Influence On Physical Work While Working With Segmental Vibration Inducing Hand Operated Power Tools

Transcription

1 Influence On Phsical Work While Working With Segmental Vibration Inducing Hand Operated Power Tools Sudhir Vinaakrao. Deshmukh #, Suresh Gulabrao Patil * # Mechanical Engineering Department, Government Poltechnic, Amravati (M S.) India-4446 sudhirvdeshmukh7@rediff.com * IBSS College of Engineering, Ghatkhed, Universit Mardi Road, Amravati (M.S.) India-4446 sgpatil@rediffmail.com Abstract Stud evaluates and assesses the work done b vibrating equipments. It includes the assessment of influence of various independent variables associated with hand tools, operators, work & environmental factors on various dependent variables. Three tools selected for stud include Rock drill (Dr tpe) (Tool-), Concrete breaker (Tool-), Hand grinder (Tool-). The impact of vibration exposure on health of operators is assessed b the help of surve. It is found that the human energ expenditure is more in the subjects having low grip strength whereas it is less in the subjects of more grip strength. The subjects having more grip strength show less change in touch sensation. The human energ expenditure of subjects of hand grinder is significantl less than the subjects of rock drill and concrete breaker. The presence of hand arm vibration Sndrome (HAVS) in the subjects under heav work, like rock drill and concrete breaker found ver high. Kewords: Segmental vibration, Grip strength, Human energ expenditure, Hand arm vibration sndrome, Touch sensation I. INTRODUCTION Power driven hand tools are used in variet of industries (e.g. agricultural, construction, logging and manufacturing). These tools are also used in dental and medical work. During the operation with power tools the workers directl come in contact with it. Due to this phsical contact, the vibration induced b these tools passed in the bod of worker through palm and finger this tpe of vibration influencing part bod of worker is called as segmental vibration [], [], [] The most important sources of hand arm vibration (HAV) are pneumatic tools (air compressed and electrical), for example, grinders, sanders, drills, fettling tools, impact wrenches, jack hammers, and riveting guns. Users of chainsaws, brush saws, hedge cutters, and grass trimmers are also at risk [4]. Hand-arm vibration sndrome is a condition associated with the use of hand-held vibrating tools. Vibration can cause changes in tendons, muscles, bones and joints as well as affecting nerves. Collectivel, these effects are known as Hand-Arm Vibration Sndrome (HAVS) [5]. HAVS is also called as Ranaud s phenomenon of occupational origin, vibration-induced white finger (VWF), dead finger, traumatic vasospastic disease and vibration sndrome [6]. HAVS is a complex sndrome caused b the constriction of blood vessels in the fingers, and involves circulator, sensor, motor and musculoskeletal disturbances [6]. Some of the presenting complaints are attacks of whitening (blanching) of one or more fingers when exposed to cold often associated with pain, tingling and numbness in the affected finger, loss of sensation, tactile discrimination & manipulative dexterit, pain and stiffness in the hands and wrists, loss of grip strength, and bone csts in the fingers & wrists [5]. The development of HAVS is gradual and increases in severit with time, often taking a few months to several ears for the smptoms of HAVS to be noticeable depending on the vibration exposure dose [5]. Histological changes in blood vessel walls and nervous tissues are irreversible, resulting in the long-term circulator and nervous dsfunction [7]. At low frequenc the perception is transmitted to the arm therefore the perception is high. The perception greatl decreases with frequenc with the reduction of vibration transmissibilit throughout the hand arm sstem [8]. When the organs are subjected to vibration at their specific resonance frequencies, the energ transfer from the source to the exposed part will be maximum and adverse effects will be more [9]. ISSN : Vol 4 No 5 Oct-Nov 8

