Jack Balitok: Maintenance, Plant Facilities, and Utilities

6.11 Maintenance, Plant Facilities, and Utilities
6.11.1 Maintenance Systems
ROBERT

N. McINDOO
Functions
The maintenance organization is no different than any
other organization in that it must perform certain management functions to be successful. The degree to which it performs these functions determines its ultimate success.
Planning-the activity that determines the goals of the
department and the means to implement those goals. This
would include planning for facilities, equipment, procedures,
and most of all, personnel.
Organizing-the activity that distinctly identifies the
work to be done and allocates it in the most efficient manner.
Leading-the activity that motivates the organization to
meet departmental goals and to satisfy individual needs in
concert with departmental needs.
Controlling-the activity that measures planned performance against actual performance. This requires detailed planning, maintenance standards, and monetary budgets.
Implicit in these managerial activities are personnel
needs. This involves recognizing organizational needs and
finding the proper people to fill those needs. Knowing the
strengths and weaknesses of the individuals dictates the need
for training.

INTRODUCTION
Maintenance systems use available materials, facilities,
and the organization efficiently and effectively. Systems for
maintenance such as preventive maintenance, planning,
scheduling, and work sampling are not new; what is new is
the computer to file and store data, produce schedules, and
to provide timely information.
Some of the more important maintenance systems will
be described in this section. Where applicable, the role of
the computer will be defined. The systems can be made to
function manually; however, the computer can greatly enhance the application in terms of man-h<1urs expended and
timeliness of information.

THE MAINTENANCE ORGANIZATION
The maintenance organization is at best a blueprint of
how the department is to meet its objectives. The best organization plan can fail if the people are inadequate or their
role is misunderstood. The most poorly conceived organization can succeed if the people expected to work within it
fully understand implied responsibilities and are highly
trained and motivated. Ideally, a maintenance organization
is designed around the needs, the facilities, and the geography
of the mine or plant, without regard to personnel. The ideal
is seldom found. Generally, the ideal is conceived and then
modified to meet the abilities, experience, and personalities
of the personnel available.
Objectives
The primary objective of a maintenance department is to
provide sufficient facilities and equipment in a safe operating
condition, at the lowest possible cost, to meet the operating
plan.
Maintenance may be called on to perform nonmaintenance work such as construction, plant modifications, equipment improvement, etc.; however, these activities must be
considered secondary to the primary function when designing
an organization. An exception to this would be the power
distribution section of electrical maintenance. Pole-line construction and relocation is essential to the orderly progression
of mining.

Types of Organizations
Normally the maintenance organization has three levels
of management:
First-Line Supervision-foremen who directly supervise
the mechanics and craftsmen.
Middle Supervision-general foremen who supervise two
or more first-line foremen. In large complex shops, there may
be a lead foreman who directs shift foremen and reports to
a general foreman.
Top-Level Supervision-maintenance managers or superintendents who direct the entire maintenance organization.
Generally there are maintenance planners, clerks, and
maintenance engineers as staff to support the levels.
There are three basic types of organizations: (1) central
maintenance organization, (2) area maintenance organization, and (3) central! area maintenance organization.
Central Maintenance Organization: This is a line organization generally built around craft skills and functions. See
Fig. 1. This type of organization clearly divides work re-

SUPERINTENDENT
a.ERICAL

PLANNING

GENERAL FOREMAN

I
El EeTR I CAl.
FOREMAN

WELDING
FOREMAN

GENERAL FOREMAN

MECHANICAL
FOREMAN

PIPE
FOREMAN

MACHINE SHOP
FOREMAN

Fig. 1. Central maintenance organization.

922
© 1990 by the Society for Mining, Metallurgy, and Exploration.
All rights reserved. Electronic edition published 2009.

MOBILE EQUIPMENT
FOREMAN

923

MINE OPERATIONS
SUPERINTENDENT
ClERlCAL--+-I-PlANNING

GENERAL FOREMAN

INSTRUMENT
FOREMAN

CONCENTRATOR
REPAIR
FOREMAN

CRUSHING
REPAIR
FOREMAN

FLOTATION
REPAIR
FOREMAN

PELLETIZER
REPAIR
FOREMAN

ELECTRICAL
REPAIR
FOREMAN

Fig. 2. Functional organization.

sponsibilities. It has the disadvantage of encouraging "inbreeding," that is, craftsmen tend to be promoted only within
their group.
A variation of the centralized maintenance organization
is the functional organization. See Fig. 2. This organization
mayor may not have some support from a central-shop
group.
The pure area organization is seldom used. See Fig. 3.
Generally, area maintenance is used with centrally controlled
shop support.
Central! Area Maintenance Organization: This organization works well in a large operation which has defined
plant functions and different mines or different ore bodies
within a mine. See Fig. 4.
A variation of the preceding organizations appears where
mobile equipment assumes a major responsibility for the
operation. See Fig. 5.
In some surface-mining operations, all mobile-equipment
maintenance and other field maintenance have been placed
under the control of the mine superintendent. A separate
central shops department performs support functions. This
has the advantage of placing the responsibility for equipment
condition on the user of the equipment. It has the serious
disadvantage of possibly disregarding maintenance requirements in favor of short-term operational gains. The basic
interests of the mine superintendent will inevitably favor
operations to the long-range detriment of maintenance. Further, there is a conflict between the interests of the one
maintenance group and the central-shops group. One may
want improvements, modifications, or just reliability; the other's interests lie in the turnover of parts or overhauls.

less important than the definition of roles and the adequacy
and motivation of the personnel available to fill those roles.
The type of organization is dictated by the size and geography
of the operation as weIl as the degree and kind of maintenance
involved.

TRAINING
To increase productivity, maintain efficiency, and to assure qualifications for advancement, the maintenance organization must provide training for both its craft group and
supervisors. Technology changes. Today's skills become obsolete. Update to meet change is essential for both the craft
group and the supervisors. The skills a foreman brings to
his job are generally technical in nature. Knowledge of human motivation, group psychology, report writing, communication, and all the other managerial requirements are
hardly inherent. New supervisors particularly need training,
but all potentiaIly promotable supervisors should be prepared
for advancement.
Craft Group Update
There are three avenues for updating craft skills:
1. Manufacturer's Training Schools-Most manufacturers of mining and plant equipment have training schools to
provide the basic understanding of their equipment as well
as the hands-on maintenance required. These are generally
excellent, but have the disadvantage of high cost. The sponsoring company must provide travel, housing, food, and in
some cases, tuition for the training. A good approach is to
send select supervisors to these schools and then have these
supervisors hand-tailor the material for presentation to the
craftsmen.
2. Vendor Training Schools-Oftentimes the manufacturer's vendors are prepared to provide training on-site for
the craftsmen. This has the advantage of being less expensive.

Summary
The maintenance organization, like any organization,
must be designed to meet goals and objectives. The form is

SUPERINTENDENT
a.ERICAl

PLANNING

AREA GENERAL FOREMAN

AREA FOREMAN
A

(CRUSHING)

AREA FOREMAN
B

(GRINDING)

AREA GENERAL FOREMAN

AREA FOREMAN
C

(flOTATION)

r
AREA FOREMAN
D

(TAILINGS)

AREA FOREMAN
E

(MINE I)

Fig. 3. Area maintenance.

