Journal of Mechanical Science and Technology 24 (12) (2010) 2367~2376

www.springerlink.com/content/1738-494x

DOI 10.1007/s12206-010-1004-1

An implementation of risk-based inspection for elevator maintenance

Seung-Tae Park and Bo-Suk Yang*
Department of Mechanical and Automotive Engineering, Pukyong National University, Busan, 608-739, Korea
(Manuscript Received October 15, 2009; Revised July 28, 2010; Accepted September 18, 2010)
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Abstract
Elevators are devices that demand a high safety requirement. The elevator faults affect not only the operations of other assets but may
also result in serious injuries or even death. Consequently, an elevator frequently requires the effective and appropriate maintenance strategy to sustain its functional operations. In this study, risk-based inspection, which is a technique for systematic decision-making to identify likely failed components and its consequences, is proposed for elevator maintenance due to a trade-off between economics and safety.
The proposed technique is evaluated by using Korean disaster and failure statistic data. The results indicate that the proposed method
offers an effective technique for elevator maintenance.
Keywords: Risk-based inspection; Failure statistics; Maintenance; Elevator
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1. Introduction
The advent of high-rise buildings in modern cities requires
high-speed elevator systems to provide quick access within
the buildings. These buildings require that elevators run at
speeds faster than ever before. To attain this requirement,
elevators achieve at the super high speed of 810 m/min, and
handle capacity loads from 9 kN to 20 kN.
Elevators have various mechanical structures according to
the rating speed and the maximum load capacity. Generally,
elevators consist of three principal mechanical parts: traction
machine, cage, and counterweight. The traction machine is
installed in a machine room located on the top of a building. It
is composed of traction motor, main sheave, and breaker. The
counterweight is used to balance with the cage and connected
to the second sheave of the traction machine through a moving
pulley. The compensation rope and the sheave are used to
eliminate the weight difference of both side ropes according to
the cage position [1].
In elevator techniques, proper installation, ongoing maintenance, and inspection are required. Long-time continuous
usage increases fault-occurrence probability, which requires
troubleshooting quickly [2]. To assess the reliability and efficiency of the elevators, a maintenance program is a significant
part of overall elevator system. Safe and reliable operations
are of paramount importance to the owners, the management

This paper was recommended for publication in revised form by Associate Editor
Eung-Soo Shin
Corresponding author. Tel.: +82 51 629 6152, Fax.: +82 51 629 6150
E-mail address: bsyang@pknu.ac.kr
KSME & Springer 2010
*

company, and the tenants as well as visitors who travel

throughout these buildings daily. The targets of elevator maintenance are as follows:

Prolong equipment life

Improve equipment safety and reliability
Reduce the cost of major repairs
Minimize the inconvenience of equipment downtime

Since the elevator was introduced in the early 1910s, the

Korean elevator industry has remarkably grown with
2,000,000 housing constructions in 1990. Currently, about
360,000 elevators are working in Korea, which is ranked 9th
in the world. However, the number of people who have been
rescued by 119 rescue teams owing to elevator accidents has
reached the second-highest level of traffic accidents. The data
obtained from the National Statistics Office on elevator accidents shows that there were 90 and 97 accidents in the years
2006 and 2007, respectively. These accidents are increasing
annually as indicated in Table 1 [3]. Therefore, the demand for
new technical solutions for lessening the safety accidents and
breakdown is necessary. It provides a technical guide to promote the progressive, selective maintenance, and improvement of the safety of existing elevator. So, the aging elevators
should be more effective, safer, more reliable and more comfortable through effective maintenance and improvement [4].
In this study, to reduce the probability of elevator breakdowns and increase safety, a risk-based inspection (RBI) for
elevator maintenance is proposed and the most appropriate
ways are sought to solve the fundamental problems in manag-

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Table 2. Appearance of accident types.

Table 1. The number of accident and installation.

Accident number
Number of The incidence of
per 10,000 peraccident
accident (%)
sons
28
0.0176
1.76

Year

Total number
of installation

1998

159,230

1999

174,261

12

0.0069

0.69

2000

190,187

22

0.0116

1.16

2001

208,497

28

0.0134

1.34

2002

231,562

16

0.0069

0.69

2003

259,850

40

0.0154

1.54

2004

289,808

25

0.0086

0.86

2005

314,495

42

0.0134

1.34

2006

336,311

90

0.0268

2.68

2007

359,098

97

0.0270

2.70

ing and maintaining elevators [5, 6].

