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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.
7 - 3© Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
Hierarchy of measuresOrder of the occupational safety measures
1. Avoid/eliminate/reduce source of danger; change potential endangering characteristics of a source
Ran
ge o
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
7 - 4© Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
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
7 - 5© Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
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
7 - 6© Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
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
7 - 7© Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
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
k an
alys
is
Ris
k as
sess
men
t
Dan
ger a
sses
smen
t
Itera
tion
of th
e pr
oces
s
7 - 8© Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
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
7 - 9© Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
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
Exercise - danger assessment
Table 1: Characterization of the danger
Table 2: Possible measures
7 - 10© Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
Exercise - danger assessment
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.
7 - 11© Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
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.
Exercise - danger assessment
7 - 12© Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
1. Characterization of the danger
2. Possible measures
Danger Type of danger Fault / personal error
Work equipmentWork objectWork personWork environment
Technical measures Organizational measures Personal measures
Solution to Example 1.1
3. Possible resistance against the implementation of the measures
Exercise - danger assessment
7 - 13© Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
Exercise - danger assessment
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
7 - 14© Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
Exercise - danger assessment
Table 2.1 Characterization of the danger
Table 2.2 Possible measures
2.3 Possible resistance against the implementation of the measures
Solution to Example 1.2
7 - 15© Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
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
7 - 16© Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
1. Characterization of the danger
2. Possible measures
Danger Type of danger Fault / personal error
Work equipmentWork objectWork personWork environment
Technical measures Organizational measures Personal measures
Solution to Example 1.3
3. Possible resistance against the implementation of the measures
Exercise – danger assessment
7 - 17© Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
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.
7 - 18© Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
Exercise – danger assessment
b) Give a few examples of safeguards for occupant protection that exists in cars.
7 - 19© Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
Exercise – danger assessment
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
7 - 20© Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
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
7 - 21© Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
Exercise – danger assessment
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
7 - 22© Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
Exercise – danger assessment
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
Safe existenceLimited failureFunctionally redundantDiverse redundant
Using different real-time software for flight controllers working in parallel for commercial aircraft
Safe existenceLimited failureFunctionally redundantDiverse redundant
After a specific amount of time airplane components are replaced no matter if they are intact or not.
Safe existenceLimited failureFunctionally redundantDiverse redundant
7 - 23© Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
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
Exercise – danger assessment
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
7 - 24© Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
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
7 - 25© Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
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
7 - 26© Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
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
Exercise – Calculating the probability of non-availability
7 - 27© Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
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
Exercise – Calculating the probability of non-availability
7 - 28© Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
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 – Calculating the probability of non-availability
7 - 29© Chair and Institute of Industrial Engineering and Ergonomics, RWTH Aachen University
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