AREA FOREMAN
F

(MINE II)

SURFACE MINING

924

SUPERIKTENDEKT
a.ERICAl_-1jl-- PLANNING
I

AREA GENERAL FOREMAN
PLANT

NlEA
FOREMAN

GENERAL FOREMAN
SHOPS

AREA
GENERAL FOREMAN
MINE

~ ~~ 1..

FOREMAN

FOREMAN
WELDING SHOP

FOREMAN
PIPE StiOP

'M~

FOREMAN

fOREMAN
MACHINE SHOP

GENERAL FOREMAN
ELEC. REP.

AREA
FOREMAN

INSTftUMENT
REPAIR

FOREMAN
FAa. SHOP

Fig. 4. Central/area maintenance.

However, this type of training should be previewed to assure
conformance with company policy and capability.
3. In-House Training-In-house training programs, developed to suit particular needs, and presented by foremen
or other supervisors, are the most successful and the least
costly. Training aids, slides, film, and technical data can be
obtained from vendors and original equipment manufacturers, but the program can be tailored to the needs and capabilities of the maintenance organization. Because the
supervisor is, in effect, the expert, he gains in stature and
credibility. Further, the followup on the job site then becomes
ongoing training.
In order to prepare journeymen for training on new equipment, new techniques, and complex componentry, it is often
necessary to provide training in basics:
Hydraulics-basic theory, valve operations, pumps, piping, and auxiliary components.
Bearings and Seals-types of bearings and seals, application, storage, and handling.
Electrical Systems and Controls, etc.
The areas of basic training should be tailored to individual
organizational needs. Again, training in basics should be done
in-house whenever possible.
Supervisory Training
Supervisory training falls into two categories: new supervisor orientation and preparation for promotion.
1. New Supervisor Orientation-The new maintenance
supervisor is generally technically oriented and trained. However, he lacks managerial skills and needs help to bridge the

GENERAL FOREMAN

TI"~SHOP
FOREMAH

FOREMAN

transition from doing to getting others to do. Some general
areas for training would be:
a) Motivation
b) Common Problem Solving-typical problems facing
the supervisor such as discipline, the reluctant worker, absenteeism, drugs, etc., and how to deal with them.
c) Company Policies
d) Union Contracts
e) Management Skills-planning, leading, organizing,
and controlling.
2. Training for Promotion-Annual evaluations, formal
or informal, are a requisite to determine career goals for
supervisors and to recognize the training to meet those goals.
Promoting from within an organization develops esprit de
corps and enhances morale. It is maintenance management's
obligation to prepare potentially promotable supervisors to
be qualified for advancement. Some areas where training may
be helpful are:
a) Technical-computer technology, metallurgy, etc.
b) Accounting-cost-control techniques, budgets, cost
analysis.
c) Communications-speech, report-writing, conducting meetings.
d) Industrial Relations-grievance-handling, arbitration, contract negotiation.
Training Methods
Training can be effective or a bore, depending on how it
is done. Visual aids are all important. Movies, slides, and
participative seminars are means to interest and stimulate

GENERAL FOREMAN

I
SHOVEL/DRILL
SHOP
FOREMAN

I
LOCO. SHOP
FOREMAN

GENERAL
FOREMAN

SHOPS
FOREMAN

GENERAL FOREMAN

I
TRUCK SHOP
FOREMAN

TRACTOR SHOP
FOREMAN

Fig. 5. Variation of maintenance organization when mobile equipment assumes a major responsibility.

MINE OPERATIONS
thought. Under no circumstances should a script be read.
Training is expensive. It behooves maintenance management
to plan and execute training with the same attention to detail
as for a plant overhaul. Training today is the key to tomorrow's success.

MANNING THE MAINTENANCE DEPARTMENT
No task facing a maintenance department is as difficult
as justifying manpower. In operations, the manpower for an
increase in production is rather straightforward: One drill
operator, one serviceman, one shovel runner, five truck drivers, one crusher crew, etc., all from easily documented standards. But with the variety of crafts involved, maintenance
has a much harder time. Then if production requirements
increase, or worse, decrease, maintenance has an even harder
time. Traditionally, maintenance has done a little guessing,
or at best, used a certain rule-of-thumb to project crew sizes.
But there are better ways.
Philosophy of Maintenance
The degree, or philosophy, of maintenance depends on a
number of factors, not the least of which is distance from
supporting vendors. The management of a mining operation
must make a decision early on as to this degree: maximum,
general, or minimum self-maintenance.
This decision will have a great effect on the maintenance
workload, and hence the size of the department.
Methods for Manning
Backlog Method: In an established maintenance department, production increases or decreases are reflected in
the shop backlog of work. With an effective work order
system, this backlog is easily measured. A stabilized backlog
of work equivalent to three to four weeks of man-hours is
considered ideal. A rising backlog of 15 to 20% would indicate the need for more craftsmen; the number needed would
equal the number of man-hours divided by hours per work
week to restore the 3 to 4-week equilibrium. Similarly, a
declining backlog would require consideration for reducing
manpower.
The backlog is an effective tool for determining the number and kind of craftsmen needed for the work force. It has
the advantage of being readily documented, but has the disadvantage of being a responsive measurement as opposed to
an anticipatory measurement. It also presupposes the ability
to increase or decrease manpower in the short run. Even if
this were possible, it might not be desirable.
The backlog method is most effective for service shops
where the work is somewhat discretionary as to timing.
Historical Data Method: The work of mobile equipment
shops is for the most part nondiscretionary. Preventive maintenance inspections, servicing, and running repairs cannot
be backlogged, although they can be preplanned (see the
section on the "Work Order System-Planning and Scheduling"). Overhauls and component replacements can be
planned and scheduled, but only with fairly large time-frame
parameters. To provide the necessary manpower for these
shops (and they include shovel repair, drill repair, truck and
tractor shops, gas-vehicle shops, etc.), there has been developed another manning method using actual repair hour per
operating hour statistics for each class of mobile equipment.
The computer accumulates the operating hours for each
class of trucks, for example, and would also accumulate the
repair hours charged to that class of trucks. It would then
produce a repair hour per operating hour statistic for a period
of time, usually a month, and a summary for six months and
a year (see Figs. 6 and 7). The mining plan would indicate

925
TOTAL
OPER

RATED

RATED HR
PER

UNIT DESCRIPtION

Cat D9 Cra.... ler Dozer
Cat 824 R Tire Dozer
Gat 988 RT Loader$

1366.00
4492.00
273.00

299.00
1282.25

.22

.00

.22

.29

.00

85.00

.31

.00

.29
.31

Cat Road Graders
Cat D8 Crawler Dozer

2832.00
1127.00

458.50
299,50

.16
.27

.00

.16

163

,DO

.27

164

Cat 988 7yd l.oader

926.00

183.00

.20

.00

.20

801
802

Unit Rig 85 Ton Ed Tk
Dart 120 Ton End D\lU1p

814.00
164,00

2.37
.54

33.00
.00

2.47
.54

29.00
976.00

3.63
.50

,00
,DO

3.63
.50

150
154

157
158

APPR.