2. Statistical analysis
2.1 Elevator accidents
Up to late 2007, the total number of elevators installed is
359,098 as shown in Table 1. The rate of elevator accidents
per ten thousand elevators accounted for 1.54. In the damage
accidents, death accounted for 148 people or 21.8%, the severe injuries accounted for 263 people or 39.8%, and lesssevere injuries reached 266 people or 38.4%. In each cause of
elevator accidents, users errors accounted for 15.3%, poor
maintenance accounted for 20.2%, while poor management
and maintenance reached 11.9%, workers errors and substandard manufacturing reached 6.1% and 3.9%, respectively. The
rest took up with 6.7%.
2.1.1 Accident types and causes
Elevator accidents are increasing every year. Even though
the same kinds of accidents have steadily occurred, the causes
have not been eliminated yet. Accidents in relation to escalators or moving walkers among total safety accidents account
for the highest rate of 20.3% as shown in Table 2. The rapid
increase of the installed escalator triggers accidents to surge
among most children and the aged.
Even though most citizens require high safety of elevators,
accidents still rise owing to the absence of the double-function
units of safety devices or the age of the elevators. Accordingly,
efforts are made to improve the safety laws which are necessary for reinforcing public safety, across the world. Also, the
same sorts of accidents frequently occur. At this point, when
the lift laws are only applied for elevators to be newly-built, it
is necessary to improve the safety level of aging elevators.
2.1.2 Risk assessment of accident by FMEA method
The failure mode and effects analysis (FMEA) technique
determines how individual elements of a system can malfunction and what combinations of failure can result in an unsafe
condition. Risk-based inspection (RBI) is the combination of

Appearance of accident type

Crushing riding after opening the landing door with
emergency key
Occurrence from escaping and rescuing process
Occurrence by trying failure repair by elevator laymen
directly
Worker accident by disobeying safety rules during
working
User accident by disobeying safety rules during working

Rate
(%)
12.4
4.4
3.2
8.0
1.6

Thoughtlessness when the car enters in the car lift

Jamming and crushing in the gap between the car
bottom and hoist walls
Poor components

4.0

15.9

User carelessness or disorder conduct

8.0

9.2

Maintenance carelessness

3.2

Dumb waiter

8.0

Accident on escalator and moving walk

20.3

Accident on a wheel chair lift for disabled persons

1.2

Others

0.8

the probability of failure and consequence of failure. Three

types of RBI assessment are generally recognized as follows:
qualitative approach which is based on descriptive data using
engineering judgment, experience quantitative approach
which is based on probabilistic or statistical models, and semiquantitative approach, being an approach that has elements of
both qualitative and quantitative methods. In this study, we
adopt the semi-quantitative RBI approach to analyze elevators.
A risk analysis is a series of logical steps that enable a systematic identification and study the hazards and their corresponding causes and effects. The identification of hazards,
followed by an assessment of their severity and probability of
occurrence shown in Table 3 [7], yields a measure of risk
associated with the individual hazards. Through the use of an
interactive process, each hazard and effect are evaluated and
either eliminated or, if necessary, controlled by means of appropriate safety measures that reduce the corresponding risk to
an acceptable level of safety as shown in Fig. 1. For this purpose, the best approach is to form a risk analysis team by selecting the members and choosing a team leader/moderator.
The cause and effect of each hazard in terms of probability
of occurrence and the severity of its effects are assessed. The
combination of severity and frequency of occurrence quantifies the risk associated with the hazard. The assessment results
are evaluated in terms of residual risk and the acceptable level
of safety. If the level of safety is unacceptable, further risk
reduction measures are required and the following procedure
should be used:
Eliminate the hazard
If the identified hazard can be eliminated, take the necessary measures to reduce the risk to an acceptable level of
safety as determined by the lift technician.

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Table 3. Relation between severity/frequency and corresponding risk

level.
Severity
Frequency

(High)

(Medium)

(Low)

(Negligible)

Highly probable

Probable

Occasional

Remote

Improbable

Highly improbable

F
Fig. 1. Risk analysis procedure.

Table 4. Risk assessment examples of accident by FMEA method.

