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Wilhite, Charles R.
Pneumatic tool hand-arm vibration and posture characterization involving U.S. navy shipboard personnel
h [electronic resource] /
by Charles R. Wilhite
[Tampa, Fla] :
b University of South Florida,
ABSTRACT: The United States Navy incorporates many different occupations to ensure it achieves its overall mission. These occupations are extremely diversified and present a wide spectrum of occupational exposures. Many of these exposures have been well studied and documented. However, shipboard pneumatic tool hand-arm vibration, (HAV) and how it relates to different body postures is an area of occupational exposurethat has received little attention.The chief objective of this study was to assess whether there is a difference in hand-arm vibration levels, while working on one of two surface orientations (e.g., horizontal and vertical) among distinctly different pneumatic tools while cleaning or not cleaning. The design of the study evaluated three pneumatic tools cleaning both horizontal and vertical surfaces and the fourth tool only cleaning a horizontal surface.HAV levels were measured to identify the effect horizontal and vertical surface orientations had on the tool. Five subjec ts were used in the evaluation of the four tools by a random sequencing order. Each subject was required to hold the tool in an idle condition, an activated without cleaning condition, and an activated cleaning condition, (surface contact) for 20 seconds each. These conditions were evaluated in two different surface orientations; horizontal and vertical (except for the 4th tool). Each subject repeated each of the cleaning/not cleaning conditions three times for a total of 7 measurements per surface. The idle condition was only conducted one time for each tool and surface. The measurements were collected from a Quest, HAVPro instrument using an accelerometer on the pneumatic tool following ISO 5349-1:2001 and ISO 5349-2:2001 methods.A three-way ANOVA (subjects by tool, by condition, (cleaning vs. not cleaning) and tool vs. condition) with replicates (not including idle conditions) was conducted on the data. The analysis included the main effects and the interaction of tool andsurface o rientation. The subjects were treated as a blocking variable. All the main effects and the interaction were significant at p < 0.0001, except for surface, p < 0.6396. Surface orientation does not affect HAV levels in pneumatic tools.
Thesis (M.A.)--University of South Florida, 2007.
Includes bibliographical references.
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Adviser: Thomas Bernard, Ph.D.
Vibration white finger.
Carpal Tunnel Syndrome.
x Public Health
t USF Electronic Theses and Dissertations.
Pneumatic Tool Hand-Arm Vibr ation and Posture Characteri zation Involving U.S. Navy Shipboard Personnel by Charles R. Wilhite A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Public Health Department of Environmental and Occupational Health College of Public Health University of South Florida Major Professor: Thomas E. Bernard, Ph.D. Yehia Y. Hammad, Sc.D. Steve Mlynarek, Ph.D. Date of Approval: June 20, 2007 Keywords: vibration white finger, dead hand, perc ussive tool, rotati onal tool, carpal tunnel syndrome Copyright 2007, Charles R. Wilhite
Dedication First, I dedicate this thesis to G od, for the Bible states in Colossians 3:23, Â“Whatever you do, work at it with all your h eart, as working for the Lord, not for men.Â” Second, I dedicate this research to th e men and women of the Armed Services who serve and have served to keep America fr ee and strong. It is my desire to protect your health in the workplace because we sacrifice all on the battlefield.
Acknowledgments Primarily, I would like to acknowledge the United States Navy for providing the opportunity to pursue my graduate degree. In addition, I would like to thank the senior officers onboard the USS ENTERPRISE, (CVN-65) and within the Medical Service Corps that had the confidence in recommending and selecting me for this DUINS assignment which ultimately allowed me to advance my career by obtaining a MSPH at the University of South Florida. I would also like to thank the Naval Medical Education and Training Command staff for their support while I pursued my education in an independent status. I would like to thank my committee memb ers for their time, advice, and mentoring during the development and completion of my research. Drs. Yehia Hammad and Steve Mlynarek provided exceptional guidance in tailoring my ideas and research. In addition, they kept me on track concerning my academic timeline and goals. I would especially like to thank Dr. Thomas Bernard for his time, effort, and expertise on the subject of this research. It was an honor working with a committee that is so kind, intelligent, and knowledgeable. I would like to thank the commanding officer, operations officer, and Deck Department personnel of the USS SIMPSON (FFG -56), home-ported in Mayport, Florida, for their cooperation and hospitality in allowing me to conduct my research onboard their vessel. Additionally, a special thanks to LT Austin and the enlisted crew who selflessly devoted their time and effort in helping me obtain quality results. On a personal level, I thank God for putting the people in my life that allowed this research to go so smoothly and successfully, my wife Caroline for her love and support and my friend LCDR(s) Scott Dunn and LT Scott Jones for their mentoring in my research.