2 The existence of sensor and vascular components in HAVS lead to the adoption of the Stockholm grading based on the subjective histor supported b the results of clinical tests [4]. Muscle weakness, particularl affecting the long finger flexors and affecting grip strength, ma occur in association with long-term vibration exposure from hand-held tools []. Progression through the stages is most likel with all components if there is no reduction in vibration exposure. However, there is a good deal of phsiological evidence that while the dose response relationships are fairl linear, the actual pathophsiological response has something of an all or none qualit [4]. The international standard for assessing exposure to hand- transmitted vibration, ISO 549- () indicates that hand coupling forces influence the vibration energ transmitted to the hand []. In most of the research work, done previousl either surve or experimentation is done, there is ver little research work on segmental vibration where both experimentation as well as surve is conducted. The objective of the stud is to evaluate and assess the work done b vibrating equipments. It includes the assessment of influence of tpe of hand tools and associated variables. It is also well known that the amount of vibration actuall transmitted to the hand arm sstem is dependent on the coupling forces at the hand handle interface []. An vibration-induced injuries or disorders must be associated with vibration actuall transmitted to the hand- arm sstem. Therefore, it is important to understand the transmission of vibration from a tool handle to the hands in interaction with the tool. [] How hard a person grips a tool, affects the amount of energ entering the hands, hence hand grip force is another important factor in the exposure assessment. The relationship in between grip strength to human energ expenditure, along with changes in touch sensation, if an is discussed. The impact of vibration exposure on health of worker is assessed b the help of surve. The questionnaire was framed to understand various Hand arm vibration sndrome (HAVS). It is again classified as per Stockholm workshop scale. II. MATERIALS AND METHODS A. Subjects Seven subjects each for three occupations were selected (Rock drilling, Concrete breaking and Hand grinding) for the purpose of structured interview. The purpose was to assess the various smptoms associated with hand arm vibration sndrome (HAVS). Out of these seven, three each were selected randoml for the purpose of experimentation. The anthropometric data of subject is shown in table I. The subjects labeled as A to A were interviewed for HAVS, touch sensation and investigation of various related consequences. Subject A to A9 were used for experimentation along with surve. B. Tpe of hand held power tools: The tools those were selected for stud include ) Rock drill ( Dr tpe ) ( Tool-) ) Concrete breaker (Tool-) ) Hand grinder ( Tool-) The specifications of these tools are shown in table II, III, IV respectivel. C. Questionnaire smptom surve The questionnaire is circulated among the subjects to access the vibration sndrome. The questionnaire is made to assess preliminar phsical disorders and to classif the hand arm vibration sndrome (HAVS) according to Stockholm workshop scale [],[9], [6]. Preliminar questions are asked pertaining to the neurological and vascular disorder of fingers and hand, The questions like Do our fingers suffer from whiteness?, Do our fingers get white in cold?, etc. are asked to access vascular smptoms. To identif neurological smptoms, the questions are asked, Do ou have numbness in finger?, and Do ou find difficult in handling small objects? Similarl questions to assess musculoskeletal smptoms are also asked to subjects. The questionnaire is designed in such a wa that smptoms can be classified on the basis of Stockholm workshop scale. For example, the questions about white fingers are based on the Stockholm scale for the classification of cold-induced Ranaud s phenomenon [4], [6], [6], [5],[7], [4]. A positive answer to the question Do ou suffer from infrequent attacks of whitening of the fingers? is understood as demonstrating the presence of smptoms of vibration induced white fingers (VWF). The workers are also asked to designate the area where the had smptoms of white fingers on the sketch of fingers & palm. The number and tpe of affected phalanges on each hand, resultant from the drawing, are used to define three stages of smptoms of white fingers. When no attack on an finger and palm are recognized then it is considered as stage. When onl the tips of one or more fingers are infected it is classified as stage. When tip distal and/or middle phalanges of one or more fingers are infected, it is put in stage class. When the tips, distal and/or middle phalanges of one or more fingers and or more phases are infected, it is ISSN : Vol 4 No 5 Oct-Nov 9