Item

Function

Release and stop

the function of
Brake
break by running
contacts
current point of
contactor

Brake
release
circuit

Release and stop

the function of
break by
supplying and
cutting off the
current by
using
magnetic
contactor

Failure
mode

Wear or
fusion

Jamming
or fusion
of
contacts

Assumed
cause

Effect

Estimation of
risk
Grade
S
F

Protective
measures
(risk reduction measure)

ySelect appropriate contact capacity for circuit design

y Surge circuit supplementation of
brake coil to absorb surge (3) Periodical check

Elevator

yDual system of brake control

circuit
yControl circuit supplementation
that can cut off the source of
brake coil when safety switches
operate

Elevator

Elevator

Elevator
Dumb
waiter

of
excessive
electric
arc or capacity shortage

Injury,
a serious
wound or death
Brake coil
because of
current
starting with
Cut by one doors open or
magnetic
when over
contactor
speed when
ascending

Directly
Movement
Brake
Release and stop
running brake
incapacity
contacts
the function of
contacts by
or
of PLC
PLC output
brake
circuit
malfunction
port
Stroke of
brake
Release and stop
Lining
Brake
plunger is
the devices of car
wear
excessive

yBrake control circuit supplementation operated by using a contactor without directly moving
method for PLC circuit

yCircuit supplementation which

release of brake can be checked
yModerate adjustment about release power

Inform the user of the residual risks.

If the risk evaluation still indicates that the remaining risk is
not within an acceptable level of safety, the whole process has
to be repeated as shown in Fig. 1 [3].
Table 3 indicates the relation between severity/frequency
and corresponding risk level. The level of risk can be divided
into four grades by using the combination of severity and frequency of the risk:

Effect

The wear or
fusion of
contactor
because
of
occurrence

After protective

Grade 1: Unacceptable (IA, IB, IC, IIA, IIB, IIIA), corrective action required to eliminate the risk
Grade 2: Undesirable (ID, IIB, IIC, IIIC), corrective action required to mitigate the risk
Grade 3: Acceptable with review (IE, IID, IIE, IIID, IVA,
IVB), review required to determine whether any action is
necessary
Grade 4: Acceptable without review (IF, IIF, IIIE, IIIF,
IVC~IVF), no action required

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Table 4. Risk assessment examples of accident by FMEA method (continued).

Item

Slip
distance

Counterweight

Function

Failure
mode

Assumed
cause

Estimation
of risk
S
F

Effect

Braking disLack of Injury or death because of

tance when car
Over stopbraking
stop during the
starting with doors open
ping distance
running in no
capability
or slip occurrence
load
Weight change
of car and
counterweight

Control
incapacity

The change Injury, a serious wound

of
or death because of
overbalance starting with doors open
or slip occurrence
rate

Function for
Door monitor Injury, a serious wound
door opening
Starting
or death because of
circuit is
Door control
and closing by with car door
designed in jamming or crushing of
circuit
the control
open
passengers
single circuit
signal
If safety
circuit is not
Function to
earthed, in
stabilize power
case of leak- Injury, a serious wound
supply and
No cut off age currents, or death because of fire or
protect men
Earth of
fuse is not cut doors open or slip occurfuse
safety circuit when leakage
rence
off and take
currents or
fire or starting
electric shocks
with doors
occur
open
Reverse
Function to stop
phase detect
elevator operaShock of
function
Reverse tion when one
occurrence
Reverse
was not
phase preven- of the three
because of
run
tion devices phases power
operated
malfunction
or not indisconnected by
stalled
mistake
The function to
Riding more
stop a start of
Over load
than the
car with door
Slip of car
Injury by crushing of car
detection
capacity of
opening if
devices
the car
people ride with
overload

This study investigates elevator accidents resulting in poor

safety parts, safety circuit, design and systems. This study also
conducts an analysis on failure modes, estimates causes and
effects of each category, and evaluates the risks and decided
maintenance ranking. By establishing safety strategies, it can
assure the safety of elevators.
Redundancy is a property of a system that is provided by
using two or more elements to influence the final action of
that system. Table 4 shows the result of risk assessment on
accident by using Korea disaster statistics that is evaluating
risk analysis by FMEA method. It is an aim to assure the safety of existing elevators by using maintenance. In Table 4, S
and F mean the severity and frequency of the risk, respectively.
2.2 Elevator breakdown
The statistical analysis on elevator breakdown is imple-

