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Industrial Engineering and Ergonomics

Jochen Nelles, M.Sc.Chair and Institute of Industrial Engineering and Ergonomics

RWTH Aachen UniversityBergdriesch 2752062 Aachen

phone: 0241 80 99 457email: [email protected]

Exercise Unit 6Occupational risk prevention

Fall 2014/ 2015

© Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University

7 - 2© Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University

S afety

Protection of working persons from damages and other impairments through:

TOP – Model of Occupational Health and Safety

T O

P

S

Quelle: Schlick, C.; Bruder, R.; Luczak, H.: Arbeitswissenschaft, Springer, Berlin 2010, ISBN 978-3-540-78332-9; e-ISBN 978-3-540-78333-6

T echnical conditions:

Constructive-technical design measures to prevent accidents from the very beginning. They act on designing safety measures of the material environment.

O rganizational conditions:

An organizational design prevents accidents with the use of failure-free execution conditions and procedures with forced, risk-free, optimal effect connections.

P ersonnel conditions:

The human as an individual or in the work group contributes to safety, actively or passively, directly or indirectly, for himself or others: for example, by designing the technical and organizational requirements.


Hierarchy of measuresOrder of the occupational safety measures

1. Avoid/eliminate/reduce source of danger; change potential endangering characteristics of a source

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f the

mea

sure

s

2. Safety-related measures(encapsulation of the source, security organs/systems)

3. Organizational measures(spatial/temporal separation from factor and human)

4. Use of personal safety equipment(spatial separation on the human)

5. Behavior-related measures

T

O

P

T

P

Quelle: DGUV/BAuA, Erläuterung von Begriffen zur Verwendung in der Ausbildung zu Fachkräften in der Arbeitssicherheit


Occupational Health & Safety Law(ArbSchG)

§ 5 Assessment of the conditions of work(1) The employer shall determine which measures of occupational safety and health are necessary by assessing the risk to workers associated with their work......

§ 6 Documentation

The employer must have at his disposal the documents required depending on the nature of the activities and the number of workers which indicate the outcome of the risk assessment, the measures of occupational safety and health determined by him and the outcome of a review of those measures. ....

Occupational Health & Safety Law(ArbSchG)

§ 5 Assessment of the conditions of work(1) The employer shall determine which measures of occupational safety and health are necessary by assessing the risk to workers associated with their work......

§ 6 Documentation

The employer must have at his disposal the documents required depending on the nature of the activities and the number of workers which indicate the outcome of the risk assessment, the measures of occupational safety and health determined by him and the outcome of a review of those measures. ....

ExerciseGeneral information about the danger assessment

Danger assessment

The employer has a duty to carry out a danger assessment

Basic idea: the condition for effective occupational safety is the knowledge of potential dangers at the working place

On the basis of the danger assessment measures of the occupational safety of technical, organizational and personal kind are to be derived


Biological dangers

Physical influences

Stress due to the working environment

Physical stress

Other dangers

ExerciseInvestigation of dangers

Dangers

Mechanical dangers

Electrical dangers

Hazardous materials

Fire and/or explosion dangers

Thermal dangers


When is a danger assessment required?

new machines and equipment are bought,

new materials and substances are introduced,

working areas and areas of transportation change

company organization and processes change,

technology changes,

accidents (or near misses), occupational diseases and other diseases occur

1. A first assessment must be carried out at every work place

2. An update becomes necessary when

Exercise - danger assessment


Exercise Process of the danger assessment according to TRBS 1111

0. preparation: provide information

New work equipment Changes in the work equipment, working materials, the work environment or the personnel using the equipment

1. Investigation of dangers

2. Danger assessment(analysis and assessment of the risks)

Risk acceptable?

3. Determination of measures (of technical, organizational and personal kind)

4. Implementation of the measures

5. Examination of the effectiveness of the measures

6. Documentation

Measureseffective?

no

yes

yes

no

Ris

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alys

is

Ris

k as

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men

t

Dan

ger a

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smen

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Itera

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ExerciseDanger assessment (analysis and assessment of risks)

Minor injuries or diseases (reversible)

Moderate injuries or diseases (reversible)

Heavy injuries or diseases (irreversible)

Possible death, catastrophe

Very low 1 2 3 4

low 2 3 4 5

medium 3 4 5 6

high 4 5 6 7

Extend A of the possible danger

Probability of occurrence E of the danger

Measured value

risk description/reduction of risk

1-2 low Risk acceptable

3-4 significant Reduction of the risk necessary

5-7 high Reduction of the risk immediately necessary

Risk R =Extent A x Probability of Occurrence E


Structure for the danger assessmentDanger Type of danger Fault/ personal error

Work equipment:

Work object:

Work person:

Work environment:

Technical measures Organizational measures Personal measures

installation of equipment for accident prevention (constructive-technicalmeans)

• determination of appropriatemeasures

• Provision of health and safety clothing

• requires determination regarding further education

• wearing workwear and/orprotective equipment

• following safety-related behaviors• increasing personal qualifications


Table 1: Characterization of the danger

Table 2: Possible measures



Assignment 1

Characterize the dangers for the following examples with the aid of Table 1 and indicate actions to be taken in Table 2. Give an example for possible resistance against the implementation of the measures.


Example 1.1

A company produces chain wheels. On the day of the accident metal discs were supposed to be fitted with 50 mm drillings on a vertical box column drill with automatic feed. The drill was equipped with a chuck to hold the work piece. After securing the work piece, the drill was manually lowered onto the work piece by metalworker K. After the first chip removal, the feed mechanism was activated. The drilling process then took place automatically. For unknown reasons K. bent over the work piece and was pulled into the drill by the sleeve of his shirt. He suffered arm and chest injuries by the drill and the protruding chuck.A colleague stopped the machine.

Supposed posture of the injured person before the shirts was pulled into the drill.

Work piece clamped in the work holding chuck; Initiated drilling process.



1. Characterization of the danger

2. Possible measures

Danger Type of danger Fault / personal error

Work equipmentWork objectWork personWork environment


Solution to Example 1.1

3. Possible resistance against the implementation of the measures




At a manufacturer of packaging material a heavy industrial accident occurred. On a robot arm which moves pallets to an assembly line packaging material got entangled. Therefore the system stopped automatically. After the responsible worker removed the packaging material the system restarted automatically. Because the worker still was located within the operating area of the robot, he got caught between the robot arm and the assembly line.

Would you please characterize the danger with the help of table 2.1 and name the technical, organizational and personal measures in table 2.2 for the increase of the occupational safety. Please name examples for possible resistances against the implementation of the measures.

Robot while moving a pallet

Example 1.2



Table 2.1 Characterization of the danger

Table 2.2 Possible measures

2.3 Possible resistance against the implementation of the measures



Example 1.3

A 43-year-old employee from Obernberg was seriously injured in a work accident on Wednesday morning. The accident happened when the worker was cutting the floor out of a barrel that used to contain degreasing agent by using an angle grinder. The labelling of the barrel had peeled off because it was stored outside. The content of the barrel was classified as dangerous good and was highly inflammable.Rests of the content in the barrel exploded because of flying sparks and the worker suffered serious injuries in the facial area and was taken to hospital after first aid treatment.The fire that broke out at the work place could be put out with a fire extinguisher.

.

Worker cutting out floor of the barrel

Exercise – danger assessment


1. Characterization of the danger

2. Possible measures

Danger Type of danger Fault / personal error

Work equipmentWork objectWork personWork environment



3. Possible resistance against the implementation of the measures



Exercise – danger assessmentExample 1.4a) For compliance with safety instructions, safeguards are used next to safety

systems and safety devices. Mark in the table below, whether the respective statements on safeguards are right or wrong.

Right Wrong

Safeguards shall be welded to machinery.

Safeguards should be quickly dissolved by hand.

Safeguards should surround danger zones by at least three sides.

Safeguards intend to prevent the ejection of parts from the working area of the machine.

Safeguards should inhibit and extend the workflow.

Safeguards should be coupled with the machine in a way that their use can be easily bypassed when having time pressure.Safeguards should be adapted to the technical process.

Safeguards react to the behavior of the machine operator.



b) Give a few examples of safeguards for occupant protection that exists in cars.



As part of product planning a manufacturer of string trimmers conducts a meeting withemployees of the city's forestry department. After further analysis by the departmentof product planning, objective criteria for the development of string trimmers should beformulated. Workers were criticizing string trimmers currently used of beingdangerous because stones can get into the trimmer which can harm the workingperson when flying around.

stringtrimmerhead

protection device

Figure 1: String trimmer with string trimmer head and protection device


Exercise – danger assessmentExample 1.5a) Name for all three categories of measures in table 3 an objective of the measure

and make a short description.

Categories Objective Measure description

Direct measure

Indirect measure

Indicative measure

Table 3: technical measures



b) To reduce the risk for the working person by flying stones a few ideas wereformulated (table 4). Mark each for each idea whether the idea is a direct, an indirect or an indicative measure. There is only one correct answer.