3 classified as stage.when a severe attacks with deteriorate skin changes in the finger tips are noticed, it is termed as stage 4. Data on the presence of numbness are derived b the questions like: Do ou suffer from occasional numbness in the fingers? Subjects who gave a positive response and who had no other complaints are classified as stage SN. Those who showed notice of increased thresholds of perception of temperature and pain are defined as stage SN. If the said that the had difficult in discovering small objects on a fat surface and experienced reduced manual agilit in precision tasks, classified as stage SN. D. Experimentation Procedure Run of five minute for each tool for different three subject (morning, afternoon, evening) was carried on. Hence nine run for each tool and total twent seven runs. The plan of experimentation is shown in table V The various independent variables associated includes ) Variables of tools (G) ) Variables of operator (A) ) Environmental variables (E) 4) Work sample variable (M) The dependent variable are Work output Human energ consumed E. Equipment and instruments ) Heart rate monitor This is an instrument used of the measurement of the heart rate monitor during the test the heart rate is an important indicator of the human energ consumed. The human energ consumed during the work can be estimated from the heart rate. The polar make heart rate monitor is used for this purpose. It has following components. i) Transmitter It is fitted with a built in lithium cell having average life of about 5 hours. It is made out of polurethane and is operable in a temperature range - C to 5 C ii) Elastic strap The fabric material of the strap is nlon, polester and natural rubber including a small amount of latex. The buckle is made out of polurethane. ii) Wrist receiver A CR5 batter having an average life of two ears ( hr/da, 7das/week) powers it. Operable in temperature range of - C to 5 C, attached with polurethane wrist strap. The accurac of this equipment is +/- % or +/- bpm, which ever is larger under stead state condition. The total working time is 9h 59 min. For less than hour, the displa indicates mm:ss, for than hours the displa indicates hh: mm. The minimum duration of recorded time is one minute. During the run the transmitter is positioned on the chest just below the chest muscles with elastic strap. The wrist receiver can be attached to wrist or kept at suitable position within - meter distance from the transmitter. (Fig. ) ) Calculation of Human Energ Input From Heart Beats The human energ HE consumed b the person performing the task is measured in KJ. The human energ can be estimated b man methods. But the heart rate measurement is the simplest and most suitable in the context of this research method for estimation of the human energ. It is calculated b using scheme of the relationship between energ expenditure and heart rate. [8] ) Hand Grip Dnamometer Hand grip of subjects is measured b using hand grip dnamometer. The dnamometer used for this purpose is known as Lafaette or Stoelting dnamometer (Figure). The subject to be tested holds the dnamometer in the hand to be tested, with the arm at right angles and the elbow b the side of the bod. The base rest on the heel of palm, while the handle rest on middle of four fingers. The hand grip of each hand is measured and added to get aggregate hand grip it is measured in Kg. 4) Hgrometer Hgrometer is an instrument for measuring the degree of moisture of the atmosphere. The instrument used for the measurement is shown in photograph (Figure ) 5) Thermometer Analog mercur thermometer is used to measure the ambient temperature during three run, it shown in photograph (Figure 4) ISSN : Vol 4 No 5 Oct-Nov