Grade

After
Protective
protective
measures
(risk reduction measure) S
F

y Periodical
maintenance

Elevator
Dumb
waiter

y Weight
compensation
of counterweight
when the interior
of a car is done
y Periodical check

Elevator
Dumb
waiter

Elevator

Elevator

y Circuit
supplementation
by dual system of
door circuit

y Earth of safety
circuit
y Periodical check

y Circuit
supplementation
of reverse phase
detect function
y Periodical check

y Circuit design of
overload switch by normal close (B contact)
y Periodical check of
over load switch

Effect

Ropes
elevator
E
Hydraulic
elevator

Elevator

mented by using the data acquired in three years of two domestic manufacturers. The number of elevators installed in
public housing and multi-use facilities is total 1174 units (682
for manufacturer A and 492 for manufacturer B). The total
number of breakdowns is 10506 (3235 in manufacturer A and
7271 in manufacturer B).
2.2.1 Breakdown parts
A comparative analysis on the breakdown parts which are
usually broken, such as button and floor indicator, hall door,
car door, controller, and hoist way, is indicated in Table 5 in
order of descending rate. Among these, faults of floor indicator, hall door, and car door account for about 58%.
2.2.2 Breakdown causes
Table 6 indicates that the causes of breakdowns owing to
the change of adjustment parts, loosened/ destructed/ and de-

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S.-T. Park and B.-S. Yang / Journal of Mechanical Science and Technology 24 (12) (2010) 2367~2376

Table 5. The order of fault components.

Table 6. Breakdown rate according to causes.

Fault components

Number of cases

Rate (%)

Breakdown causes

Button and position indicator

2,448

23.3

Changed adjustment parts, looseness, transformation

46.2

Destruction, damage

20.2

Abnormal sound, vibration

4.6

Rate (%)

Hall door

1,900

18.1

Car door

1,801

17.1

Controller

958

9.1

Car

820

7.8

Hoist way

484

4.6

Governor

386

3.7

Malfunction

1.1

Counterweight

179

1.7

Jamming

0.9
0.8

Life excess, component aging, abrasion

4.0

Contact badness

2.8

Contamination

1.8

User carelessness

1.4

Traction machine

77

0.7

Trip

Others

1,453

13.8

Snapping of a wire

0.8

100.0

Others

15.5

Sum

100

Sum

10,506

stroyed breakdowns account for 66.64%. Other breakdowns

resulting in sound or vibrations are of high ratio.
2.2.3 Analytic results of breakdowns
The breakdown parts are button and position indicator, hall
door, car door, controller, and hoist way. The breakdown parts
often derive from incapability in operating. The noise and
vibration including sub standardized door and button cause
much breakdown. The elevator malfunction is mainly the
change and loose adjusted parts. The old worn-out, damage,
destruction of component, poor conjugation, and alien substance-caused contamination breed such breakdowns.
y This result evidently shows that elevator buttons, floor in-

dicators, old worn-out, and ill treatment triggers are the

most enormous elevator damages and breakdowns.
y The alien substances-caused contamination and maladjusted parts in hall door and car door trigger are the second-most enormous breakdowns.
y Factors such as tensile blocks, balance chains in regulator,
because noises, interphone and regulator switch are often
out of order. Noises out of balance weight result from the
relatively frequent breakdowns.
y All of the hall buttons and indicators are often switched
and repaired. The damages owing to common quality
maintenance difference from each manufacturer and users carelessness in maintaining parts are analyzed as the
major cause of elevator breakdowns.
y Among break-downs related to part durability, the shortdurable switch contactor and magnetic contactor have to
be substituted in advance, but they tend to be replaced after the breakdowns happen.
y The contamination-causing breakdowns can be prevented
in advance about 9% by making regular maintenance and
cleanliness. Parts that require special attention are hall
door sill, car door sill, push button, hall door switch contact, and gate switch contact in that order.

