies use a range of engineered objects for many different purposes. The objects are designed and built for specific functions. These include a variety of products (used by households, businesses, and government in their daily operations), plants, and facilities (used by businesses to deliver goods and services) and a range of infrastructures (networks such as rail, road, water, gas, electricity; dams, buildings, etc.) to ensure the smooth functioning of a society. Every engineered object is unreliable in the sense that it degrades with age and/or usage and ultimately fails. A dictionary definition of failure is “falling short in something expected, attempted, desired, or in some way deficient or lacking.” From an engineering point of view, an engineered object is said to have failed when it is no longer able to carry out its intended function for which it was designed and built. Failures occur in an uncertain manner and are influenced by several factors such as design, manufacture (or construction), maintenance, and operation.

 

 

 

Maintenance

Maintenance involves actions to control or prevent the deterioration process leading to failure of an engineered object and restore the object to its operational state through corrective actions after a failure. The former is called preventive maintenance (PM) and the latter corrective maintenance (CM). Maintenance is the combination of all technical and associated administrative actions intended to retain an item in, or restore it to, a state in which it may perform its required function.

 

 

Example - Vehicle Maintenance

Head gaskets: The head gasket in an automobile engine seals the cylinder head of the engine to the engine block. There are coolant and oil passages that transfer the oil and coolant from the engine to the head and back. The reason for these passages is for the oil to lubricate the valve train and the coolant to remove heat from the cylinder head.

 

The other job of the head gasket is to seal the top of the cylinder to keep the compression contained. Head gasket problems arise generally due to poor maintenance of the cooling system. Acidic coolant may begin to eat away or erode the sealing area of the coolant passages in the gasket. This may cause a weak area and a leak may start to form. The head gasket leakage may travel either internally or externally. An external leak is visible outside the engine; an internal leak means that coolant may seep into oil passages or erode the compression sealing ring in the head gasket, allowing coolant to enter the cylinder or compression to enter the cooling system.

 

This is what is called a blown head gasket. Brakes: A coach driver and his business partner were jailed for the manslaughter of a couple who died in a road crash in the UK. An investigation by police concluded that the cause of the crash was acute brake failure due to poor maintenance. At the Crown Court, the coach driver was sentenced to five years and three months in prison after he admitted charges of causing death by dangerous driving and gross negligence manslaughter. His business partner, who pleaded guilty to gross negligence manslaughter, was jailed for three years. This resulted in a warning to all drivers who ignore vehicle maintenance warning signs particularly in relation to tire and brake wear that could result in a fatal road crash and land themselves and their bosses in court.

 

Example - Rail System Operations

An investigation by the Rail Accident Investigation Branch (RAIB) into a passenger train that overshot a station in East Sussex, UK by almost two‐and‐a‐half miles revealed that it was because of poor maintenance. The report said that the train did not deposit sand (Needed to assist the braking process) when the driver braked because the leading sand hoppers were almost empty. Maintenance procedures did not ensure the sand‐hoppers were refilled despite there being information that the sand was low.

 

 

 

Maintenance Management

Maintenance management deals with maintenance‐related decision making (for example, recruiting of skilled labor, resource allocation, and scheduling of resources, etc.) at the strategic, tactical, and operational levels, and then initiating actions to implement the decisions. Businesses and government agencies need to make decisions relating to maintenance of engineered objects at three different levels: strategic, tactical, and operational. Figure - 1 lists some of the decision problems at each of these three levels.

 

Proper maintenance with periodic in‐service inspections of an engineered object has a positive influence on the technical state of the object and may extend its lifetime considerably. A proper framework is required for planning and executing the decisions, with data playing an important role. Figure - 2 shows the sequence of activities for implementing the decisions at the operational level.

 

Fig-2

 

Main historical developments in maintenance up to the present day?

 

Until about 1940, maintenance was considered an unavoidable cost and the only maintenance used was corrective maintenance. When equipment failed it was the task of a specialized maintenance workforce to return the failed item to its operational state. Maintenance was not addressed during the design of the system, nor was the impact of maintenance on system and business performance recognized. The evolution of Operations Research (OR) from its origin and applications during the Second World War to its subsequent use in industry led to the widespread use of preventive maintenance at component and higher levels.

 

Since 1950, OR models for maintenance have appeared at an ever‐increasing pace. The models examine many different maintenance policies and the optimal selection of the parameters of these policies. The impact of maintenance actions on the overall business performance is not addressed. Starting in 1970, a more integrated approach to maintenance evolved in both the government and private sectors. New, costly defense acquisitions by the US government required a life cycle costing approach, with maintenance cost being a significant component. The close link between reliability and maintainability formed the basis for this change. The term “R&M” began to be used more widely in defense acquisitions to denote reliability and maintainability. This concept was also adopted by manufacturers and operators of civilian aircraft and formed the basis for Reliability Centered Maintenance (RCM) in the USA. In the RCM approach, maintenance is carried out at the component level and the maintenance effort for an item (component or higher level) is a function of the reliability of the item and the consequence of its failure under normal operation. The core of the RCM philosophy is that maintenance will be performed only after evaluating the consequences of failures (Safety, economic, operational, and environmental) at component level. In other words, it deals with optimization of preventive maintenance activities considering failure consequences. The RCM approach is system‐oriented and may be implemented free of a company’s organizational culture.

 

Trends in Maintenance

 

Engineered objects are becoming more complex to meet the ever‐increasing demand of customers. Detecting failures and faults is becoming harder and more time‐consuming. The cost of labor to carry out maintenance has also been increasing. As a result, maintenance will continue to evolve and the two main drivers for this are

1-technology

2-management. 

 

Technology Trends

Many different types of technologies are beginning to impact on maintenance. These include:

 

• Sensor technologies: These are used to monitor the condition of an object and to decide on maintenance based on the condition.

• Information and communication technologies (ICTs): These technologies are used to access, store, transmit, and manipulate relevant information for maintenance decision making.

 

Management Trends

Maintenance is no longer viewed as a cost but as a function which creates additional value in the business process. The focus has shifted from fail‐and‐fix to root cause elimination, and from functional thinking to a process‐oriented approach with the end customer being the focus. Trends include:

• A risk‐based approach to maintenance: The focus is to reduce the business risk.
• Maintenance outsourcing: Here, a business outsources some or all of the maintenance actions to an external agent under a maintenance service contract.

 

 

Focus of the Maintenance

Maintenance of engineered objects requires finding and implementing the solutions to a wide range of decision problems. The starting point is the list of business objectives. These determine the production rates and they, in turn, impact on the state of the asset which degrades with age and usage. Maintenance strategies need to take these issues into account. Formulating effective maintenance strategies requires

(i) proper data collection and analysis

(ii) models to assist the decision‐making process. This, in turn, requires a proper understanding of many different concepts, tools, and techniques.

 

A proper understanding of maintenance requires a comprehensive framework. There are many different definitions of a framework and the one that is appropriate in the context of the article is the following:

 

The framework needs to deal with one or several of the following issues depending on the maintenance problem under consideration:

 

• Use of scientific methods to understand the degradation processes;

• Proper collection and analysis of relevant data;

• Use of models for decision making;