4 III RESULT & DISCUSSION Table VI, VII, & VIII shows the relationship of grip strength with heart beats and energ consumed. Table also shows how touch sensation varies with grip strength. The effect of environmental factor is also shown on output variables like heart beats, energ consumed and touch sensation. A. Grip strength ) Grip Strength and Energ Expenditure Figure 4 to 6 shows how grip strength is related with human energ expenditure for three tools. It can be observed that the human energ expenditure is more in the subjects having low grip strength whereas it is less in the subjects of more grip strength. This is revealed in all three cases i.e. rock drill, concrete breaker and hand grinder. ) Grip Strength and Touch Sensation Figure 7 to 9 shows how the touch sensation of subjects varies with grip strength. The subjects of less grip strength demonstrate maximum effect on touch sensation, after five minute run on respective tool. The subjects having more grip strength shows less change in touch sensation. B. Effect of Environmental Factors Figure to shows how the average heart rate varies with ambient temperature. In the afternoon, the average heart rate of subject is more whereas in morning and evening it is quite equal. This could be observed in all three tools. The humidit does not show an significant effect on the performance of subjects C. Comparative Analsis of Three Tools The performance of first three subjects out of seven in each batch is compared while working with three different tools. It has been observed that the human energ expenditure for rock drill (tool-) is maximum followed b concrete breaker (tool-) and hand grinder (tool -), respectivel. The material on which the rock drills work was hardest amongst the material on which the other two tools worked. The work of rock drill was continuous. The subjects did not take pauses until one hole was drilled. The impact rate and stroke of rock drill was more than concrete breaker. Among the three tools, the weight and speed (rpm) of hand grinder was least. Therefore, the human energ expenditure of subjects of hand grinder was significantl less than the subjects of rock drill and concrete breaker. The performance on the hand grinder was under roof. This is another reason of less human energ expenditure. Figure shows the comparisons of the human energ expenditure during the use of three different tools. D. Presence of Hand Arm Vibration Smptoms (HAVS) The workers were interviewed to assess the presence of hand arm vibration smptoms. Seven subjects working on each tool were asked different questions. The presence of hand arm vibration smptoms in the subjects under heav work, like rock drill and concrete breaker found ver high. It is comparativel less in case of light work like hand grinder. The Hand arm vibration was also classified according to Stockholm workshop scale. Figure 4 shows the stages of vascular smptoms among the subjects. The subjects are at stage I or at higher stage in case of rock drill and concrete breaker. The subjects of hand grinder are mostl at stage. No subject is identified in stage 4. Figure 5 described how the neurological smptoms identified in subjects. Similar to vascular smptoms, it is more in rock drill and concrete breaker but less in case of hand grinder. Figure 6 to 9 shows the presence of Numbness, Blanching, Tingling, Musculoskeletal (Presence of pain stiffness) in subjects of different occupations. It is evident that HAVS shows more existence in subjects of occupations with heav work tools. E. Quantitative Analsis Table IX shows the relationship between percent increases in grip strength to percent decrease in energ expenditure. Though subjects of more grip strength consume less energ, the reduction in energ expenditure is not in exact proportion to increase in grip strength. This is applicable for all three tools & for all runs. IV. CONCLUSION The conclusions drawn are as follows- ) The rock drill consumes maximum human energ as compare to concrete breaker and hand grinder ) Ambient temperature influences the performance of worker. Where as there is no significant influence of humidit, on the performance. ) Appearance of hand arm vibration sndrome is more in occupations like rock drilling and concrete breaking while it is minimum in case of hand grinding. ISSN : Vol 4 No 5 Oct-Nov

5 4) The appearance of musculoskeletal sndrome found in large number of subjects as compared to blanching, numbness and tingling. 5) There is a relationship between grip strengths and human energ expenditure. Yet energ expenditure does not change with exact proportion as change in grip strength. 6) Influences on the touch sensation var with grip strength. REFERENCES [] Halender Martin 98. Human factors: Ergonomic for building and construction. Jhon Will and sons, New York. [] Murrel K. H. F., 969. Ergonomics. Capman and Hall, London. [] Sona H. Blund, Lage burstrom, Anders Knutsson,. A descriptive stud of women injured b hand arm vibration. Ann. Occup. hg, 46 (), [4] Peter L. Pelmear, David leong,. Review of occupational standards and guidelines for hand- arm (segmental) vibration sndrome (HAVS). Appl. occup. and environ. hg., 5(), 9-. [5] B Dias & E Sampson, 5. Hand arm vibration sndrome: health effects and mitigation. Int. Occup. Hg. Assoc., B-4. [6] Colleen E Hill, Wend J Langis, John E Petherick, Donna M Campbell, Ted Haines, Joel Andersen, Kevin K Conle, Jason White, Nanc E Lightfoot, Rand J Bissett,. Assessment of Hand-Arm Vibration Sndrome in a Northern Ontario Base Metal Mine. Chronic Dis. In Can.,, (/4), [7] Shina Ymada, Hisataka Sakakibara, 998, Prevention strateg for vibration hazards b portable power tools national forest model of comprehensive prevention sstem in Japan. Ind. health, 6, 4-5. [8] P Donati,.Evaluation of occupational exposures to hand-transmitted vibration: frequenc weighting and exposure duration. Vibration injur network, Appendix H4A to final report. [9] Mandal B. B., Srivastava A.K., 6. Risk from vibration in Indian miners. Indian J. of Occup. and Environ. Med. (), [] Mirta Widia, Siti Zawiah Md Dawal,. Investigation on Upper limb Muscle Activit and Grip Strength During Drilling Task. Proceedings of international conf. on engineers and computer scientist,(iii), 7-9. [] T. W. Mc Dowell, S.F. Wiker, R.G. Dong, D. E. Welcome, 7. Effects of vibration on grip and push force-recall performance, Int. J. Ind. Ergon, 7, [] Ren G. Dong, Thomas W. Mcdowell, Daniel E. Welcome, 5. Biodnamic Response at the Palm of the Human Hand Subjected to a Random Vibration, Ind. Health 5, 4, [] I. J. Lawson, D. A. Nevell, 997. Review of objective tests for the hand-arm vibration sndrome, Occup. Med, 47(), 5-. [4] Michael j. Griffin, Massimo Bovenzi,.The diagnosis of disorders caused b hand- transmitted vibration: Southampton Workshop, Vibration injur network, Appendix X5B to Final Report Ma EC Biomed II concerted action BMH4-CT98-9. [5] Busi Nantumu, Chris M. Barber, Marr Ross, Andrew D. Curran, David Fishwick, Belindo Dias, Spo Kgalamono, James I. Phillips, 7. Hand-arm vibration sndrome in south African gold miners. Occup. Med., 57, 5-9. [6] Kenneth L. Mcgeoch, W. Harper Gimour,. Cross sectional studof workforce exposed to hand-arm vibration: with objective tests and the Stockholm workshop scales. Occup.Environ. Med., 57, 5-4. [7] Keith T Palmer, Barbara Haword, Michael j Griffin, Holl Bendall, David Coggaon,. Validit of self reported occupational exposures to hand transmitted and whole bod vibration. Occup. Environ. Med., 57, 7-4. [8] Kroemer Karl, Henrike Kroemer, Katrin Kroemer Elbert 994. Ergonomics, How to design for ease of efficienc. Prentice Hall, International series in industrial & Sstem engg. ISSN : Vol 4 No 5 Oct-Nov