i Table of Contents List of Tables iii List of Figures v Abstract vi Symbols and Abbreviations viii Introduction 1 Literature Review 3 Background 3 Health Effects Resulting From Hand-Arm Vibration Exposure 4 Evaluation and Diagnosis of HAVS 6 Physics of Vibration, Terminology, Equations 9 Occupational Standards and Guidelin es for Hand-Transmitted Vibration 15 Hand-Transmitted Vibration Measurements 22 HAV Studies Associated with Pn eumatic tools and Posture 25 Study Objectives 27 Methods 28 Materials & Equipment 28 Vibration Producing Pneumatic Tools 29 Protocol 31 Results 33 Discussion and Conclusions 38 References Cited 42 Appendix A: PCB ICP Acceler ometer Specifications 46 Appendix B: DOTCO 12L12. Series Specifications 48 Appendix C: Viking V364 Mid-Sized Angl e Head Die Grinder Specifications 50 Appendix D: Dayton 4CA41 Needle Scaler Specifications 52
ii Appendix E: Desco Deck Crawler (Knuckle Buster) Specifications 54
iii List of Tables Table 1 TaylorÂ–Pelmear Stages of VWF 8 Table 2 Stockholm Workshop Scale for the Classification of Cold-Induced RaynaudÂ’s Phenomenon in HAVS 8 Table 3 Stockholm Workshop Scale for th e Classification of Sensorineural Effects of HAVS 8 Table 4 Japanese Staging Classification for HAVS 9 Table 5 TLVs for Exposure of the Hand to Vibration in Either Xh, Yh, Zh Directions 16 Table 6 Summary of ahv for All Subjects, Trials, Pressure (60 & 80 PSI), and Contact/No Contact 27 Table 7 Tool Trials by Surface: Horizontal and/or Vertical 32 Table 8 Summary of Needle Gun ahv for All Subjects, Trials, and Idle/Contact/No Cont act on Bulkhead 33 Table 9 Summary of Needle Gun ahv for All Kneeling Subjects, Trials, Pressure (120 PSI), and Idle /Contact/No Contact on Deck 34 Table 10 Summary of Wire Wheel ahv for All Standing Subjects, Trials, Pressure (120 PSI), and Idle/C ontact/No Contact on Bulkhead 34 Table 11 Summary of Wire Wheel ahv for All Kneeling Subjects, Trials, Pressure (120 PSI), and Idle /Contact/No Contact on Deck 35 Table 12 Summary of Angle Grinder ahv for All Standing Subjects, Trials, Pressure (120 PSI), and Idle/C ontact/No Contact on Bulkhead 35 Table 13 Summary of Angle Grinder ahv for All Kneeling Subjects, Trials, Pressure (120 PSI), and Idle /Contact/No Contact on Deck 36 Table 14 Summary of Knuckle Buster ahv for All Kneeling Subjects, Trials, Pressure (120 PSI), and Idle /Contact/No Contact on Deck, (accelerometer next to hand closest body) 36
iv Table 15 Mean Summary ahv and P-value Data for Standing vs. Kneeling Postures, No Contact vs. Cont act Excluding Knuckle Buster 37
v List of Figures Figure 1 Description of Biodynamic a nd Basicentric Orthogonal Coordinate Axis Systems 10 Figure 2 Description of Biodynamic Or thogonal Coordinate Axis Systems 10 Figure 3 Harmonic Oscillation 12 Figure 4 Frequency Weighting Curve Wh for Hand-Transmitted Vibration, Band-Limiting Included 14 Figure 5 ANSI Health Risk Zones for DEAV and DELV 18 Figure 6 ISO Predicted 10% VWF 21 Figure 7 HSE HAV Vibration Le vel and Duration Affect 22 Figure 8 EU Examples of Vibrat ion Magnitudes for Common Tools 26 Figure 9 Examples of Pn eumatic Tools Studied 28 Figure 10 Air Line Hose Set-up 29 Figure 11 Mechanical Filter, Accelerometer and Hand Placement 30 Figure 12 Comparison Mean Values of Pneumatic Tools in Horizontal Orientation: Cleaning vs. Not Cleaning 37
vi PNEUMATIC TOOL HAND-ARM VIBRATION AND POSTURE CHARACTERIZATION INVOLVING U. S. NAVY SHIPBOARD PERSONNEL Charles R. Wilhite ABSTRACT The United States Navy incorporates ma ny different occupations to ensure it achieves its overall mission. These occupations are extremely divers ified and present a wide spectrum of occupational exposures. Many of these exposures have been well studied and documented. However, shipboa rd pneumatic tool hand-arm vibration, (HAV) and how it relates to different body pos tures is an area of occupational exposure that has received little attention. The chief objective of this study was to a ssess whether there is a difference in hand-arm vibration levels, while working on one of two surface orientations (e.g., horizontal and vertical) among di stinctly different pneumatic tools while cleaning or not cleaning. The design of the study evaluate d three pneumatic tools cleaning both horizontal and vertical surfaces and the fourth tool only cleaning a horizontal surface. HAV levels were measured to identify th e effect horizontal and vertical surface orientations had on the tool. Five subjects were used in th e evaluation of the four tools by a random sequencing order. Each subject wa s required to hold the tool in an idle condition, an activated without cleaning condition, and an activated cleaning condition, (surface contact) for 20 seconds each. These conditions were evaluated in two different
vii surface orientations; horizontal and vertical (except for the 4th tool). Each subject repeated each of the cleani ng/not cleaning conditions thr ee times for a total of 7 measurements per surface. The idle conditi on was only conducted one time for each tool and surface. The measurements were collected from a Quest, HAV Pro instrument using an accelerometer on the pneumatic tool following ISO 5349-1:2001 and ISO 53492:2001 methods. A three-way ANOVA (subjects by tool, by c ondition, (cleaning vs. not cleaning) and tool vs. condition) with replicates (not including idle conditions) was conducted on the data. The analysis include d the main effects and the inte raction of tool and surface orientation. The subjects were treated as a blocking variable. All the main effects and the interaction were significant at p <0.0001, except for surface, p<0.6396. Surface orientation does not affect HAV levels in pneumatic tools.
