Engr. Omorogbe Osaze B. Eng. (Mech. Eng.), PGD(Petro. Eng.) MSc (Mech. Eng.) MIMECHE, MNSE, Regd. COREN

ABSTRACT

As human have life-span and expectancy so also does machines.

Planned maintenance helps to prolong the machine’s life and expectancy

will be high. The maintenance of Machine in an industry is criteria for

investment decision and thus has a high economic value. A Machine

functioning properly gives room for increase in production and reduction

in stress on man power: Thus “gain in man-hour”. Many of our local

industries do not have Planned maintenance. They believe that the

machine is self sustaining and thus can withstand any situation. When

there is no Planned maintenance the machine’s life span is reduced. In a

lay man’s language “the machine will die quick”.

INTRODUCTION

The purpose of maintenance in the Industry is to preserve plant and

machinery in a condition in which it can operate, and can do so

safely/economically. It is the component of plant and machinery which fails

individually, and can lead to the loss of the whole unit or system. The activity

needs therefore to concentrate on these components which are critical.

The maintenance of the machines is in two parts, Mechanical and Electrical.

In the industries we have more emergency with electrical apparatus than

with mechanical ones. In-fact with good maintenance schedule/monitoring

there will be no mechanical emergency.

Installation/Erection:

At the stage of installation of the machine by the vendors, the company

normally attaches their own Engineer to be part of the installation of the

machines. It will be proper for the engineer study the erection procedure

as the vendors are still working in the company and to know all standards

being used by the machines. Faulty installations have a role to play in the

operation of the machines. In fact failure of the machine starts from here.

In the case were the Engineer was not hired as at time of erection, the

manuals of each machines should be gathered and studied to know the

working principles surrounding this machines before talking of

maintenance. It is necessary to create a simple way of studying the

machine in order to be able to maintain them properly.. You create a life

span for your machine and this go a long to help you in the know your

machine properly

The most commonly maintenance systems in use are: planned, preventive,

scheduled, corrective and emergency.

PLANNED MAINTENANCE; use information issued by manufacturers

and suppliers, the experience and knowledge of the service department

staff, and reports and records from previous service visits.

PREVENTIVE MAINTENANCE; is work to be carried out at a specific

frequency as indicated by potential failures or known reduction in efficiency of

the plant and equipment, thereby avoiding failures or a decrease in

performance.

SCHEDULED MAINTENANCE is work based on known information, such as

number of operations, hours run, mileage, etc., and can therefore be carried

out at a predetermined time interval.

CORRECTIVE MAINTENANCE is work carried out following

the failure of the plant and equipment, and is so designed to

return the component to its normal operating condition.

EMERGENCY MAINTENANCE is that work which is required

to be actioned without delay due to a failure of a component

which, if not implemented, would lead to further failures or even

permanent damage, resulting in the total loss of the plant and

equipment. Plant and equipment in such a condition may also

be dangerous to personnel

The main focus of this lecture will be on PLANNED MAINTENANCE.

Planned Maintenance encompasses all types maintenance and the

preventive or scheduled systems are examined in more detail. The planned

maintenance involves the entire industry and ranges from all department to

management. An in-house maintenance department can be setup as it with

most standard companies and the planned maintenance program is

designed by the team of Engineers or a Maintenance Consultant could be

contracted. In planning the following procedure could be adopted:. Asset register;Maintenance and repair record;Technician and craftsmen guidance notes;Planning schedule;Week tasks;Work dockets;Year visual aid plan.

Asset register: This is done by allocating numbers to each of the

equipment. It is advisable to restrict this numbering sequence to a

minimum while ensuring that it meets the specific needs of the

company and location. The asset number is built up from certain

elements, e.g.:

Location: Plant Code: Plant/equipment number

Plant room 1: Boiler: No. 1 Boiler = PR1-01-01

Plant room 1: Boiler: No. 2 Boiler = PR1-01-02

Pump units, including valves, gauges, etc., are classified as

individual assets.

Maintenance and repair record: This is designed to record all work

carried out and parts fitted on each of plant and equipment. Service

visits by contractors are also entered. To reduce the amount of

information entered in the record, predetermined work of a planned

maintenance nature can be entered in code form, while additional

work or breakdowns may be more fully detailed. A simple system

may be used to provide recognition of the different methods by which

the work has been carried out, e.g.

Planned maintenance work is entered in black pen.

Preventive or corrective work is entered in blue pen.

Emergencies (i.e. breakdowns) are entered in red pen.

Thus from this method the Engineer can observe at a glance if

planned maintenance is working or not.

Technician and craftsmen guidance notes: The guidance notes can be produced

either as a composite handbook containing task instructions for all types of plant

and equipment for each trade group, or as specific task/advice notes for each

asset of the service requirements of the plant equipment. Its contents are as

follows:

 

Health and Safety: Stresses the importance of carrying out the work in a safe

and responsible manner.

Introduction: Details how the handbook contents and the individual's

responsibility in the application of his skills are to be implemented.

Frequency of Services and Work Tasks: Details the work to be carried out, and

at what frequency, as indicated by the instruction on the work docket.

Plant Code: Lists the plant codes for the plant and equipment covered by the

handbook, prefixed by the appropriate trade reference (e.g. Mechanical

Fitter = M).