6 Table I. Anthropometric Data Of Subjects Tools Subjects No. Age (Yrs) Weight (kg) Height (cm) Functional overhead reach (cm) Knuckle height (cm) Elbow height (cm) Left Right Grip Strength (Kg) Aggregate grip strength A* A A A A A A Mean SD A A A A A A A Mean SD A A A A A A A Mean SD Note: Subject A to A9 are subjected to experimentation. Subject A to A all are interviewed for HAVS and investigation of various related consequences. ISSN : Vol 4 No 5 Oct-Nov

7 Table II. Specifications Of Tool (Rock Drill) Model Weight Air requirement at 6 bar Piston diameter Piston stroke Impact rate Drilling rate Hose connection (Air) Rotation speed HAVA RH-658-5L 5 kg.4 m/min 65 mm 6 mm blows/min 45 mm/min 9 mm 5 rpm Table III. Specifications Of Tool (Concrete breaker) Model Weight Length Shank size Stroke Frequenc Piston diameter Air consumption Hose connection for air Drillman DM 5 kg 74 mm *6 mm 65 mm blows/min 57.5 mm.5 m /min 9mm Table IV. Specifications Of Tool (Hand Grinder) Model KPT 57-9 Weight 6.9 kg Rated voltage -4 Frequenc Speed Input power Grinding wheel diameter 5-6 Hz 8 rpm. kw 8mm ISSN : Vol 4 No 5 Oct-Nov 4

8 Table V Plan Of Experimentation Run Level G A E M O a A A a a B B a a C C a 4 a A A a 5 a B B a 6 a C C a 7 a A A a 8 a B B a 9 a C C A Table VI. Observations During The Three Runs Of Tool For Five Minutes Each Run Subjects Aggregate grip strength Start Hearts Beats Max. Avg. Energ consumed KJ Temp. C Environmental Variables Humidit % High Touch Sensation Nail test Moderate Low No. effect A Afternoon A A A A A A A A ISSN : Vol 4 No 5 Oct-Nov 5

9 Table VII. Observations During The Three Runs Of Tool Of Five Minutes Each Run Subjects Aggregate grip strength Start Hearts Beats Max. Avg. Energ consumed KJ Temp. C Environmental Variables Humidit % High Touch Sensation Nail test Moderate Low No. effect Afternoon A A A A A A Y A A A Y ISSN : Vol 4 No 5 Oct-Nov 6