2.2.4 Risk assessment of breakdown by FMEA method

The cause and effect of each hazard in terms of probability
of occurrence and the severity of its effects is assessed. The
combination of severity and frequency of occurrence quantifies the risk associated with the hazard. The assessment results
are evaluated in terms of residual risk and the acceptable level
of safety. If the level of safety is unacceptable, further risk
reduction measures are required.
Table 7 shows the result of risk assessment of the elevator
breakdown data obtained from domestic manufacturers using
FMEA method. It is an aim to assure the safety of existing
elevators by using maintenance. In Table 7, the results of the
function of item, failure mode, assumed cause and the effect
by failure are shown.

3. Strategies for elevator safety

3.1 Elevator accidents
Elevator performance assessments are determined by the
factors such as safety, reliability, ride quality, sound and vibration, including energy-consuming amount, traffic amount,
traffic system efficiency, efficient maintenance, and dooropening and closing hours. Whenever elevator users enter an
elevator, safety is the most direct effect. The quotient of reliability and comfort in relation to part breakdowns and durability serves as the sense of riding. The functions of electric motor, speed reducer and revolving body machine are the direct
effects on reliability and sense of ride. However, it is difficult
to make the right analysis on how they function well. Consequently, it takes some hours to find out problems or breakdowns so as to make ambiguous predictability on such problems or breakdowns. Most maintenance and management
industries need to maintain and manage possible poor equipment, by gathering regular data with the aid of machine discrepancy-diagnosing equipment. And, it is a requirement to
make premium management and maintenance of elevators by

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Table 7. Risk assessment examples of accident by FMEA method.

Item

Function

Button

Car calling registration,

registration function of
the desired floor

Hall door
device

Car door
device

The device to protect a

passenger from being
intercepted by door
between the platform
and hoistway when car
departs
The device to protect a
passenger from being
fallen to the entrance
and exit during the
running

Failure
mode

Presumption
cause

Effect

The button
malfunction
caused by

inconvenience

superannuation

Life superannuation,
damage, the operational inability which is caused by
variation of the regulation
region

Operation
standstill,
noise and
vibration

Interlock switch, the operational inability which is

caused by foreign substance
etc. of the sill groove

Operation
standstill,
noise and
vibration

Control
panel

The function to control

the operation of the
elevator

Operation
standstill

Cage

Movement means of the

passenger who is direct
in the space where
boards the passenger

Operation
standstill,
noise and
vibration

Traction
machine
etc.

Power unit to lifting up

and down the car by
using the wire rope

Operation
standstill
and
function loss

Adjustment badness of the

switch type, variation and
contact badness

early detecting vibration damages and analyzing the damage

frequency.
In this regard, this chapter is going to earmark the standardized value of potential vibration and noises by using data
measured on the spot with the help of vibration and noisemeasuring outfits in relation to predictability (precision) technologies. And then, this chapter is putting the analytic results
of damage cases into elevator management and maintenance.
3.2 Elevator breakdown
Ride quality is one of the key indexes to evaluate an elevators system performance. Elevator vibration is one of the
other factors affecting passengers feeling. The quantity of car
vibration is related to external exciting energy, its frequency
distribution and the robustness of system design.
The proposed value of Table 8 is conducting a statistical
analysis on the measured value of ride quality and vibration of
the traction machine. Thus, it is necessary to use the analysis
as performance assessment standards. If such standards are
exceeded, the causes need to be analyzed through FFT analysis. It is deemed that the measurement and analysis on elevator

Grade

Protective
measures
(risk reduction measure)

Use
4

of passenger

The shock
caused with
Change of the adjustment part,
noise and
superannuation and attrition,
vibration,
the operation inability which
or
is caused by malfunction etc.
breakdown
confining
Parts superannuation, variation and coming loose, adjustment badness

Parts superannuation, the

damage of bearing, gear,
unbalance, misalignment,
looseness,

Estimation of
risk elements
S
F

yPeriodical inspection
yThe periodic part replacement
which considers a useful life

yThe tendency management

which leads the periodic
measurement of the noise
and vibration
yThe periodic parts replacement which considers a useful life

ride quality and vibration of traction machine in combination

with prevention maintenance and prediction maintenance
would guarantee the higher stability and reliability [11].