viii Symbols and Abbreviations ACGIH American Conference of G overnmental Industrial Hygienist ahw( t ) instantaneous single-axis acceleration value of the ISO frequencyweighted hand-transmitted vibration at time t in meters per second squared (m/s2) ahw root-mean-square (rms) single-axis acceleration value of the ISO frequency-weighted hand-transmitted vibration, in m/s2 ahw x, ahw y, ahw z values of ahw, in m/s2, for the axes denoted x y and z respectively ahv vibration total value of the ISO frequency-weighted rms acceleration; it is the root-sum-of squares of the ahw values for the three measures axes of vibration in m/s2 ahv(DEAV) vibration total value for a time Tv other than 8 h that will result in a DEAV of 2.5 m/s2 ahv(DELV) vibration total value for a time Tv other than 8 h that will result in a DELV of 5.0 m/s2 A (8) a convenient alternative term for the daily vibration exposure ahv(eq, 8h) CTS Carpal Tunnel Syndrome DEAV or EAV Daily Exposure Action Value Â– A (8) is equal to 2.5 m/s2 DELV or ELV Daily Exposure Limit Value Â– A (8) is equal to 5.0 m/s2 Dy group mean total (lifetime) exposure duration, in years EU European Union HAV Hand-arm vibration HAVS Hand-Arm Vibration Syndrome HTV Hand-transmitted vibration
ix HSE Health and Safety Executive Hz Hertz, cycles per second ISO International Organiza tion for Standardization NIOSH National Institute for Occupational Safety and Health OSHA Occupational Safety and Health Agency PPE Personal Protective Equipment rss root sum of squares Â– the square root of the sum of the squares of the x, y, and z axes. T total daily duration of exposure to the vibration ahv T0 reference duration of 8 h TLV Threshold Limit Value VWF Vibration White Finger Wh frequency-weighting characteristic for hand-transmitted vibration Z(hand) longitudinal axis of the bone receiv ing vibration acceleration from tool
1 Introduction Industrial work environments contain many obvious hazards that have been studied to determine exposure levels. One exposure hazard that is often present but rarely addressed is hand-arm vibration (HAV) Dong et al. (2006) explained Â“vibrations caused by power tools, machinery, vehicles an d heavy equipment are a ubiquitous feature of modern work environments.Â” In the U.S., an estimated six million workers are in occupations exposed to whole-body vibration and more than one million workers are in occupations exposed to hand-transmitted vibr ation (U.S. Bureau of Labor Statistics, 2004). The occupations of me n and women serving in U.S. Navy are no exception. Many enlisted Sailors are re gularly exposed to HAV via pne umatic tools, chain saws, weed eaters, etc. (OPNAV 5100.23G, 2005). Diseases of occupational origin cau sed by HAV include RaynaudÂ’s Phenomena, hand-arm vibration syndrome (HAVS), vibra tion induced white finger (VWF), traumatic vasospastic disease, and dead hand (Pelmear et al., 1998). HAV is defined by Weeks et al. (1991) as Â“a disorder of th e blood vessels and nerves in th e fingers that is caused by vibration transmitted directly to the hands (Â“se gmental vibrationÂ”) by tools, parts, or work surfaces.Â” In addition, there is epidemiol ogical evidence showing a positive association between HAV exposure and carpal tunnel syndr ome (CTS) (NIOSH, 1997). The Bureau of Labor Statistics (1995) re ported the median number of da ys away from work for CTS was 30 which are even greater than the median reported for back pain cases.
2 HAV is a real concern for employers, occupational safety and health professionals, and the worker. The Direct or of NIOSH stated Â“vibration-induced disorders, such as work-related RaynaudÂ’s dis ease, are serious and pot entially disabling. They may result in loss of feeling and inte rfere with oneÂ’s abil ity to workÂ” (Howard, 2006). In addition, Griffen (2006) pointed out that Â“we do not know, or at least there is no consensus on, the full extent of the disorders caused by HAV, (e.g., vascular, neurological, muscular, articula r, central), or the pathogene sis of any specific disorder caused by HAV, or the roles of other factor s (e.g., ergonomic factors, environmental factors or indivi dual factors).Â” Currently, there is a lack of exposure categorizati on and guidance concerning pneumatic tools and HAV exposure levels for Navy forces afloat (OPNAV 5100.19D, CH-1, 2001). With respect to the Navy, Dunn (2006) observes that Â“t he exposure levels to these tools [pneumatic, sh ipboard tools] have not been fully characterized and the exposure levels are unknown.Â” The major obj ective of this study was to assess whether there is a difference in hand-arm vibration levels while working on one of two surfaces orientations (e.g., horizontal a nd vertical) among different pn eumatic tools while cleaning or not cleaning.
3 Literature Review Background During the second industrial revolution (1871-1914) the wo rld sought an efficient way to mass produce goods and services. Traditional horse power was replaced with static hydro and portable steam power. Du ring this era, many large machines and pneumatic hand-held tools were invented to facilitate factory and assembly line production (Rand 2007). The advent of technological ly advanced steam powered machines and tools came with a price to the workerÂ’s health, including their hands and arms. The steam driven machines and tools produced vibrations due to the percussion or rotational properties of the tool. The absorbed vibrations produced re gionalized trauma that affected the nervous and vascular systems of the hand (Pelmear, et al., 1998). In 1862, a French student, Maurice Raynaud, first described this disease when he received his doctorate degree fr om the Faculty of Medicine in Paris for a thesis entitled, Â“De LÂ’Asphyxia Loale et de la Gangrene Sy metrique Des Extremities.Â” This thesis portrayed a disease, RaynaudÂ’s Disease, which had both clinical and occupational manifestations (Pelmear, et al., 1998). Rayna udÂ’s initial identificati on of the disease was linked to the clinical presen tation and not the occupational phenomena. However, the occupational manifestation, Ra ynaudÂ’s Phenomena, was later credited to Raynaud due to the similarity in symptom manifestation a nd disease pathophysiology. Pelmear et al.
