Evaluation of work-related musculoskeletal disorder risk ... · PDF fileEvaluation of work-related musculoskeletal disorder risk of forestry workers: a case study using OWAS The 10

Evaluation of workEvaluation of work--related musculoskeletal related musculoskeletal

disorder risk of forestry workers: a case study disorder risk of forestry workers: a case study

using OWASusing OWAS

Angela Calvo Angela Calvo -- ItalyItaly

15. Arbeitswissenschaftliches Seminar - 15th Seminar of Work Science

Evaluation of work-related musculoskeletal disorder risk of forestry workers: a case study using OWAS

The 10 most important emerging physical risks identified by the Risk Observatory of the European Agency for Health and Safety (2002-2006)

4,57 4,56 4,5 4,43 4,42 4,4 4,38 4,35 4,21 4,17

0

1

2

3

4

5

Lack

of ph

ysica

l acti

vity

Vibrati

on&aw

k. po

sture

Thermal

risks

x low

-statu

s

MSD&psich

osoc

ial risk

Multi-fac

torial ri

sks

Thermal

disco

mfort

Vibrati

on&mus

cular

work

Human-m

achin

e inter

face

Long

-stand

ing er

gon.ris

ks

Expos

ure to

UV ra

diatio

n

Like

rt s

cale

val

ues

RISKS

MSD disorders

Thermal discomfort

Vibration and awkward postures

Noise

Long-standingergonomic risks

Vibration and muscular work

Dangerous machineries

Forestry operators’ main risks


MANUAL WORK LOAD

MSD RISKS


MSD risk evaluation

• OWAS – Ovako Working-posture Analysis System;

• NIOSH – National Institute of Occupational Society and Health;

• OSHA – Occupational Safety and Health Administration;

• PATH – Posture, Activity, Tools and Handling.

Some known systems


THE NIOSH METHODOLOGY

NIOSH – National Institute of Occupation Society and Health

RWL: Reccomended Weight Limit

RWL=CP*A*B*C*D*E*F*G*H (de-multiplicative factors)

Lifting Index LI

LI = Weight to be moved

RWL


THE OSHA METHODOLOGY

OSHA – Occupational Safety and Health Administration

Guidelines

Integrated system for the work organization

Risk evaluation

Procedures to limit the riskexposure


PATH METHODOLOGY

PATH – Posture, Activity, Tools and Handling

Ergonomic risk

Positions:

5 for back

2 for neck

3 for arms

10 for legs

Used tool

Activitytype

Manual work load


OWAS METHODOLOGY

252 configurations

4 for back

3 for arms

7 for legs

3 for the weight



OWAS positions

Back Arms Legs Load

Bendingback

Standing back

Twistingback

Twistingand bendingback

Armsunder the shoulder

One armover the shoulder

Both the armsover the shoulder

Sit

Standing weighton 2 legs

Standing weighton 1 leg

Standing kneesbent

Standing, weight on 1 leg, knee bent

Kneeling, 1 or 2 kneestouchingthe ground

Walking

Lessthen 10 kg

Between10 and 20 kg

More then 10 kg

Risk classes

252 configurations

Class 1: natural position

Class 2: positions which may be dangerous

Class 3: dangerous positions

Class 4: very dangerous positions

4 risk classes



Legs-w

eight

back

arms

3372Walking, 10-20 kg

load, twistingback,

both the arms

over the shoulder

1141Standing

kneesbent, <10kg load,

standing back, arms

under the shoulder

2113Sitting, >20kg load,

bendingback, armsunder

the shoulder

2313Sitting, >20kg load,

bendingback,

both the arms

over the shoulder

OWAS method: the index risk

( ) ( ) ( ) ( )[ ] 1004321 ⋅⋅+⋅+⋅+⋅= dcbaI

a, b, c, d : frequency rates into classes 1, 2, 3 e 4.

Index risk (I)

Risk class Frequency

I = 100, minimum risk

I = 400, maximum risk


Forestry yards location:• Buthier (Gran S. Bernard)• Ozein (Cogne)•1500 meters over the sea level, in a very sloped area (>30°), slippery and uneven ground

Analized works• cut of the tree;• manual tree extraction;• skidding and stacking of the logs.