10 Table VIII. Observations During The Three Runs Of Tool Of Five Minutes Each Run Subjects Aggregate grip strength Start Hearts Beats Max. Avg. Energ consumed KJ Temp. C Environmental Variables Humidit % High Touch Sensation Nail test Moderate Low No. effect Afternoon A A A A A A A A A9 9 6 ISSN : Vol 4 No 5 Oct-Nov 7

11 Table IX. Relation Of Percent Change In Grip Strength To Percent Change In Energ Expenditure. Tool- Tool- Tool- Run Aggregate grip strength in kg Energ consumed in KJ % increase in grip strength % reduction in energ expenditure Afternoon Aggregate grip strength in kg Energ consumed in KJ % increase in grip strength % reduction in energ expenditure Aggregate grip strength in kg Energ consumed in KJ % increase in grip strength % reduction in energ expenditure Fig. Polar Heart Rate Monitor ISSN : Vol 4 No 5 Oct-Nov 8

12 Fig. Hand Grip Dnamometer Fig. Hgrometer Human enrg expenditure, in KJ Afternnon Grip strength of subjects, kg Fig 4. Relationship Of Human Energ Expenditure With Grip Strengths Of Subjects For Tool Human enrg expenditure, in KJ Afternnon Grip strength of subjects, kg Fig 5. Relationship Of Human Energ Expenditure With Grip Strengths Of Subjects For Tool ISSN : Vol 4 No 5 Oct-Nov 9

13 Human enrg expenditure, in KJ Afternnon Grip strength of subjects, kg Fig 6.Relationship Of Human Energ Expenditure With Grip Strengths Of Subjects For Tool *Effect on touch sensation Afternnon Grip strengths of subjects, in kg Fig 7. Effect On Touch Sensation Due To Grip Strengths Of Subjects For Tool (- No effect, - Low effect, 4- Moderate effect, 6 High effect) *Effect on touch sensation Afternnon Grip strengths of subjects, in kg Fig 8. Effect On Touch Sensation Due To Grip Strengths Of Subjects For Tool (- No effect, - Low effect, 4- Moderate effect, 6 High effect) *Effect on touch sensation Afternnon Grip strengths of subjects, in kg Fig 9. Effect On Touch Sensation Due To Grip Strengths Of Subjects For Tool (- No effect, - Low effect, 4- Moderate effect, 6 High effect) ISSN : Vol 4 No 5 Oct-Nov

14 5 Average heart rate Subject A Subject A Subject A Ambient temperature, C Fig. Effect Of Ambient Temperature On Average Heart Beats Of Subjects For Tool 5 Average heart rate Subject A4 Subject A5 Subject A6 Ambient temperature, C Fig. Effect Of Ambient Temperature On Average Heart Beats Of Subjects For Tool Average heart rate Subject A7 Subject A8 Subject A9 Ambient temperature, C Fig. Effect Of Ambient Temperature On Average Heart Beats Of Subjects For Tool Human energ expenditure KJ Afternnon Tool Tool Tool Fig. Comparison Of Human Energ Expenditure Of Three Tools ISSN : Vol 4 No 5 Oct-Nov

15 6 Number of subjects 5 4 Tool Tool Tool Stage Stage Stage Stage Stage4 Satge of vascular smptons Fig 4. Classification Of Smptoms As Per Stockholm Work Shop Scale (Vascular Smptoms) 5 Number of subjects 4 OSN SN SN SN Tool Tool Tool Stages of neurological smptons Fig 5.. Classification Of Smptoms As Per Stockholm Work Shop Scale (Neurological Smptoms) Number of Subjects Tool Tool Tool Fingers go numb In response to cold During work onl With blanching Difficult in handling small objects Fig 6. Numbness.5 Number of subjects Tool Tool Tool Suffer from finger going white While working Other time In response to cold & Wet conditions Fig 7.. Blanching ISSN : Vol 4 No 5 Oct-Nov

16 Number of subjects Tool Tool Tool Suffer from tingling in the fingers Responses to cold With blanching While working Other time Fig. 8.. Tingling Number of Subjects Tool Tool Tool Back Neck tension Sndrome Shoulder Elbow Wrist Fig 9.. Musculoskeletal (Presence Of Pain Stiffness) ISSN : Vol 4 No 5 Oct-Nov