4 (1998) stated Â“RaynaudÂ’s Phenomena of o ccupational origin, today called Hand-Arm Vibration Syndrome (HAVS), derives fr om hand-arm vibration exposure.Â” In the early 1900s, Alice Hamilton, a leadi ng American expert in the field of occupational health and an A ssistant Professor at HarvardÂ’ s Medical School also noted RaynaudÂ’s Phenomena in the mining among industry workers who operated jackhammers. She named this disease dead finger syndrome (NIOSH, 2000). Though noted periodically in the liter ature, RaynaudÂ’s Phenomena had not received the attention deserv ed until the late 1900s. In 1982, Brammer et al. stated Â“exposure of the hand to vibration, leading to Â“white fingerÂ” and Â“dead handÂ” is rapidly becoming recognized as an important occupa tional health hazard.Â” In 1998, NIOSH estimated that over 1.5 million American and British workers were exposed to hand-arm vibration that may potentiall y lead to RaynaudÂ’s phenome non of occupational origin (Pelmear, et al., 1998). In 1999, The British Health and Safety Executive agency reported a prevalence rate of 288,000 worker s suffering from vibration white finger (RaynaudÂ’s Phenomenon) with an estimated 4.87 million workers exposed per week to hand transmitted vibration (HTV) (HSE, 1999). Health Effects Resulting From Hand-Arm Vibration Exposure RaynaudÂ’s Phenomena of occupational origin is also known as hand-arm vibration syndrome (HAVS), vibration indu ced white finger, traumatic vasospastic disease, and dead hand to name a few (P elmear, et al., 1998). HAVS was defined by Weeks as Â“a disorder of the blood vessels a nd nerves in the fingers that is caused by vibration transmitted directly to the hands (Â“se gmental vibrationÂ”) by tools, parts, or work surfacesÂ” (Weeks, et al., 1991). Weeks et al. (1991) added Â“The condition [HAVS] is
5 primarily characterized by numbness, tingling, and blanching, (loss of normal color) of the fingers. Initially, there is intermittent numbness and tingling; blanching is a later sign, first in the fingertip and eventually over the entire finge r. Symptoms usually appear suddenly and are often precipitated by exposure to cold.Â” To further complicate the diagnosis of HAVS in workers NIOSH (1983) stated that Â“workers tend to underreport the syndrome because symptoms are intermittent and occur most frequently under conditions not pres ent in a doctor's offi ce (e.g., early in the morning or when the hands are cold or we t). In addition, many workers are unfamiliar with the potential seriousne ss of vibration syndrome.Â” Cases of HAV tend to be underreported by physicians because most have not received training on how to distinguish the symptoms of Raynaud's pheno menon from other medical conditions that emulates this syndrome. As a consequence, many doctors do not perform the appropriate clinical examination and interview to test for vibration syndrome (NIOSH, 1983). Hand-held tools do not only affect the nerv es and vascular structures of the hands they also affect the nerves and articulating bone structures in adjacent regions (Weeks, et al., 1991). Carpal tunnel syndrome is Â“a nerv e compression disorder affecting the median nerve, one of the three nerves that supply th e hand with sensory and motor capabilities. The median nerve runs through a tunnel, (c arpal tunnel) into the hand. The syndrome develops when there is an entrapment of the nerve in the wrist areaÂ” (Weeks, et al., 1991). This entrapment, resulting in CTS, has been associated with hand-held tool vibration exposure in several studies (Pelmear, et al., 1998). In 1997, NIOSH reported on a review of the epidemiological literature that Â“Over 30 epidemiologic studies have examined physic al workplace factors and their relationship
6 to carpal tunnel syndrome. There is evidence of a positive associ ation between work involving hand/wrist vibration and CTSÂ” (NIOSH, 1997). As interest in HAVS epidemiological rese arch increased, it became apparent that HAVS and CTS were affecting the workplace via occupational illness and increased medical insurance claims. In 1994, the Assist ant Secretary for the Department of Labor reported that Â“the Bureau of Labor Statistics showed the median lost work time for carpal tunnel syndrome was more than 30 days and was greater than for any other illness or injury, including fractures and amputations.Â” He further st ated Â“the good news was that there were real solutions to the problem. There are a growing number of companies across this country who have implemented ergonomic programs and processes to reduce the frequency and severity of work-related musculoskeletal disorders as well as having secondary benefits of improved perfor mance and reduced turnoverÂ” (Dear, 1994). Coffman (1989) explained that it is impor tant to note there are also secondary factors that have been linked to or caus e RaynaudÂ’s phenomena. The two most common secondary factors noted in the literature were: ex posure of hands to cold environments and -adrenoceptor blocking drugs. It is im portant to ensure employeeÂ’s hands are protected from cold environments and occ upational medicine physicians understand the employees work exposures before prescribing -adrenoceptor blocking drugs. Both inhibit proper blood circulation of the hands and increase the risk of HAVS. Evaluation and Diag nosis of HAVS RaynaudÂ’s phenomena (HAVS) is unique in that each patient may present to the medical clinic with different symptoms yet have the same disease. This is due to the disease having sequential stages based on the amount and time of exposure to workplace
7 vibration. The best way to diagnosis RaynaudÂ’s phenomena is generally made by obtaining a careful history from the patient (Coffman, 1989). He suggested Â“If a patient gives a discreption of episodic atacks of well demarcated color changes of the digits on exposure to cold, most often this suffices for diagnosis The classic symptoms, a triad of white followed by first blue and then red digital colo r changes is dramatic but not always present; many patients experience only one or two of the ischemic color pha ses indiciative of RaynaudÂ’s phenomena. Many times, clinical diagnostic tests such as blood and urine studies are normal in patients exhibiting the symptoms of HAVS. This is why the patientÂ’s account of symptoms is so valuable in diagnosisÂ” (Coffman, 1989). In an effort to help physicians and th e scientific community diagnosis HAVS and determine the various stages of disese, Taylor and Pelmear (1998) de vised a grading index in 1968 by comparing stage of sy mptoms to work or social interference. This grading system proved to be very useful to clinically express and define the stage of severity of vibration white finger disease (VWF) and monitor improvement in affected subjects. In 1986, the Stockholm Workshop Scale modified Taylor an d PelmearÂ’s 1968 scale to incorporate the patientÂ’s history of sympto ms for classification of HAVS by grade (e.g., mild Â– very severe.) Sim iliarly, the Russian and Japanese formulated an index that classifies the relative degree of the disord er to include subjective symptoms, objective responses to tests, and clinical evaluations. The degree of impairment ranges from Stage 1 with minimal impairment to Stage 4 with ex tensive impairment (NIOSH, 1989.) The four scales are provided in Tables 1-4.