805

343.00
301.00
Dart 150 Ton End Dump
8.00
80T T~rex. E. D. Truck 196].00
120 T Lectra Haul
1031.00

206.50

,20

806

Euclid 50 T ED Truck

1212.00

1213.25

,92

807
809

Unit Rig lOOT ED Trk
Unit Rig lOOT ED Trk

1152.00
2297.00

2008.00
1155.00

1.74
.50

.00
.00

1.74
.50

810

Euclid lOOT End Dump

975.00

177.50

.18

.00

.18

815

Austin West Grader

26.00

13.00

.50

.00

.50

820
822

Mich 275A RT Loader
Mich 280 Dozer

1204.00
44.00

221.50
4.00

.18
.09

.00

.18

.00

.09

824

Cat R.T. Dozeu

854.00

278.00

.33

.00

• J3

83l

Cat 834 RT Dozer
90't Euclids 1970
90 Ton Dart; SD Truck
90 Ton Buc SD Truck

160. 00
981.00
684.00
726.00

52.00
1380.75
567.25
884.75

.33
l.41
.83
1.22

.00
.00
.00

1.41

1975 Darr. 90 Ton SO
90 Ton Euc SD Truck

7399.00
16.00

3055.75
120,50

.41
7.53

90 Ton Trailer
Oxygen Tractors
Water Sprinkler Trks
Fuel Tru(,'.ks

9806.00
864.00

,08
1.60

1224.00
844.00

823,75
1378.50
364.50
656.50
19151.15

a03
804

870
871
872
873

874
869
881

883
884
Totals

45235.00

Total Repair Hours

18190.2:5

Total Labor Hours

22699.00

Percent Repah Hours to Labor

.00

.00
8.00
.00

.20

.92

.33

.83
1. 22
.41
7.53

.30
.78

.00
.00
.00
.00

.08
1.60
.30
.78

.42

41.00

.42

.80

Hours

Fig. 6. Automotive mechanic, repair hour I operating hour.

TOrAL
OPER
!!!~LDES~l'.

1)0
i54

C.. 1.. D9 Crawler Dozt:r

157
15S

Coat 988 RT Load~rs
CAt Road Graders
Cat DS C/:'aw1er DOzer

163

Cat 824 R Tire Oozer

H()Ul~S

RATED
l!ill!!~

1366.00
4492.00
273.00

205.00
306.00
3.0n

.15
.07

.00
.00

.01

.00

2832.00
1127.00

71.00

103.00

.03
.09

926.00

51.50

.06

.00
.00

91. 50
23.00

.27
.08
.25

17.50
.00
.00

.32

2,50

.05

.00

.02

.00

.15
.07
.01

.03
.09
.06

164
801
802

Cat 98B 7yd Loa.der
Unit Rig 85 Ton Ed Tk
Dart 120 Ton End D\,lmp

803
804

Dart 150 Ton End Dump

343.00
30LOO
8.00

eOT Terex E. D. Trul;k

1967.00

90.50

805

120 T Lectra Haul

1031.00

16.00

.05
.02

80.

Euclid 50 T ED Truck

1313.00

258.00

.20

3.00

.20

807
809

Unit Rig lOOT EO Trk
Unit Rig 1001' En Trk

1152.00
1197.00

549,75
186.00

.48

8.00

.48

.08

.00

.08

810

Euclid lOOT End Dump

975.00

42.00

.04

.00

.04

815

Austin West Gra.der

820
822

Mich 275A ttT Loader

824
831
870
871

Cat R.T. Dozers
Cat 834 RT Dozer
90T Euclid1j 1970
90 Ton Dart SD Truck
90 Ton Euc SD Truck

Mich 280 Dozer

2.00

.08
.25

26.00

3.00

.12

.00

.12

1204,00
44.00

45,00
2.00

.04
.05

.00
.00

.04
.05

854.00
160.00
981.00
684.00
726.00

33.25
1.00
158.50
52.00
49,50

.04
.01

.00
.00

.04

.16

3.50

.08

.00

.01
.17
.08

.07

,DO

.07

15.00
.00

.04
.19
.10

872
873
874

1975 D<lrt 90 Ton SD
90 Ton Euc SD Truck

7399.00
16.00

280,00
3.00

869
881

90 Ton Trailer

9806.00

970.25

.04
.19
.10

O;~ygen

864.00

127.00

.15

.00

883
884

Water Sprinkler Trks
Fuel Trucks

1224.00
B44.00

53.75
44.00

.04

.00

.05

.00

.15
.04
.05

45235.003820.50

.08

51.50

.09

Tracto"t"$

Totills
Total Repair HOurs

3756.75

Total Laber Hours

12360.50

Pc<rccnt Repuir: Hours to

2.no

.30

fig. 7. Welder, repair hour / operating hour.

926

SURFACE MINING

tonnages or yardage that can be translated into truck operating hours. If there is a mix of sizes and kinds of trucks,
the production requirements would be assigned first to the
fleet with the highest availability, or greatest possible use,
then to the next fleet with the second highest availability,
and so on until the production requirements are met.
The fleet operating hours are then multiplied by the repair
hour per operating hour statistic for that fleet. Each fleet
will then generate the repair hours required to produce the
operating hours assigned to it. The total of all the fleets
would then represent the total repair hours (in this case,
automotive diesel mechanics; see Fig. 8) needed under this
operating plan. The same approach can be used for welders,
shovel, and drill mechanics. In the case of a shop which
services a number of mobile equipment shops, such as a
machine shop, the repair hours needed would be the sum of
the hours generated by multiplying the machinist's repair
hour per operating hour for shovels, drills, trucks, etc. by
the operating hours of that equipment.
These repair hours are then divided by a statistic that is
the percent of the labor hours of a shop that historically has
been expended on the equipment in the mining plan. For a
truck shop, approximately 80% of the labor hours of the
shop are expended on the equipment maintained by the shop.
(The computer can easily produce this figure along with the
repair hour per operating hour.) The remaining 20% is expended on project work, safety meetings, shop tools, and
unmeasured equipment.
The repair hour-total now represents the needed total to
meet the plan, including labor hours for construction, equipment modifications, safety meetings, etc.
To this total must be added absentee hours and vacation
obligation.
Summary
During times of economic uncertainty, the production
requirements may fluctuate greatly. It is imperative that the
maintenance organization have a reliable tool to predict manpower needs. The repair hour per operating hour method
provides such a tool (Fig. 9). It is reliable, dynamic, and
flexible. As productivity improves, the repair hour per op-

REP.liR/
OP/HR

EgUIP. DESCRIPTION

12
21
10
14
8
1
1

Crawlt!r Tractors

Rubber Tired Dozers
Front End Loaders
Graders

Mobile Cranes
85T Unit Rig E, D.
120T Dart E. D.