Table 4: Ideas to reduce the risk of physical injury by small stones

Ideas Direct Indirect Indicative

Attaching a rubber strap (stone trap) on the protection device, which permanently touches the ground

Reduce speed of rotation of string trimmer head

Enhance protection device

Attach the following pictogram

Increase distance between the string trimmer head and the user



Example 1.6To ensure the reliability of operational safety, the principles of safe existence (safe-life), the limited failure (fail-safe) and the principles of redundancy (functional anddiverse redundancy) are distinguished. Allocate the following examples to theappropriate principle in the table.

Example AllocationParallel connection of two red light bulbs within the red light of a light-sign-signal-system

Safe existenceLimited failureFunctionally redundantDiverse redundant

Introduction of an emergency brake by a non- activation of a vigilance button by a train driver


Using different real-time software for flight controllers working in parallel for commercial aircraft


After a specific amount of time airplane components are replaced no matter if they are intact or not.



Safe existence (safe-life) Layout of the product and its dimension to ensure that no failure occurs during the operating time. Requirement: Detailed analysis of critical system status.e.g., mechanical steering linkage, cooling system of nuclear reactors


Functional principles to guarantee of occupational safety

Principle of redundancyFunctional redundancy: Multiple use of systems with the same function. In case offailure the second systems completely takes on the function.

e.g., lift with two ropes / backlights on carsDiverse redundancy: Avoidance of systematic failure through use of systems with different functional principles (e.g., electrical and mechanical brake)

Limited failure (fail-safe)Calculation of possible failure cases to ensure that the system is led back to a safe state in the event of a failure. Interception of overload by hyphenation points / fuses, where an apparatus has to indicate damagee.g., backup-systems for brake or steering


Exercise – Calculating the probability of non-availability

To detect lacks in a socio-technical system it is helpful to know the probability of certain damaging events

Characteristics of reliabilityIt is important to distinguish the following characteristics: The frequency of failure of a system in a predetermined interval, e.g. starting with

the initiation or in between two inspections

The non-availability of a system at a certain time or the average of this characteristic in a determined interval

Definition non-availability U(t): Probability to meet a unit at a time [t] being out of order

Goal:Calculation of the characteristics of reliability of the complete system from the characteristics of reliability of the single units subsystems


Exercise – Calculation of the probability of non-availability

AND gates as a statistical model for redundant systems are in a state of non-availability only if all events belonging to the AND gate are in a state of non-availability

U1

U2

...

Un

Probability of non-availability (U) (independent damaging events):

Ui : probability of non- availabilitysubsystem i

U : probability of non- availability completesystem

n

iiUU

1


OR gates as a statistical model for linked systems are already in a state of non-availability if one event belonging to the OR gate is in a state of non-availability.

Probability of non-availability (U) (independent damaging events):

Ui : probability of non- availabilityof subsystem i

U : probability of non- availability for thecomplete system

U2U1 ... Un

n

iiUU

1

11



Assignment 2.1

a) Calculate the probability of non-availibility U of the complete systems 1, 2and 3 for each 2, 3 and 4 redundant subsystems.

Please use the following data for the single subsystems:U1= 0.010; U2= 0.012; U3= 0.009; U4= 0.011

b) What is noticeable?

n

iiUU

1

U1

U2

U3

U4

U1

U2

U3

U4

U1

U2

U3

U4

Complete system 1Complete system 2Complete system 3



Assignment 2.2

a) Calculate the probability of non-availability Uges of the complete systems 1, 2 and 3 for each 2, 3 and 4 linked subsystems.

Use the same data for the single subsystems as in assignment 3:U1= 0,010; U2= 0,012; U3= 0,0090; U4= 0,011

b) Compare the developing of the values for U of redundant subsystems to those of linked subsystems.

n

iiUU

1

11

U2U1 U3 U4

Complete system 1Complete system 2Complete system 3



Exercise – Determination of the exposure to hazardous substances

Assignment 3

SituationIn the fabrication process of a product, a worker uses clue inside a factory building. During 30 min a total amount of 1 kg of clue is used. The clue contains 82 % solvent (limit 270 mg/m3). Due to the vapor pressure it is assumed, that the solvent evaporates completely during the 30 min. The room has a cross section of 8 m2 and is ventilated, with a constant airflow of 1.5 m/s.

ExerciseDetermine if the exposure to hazardous substances exceeds the limit.

C = average concentration of hazardous substance in the air during exposition timeE = emission rate of the hazardous substances in mg during exposition timeV = amount of air in m3 during exposition time

ECV

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