8Table 1. TaylorÂ–Pelmear Stages of VWF (Pelmear et al., 1998, Table 3-1, p. 29) Stage Condition of Digits Work and Social Interference 0 No blanching of digits No complaints. OT or ON Intermittent tingling, numbness, or both. No interference with activities. 1 Blanching of one or more fingertips with or without tingling and numbness. No interference with activities. 2 Blanching of one or more fingers with numbness; usually confined to winter. Slight interference with home and social activities. No interference at work. 3 Extensive blanching. Frequent episodes, summer as well as winter. Definite interference at work, at home, and with social activities. Restriction of hobbies. 4 Extensive blanching; most fingers; frequent episodes, summer and winter. Occupation changed to avoid further vibration exposure because of severity of symptoms and signs. Table 2 Stockholm Workshop Scale for the Classification of Cold-Induced RaynaudÂ’s Phenomenon in HAVS (Pelmear et al., 1998, Table 3-2, p. 30) Stage Grade Description 0 No attacks 1 Mild Occasional attacks affecting on ly the tips of one or more fingers 2 Moderate Occasional attacks affecting di stal and middle (rarely also proximal) phalanges of one or more fingers 3 Severe Frequent attacks affecting all phalanges of most fingers 4 Very severe As in stage 3, with trophic skin changes in the fingertips Table 3 Stockholm Workshop Scale for the Classification of Sens orineural Effects of HAVS (Pelmear et al., 1998, Table 3-3, p. 33) Stages Symptoms 0SN Exposed to vibration but no symptoms 1SN Intermittent numbness, with or without tingling 2SN Intermittent or persistent numbness, reduced sensory perception 3SN Intermittent or persistent numbness, reduced tactile discrimination and/or manipulative dexterity
9Table 4 Japanese Staging Classification for HAVS (NIOSH, 1989, Table IV-6, Ch IV, p. 7) Classification Signs and Symptoms Stage 1 Episodic blanchin g of distal phalanges Borderline decrease in motor and sensory conduction velocities Minimal changes in hand radiographs Periodic numbness and pain in fingers Paresthesia may be present Stage 2 Extended episodic blanching Further decrease in motor and sensory conduction velocities Slight EMG abnormalities Moderate changes in hand and arm radiographs Pain and numbness lasting longer at rest and at night More pronounced hyperesthesia Stage 3 Blanching extended to all fingers but not the thumbs Greater decreases in motor and sensory conduction velocities Pronounced EMG changes Pronounced changes in hand and arm radiographs Some restriction of hand and arm movement Atrophy of hand/arm muscles Exaggerated subjective symptoms Stage 4 Frequent blanching of all fingers but not thumbs Pronounced decrease in motor and se nsory nerve conduction velocities Very pronounced EMG changes Pronounced changes in radiograph Increased motility restriction and muscle atrophy Further exaggerated subjective symptoms Physics of Vibration, Terminology, and Equations Vibrations and waves have been studied in the field of physics for centuries. Â“When one speaks of a vibration or oscillat ion we mean the motion of an object that repeats itself, back and forth, over the same path. That is, the motion is periodicÂ” (Giancoli, 1985). Wasserman (1998) added Â“For simplicity, this linear motion can be viewed as moving in three mutually perpendi cular directions or axes. Around each of these axes rotational motions can occur, called pitch, yaw, and roll. Thus there are up to three linear motions and three rotational moti ons at any given single measurements point on the body. For simplicity we measure only th e linear motion in each of these axes.Â” A visual depiction of the three axes is provide d in Figures 1 and 2 based on the orientation of hand grip and tool morphology.
10 Figure 1 Description of Biodynamic and Basicentric Orthogonal Coordinate Axis Systems ( diagram from ANSI S2.70-2006, Figure 1(a), p. 6) Figure 2 Description of Biodynamic Orthogonal Coordinate Axis Systems ( diagram from ANSI S2.702006, Figure 1(a), p. 6) As shown above in Figure 1, there are tw o options in defining coordinate systems based on the respective points of origin. Th e two coordinate system s that may be used are termed biodynamic or basicentric coordinate systems (ANSI S2.70-2006).
11 Biodynamic measurements are defined by ANSI S2.70-2006 as Â“the origin of the system lies in the head of the third metacarpal, and the Z(hand) axis is defined by the longitudinal axis of that bone. The x-axis projects forw ard from the origin when the hand is in the normal anatomical position (palm facing forwar d). The y-axis passes through the origin and is perpendicular to the xaxis. When the hand is gripping a cylindrical handle, the coordinate system sha ll be rotated so the Yh-axis is parallel to the axis of the handleÂ” (ANSI S2.70-2006). The ISO 5349-1 standard expl ained that the basicentric coordinate system is the most commonly used of the two and is generally rotated in the y-z plane so that the Yh-axis is parallel to the toolÂ’s handle axis (ISO 5349-1, 2001). Vibration originating from a tool may be defined as Â“basicentric motionÂ” which is the maximum vibration from the tool that is av ailable to the worker. It is important to note that vibration is a vector quantity c onsisting of both direction and magnitude as shown in Figure 1 (Wasserman, 1998). The following definitions are common scien tific terms that define vibrational motion: Displacement Â– the distance x of the ma ss from the equilibrium point at any moment. Amplitude Â– the greatest distan ce from the equilibrium point. Cycle Â– complete to-and-fro motion from so me initial point back to that same point. Period Â– time required for one complete cycle. Frequency Â– number of complete cycles per second, usually specified in Hertz, (Hz) (Giancoli, 1985.) Figure 3 and Equation 1 illustrate these concepts.
12 Figure 3 Harmonic Oscillation, ( Diagram from NIOSH Recommendations for a Standard, 1989, figure III-1, ch. 3, pg. 13) X(t) = X sin( t) (1) Where: X is the peak displacement amplitude in meters, is the angular frequency of os cillation in radians/sec, and t is the time in seconds Acceleration is an important component of vibration and is believed to be the mechanism that causes damage to the handarm system (NIOSH, 1989). All vibration exposure data looks to acceleration levels in each of the three axes shown in Figures 1 and 2. Equation 2 represents acceleration: a = -2X sin(t) = apeaksin(t) (2) Where: a = acceleration (m/s2) apeak = maximum acceleration f = frequency (Hz or cycles/s) t = time (s) = angular frequency or 2 f X = maximum displacement (m)