.31

.25
.52
.17
.64
.60
.65
.80
.62
.45
.50
.94
.45
.30
.60

150T Dart E. D.
85'1' Terex E. D.
120r Unit Rig E. D.
RSO Euclid E. D.
lOOT Unit Rig E, D. (Old)

2
5
9
6

i~~ii~ni~o~i~n~' D~O (New)

1
11

Euclid Side Dump Tractors (Old)
Dart Side Dump Tractors (Old)
Euclid Side 'Dump Tractors (New)
Dart Side Dump Tractors (NeW)
Ore Haulage Trailers
Oxygen/Water/Fuel trucks

.55

7
4
22
41
22

.49
.28
.06
.38

OP/HR

REP/HRS OP/HR REP/HR

217

720

380

1640

880

245
160
189
335

800
100
800
600
400
2320
4120
1240

224
410
146
184
26
48
52
64
155
81
250
207
360
30
480
330
196
650
248
472

12900

3915

15530

4613

700
1520
180
840
40
100
100
100
300
200
500
240
800
100
400
250
500
2000
3150

143
26
60
65
80
186
90
250
226
360
30
240

138

280
1080
40
80
80
80
250
180
500

220

Total Repair Hrs/Week

•

Repair Hour$ divided by .19
Abeentee % is 6.1
Total Hours Required
5259 divided by 40
Vacation Replacements Required
total Mechanics Required
Present FOrce
Additional Mechanics Required

3915

•

4956

303
5259
132
15

Total Repair Hrs/Week
"" 4613
Repair Hout'S divided by .79'" 5840
Absentee % is 6.1
"'- 357
Total Hours Required
... 6197
6197 divided by 40
z
155
Vacation Replacement Req'd.,
15
Total Mechanics ReQuired
170
Present F o r c e ·
lS 7
Additional Mechanics req'd ""
13

14)

157
-10

1. Repai"{" Hour/Operating l-lours X Operating HOl).rs "" Repair Hours
2, Percentage of 'rotal Department Hours charged to above Mobile Equipment"'79%
3. Operating Hour~ Obtained from Mine Department Equipment Requirements.
Die~H:l

4. Repair Hours are Automotive

Mech<lnic Hours.

Fig. 8. Automotive maintenance manpower requirements.

erating hour reflects the improvements, reducing the statistic.
As the equipment gets older, the statistic increases (see Fig.
10). Best of all, the logic of the approach is appealing to
mine and plant management, eliminating the usual adversary
posture toward maintenance manpower.
EQUIPMENT AND COMPONENT HISTORIES

Equipment and component records are essential to a
maintenance organization. Records dictate the preventive
maintenance program, control component replacement, in-

1,75

1,5

TEREX-85 TON
EUCLID-50 TON
UNIT RIG-Iaa TON
DART-I 10 TON
EUCLID-50 TON
UNIT RIG-10a TON

E
P

I
R
H

1.25

Fig. 9. Repair hour I operating hour for end
dump trucks.

R
S
/

o
P

0.76

E
R
H
R

0.5

0.25

4121

OPERATING HOURS! la00 HOURS

MINE OPERATIONS

927

0.8

R
E
p
A

13.7

0.6

R
H

0.5

0
U

R
5

0.4

Fig. 10. Repair hour I operating hour for side
dump trucks.

0
P

0.3

R
H

DART-NEil
EUCLID-NEil
DART-OLD
EUCLID-OLD
EUCLID-OLDEST

0.2

R
S
0.1

OPERATING HOURS

25
I

1000 HOURS

dicate the need for remedial investigation, and provide documented evidence for equipment replacement. Records can
also be used to project major overhauls and thus maintenance
budgets.
Good equipment and component histories can be maintained manually, but a manual system requires a prodigious
amount of clerical time. The computer can eliminate that
problem. With an appropriate software program, the computer is eminently qualified to perform record keeping with
little or no paperwork.
The kind of information required will vary with the kind
of equipment. The following data would be typical for mobile
equipment, in this case, off-highway haulage trucks:
1) Unit number
2) Model and serial number
3) Basic specification: engine, transmission, wheel motors,
etc.
4) Date in service
5) Total operating hours
6) Components
a) Engine serial number, previous rebuilder
1) Operating hours since last change
2) Date of last change
3) Serial numbers of previous engines in sequence
b) Transmission serial number, previous rebuilder
1) Operating hours since last change
2) Date of last change
3) Serial number of previous transmissions in sequence
c) Wheel motors
1) Operating hours since last change
2) Date of last change
3) Serial number of previous wheel motors in sequence
d) Generator
1) Operating hours since last change
2) Date of last change
3) Serial number of previous generators in sequence
e) Differential
1) Operating hours since last change
2) Date of last change

Drivelines, front, rear, interaxle
1) Operating hours since last change
2) Date of last change
g) Brakes, front, rear
I) Operating hours since last change
2) Date of last change
3) Standard or XX drums by location
h) Hydraulic system, pump, left and right hoist cylinder
control valve, kickover valve, flow control valve
1) Operating hours since last change
2) Date of last change
i) Radiator
1) Operating hours since last change
2) Date of last change
j) Steering system, pump
1) Operating hours since last change
2) Date of last change
k) Suspension, left front, right front, left rear, right rear
I) Operating hours since last change
2) Date of last change
I) Front axle, left and right: king pins, spindle, inner
and outer wheel bearings
1) Operating hours since last change
2) Date of last change
m) Rear axle, left and right: spindle, wheel bearings,
planetaries, bull gear, axle shaft
1) Operating hours since last change
2) Date of last change
n) Dump body
1) Operating hours since last change
2) Date of last change
Component changes are entered into the program on a
daily basis. With this information, a glance at the CRT will
give the current status of any truck.
Individual component histories are important to determine trends, predict overhauls, and to find the problem areas.
Typical component records for trucks would include the
engine and transmission histories, as shown in Figs. 11 and
12. Other components such as wheel motors, generators, final
drives, etc. can be handled in a similar manner.
Basic equipment histories for plant equipment have been
f)

928

SURFACE MINING

~el

Serial Number

l1orsepower

Number

In Unit

Operating hours _ _ _ _ __

Date in$talled _ _ _ _ _ _~

Total hours in service _ _ __

Repa.ir IHstofY

mJm~r

_ _ _ _ _ _ __

Fleet OVerhaul Ave. Hrs.

Ntmlber of Overhauls _ _ _~
Average HI's. at Overhaul _ _

Date removed_ _~Oper. Hrs, _ _ _Cause of Failure _ _ _~
Overhaul W.O.# _ _~Reinstalled in Unit # _ _~Spe.re _ _ __

Total Cost This Repair_ _ _ _~'COst per HQur _ _ _ _ _~

Fig. 11. Engine component history.

put into a computer program by Kennecott (now BP Minerals America) using their MAP or Maintenance Assist Program. This program integrates a parts catalog cross-reference
catalog, equipment spare parts, work order system, equipment specifications, preventive maintenance, and equipment
histories into an integrated matrix.
Summary
Equipment and component histories are vital to a maintenance operation. By keeping track of equipment and component life and cost, the outputs will show which brands of
equipment and components give best value. With this information the maintenance personnel may make the kind of
decision that is required to keep the mining cost low. They
can be maintained manually, but the manipulation of data
is well suited to a computer program. The advantages of
computer programs are many: saving clerical time, ease of
input, ease of access, ability to recall information in different
formats, and timeliness of information.