4. Case studies: performance assessment

4.1 Car resonance
For a driven machine with a rotating speed of 1460 rpm,
which has a reduction gearbox of worm-wheel, the rotating
frequency is 1460/60 = 24.33 Hz and the gear mesh frequency
is 48.6 Hz because the worms have two threads. This elevator
resonance occurs by resonance phenomenon, which is shown
in Fig. 2, in the conjugation zone of cage frequency and the 48
Hz element as gear mesh frequency (GMF) combined with
excited frequency of motor. For reducing the vibration, a dynamic absorber is employed as shown in Fig. 3.
4.2 Rail installment check by car vibration measurement
In the time domain, apparent impact appears every 5 meters
periodically as shown in Fig. 4; for each guide rail, length is 5
m. It can be improved by readjusting the rail installment as

S.-T. Park and B.-S. Yang / Journal of Mechanical Science and Technology 24 (12) (2010) 2367~2376

Table 8. Proposed performance assessment criteria.

Item

Car inside
vibration

Traction
machine
vibration
Car inside
sound

Horizontal vibration
X axis
Horizontal vibration
Y axis
Vertical vibration
Z axis
Motor load
(vertical/horizontal)
Gearbox
(vertical/horizontal)
Sound in car at
rated speed

Table 9. Vibration frequency due to mechanical faults.

Hong Kong
(acceptance
criteria)
less than
6 m/min

Proposed
criteria
(1.75m/s)

25

25

15 gal

25

25

15 gal

25

25

15 gal

2.8
mm/s rms

60

25

55 dB (A)

NEII
(1.75m/s)

2373

Fault

Characteristic frequency

Misalignment

Dominant 2X component

Unbalance

Dominant 1X component

Guide roller vibration

guide roller diameter RPM

Bearing fault

Bearing fault frequency

Coincidence of GMF element and cage
frequency
Periodic peak vibration waveform

Resonance
Rail vibration

Fig. 4. Periodical vibration occurrence because of installation badness

(Y axis: 25 gal).

Fig. 2. Excessive vibration due to resonance (Z axis: 94 gal).

Fig. 5. Data of installation state of the rail after adjust (Y axis: 11 gal).

Fig. 3. Vibration reduction by dynamic absorber (Z axis: 7 gal).

shown in Fig. 5.
4.3 Mechanical faults
Table 9 indicates frequency features of various faults that
are obtained through a site inspection.
For a driven machine with a rotating speed of 1460 rpm,
which has a reduction gearbox with a worm and worm-wheel,
the frequency feature appears by 1X element (1460/60 = 24
Hz) dominantly because of elevator motor unbalance. Fig. 6
shows a measuring result at a site.

Fig. 6. Unbalance fault.

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S.-T. Park and B.-S. Yang / Journal of Mechanical Science and Technology 24 (12) (2010) 2367~2376

Table 10. Maintenance guidance for elevators.

Name of
parts

Reduction
gear

Inspection
method
Vibration
waveform
& FFT
Analysis
Visual

Traction
machine

Controller

Sheave

Visual,
size
verification

Bearing

Vibration

Oil seal

Visual

Motor

Deterioration

Motor
Bearing

Vibration

Brake

Visual,
size,
electric circuit
Relay

Visual

Main
contactor

Visual

Brake
contactor

Visual
Surge
waveform

Safety
circuit

Visual

Governor

Door

Operation test
Visual

Safety
shoe

Visual
Operation test

Guide
shoe

Visual
Size inspection

Hanger
roller

Visual
Operation test

Interlock
switch

Visual
Operation test

Door
motor
Controller
Door
switch

Visual
Operation test
Visual
Operation test
Visual
Operation test

Fault feature

Countermeasure

Inspection
cycle (month)

Adjustment or
change for baseline
value

Change for baseline

value

Slip or fall

Change for baseline

value

Shutdown

Change for baseline

value

Vibration Noise

Change

Effect of breakdown

y Dominant gear mesh frequency

(above 2.8 mm/s, rms)
y Unbalance, misalignment &
bearing fault frequency
y Increased noise & vibration

Shutdown

y Pitting in worm wheel

y Crack of sheave
y Excessive wear of sheave groove
y Excessive creep
y Undercut residue
y Excessive rope slip
y Bearing fault frequency
y Increase of noise & vibration
y Deterioration of seal
y Leakage of gear oil
y Weakness of insulation resistance
y Abnormal vibration
y Overheating
y Bearing fault frequency
y Increase of sound & vibration
y Insulation weakness of coil
y Plunger wear & deformation
y Switch wear & rust
y Crack & torsion of spring
y Wear of contact
y Trembling of contact
y Wear of contact
y Melting
y Capacity shortage
y Wear of contact
y Melting
y Capacity shortage
y Use of single brake and door circuit
y Aging, wear
y Not working
y Shoe deformation
y Operational badness
y Electric wire contact badness
y Wear, corrosion
y Buried quantity of guide shoe
(6 mm below)
y Urethane damage
y Noise
y Bearing fault