13 When a vibrating system, such as the ha nd, acts in concert with an externally applied vibrating source (e.g., hand-held tool ) so that certain vi bration frequencies impinging on the system are amplified, the fr equencies at which maximum amplification occurs are referred to as resonances or natural frequencies (Wasserman, 1988). The health effects related to resonance frequenc ies are based on the fre quency level absorbed by the hand-arm system. Most mathematical hand-arm vibration models imply that (1) vibration energy directed into the hand at frequencies below 80 Hz is transmitted to and can be perceived in the arm and (2) vibration energy directed into the hand at frequencies above 100 Hz is generally local to the area of th e hand in contact with a vibrating surface. These implications are confirmed by vibrati on transmissibility tests in the hand and arm (NIOSH, 1989). It is well documented that the majority of pow er tools produce vibra tions that enter the hand through all three measurement directions or axes (Figures 1 and 2). It is assumed that vibration in each of th e three directions is equally detrimental (ISO 5349-1, 2001). The ISO 5349-1 standard recommends taking acceleration measurem ents in all three directions. The evaluation of vibration exposure is based on a quantity that combines all three axes. This is the vibrational total value, ahv, and is defined as the root-sum-ofsquares of the thre e component values: (3) Where: ahv = value a2 hwx= hand, x-axis a2 hwy= hand, y-axis a2 hwz= hand, z-axis
14 Another important concept of measur ing vibration exposure is frequency weighting. The frequency weighting, Wh, reflects the assumed importance of different frequencies in causing injury to the hand. The range of application of the measured values to the prediction of vibration injury is restricted to the working frequency range covered by the octave bands from 8 Â– 1000 Hz (e.g., a nominal frequency range from 5.6 Â– 1400 Hz). Band-limiting and high-pass and lowpass filters restrict the effect on the measured value of vibration frequencies outside this range where the frequency dependence is not yet agreed. Figure 4 Frequency Weighting Curve Wh for Hand-Transmitted Vibration, Band-Limiting Included, ( From ISO 5349-1:2001(E), Figure A.1, p. 9 ). NIOSHÂ’s Criteria Document for HAV (1989) does not agree with the ISO, ANSI, and ACGIH concept of 1/3-oc tave-band center-frequency wei ghting of the acceleration values to express the magnitude of the vibration exposure. That is, NIOSH proposed that frequency weighting not be used. NIOSH (1989) stated Â“The frequency-weighted acceleration concept assumes th at the harmful effects of 1/3-octave-band center-
15 frequency accelerations are independent of frequency between 6.3 and 16 Hz but progressively decrease with higher fr equencies between 16 and 1,500 Hz. The unweighted concept assumes that the magnitude of pathophysiologic e ffects from exposure to vibration are proportional to the acceler ation and are frequency independent at all frequenciesÂ” (NIOSH, 1989). HAV studies conducted by Enstrom and Dandandell (1986) supported NIOSHÂ’s view that pathophys iologic effects are frequency independent (NIOSH, 1989). Occupational Standards and Recommendations for HAV Exposure Many scientific organizations in the international community and the United States have published occupational standard s or provided recommendations for hand-arm vibration exposure and control. The United St ates has two organiza tions that have set quantifiable limits for HAV exposure: ANS I (2006) and ACGIH (2006). NIOSH and OSHA have not published specific occupatio nal limits for HAV exposure but they do recognize the occupational di sease as serious. NIOSH recommended control of HAV through engineering means and personal protective equipment (PPE) (NIOSH, 1989). The ACGIH TLV for HAV (2006) recomm ends the following table for HAV exposure.
16Table 5 TLVs for Exposure of the Hand to Vibration in Either Xh, Yh, Zh Directions (ACGIH, TLVs and BEIs., 2006, Table 31, p. 128) Values of the Dominant,** Frequency-Weighted, Component Acceleration Which Shall not be Exceeded aK, (aKeq) Total Daily Exposure Duration* m/s2 g 4 hours and less than 8 4 0.40 2 hours and less than 4 6 0.61 1 hour and less than 2 8 0.81 Less than 1 hour 12 1.22 The total time vibration enters the hand per day, whether continuously or intermittently. ** Usually one axis of vibration is dominant over the remaining two axes. If one or more vibration axes exceed the Total Daily Exposure, then the TLV has been exceeded. g = 9.81 m/s2 The ACGIH TLVs in Table 5 refer to component acceleration levels and durations of exposure that represent conditions under which it is believed that nearly all workers may be exposed repeatedly w ithout progressing beyond Stage 1 of the Stockholm Workshop Classification System fo r VWF (Table 1). ACGIH added, Â“Since there is a paucity of dose-re sponse relationships for VWF, these recommendations have been derived from epidemiological data from forestry, mining, and metal working. These values should be used as guides in the c ontrol of HAV exposure; because of individual susceptibility, they should not be regarded as defining a boundary between safe and dangerous levelsÂ” (ACGIH, 2006). The AC GIH concurs with NIOSHÂ’s view point placing priority on vibration prevention through c ontrol measures rather than adhering to exact exposure levels that are arbitrary in relation to workerÂ’s safety. The ANSI 2006, American National Standa rd Â– Guide for the Measurement and Evaluation of Human Exposur e to Vibration Transmitted to the Hand, ANSI S2.70-2006, follows the European 2002 Directive and ISO 5349-1 & 2 standards. ANSI described vibration in their standard by using the r oot-mean-square (rms) equation for acceleration
17 in meters per second squared (m/s2). The rms single axis ISO frequency-weighted acceleration value, ahw was ANSIÂ’s recommended method of measuring vibration which was in agreement with the ISO 5349-1 sta ndard (ANSI 2006). ANSI prescribed the frequency range for HAV measurement to be between 5.6 Â– 1,400 Hz, sufficient to cover the 1/3 octave frequency bands with cente r frequencies of 6.3 to 1,250 Hz (ANSI 2006). ANSI described exposure assessment as the Daily Exposure Action Value (DEAV) and the Daily Exposure Limit Value (DEAL). The DEAV and DELV are set at 2.5 and 5.0 m/s2 respectfully. The following are the fo rmulas associated with each value: 2 1 v hv(DEAV)8 5 2 t a (4) 2 1 v hv(DELV)8 0 5 t a (5) Where tv is greater than 15 minutes and less than 12 hours in a 24 hour period, (ANSI, 2006) The following are ANSI, 2006 definitions for DEAV and DELV: DEAV the dose of hand-transmitted vibration exposure sufficient to produce abnormal signs, symptoms, and laboratory find ings in the vascular, bone or joint, neurological, or muscular systems of the hands and a in some exposed individuals. DELV the dose of hand-transmitted vibration exposure sufficient to produce abnormal signs, symptoms, and laboratory find ings in the vascular, bone or joint, neurological, or muscular systems of the hands and a in a high proportion of exposed individuals.