PREVENTIVE MAINTENANCE
Preventive maintenance (PM) is the predetermined inspection and subsequent repair of equipment and facilities
to maintain high performance, prevent premature failure,
and extend life.
Cleaning, inspecting, testing, adjusting, and lubricating
are all functions of preventive maintenance.
TRANSMISSION
Model Number

In Unit

ASHY. Number

HISTORY

Serial Number

number~_~._

Operating hours

Date installed

Total hours in

Repair history

fleet OVerhaul Hours
Number of OVer-ha.uls
service_~

Ave. hours at overhaul _ _ _ __

Date removed _ _ _Oper. Hours _ _._Cause of Failure, _ _
Overhaul W.O. # _ _Reinstal1ed

Unit # _ _~Spa.re. ____

Total Cost This Repair _ _ _ _ _'Cost per Hour _ _ _ __

Fig. 12. Transmission component history.

The key to establishing an effective PM program is record
keeping (see "Equipment and Component Histories"). With
adequate records of equipment and component failures, frequency of inspections can be determined. Too frequent is a
waste of equipment time and manpower; not frequent enough
will defeat the program.
Advantages
Some of the advantages and rewards of a successful preventive maintenance program are:
l. Safety-well-maintained equipment is safe equipment.
Safety features such as guards, brakes, horns, alarms, etc.,
provide the reliability to protect the operator as well as the
equipment.
2. Cost-the aim of a good preventive maintenance program is to repair small problems to prevent catastrophic
failures, or "for the want of a nail, the shoe was lost ... "
approach to maintenance. After initial installation, preventive maintenance can reduce labor costs as much as 15%
with a corresponding reduction of parts costs.
3. Availability-nothing is as frustrating to operations as
unscheduled downtime of equipment. Preventive maintenance provides for an orderly inspection of equipment, resulting in timely scheduled repairs, thus minimizing failures
in operation. Except for safety items, it is possible to defer
repairs determined by inspection until a more propitious
time, when manpower can be scheduled or the equipment
can be released. This is particularly important in plants where
down days are scheduled. Availability as a quantitative measure

Total hours ~ downtime hours
Total hours
can be increased as much as 20%. The value of this improvement can be easily measured by the cost of the units
and operators not required to produce the required tonnages.
4. Planned vs. Emergency-planned and scheduled work
is done on straight-time hours. Emergency work is often
overtime work. Preventive maintenance reduces emergency
work, hence the need for overtime.
5. Productivity-unscheduled downtime interrupts production and causes inefficiencies in the operation. PM will
reduce unscheduled downtime and increase productivity.
Further, equipment that is well maintained, adjusted, and
lubricated will operate at peak efficiency, thus improving
productivity. Operator acceptance alone will improve performance when there is confidence in and satisfaction with
well-maintained equipment.
6. Equipment Life-a good PM program will extend the
productive economic life of equipment.
Designing the System
The first step in designing a preventive maintenance program is to define the frequency of inspections. This can best
be determined from records of equipment or component failures. Probably the best measurement is operating hours, although calendar time, tons, miles, and even gallons of fuel
burned are sometimes used. Each basic kind of equipment
may require a different frequency of inspection.
The checklist or PM form provides a guide for the inspector. It is a quantitative judgment of the equipment being
inspected, and a directive to planning supervision as to what
repairs are necessary. Inspections on the same equipment
may have different degrees of inspection to be performed.
For example, an off-highway truck may have a 100, a 500,
and a 2000 hr inspection form, each varying as to the depth

929

MINE OPERATIONS
of the inspection. Calendar-time inspections work well if
operating levels are constant, but can cause problems when
mine plans fluctuate. The use of calendar time leads to a
tendency to overinspect during periods of low operations and
underinspect when operations are at a higher level.
When devising checklists, equipment manufacturers, vendors, and lubrication suppliers can be most helpful. A word
of caution: Equipment manufacturers and lubrication specialists generally have a tendency to "guild the lily," suggesting overinspection, so take their advice and adjust to suit
(see typical mobile equipment checklists: Figs. 13, 14, and
15).
Structuring the Preventive Maintenance

Because preventive maintenance includes servicing, the
program should include two levels of skills. The serviceman
or oiler can be very helpful in providing information, but
the actual inspection should be performed by a craftsman.
Ideally, these two skills would work together.
There are two schools of thought on the craftsman selected to perform PM inspections.
I) PM inspections are considered an integral part of the
workload, and assignment of the inspections is made to any
qualified craftsman from the daily pool not committed to
other work.
2) The PM inspections are assigned to specific individuals in the craft group who have an interest in and are trained
for PM inspections.
Both approaches can be successful. However, in a large
operation the problem of training a large workforce suggests
selecting and training those craftsmen needed who have an
interest in PM. Many good craftsmen make poor inspectors
if their driving interest is in normal trade work. Some craftsmen will overinspect or underinspect. The PM inspector must

_"'_GOOD REPAIR

_X_REPAIRED

_O_TO BE REPAIRED

~Nor

APPLICABLE INSPECTED 8Y _ _ _ _ _ __
FOO£MAN _ _ _ _ _ _ _ __

Fig. 14. For diesel trucks, 2000-hr preventive maintenance inspection.

UNIT NO,
DATE _ _ _ _ _

!;'tHT NO, _ _ _ __
W. 0,

r>O,

1.
2.
3.
4.
5.

2.
J.
4
5.
6
7.
8

1.
2.

ELECTRICAL SYSTEM

Lights

SwitchtlS

Alternator (., MOunting
Batteries & Cables
Windshield Wipers
Other

1.
2.

9.
10.

11.

1.
2.
3.

6.
7.

H.
1.

2.
3.

4.
S.
6

1.
1.

2.
3.

1.
2.
3.
4.
5.
6.
7.
8.
9.

C.
1.
2.
3

12.
3.
4.

n.
1
2,
3.
:.

--10.
11.

12.

AXLES

IITTr. Hsg. Mounting Bolts

Drive1ines (. Flanges
lfueel Brglil. 6; Seals
Steering Trunnions &

1.
7.

1.
7.
3.
4.

3.
4.
5.

5.
6.
Test

l
2.

5.
6.

_X~REPi\IR.ED

--L-GOOD REPAIR
_O_TO

_ ,_REPAIRED

BEREPAiRED~NOT

Fig. 13. For diesel trucks, lOO-hr preventive maintenance inspection.

APPLICABLE

DATE _ _ _ _ _ _ _ _ __
INSPECTED BY _ _ _ _ _ _ __

f'ORE~iAr;

Fig. 15. For dozer-loader-grader, lOOO-hr preventive maintenance inspection.