Shutdown
Uncontrol
movement

Operation shutdown

Opening departure

Jamming
accident

y Insulation breakdown
y Abnormal vibration
y Motor overheating
y Insulation resistance
Weakening
y Aging, wear and carbonization
of contact

Insulation
reinforcement
Change
Change for baseline
value

3
3

Change

Change

Change

Change
Circuit complement

1
12

Circuit correction

12

Opening departure

Fall of car

y Aging, wear

Fig. 7 shows the bearing frequency feature occurring because of bearing abrasion. In the time domain, the waveform
feature appears by a period of 13.39 ms. In the frequency domain, the frequency feature is shown by ball pass frequency of

Shutdown Fire

Repair
Change
Repair
Change
Circuit correction

1
1

Door separation
Fall accident

Repair
Change

Noise, Vibration

Repair
Change

Operation shutdown

Repair
Change

Operation shutdown
Noise Vibration

Repair
Change

Operation shutdown
Noise Vibration

Repair
Change

Operation shutdown

Change

outer race (74 Hz) as shown in Fig. 8.

For a driven machine with a rotating speed of 1460 rpm,
which has a reduction gearbox with a worm and worm-wheel,
the frequency appear to be double frequency (21460/60 =

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S.-T. Park and B.-S. Yang / Journal of Mechanical Science and Technology 24 (12) (2010) 2367~2376

Table 10. Maintenance guidance for elevators (continued).

Name of
parts

Vibration
Sound
Cage

Button
lamp
indicator

Inspection
method

Fault feature

Effect of breakdown

y Increase of the vibration & noise

- Resonance
- Gear mesh frequency
Vibration & noise - Misalignment frequency
- Unbalance frequency
- Rail shock vibration
- Guide roller vibration
- Fan noise
Visual

y Button getting stuck

y Aging, wear

Visual
Laser
equipment

Various fuse

Visual

Spring buffer

Visual

Oil buffer

Operation
Visual

Fig. 7. Misalignment fault (48 Hz).

y Fuse cutting
y Damage of spring
y Spring rust
y Operation badness
y Insufficient oil

Operation shutdown

User inconvenience
Unnecessary operation

y Corrosion
y Bending
y Periodic vibration
Rail guide
y Wear, aging
Visual
Shoe
y Vibration
Rail guide
y Wear, aging
Visual
Roller
y Vibration
Visual
y Aging, performance degradation
Overload
Counterpoise y Normal A contact
Device
inspection
y Overbalance ratio change
Protection against dust
y Deterioration
Visual
rubber
y Function loss
Operation inspec- y Wear, corrosion
Safety gear
tion
y Malfunction
y Aging, performance
Landing switch
Visual
degradation
y Malfunction
y Wear, element wire rupture
NDT
Main rope
Visual
y Excessive slip
Size
y Wire rupture
y Aging, damage
Limit switch, deceleration
Operation
y Return spring separation
and terminal switch
Visual
y Roller crack or damage
Guide rail

Vibration
Noise

Countermeasure

Inspection
cycle (month)

Repair
Adjustment

Repair
Change

Vibration
Sound
Vibration
Sound

Adjustment
Repair
Change
Design change
Change
Design change

Slip
Fall of car

Repair
Design change

Vibration

Change

12

Fall

Change

Operation shutdown

Change

Fall
Sliding

Change

Change

Change

Vibration
Sound

Operation shutdown
Operation shutdown
Malfunction
Shock unabsorbed

Repair
Change
Oil supply
Repair

Fig. 8. Bearing outer race fault (74 Hz).