18 ANSI stated Â“when the DEAV is exceeded, a program to reduce worker exposure to HAV should be initiated to reduc e health risksÂ” (ANSI, 2006). The following DEAV and DELV graphical representati on is provided in Figure 5: Figure 5 ANSI Health Risk Zones for DEAV and DELV ( ANSI S2.70-2006, Figure A.1, p. 12 ) The United States Navy has no publishe d exposure guidance for HAV exposure relating to forces afloat (OPNAV 5100.19D, CH-1, 2001). The ashore safety publication, OPNAV 5100.23G, instructed occupational safe ty and health professions to seek guidance from the ACGIH TLVs for Hand-Ar m Vibration. The Navy recognized two different exposure scenarios in the ashore instruction: one for a Sailor exposed to high vibrating tools for greater than 30 minutes and a second for a Sailor exposed to a moderately vibrating tool fo r 2 hours or greater. The Na vy defined high and moderate vibration tools by type of tool not by a quantifiable accelerat ion range or value. High
19 vibration tools were generally percussive in nature or produce high acceleration values to include chain saws, weed eaters, jack-hammers impact wrenches, and needle scalers. The moderately vibrating tool category in cluded hand-held grinders, jig-saws, and pneumatic wire wheels (OPNAV 5100.23G, 2005). The International Organization for Standa rdization (ISO) is an international community that is comprised of a worldwid e federation of national standards bodies to address HAV exposure and measurement. These bodies included international organizations, and governmental and non-governmental agencies. ISO was also in close liaison with the International Electrotec hnical Commission (IEC) on all matters of electrotechnical standardizat ion, which relate to vibra tion measurement (ISO-5349-1). The ISO standard 5349-1 discussed HAV expos ure and was unique in that it did not specifically deno te a quantifiable, daily HAV acti on or exposure level. The ISO standard took an alternate a pproach to HAV exposure levels through their careful review of epidemiological studies i nvolving VWF for workers with near-daily exposures up to 25 years. From this epidemiological data the ISO published a graph in the ISO 5349-1 standard which predicted a 10% prevalence ra te of VWF in a working population. These workers were exposed near-daily to HAV acceleration levels up to 30 m/s2; see Figure 6 (ISO 5349-1, 2001). The ISO 5349-1 standard cautioned that th e epidemiological studies used data from workers who were exposed to or above the frequency levels of 30 to 50 Hz (e.g., chain saws, grinders, rock drills). This frequency range was associated with higher acceleration levels up to 30 m/s2. If one is exposed to lower frequency ranges, mainly below 20 Hz, special caution should be take n when applying Figure 6 because that
20 frequency range has been noted to cause inju ry to bones and joints of the upper limb in addition to causing VWF (ISO 5349-1, 2001). The ISO 5349-1 standard equips the safety and health professional with a visual graph and mathematical formula to predict potential VWF in comparison to near-daily vibration exposure. Formula 6 allows one to calculate a workerÂ’s estimated lifetime exposure, in years, from an average daily vi bration exposure value. Next, the calculated Dy value is used to compare to a 10% estimat ed prevalence rate for VWF. Lastly, this data can be used to predict and implemen t needed controls to minimize potential occupational disease in the future. 06 1) 8 ( 8 31 A Dy (6) Where A (8) is the daily vibration exposure and Dy is the group mean total (lifetime) exposure in years
21 Figure 6 ISO Predicted 10% VWF ( ISO 5349-1, Figure C.1, p. 17 ) The European Union (EU) issued directive 2002/44/EC on June 25, 2002 to address HAV exposure. The EU prescribed specific daily exposure limits and action values of 5.0 m/s2 and 2.5 m/s2 respectfully. The EU also addressed partial vibration exposures for workers who use two or more di fferent tools or proce sses during the day. The partial vibration values are calculated fr om the magnitude and duration for individual tool. The partial vibration values are then combined to give the overall daily exposure value, A (8) for the individual worker. The EU warned that the A (8) values can be as much as 20% above the true value to 40% belo w. The EU also encouraged one to look at
22 the processes that produce the highest partial vibration expos ure for priority in control measures (EU Directive, 2002). The British published a regulation Â“The C ontrol of Vibration at Work Regulation 2005Â”. This regulation directly emulates the EU, 2002 directive concerning prescribed exposure limit values (ELVs) and ac tion limit values (ALVs) of 5 m/s2 and 2.5 m/s2 respectfully. In addition, the British Hea lth Safety Executive issued the following graph, Figure 7, to help safety and health professi onals understand how acceleration levels relate to daily exposure action and limit values as compared to an hourly dose. Figure 7 HSE HAV Vibration Level and Duration Affect (HSE Control the Risks from HAV, 2005, Figure 1, p. 7 ) Hand-Transmitted Vibr ation Measurements Hand-transmitted vibration can be measur ed for both impact or nonimpact-type tools. The ISO-5349-2 standa rd defined impact tools by examples to include chipping hammers, scalers, pneumatic riveting hammers, pneumatic nailers, jack hammers, and any other tool that generates impulse vibration si gnals that dominate the vibration spectrum.
23 Nonimpact tools include chainsaws, nibblers, pneumatic wrenches, grinders, routers, circular saws, reciprocating saws, and other similar tools (ISO-5349-2, 2001). Tool vibration is measured via a piezoel ectric accelerometer that can be designed to measure vibration within the frequency range of 1 to 50,000 Hz. NI OSH explained, Â“when vibration impinges on a piezoelectric acceleromet er, it moves a small ma ss against the face of a crystal element. The crystal element pro duces an electric voltage proportional to the compression of the mass against the crystal. This voltage is proportional to acceleration.Â” (NIOSH, 1989) The ISO 5349-2 standard stated that ther e are two variables that must be measured to determine a daily exposure lim it: vibration total value (m/s2) and the duraion. As mentioned previously, vibration is a vector quantity and it is necessary to make vibration measurements in the three orthogonal axes (NIOSH, 1989). The ISO 5349-2 standard stated Â“triaxial measurement of vibration, usin g the basicentric coordinate system defined in ISO 5349-1 is preferredÂ”. Time is genera lly denoted by hour(s) a worker is exposed to HAV per day or shif t (ISO 5349-2, 2001). The placement of the accelerometer on a hand-held tool is defined for many tool types and subjective for others. The general concensus was that the accelerometer should be placed as close to the hand as possible w ithout obstructing control panels (e.g., on/off switches) and hampering the workers ability to use the tool (ISO 5 349-2, 2001). The ISO 5349-2 and 8662 standards gave a specific list with diagrams to show where accelerometers should be placed to receive reliable accelera tion results. The ISO 5349-2 standard also provided many options for mounting accelerometer s to hand-held tools to include stud, glue, cement, and clamp mounts or hand-held ad aptors that are mounted on either side of