930

SURFACE MINING

be able to distinguish between worn and worn out. It is much
simpler to train a select group to apply predetermined reasonable standards of performance.
Scheduling Preventive Maintenance
Once the program has been designed, the problem of
scheduling becomes paramount. Records for each piece of
equipment must be maintained, correlating inspection with
operating hours, tons, or whatever appropriate measure is
used. This can be done manually, but is a natural for the
computer. Programs can be designed to list each piece of
equipment, hours since last inspection, those which are due
for inspection, and any other pertinent data required, such
as filter sizes, part numbers, oil quantities, coolant, and gear
lube capacities, etc. Hard copies can be produced from onsite printers, which in effect become schedules. Operating
hours and completed inspections are the input. The program
can produce summaries of fleet or section PM performance,
labor expended, etc., to provide maintenance management
with a measure of the overall PM program.
Introducing the Program
It is essential that a preventive maintenance program, or
any other maintenance system, have not only the blessing of
management, but its whole-hearted support. The advantages
must be cogently presented, with realistic quantitative cost
benefits outlined.
Once this support is obtained, it is equally essential to
consult with the operating superintendents. They must be
convinced that the program is to their advantage. They
should be involved in the decision process as to what equipment should be inspected, the frequency of inspection, and
what flexibility is allowable to maintain production. With
their cooperation, the program can be successful; without it,
the PM program becomes only a maintenance problem, rife
with maintenance vs. operating confrontations.

WAREHOUSE COMPUTER-AIDED PARTS
REQUISITIONING AND DELIVERY SYSTEM
A maintenance program is only as good as its skilled
craftsmen and supervisory organization. But a corollary to
that is: a good maintenance program is only as effective as
the availability of parts.
Generally, in most mining operations, maintenance determines the kind and quantity of parts required (maximumminimums, or order points, order quantities), but is not
directly responsible for the warehouse function. Cooperation
between these two responsibilities is essential to the health
of any maintenance organization and to assure obsolete parts
do not build up in the warehouse.
The usual arrangement is to have a central warehouse or
a central warehouse with satellite warehouses throughout the
mine and plant to supply operations and maintenance. Withdrawal cards signed by supervisors are presented to the warehouse counter by craftsmen or service truck drivers for parts.
Part numbers are obtained by supervision or the craftsmen
from equipment parts manuals, with or without superceding
part numbers or cross-referencing. The warehouse usually
supplies a parts location reference which mayor may not be
obsolete. The cards would be punched for computer processing or would be manually sorted to provide inventory
control and cost data.
This standard scenario satisfies only the function of warehousing and inventory controL Maintenance suffers from
the many inefficiences built into it.
I) Craftsmen travel to and from their place of work to
obtain parts. Queuing at the warehouse is common. Work

sampling suggests that 15% of a craftsman's time is wasted
obtaining parts (see "Work Sampling").
2) Supervision will spend from 25% to 40% of their
time looking up part numbers in parts books, checking superceding numbers, or trying to cross-reference parts.
3) Parts that are normally in the warehouse may be outof-stock. The craftsmen make the trip and come back emptyhanded.
It has long been the maintenance manager's dream to
have a complete up-to-date catalog of parts at supervision's
fingertips, to be able to order parts remote from the warehouse, and to have those parts delivered to the job site. With
the advent of the computer with remote cathode ray tube
(CRT) audio-video display units, the dream has become a
reality.
The first step requires the cataloging of every part in the
warehouse. Parts are entered into the computer program by
fleet and cost center, by all known part numbers including
cross-referencing to other equipment, and by description of
part and warehouse location. The catalog information appears as a screen on the CRT as shown by the inventory
control main menu, Fig. 16 and detail screens, Fig. 17.
With this program, information screens may be called
up by part number, description, location, equipment number,
or cost center to determine if the desired part or parts are
available in the warehouse. If they are available, the ordering
screen, Fig. 18 is called up and up to seven separate orders
can be placed. After entering the appropriate data (see instruction screen, Fig. 19), the order key is depressed on the
CRT (Fig. 20), and a printer in the warehouse prints out a
three-part order, Fig. 21. A hard-copy printout can also be
obtained from the shop printer. The warehouseman puts up
the order and, depending on location for delivery and size
of order, delivers to the designated location by electric truck
[O.4t (0.5 st) golf cart], forklift, or pickup delivery truck,
Fig. 22. One part of the order form is retained by the warehouse. The other two parts are signed by the receiving responsibility, with one part returned to the warehouse as
evidence of receipt. Warehouse inventories are adjusted daily
to account for material received and disbursed. Cost accounting information is distributed to the proper accounts.

RESTRICTIONS

Order Parts From Warehouse

Ordering Parts General Info
Order File Procedures

None

Stores & Acctg. Only
None

PF4

Catalog File Brows€':

PFS

Class and Location Inquiry

None.

PF6

Part Number Or Desc. Browse

None

PF7

Class and Location Browse

None

PF8

Complete Description Browse

None

Receiv Items rnto Stock
Employee No.

Stores Dept. Only

The number will not display as you
are keying it.

- - - - .. -- - - Ins truet ions - - - - - - - - -1.

Key in the code or hit tne appropriate PF key that you desire.

If a code 1 is selected, key employee number also.

For

codes 1. 2, 3, 9 hit the enter key.

Fig. 16. Inventory control main menu on the CRT screen.

MINE OPERATIONS
DtRECT ORDERING OF PARTS GENERAL INFORMATION SCREEN

CATALOG FILE BROWSE

KEY CST-UNT-FAC-COM

1)5

Pad, Cushioning-End

17892

11-019201

7 e.

25.88

Here are some things to reme:mber when ordering parts from the Warehouse.

1. Use the inquiry screens to find the items you wish to order.

135

Ring,Rub

948022

11-019432

3 eo

55.75

135

Screw,Cap 1/2X2-1/2

10033

11-319482

8 eo

. 20

135

Screw,Cap 5/8Xl-l/2

17877

11- 218472

1)5

Seal

16949

11-019472

1.00

2 ea

41. 25

135

Seal ,Oil Frt Wh@el

53X3646. Garlock

11-019424

6 e.

48.60

1)5

Stud,l X 4 -1 /2 Front

947898

13-116384

24 e a

4.75

26389,71796A

11-019683

Washer, thrust Fr t Wh
Euclid lOOT End Dump

description of each item you wish to order .
2. If you do not need /:lny inquiries to order any items you can proceed
directly to the order screen and ke:y in the items.
3. When filling in the cost coding on the items you wish to order , be

137

Belt

4042188

63-011802

3 ea

177 .93

137

Bolt,Brake Va lve

0179839

63-029212

2 ea

.04

very careful that you key it in properly.
505 RI00 Euclid

I f you do not key any

coding in for an item, it is assumed to be the same as the previous

100 Cooling System

item,

--------------- It.ems To Be Ordered---------l. To see next group, hit enter.
QTY

Key

c:he class and location, quantity, unit of measure and a brief

49.25

135
810

CL &: LOC

931

U/M

BRIEf DESe

2. To backup

page I hit PF9. If

4. When entering t he quantity, remember to key in the leading 7.eros i f
you are ordering le:ss than 10000.
5, One important thing must be remembered.