Planning schedule: At this stage the experience of the Engineer,

Technician and Craftsmen is very important as the some machine’s

manual may not be available or lost with time. While planning, holiday

period and seasonal or shutdown should be checked on the calendar

and highlight. Thus major maintenance work should be schedule at

these period.

The work task that requires greatest resources (i.e. man-hours)

should be entered on the planning schedule first. Planning the

frequency, work tasks and man-hours for each asset then follows.

Choose the week in which the least-frequency service is to be

undertaken (e.g. yearly; enter a 'Y/'). Other frequencies can then be

entered (e.g. quarterly, 'Q/ ; monthly, 'M/’).

To complete the planning scheduled for the specific asset the hours required to

carry out the work at the nominated frequencies are then entered (e.g. 'Y/12';

'Q/4'; 'M/1', etc.).

Plant and equipment that require a service on completion of a certain specified

period of 'hours' may be catered for on a fixed frequency basis. it is essential

that the maintenance of the plant and equipment be carried out on the

completion of a certain number of operating hours or mileage, then this must

be allowed for in the allocated work hours of the relevant trade group.

Man-hours can be accounted for in two ways:

1. The actual hours necessary to carry out the planned maintenance work

task.

2. The 'total' hours to complete the planned mainte nance work task

(including non-productive hours). Non-productive hours would include such

items as collecting spares, tea breaks, discussions, etc.

Week tasks: This is a form that shows maintenance task to be

carried out weekly. Departments in which work is to be carried out

may be issued a copy of their department's week tasks four weeks in

advance, so that the maintenance work can be carried out without

disruption to the department's output. Week task forms should only

require amending when either additional plant and equipment is

introduced or the frequency of planned maintenance tasks is being

adjusted to meet revised operational or maintenance demands. The

information contained on the week task forms is presented in a

format that enables that information to be easily transferred onto the

work dockets, e.g.:

Location/Area: Plant/Equipment: Plant/Equipment No.:

Job Code: Check List

Work dockets: This is a document prepared by the Engineer from the

forthcoming week task form. Here the experience of the Engineer

matters a lot. It is at this stage that, having the information about the

machines, as decision can be made on which planned maintenance

tasks are to be carried out and which may be postponed or

cancelled. The engineer or supervisor responsible for planned

maintenance may issue the work dockets on an individual, daily or

weekly basis. The work dockets would be normally issued on Fri

days for the following week. This enables the technician/craftsman to

plan his work for the forthcoming week. All work dockets should be

returned to the engineer's office daily. Work dockets that have not

been actioned should also be returned for the engineer's attention,

with comments on why they have not been actioned.

Week dockets          

Location/Area Plant/Equipment Plant/Equipment No.

Job Code

Check list Week

           Work carried out:                        Recommendation/ Action:  Date: Time taken: Signature:                    

Year visual aid plan: Visual aids are developed from the planning

schedule, in that the asset and the asset numbers are repeated as

they are due for maintenance service e.g. changing of oil and

grease. The benefit to be gained by the engineer and

technician/craftsmen from the visual aid is that it provides them with

a visual picture of the full year's programme, covering all the

recorded assets and their associated work tasks. The format of this

visual aid depends on the number of assets within the system, and

each visual aid may cover approximately 100 assets.

Condition Monitoring:-This is the method of establishing the condition of the

respective plant and equipment, usually while it is in operation. Monitoring can be

carried out continuously or at periodic intervals, depending on the plant or equipment

being monitored. The most common equipment in use is for temperature, vibration

and oil condition, i.e.:

1.Temperature meters: Temperature meters are now available in the form of infrared

cameras which enable the operative to take readings from a distance.

2.Vibration monitors: This provides an early warning of any deterioration in bearings,

gear damage and wear, valve leaks, imbalance of rotating parts, misalignment or

effects caused by incorrect displacement of fluids. Hand-held vibration monitors are

also available.

3.Fluid condition monitors: This method identifies whether there is any trace of wear

from moving parts and, if found, enables the appropriate maintenance to be carried

out.

4.Operator’s Attitude: The operators have to undergo lectures on machine usage by

the resident engineer. This could be argued, but have yielded positive result.

Conclusion: A major concern within maintenance departments and service contractors

is the lack of experienced maintenance technicians and craftsmen. Planned

maintenance can reduce the demand for highly experienced craftsmen in

that, if the instructions issued in work docket and advice/guidance notes are

adequate, a less-skilled person should be able to perform the work task

correctly. It follows that adequate training must be provided to ensure that,

irrespective of the degree of the operative's skills and experience, the work

task given will be carried out to the required standard.

Training should not be restricted to any specific individual but should

include engineers, technicians, craftsmen and, where appropriate, semi-

skilled staff.

Reference: Dennis A. Snow (2002) “Plant Engineer's Reference Book” Butterworth-Heinemann Linacre House, Jordan Hill, Oxford OX2 8DP. 225 Wildwood Avenue, Woburn, MA 01801-2041.A division of Reed Educational and Professional Publishing Ltd.

American Bureau of Shipping (2004) “Guidance notes on Reliability-Centered Maintenance” ABS Plaza, 16855 Northchase Drive, Houston, TX 77060 USA

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