5 operators considered (age:30-50)

Cut phase: 1 operator

Used tools: 6 kg chainsaw, hoe and 1,5 kg peavey

Position: the operator is standing or with the knees bent, bending and twisting back, the arms always under the shoulder

Risks: noise, vibration and muscularwork, exhaust gas, position and chainsaw potential danger

Cut mark realization: 4131posture, class 2


Manual tree extraction: 4 operators

Manual extraction: 4173 posture, class 4

Used tools: 2 kg short-handled timber hoe to movelogs (3-7m long and 10-30cm diameter)

Position: the operators workswith the bending or twistingback, standing with the weighton one leg or knee bent, the arms under the shoulder and moved weight > 20 kg

Risks: awkward postures, thermaldiscomfort, heavy muscular work


Skidding and log stacking: 4 operators. Phase 1

Used tools: hoe, tractor and pulley with chains

Position: 2 operators works withthe bending back, standing withthe weight on one leg or kneebent, the arms under the shoulder

Risks for the tractor driver: noise and vibration

Risk for the operators: awkward postures, thermal discomfort, noise


Skidding and log stacking: 4 operators+tractor driver

Stacking: 2143 posture, class 3

Used tools: none. 2-3 operatorsstack the logs manually

Position: bending back at the first time, then standing, knees bendingat the beginning, arms under the shoulder.

Risks: heavy manual work load, thermal discomfort,


Skidding and log stacking: 4 operators. Phase II

Data collection and elaboration

32123P3G2B1S220,26340,527429

32143P3G4B1S251,874103,748828

32143P3G4B1S220,26340,527527

32143P3G4B1S241,56383,127726

32143P3G4B1S241,56383,127825

44143P3G4B1S477,931155,862924

32142P2G4B1S212,82925,659423

…………………………

…………………………

32143P3G4B1S221,38242,76564

32141P1G4B1S26,75413,50963

32143P3G4B1S220,26340,52792

32143P3G4B1S225,65951,31861

RiskClass

Owascode

Weight

codeLegsArmsBack

Movedweight

(kg)

Log weight

(kg)Time (s)Sample

For each phase and for each operator, all the postures and the movedweight have been evaluated

825 risk classes values have been calculated


THE WINOWAS Software

The WINOWAS software haas beenused for the data analysis (frequencyrates and risk classes evaluation)


Results

Considering the index risk between 100 and 400 and 4 riskclasses from 1 to 4:

Cut phase: IR = 287 (frequency rate in class 3+4: 50%)

Manual extraction: IR = 311 (frequency rate in class 3+4: 77%)

Skidding+manual log stacking: IR = 300 (frequency in class 3+4: 91%)


Results: manual extraction


0

10

20

30

40

50

60

Operator 1 Operator 2 Operator 3 Operator 4

frequ

ency

rate

(%)

Class 1Class 2Class 3Class 4

Class1: 1%. Class2: 22%. Class3: 42%. Class4: 35%

CONCLUSIONSAll the operations in both the yards are characterized by anhigh index risk value

The more critical operation is the manual extraction, with the highest frequency rate in class 4: therefore, the unfavourable environment conditions do not permit the use of machineries

Index risk values

287

311

300

CutManual extraction Log stock


CONCLUSIONS(continue)

Some indications to limit the MSD risk for forestry workers:

• augment the pause frequency

•train and inform the operators about the correct positions and load methods

•reduce the moved log dimension



• use wincheswhenever it’s possible



• use a sled for movinglogs



•When it is possible, use a tractor with hydraulic pliers for stacking


Some results about the vibrations surveied in the same forestryyards

Vibrationtransmitted to the whole-body

Vibrationtransmitted to the hand-arm system

0,901Tractor driverDaily value A(8) ms-2Operator

A(8) daily limits (2002/44 Directive): 0.5-1.15 ms-2 for the wholebody, 2.5-5 ms-2 for the hand-arm

Operation Daily value A(8) ms-2

Cut (right) 6,5Cut (left) 5,3Cut (right) 6,1Cut (left) 3,7Cut (right) 4,4Cut (left) 5,4

Necessity to consider:1. Vibration

And2. Awkward postures

And3. Muscular work

And4. Thermal discomfort

Togheter(as emerging physical risks declared)


Thank you forthe attention

Evaluation of workEvaluation of work--related musculoskeletal related musculoskeletal

disorder risk of forestry workers: a case study disorder risk of forestry workers: a case study

using OWASusing OWAS

Angela Calvo, DEIAFA, Italy, [email protected]

Documents

Evaluation of work-related musculoskeletal disorder risk ... · PDF fileEvaluation of work-related musculoskeletal disorder risk of forestry workers: a case study using OWAS The 10