No error checking is

being done fo r you on any thing that you key in.

If what you key

00000

you backup. use PFlO to go

in is not correct, your order will not be processed properly.

00000

forward .

in order to insure that your order is filled be sure to double

00000

3. For another browse key in
CST-UNT-FAC-COM and hit the
PF4 Key

So,

check your order thoroughly before sending it to the Warehouse .
6. If you only have a 4 digit employee number. be sure to preceed it
with a zero when keying it in.

PFl-ORD FORl"

4. PF5 - CLS/LOC

PF6 - PT NO BROWSE PFl2-ABORT

7, Whenever using the PF k eys you must hold down the alter key at the
same time.

PF7 - CLS/LOC BROWSE

prs -

-·----------·---HIT THE ENTER KEY TO RETRUN TO THE MAIN MENU-- - ----- -- COMP DESC BROWSE

Fig. 17. Catalog file browse on the CRT screen.

Fig. 19. General information for direct ordering of parts on the
CRT screen.

The delivery system can be set up on a regular timedelivery schedule. However, the ideal is delivery on demand.
In a central-shop complex experience has shown that in
excess of 100 deliveries a shift are possible using the demand
system. Distances to receiving areas would be the determining factor.
The inventory can be adjusted as each transaction occurs
providing current inventory status. The transactions can also
be held and the adjustments batched every 24 hr. The real
time approach is best for maintenance. The batching method
provides better inventory control. Parts receiving by the
warehouse also becomes a part of the overall program.

Fig. 20. Ordering parts on a CRT in the planning office.
STORES MATERIAL WITHDRAWAL

ORDER NO.
0859203
DATE

CHARGE TO BE USED ON:

06/30/82

DELIVERY POINT
COUNTERMAN NO

ORDERED BY HAUSCHILD MARK H

RECEIVED BY
CST

UNT

FAe

\.1-0

CL & LaC

QTY

U/H

8RIEF
DESCRIPTION

QUANTITY
DELIVERED

00000
00000
00000
00000
00000
00000
00000
-- ------ --- -I NST RUCT IONS- -------- - ----FOLLOW EXACTLY AS STATED--- -----.---

Add cha r g e to be used on (. delivery point to order.
coding to order.

Sight verify complete order.

Add all cost

Hit PFl again to

tr ansmi t to Warehous e.
If you wish to return to inquiries (not order ye:t) hit the PF2 key .

Fig. 18. Stores material withdrawal on the CRT screen.

Fig. 21. Receiving the order in the warehouse.

932

SURFACE MINING

Fig. 22. Delivering the order.

Summary

The time lost procuring parts has a three-pronged effect;
time lost by craftsmen obtaining the parts, the supervisor's
time searching for part numbers, and the delay in completing
the job itself. The computer·aided parts-requisitioning and
delivery system will reduce labor by 15%, will reduce the
time to perform the work a similar amount, and will give
the foreman more time to supervise.
WORK-ORDER SYSTEM-PLANNING AND
SCHEDULING

The most effective tool maintenance can have for the
control of parts and labor is a functioning work·order planning and scheduling system.
An effective work-order system precedes planning and
scheduling. The maintenance work order is an authorized
document to perform a maintenance function or an improvement to equipment. Plant engineering work orders would be
nonroutine capital or expensed work, such as construction,
remodeling, or work entailing major expenditures and requiring detailed drawings. Both types of work orders can use
the same format and procedures for handling.
Much has been written on the forms and procedures for
a work-order planning and scheduling program. This section
will detail in outline form one approach to the problem,
utilizing the computer and CRTs instead of paper forms.
The advantages of a work-order planning and scheduling
system are:
I) It provides preparation and planning to insure the
effective use of labor and materials. With proper planning
there are no surprises. Jobs are not started, then stopped for
lack of materials. Work is scheduled and personnel are dedicated to the task. Planned and scheduled work is from 5%
to 15% lower in cost.
2) It reduces downtime. Work is not interrupted. Crises
do not develop. Equipment is returned to operations as scheduled.
3) Priorities are established. Essential work is done first.
Each ordering responsibility knows when his work will be
done. Flexibility of the system allows for changes as priority
changes occur.
4) Supervision is relieved of details and expediting. Supervisors can depend on the system for detail planning, allowing them to function as supervisors.
These advantages of the basic system are much enhanced
by utilizing the computer and CRTs to provide the memory
filing, the work-order request, and the timely cost accounting.
The computer can provide 48-hr cost data using the batch

method. If programmed for on-line data update, the cost
information can be available on a shift basis. The cost information is intended to provide maintenance with the means
to quickly evaluate progress of a project against current
expenditures of labor and materials. Timely information can
be used to correct problems before they become serious.
The system as outlined in the following distinguishes
between the traditional work order for a fabricating shop,
machine shop, pipe shop, etc., where there is generally discretionary time for planning and scheduling, as opposed to
mobile-equipment shops, such as truck shops, shovel repair,
drill repair, etc., where work is generated by preventive maintenance and breakdowns and is repetitive in nature.
In the traditional shops, work can be repetitive, but oftentimes it is unique, one-shot type of work requiring detailed
step-by-step planning. The planning often requires more than
one craft. The Work-order planning form (screen) allows
for step planning and subsequent accounting so that estimates
for each step can be compared against the actual.
The Mobile equipment shop work order would be processed in the same manner as the traditional work order, but
because the work is repetitive, the work has been preplanned,
defining work procedures, safety hazards, and parts lists (as
outlined under "Mobile Equipment Work Order Request") .
The intention of preplanned jobs is to provide the one best
approach to the job and to expedite parts ordering (see
"Warehouse Computer-Aided Parts-Requisitioning and Delivery"). In this case, each job will use the same five-digit
work-order number but will have a sequential suffix number
to identify each time the job is done. The program is designed
to give the labor and material for each job performance, with
an average of all previous jobs, thus providing an historical
standard.
WORK SAMPLING

Mine and plant management are most happy with direct
measurement of performance. A shovel produces so many
tons per hour; a truck hauls so many ton-miles per hour; a
drill produces so many feet per hour; and the total work
force produces so many tons per man-day. Maintenance cost
per productive unit based on labor and supply costs if reported on a month-by-month basis shown for a 12-month
rolling period shows trends and anomalies that are important
to management and that should be explained where they
deviate from a normal or predictable pattern. But maintenance defies such direct standard measurements. The need
for measurement is not just to satisfy management, but also
to provide a tool to examine problem areas and to measure
the effect of change. The simplest, most reliable, and least
expensive measurement is provided by the technique of work
sampling.
Theory of Work Sampling

Work sampling is a statistical-measurement technique
which observes and records an activity at a point in time.
Based on the laws of probability and the binomial distribution
curve, work sampling states that the percentage of observations of an activity reflects to a known degree the average
percent of time spent on that activity. Work sampling can
be applied to any nonrepetitive activity, such as machine
operation or product quality, but as applied to maintenance,
it is basically concerned with human activity.
Activities to be Measured

The basic human activities of maintenance are ( 1) work,
(2) travel, and (3) idle. These activities are often modified
to include preparation, a necessity in any maintenance work,

MINE OPERATIONS

933

and cleanup. Depending on circumstances, other activities
may be added to further pinpoint problems.

compromise between subjective observation and continuous
certain time studies.