24
3
3

3
3

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S.-T. Park and B.-S. Yang / Journal of Mechanical Science and Technology 24 (12) (2010) 2367~2376

48 Hz) of rotating speed as shown in Fig. 8 due to misalignment.

5. Guidance for effective maintenance

Although elevator machines are designed, produced or/and
installed through accurate quality maintenance, they could
lose not only their original functions but also have low performance and safety accidents, without scientific management
and maintenance. Thus, this research studies the possible deficiency arising from each part test, individual parts or systems.
And, this study has conducted an examination about the effects on each part breakdown and steps against it along with
their regular check-up period.
The management and maintenance strategies right for an
elevator are expected to exert very important effects on preventive check-ups in accordance with the regular substitution
period. Safety, reliability and comfort would contribute to
managing and maintaining elevators. It is also indispensable to
make a regular performance test. Table 10 shows an elevator
maintenance guide that can inspect effectively according to
fault feature and decide the appropriate inspection period [5].

6. Conclusion
This paper presents an investigation of risk management,
elevator fault analysis, and life-cycle assessment based on
studying and surveying of the elevator component replacement life-cycle. It also provides the elevator performance
management development as well as elevator evaluation criteria to apply the condition prognosis and maintenance. The risk
management by RBI method gives the proposed guidance for
optimal RBI. This paper studies the risk assessment based on
the elevator accident and breakdown statistics data by using
FMEA techniques. We implement the RBI for the elevator
maintenance on the site. This paper also predicts the remaining lifetime, optimizing the maintenance decision making for
an elevator by using RBI. It then offers propositions on how to
prevent elevator accidents for premium management and
maintenance.

Acknowledgement
This research was financially supported by the Ministry of
Knowledge Economy (MKE) and Korea Industrial Technology Foundation (KOTEF) through the Human Resource
Training Project for Strategic Technology.

References
[1] H. M. Ryu, S. J. Kim, S. K. Sul, T. S. Kwon, K. S. Kim, Y.
S. Shim and K. R. Seok, Dynamic load simulator for highspeed elevator system, Proc. of IEEE Power Convergence
Conference, Osaka, Japan (2002) 885-889.

[2] G. Niu, S. S. Lee, B. S. Yang and S. J. Lee, Decision fusion

system for fault diagnosis of elevator traction machine, J. of
Mechanical Science and Technology, 22 (2008) 85-95.
[3] Korea Elevator Safety Center, The Study on Elevator Safety
Component Life Evaluation Methodology, Technical Report,
Korea (2002).
[4] L. Rivet, Improving Safety and Accessibility of Existing Lifts
in Europe, Version 1, SNEL (2004).
[5] Korea Technology Laboratory, A Study on Elevator Main
Component Life Cycle Investigation, Technical Report, Korea (2004).
[6] Korea Elevator Safety Technology Institute, Safety Assessment and Management Plan of the Aging and Non-entry Elevator, Technical Report, Korea (2008).
[7] Korea Consumer Agency, The Study on Elevator Safety
Management System, Report, Korea (2004).
[8] ISO 14798:2009, Lifts (Elevators) Escalators and Moving
Walks- Risk Assessment and Reduction Methodology, 2009.
[9] ISO/TS 22559-1:2004, Safety Requirements for Lifts (Elevators) - Global Safety Requirements (GESRs) for Lifts (Elevators), (2004).
[10] National Elevator Industry Inc., Building Transportation
Standards and Guidelines, Salem, New York, USA (2000).
[11] Elevator Technology 15, Lift Ride Quality Standard for
Public Buildings, The Government of Hong Kong Special
Administrative Region, Honk Kong (2000).
[12] ISO 18738:2003, Lifts (Elevators) - Measurement of Lift
Ride Quality (2003).

Seung-Tae Park received Ph.D. degree

in Mechanical Engineering from Pukyong National University, Busan, Korea in 2010. He is a principal researcher
and managing director of Seoul-Seobu
Branch Office at the Korea Elevator
Safety Technology Institute, Korea. His
research interests include fault diagnosis,
risk-based inspection and risk-based maintenance in elevators.

Bo-Suk Yang is a professor at the

Pukyong National University in Korea.
He received his Ph.D. degree in
mechanical engineering from Kobe
University, Japan in 1985. His main
research fields cover machine dynamics
and vibration engineering, intelligent
optimum design, and condition
monitoring and diagnostics in rotating machinery. He has
published well over 200 research papers in the research areas
of vibration analysis, intelligent optimum design and diagnosis of rotating machinery. He is listed in Who's Who in the
World, Who's Who in Science and Engineering, among others.