Dairy Plant Management and Pollution Control

Module 5. Plant maintenance

Lesson 9
PLANT MAINTENANCE: PREVENTION & BREAK-DOWN MAINTENANCE

9.1 Introduction

The determination of plant efficiency at all essential points of the process is the first step in creating a maintenance system which is fundamental to achieving optimal performance in any milk plant.

9.2 Types of Maintenance

9.2.1 Preventive maintenance

It is a daily maintenance (cleaning, inspection, oiling and retightening), design to retain the healthy condition of equipment and prevent failure through the prevention of deterioration, periodic inspection or equipment condition diagnosis, to measure deterioration. It is further divided into periodic maintenance and predictive maintenance. Just like human life is extended by preventive medicine, the equipment service life can be prolonged by doing preventive maintenance. Preventive maintenance is further divided into periodic and predictive maintenance.

• Periodic maintenance (Time based maintenance-TBM) which consists of periodically inspecting, servicing and cleaning equipment and replacing parts to prevent sudden failure and process problems.

• Predictive maintenance is a method in which the service life of important part is predicted based on inspection or diagnosis, in order to use the parts to the limit of their service life. Compared to periodic maintenance, predictive maintenance is condition based maintenance. It manages trend values, by measuring and analyzing data about deterioration and employs a surveillance system, designed to monitor conditions through an online system.

9.2.2 Corrective maintenance

It improves equipment and its components so that preventive maintenance can be carried out reliably. Equipment with design weakness must be redesigned to improve reliability or improving maintainability.

9.2.3 Breakdown maintenance

It means that people wait until equipment fails and repair it. Such a thing could be used when the equipment failure does not significantly affect the operation or production or generate any significant loss other than repair cost.

9.2.4 Maintenance prevention

It indicates the design of new equipment. Weakness of current machines is sufficiently studied and is incorporated before commissioning new equipment.

9.3 Meaning of Preventive Maintenance

The precise meaning of the term "preventive maintenance" depends on the concept of the organization of the plant, of its capacity and processing and manufacturing programme as well as on the availability of, and accessibility to specialized services of machinery manufacturers or their agents, who are usually equipped with an ample supply of spare parts. It also involves in

• Planning and scheduling

• Proper installation

• Periodic inspection

• Planned lubrication

• Adjustment of machines and instruments

• Replacement of worn and damaged parts

• Recording and reporting observations, adjustments, repairs, and replacements

• Periodically reviewing records on inspection, lubrication, repairs and performance of equipment

• Keeping an adequate supply of spare parts

• Determining maintenance costs

• Cleaning and painting equipment and buildings

• Inspection and maintenance of all emergency, personnel and plant protective equipment

• Maintaining full serviceability of all utilities

• Advantages of Preventive Maintenance

• Less production interruptions

• Fewer large-scale repairs

• Less raw material and product spoilage

• Increased life expectancy of equipment

• Less standby equipment needed

• Identification of items with high maintenance costs leading to investigation and correction of causes, such as misapplications, operator abuse or obsolescence

• Better spare parts control, greater work safety and lower manufacturing cost.

The preventive maintenance programme (PMP) is the most essential part of the programme of work of the dairy engineer's group. It is divided into several parts.

The first comprises collecting and recording all basic information on machines and installations: the equipment records of the plant. This may be classified as the preparatory part of the PMP.

The second comprises identification of inspection objectives, frequency and location, and is known as the Inspection Schedule. This includes lubrication schedules and routine spare parts replacement programmes and may be classified as the plan of operations in which also the recording and reporting systems are defined. The third part of the PMP procedure is the action which starts with the analysis of the records and is followed by decisions on what must be done, by whom, when and by what means. It also includes decisions on who inspects and accepts the completion of the action ordered.

The last component of the action part of the PMP is the maintenance cost estimate. The application of PMP depends on well-equipped workshop facilities and trained staff. The variety of skills needed for performing all the duties specified above implies that training in the dairy engineer's group is an essential requisite of success.

9.4 Objectives of Preventive Maintenance (Pm)

Preventive Maintenance is a procedure utilizing programmed and coordinated lubrication, internal and external inspections, timely adjustments, repairs and replacements by skilled and trained personnel under qualified supervision for the purpose of preventing unscheduled downtime, preserving equipment, maximizing overall plant performance, minimizing maintenance cost, and thereby contributing to an improved profit position. So, by definition we can draw the following principal objectives of the preventive maintenance.

• Increase the efficiency and improve the performance of all processing and auxiliary equipment.

• Increase the overall productivity of the entire plant by achieving coordinated and continuous operation of all plant equipment.

• Increase the certainty of meeting daily production schedule.

• Reduce unscheduled downtime.

• Reduce costs of maintenance and repair.

• Reduce overall processing costs.

• Reduce utility usage.

• Reduce Bio-chemical Oxygen Demand (BOD) of sewage.

• Minimize property and personal hazards.

• Conserve raw materials.

• Conserve fuel.