Confidence Level
Reliability of work sampling is dependent on random
observation and on a sufficient number of observations. Randomness is achieved by selecting the time of observation by
random numbers or by throwing a die, and by varying the
observer's route randomly.
The estimated number of observations required can be
calculated after making some assumptions. A 95% confidence level with +5% tolerance limit is generally acceptable.
The given activity, say work, is then estimated. The formula
is then:

The advent of the microprocessor coupled with a computer can provide maintenance management with a means
to diagnose the condition of engines, transmissions, hydraulic
systems, or other componentry, quickly and surely. With
appropriate sensing devices signaling the microprocessor (or
directly to the computer), abnormal values are detected.
There are two approaches to providing the data to the
computer: the static system and the dynamic warning and
diagnostic system.

4(1 - P)

E'P
where N is the required number of observations, P is the
percent of time activity occurs, and E is the element tolerance
of error.
If we assume a craftsman's work activity at 60%, + 5%
element tolerance, we have:
4(1 - P)

E'P

4(1 - 0.60)
(0.05)' 0.60

1.6
0.0015

1067

This means that 1067 observations would have to be made
to achieve a 95% confidence level with + 5% error.

Observers
An ongoing work sampling program would normally be
conducted by the industrial engineering department. Their
technicians would be the observers and would produce the
reports. There is an advantage to this arrangement in that
the observer would be unbiased and trained as an observer.
However, using supervisors as observers has the advantage
of imprinting the skill of objective observation on them that
they will consciously or unconsciously use from that time
forward.
Using the Data
Work sampling does not of itself provide answers, but it
can point out problem areas requiring methods improvement.
When changes are made, working sampling can measure the
effect of that change.
The following is a comparison of typical work-sampling
results:
%
%
%
%
%

Work
Travel
Idle
Preparation
Cleanup

A
41.5
16.3
27.5
12.1
2.5

B
58.5
9.6
24.4
6.4
1.1

The initial study A indicated that travel was high and
preparation was high, adversely affecting the work activity.
A warehouse computer-aided parts-requisitioning and delivery system was installed. The results are shown in study B.
The idle remains high, indicating further efforts are needed.
It is not uncommon for first-time work sampling to reveal
a 35 to 40% work activity. The shock to the maintenance
management can produce amazing improvements. As
method improvements are applied to trouble areas, the work
activity will increase from 10 to 20%.
Work sampling is a tool to be used in conjunction with
other management tools. It is not a panacea. It is a happy

COMPUTER-AIDED DIAGNOSTICS

Static System
Hamilton Testing, Inc. has developed a static system for
checking the condition of bus components and for component
fault diagnoses. Pressure sensing transducers are external
with a multiport disconnect to the bus. On-board sensors are
brought to an electronic circuit box and interfaced with a
computer device. Various tests have been programmed to
provide high and low limits and actual test values. Unacceptable values are indicated on a printout with an asterisk.
This system has not as yet been developed for off-highway
mining equipment, although work is in progress.
The objection to this approach is that it does not measure
the values under actual operating conditions. Too often problems that show up under operating conditions cannot be
duplicated under no-load conditions in the shop. The main
advantage is that all of the pressure-related sensors are separate from the unit, resulting in lower cost per unit and
possibly greater reliability.
Dynamic Warning and Diagnostic System
A large taconite mining company and a communications
manufacturing company have designed an automated MineManagement System. The main purpose is to utilize computer software to optimize mine output and truck utilization
while minimizing operating costs. Incorporated into the system is a microcomputer on-board each unit with appropriate
sensors. These sensors signal on an exception basis, directed
toward preventing catastrophic failures, or to signal a trend
toward upper Ilower limits. The signal would be sent to the
sensor processor (microprocessor) and transmitted through
a radio signal to the main computer and CRT display for
appropriate action. The functions to be monitored are:
I) Engine speed
analog
2) Oil pressure
analog
3) Coolant temperature
analog
4) Transmission temperature
analog
5) Crankcase pressure (high)
binary
6) Coolant level (low)
binary
7) Oil level (low)
binary
8) Air restriction (high)
binary
9) Vehicle motion
binary
This system will be polled by the computer every 20
seconds to provide protection from catastrophic failures.
For diagnostic work, a .. piggyback" microprocessor will
be required. This will provide for additional functions to be
measured and integrated against engine speed. For example,
sensors will measure air restrictions after the air cleaner,
ahead of the blower, and in the air box, thus pinpointing
any air induction problems. The second microprocessor will
also signal through the sensor processor whenever abnormal
conditions occur. The piggyback processor will have a nonvolatile memory and will be polled by the main computer.

934

SURFACE MINING

The epitome of a dynamic system would be to have a
software program that would take each troubleshooting problem through a step-by-step examination of the data until the
cause is located. This concept is not too far from reality.
Other Systems
Cummins Engine Co. has developed a static system for
engine diagnosis called Compuchek. Because of the unique
nature of their fuel pump, they feel the system very closely
simulates actual operation.
Summary
On-board diagnostics for trucks will be a reality. With
nonvolatile memory and an appropriate interface, any maintenance department with access to a computer could use the
system. With troubleshooting programs, diagnosing problems can be performed by technicians with "best mechanic"
results.

REFERENCES
Anon. 1981, "Computer Helps Build Machine Availability." Construction Equipment, Aug.
Anon, "Maintenance Assist Program," Kennecott Copper Corp.
Johnson, D., 1982. "Vehicle Monitoring with Microcomputers in
a Mine Management Systems" Proceedings, American Mining
Congress, Oct.
Jonkman, J., 1982. "Maintenance Control at the Kennecott Minerals
Company," 17th Application of Computers and Operations Research in the Minerals Industry, AIME. New York.
Mackie, J., 1982, "Development of the Computer-Aided Mine Management System at Reserve Mining Company," Proceedings. Minnesota Section, of AIME. Jan.
Syska and Hennessy, "A Guide to Improved Maintenance Management," Vol. 7, Engineering Management Division.
. .
Tomlinson, P.D., 1980, "Maintenance Management for the Mmmg
Industry," Paul D. Tomlinson Associates, Inc., Sept.
Winkel, T .• 1981, "The Evolution ofthe Computerized Mine Maintenance Recordkeeping at KMC," Proceedings. American Institute of Industrial Engineers Fuel Conference. Dec.

Jack Balitok

Huwebes, Setyembre 13, 2018

Maintenance, Plant Facilities, and Utilities

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