industrial machines maintenance
TRANSCRIPT
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