24 the hand between the middle most fingers and as close to the tool as possible to minimize amplification of rotational vibration compone nts that may skew re sults (ISO 5349-2 2001). The ISO 5349-2 standard suggested that th ere were four sources of uncertainty in vibration measurement that the researcher must be aware of to include: cable connector problems, electromagnetic interferences, triboe lectric effect, and DC-shift. The most common problem w ith the measurement of hand-tran smitted vibration was ensuring a reliable connection was maintained between th e accelerometer and the signal cable. The standard encouraged taping the signal cable to the tool for stabiliza tion with a pneumatic tool, periodically taping the cable to the suppl y air hose. Another added benefit of securing the signal cable with tape was that it minimize d the chance of triboelecctric effects due to high amplitude vibrational stress from the tool which bends the signal cable and produces false electrical eff ects (ISO 5349-2, 2001). Enevitable electromagnetic interferences can be minimized by using sceening cables, twisted cables, and earthing the signal cablesÂ’s screening at one end only, normally at the amplifier end. Lastly, exposing piezoelec tric transducers to very high accelerations at high frequencies on percussive tools pot entially induces DC-shift Dong et al. (2004) warned Â“DC-shift may also occur in the me asurement of vibration generated by some grinders.Â” A DC-shift occurs when the vibr ation signal is distorte d such that a false additional low-frequency component appears in the vibration signal. The DC-shift distortion occurs in the transducer and is due to excitation of transients which are too large for the transducer, overloading the piezoelect ric system mechanica lly (ISO 5349-2, 2001). NIOSH and ISO 5349-2 r ecommend using a mechanical filter as a means to avoid DC-shift (NIOSH 1989). Dong compar ed the acceleration results measuring a chipping hammer
25 with a handle mounted mechani cal filter to a non-contacting la ser vibrometer (Polytec PI, PSV-300H). He found Â“A g ood match between the two meas urements generally extended from high frequencies to lower frequencies with the reduction of the ti ghtness [clamp]. It was, however, extremely difficult to eliminat e the entire DC shift at low frequencies (<10 Hz) without significantly losing some high frequency components Â” (Dong, et al., 2003). HAV Studies Associated with Pneumatic Tools and Surface In 2002, the European Union published a document titled Â“Guide to Good Practice on Hand-Arm VibrationÂ” which provided a figure that classified many hand-held vibratory tools (Figure 8). The EU char t conveniently depicted common vibration acceleration ranges and plotted 25th and 75th percentile points which show the vibration magnitude that 25% and 75% of samples were eq ual to or below. The chart also denoted the variability in total vibration acceleration range by showing where all acceleration data points actually lie above and below the 25th and 75th percentile ranks (EU, 2002). The EU data displayed in Figure 8 is representati ve of the data collected in this study and allows one a quick visual representation of acceleration values concerning a particular tool. The EU and HSE both encourage an em ployer to seek the manufacturerÂ’s published vibration data (HSE 2005; EU 2002) Please note that these tests were conducted under laboratory conditions using the ISO 8662-2, 1992 method. Mr. Wasserman warned that Â“grinders receiving average to poor maintenance showed higher vibration acceleration levelsÂ” (Wasserman, 2002 ). ManufacturerÂ’s data is derived from tools in excellent condition and degradation of tools via use and lack of maintenance will affect vibration acceleration levels (Dong et al., 2003).
26 Figure 8 EU Examples of Vibration Magnitudes for Common Tools. (EU, Guide to Good Practice on Hand-Arm Vibration, 2002, Figure B.3, p. 36 ). Caption reads, Â“Sample da ta based on workplace vibration measurements of total vibration values by HSL and INRS between 1997 and 2005. These data are for illustration only and may not be representative of machine use in all circumstances. The 25th and 75th percentile points show the vibration magnitude that 25% or 75% of samples are equal to or below.Â”
27 In 2005, The British Health and Safety Executive recommende d employers obtain suitable vibration data from equipment handbook s or from an equipment supplier. The HSE provided a table in their leaflet on implementing the Bri tish Â“Control of Vibration at Work Regulations, 2005Â” for common tools. Table 6 has common vibration acceleration levels for two pneumatic tools (HSE, 2005). Table 6 Typical Vibration Levels for Common T ools (HSE, 2005, Table I, p. 10) Tool type Lowest, (m/s2) Typical (m/s2) Highest (m/s2) Needle scalers 5 18 Angle Grinders 4 8 In 2006, Dunn conducted a study to characte rize the pneumatic tool acceleration levels of a Taylor needle scaler used onboa rd U.S. Navy ships at 60 and 80 psi. Dunn noted lower acceleration values while the need le scaler was cleaning vs. not cleaning. This was consistent for all subjects and pressures. The 80 psi trial produced the highest vibration acceleration levels with averages from all tria ls ranging from 11.5 Â– 16.3 m/s2. Study Objectives The chief objective of this study was to a ssess whether there is a difference in hand-arm vibration levels, while working on one of two surface orientations (e.g., horizontal and vertical) among different pneumatic tools wh ile cleaning or not cleaning (i.e., with contact versus no contact) surfaces The second objective was to determine if Navy Sailors are exposed to hand-arm vibrat ion levels above the American National Standards Institute (ANSI) standards. The null hypothes for this study was: Â• There is no difference in hand-arm vibr ation exposure levels among different pneumatic tools, surface orientation, and contact status.
28 Methods Materials and Equipment Four different pneumatic tools were used in this study to include: Dayton 4CA41 needle scaler, Viking Tool Company V364 mid-size angle head die grinder, Dotco 12L12. series, 0.3 hp ERGO right angle grinde r & sander, and the Desco, Â“knuckle busterÂ” (Figure 4). (a) (b) (c) (d) Figure 9 Examples of Pneumatic Tools Studied. (a) Photo Dayton 4CA41 needle scaler. (b) Viking Tool Company V364 mid-size angle head die grinder. (c) Do tco 12L12 series, 0.3 hp ERGO wire wheel sander. (d) Desco Â“Knuckle BusterÂ”
29 Vibration Producing Pneumatic Tools The tools used in this study were connected to the shipÂ’s low pressure air system via a standard 50-foot section of hose (Figure 5a-b.) The shipÂ’s low pressure air system was maintained at 120 psi. Care was taken to ensure the fifty-foot ai r line hose was either coiled in a loose circle or stretched out in a straight line to prevent losses in airflow (Figure 5a-b.) (a) (b) Figure 10 Air Line Hose Set-up. (a) Photo of air line hose gently coiled. (b) Photo of air line hose maintained in a straight line The Quest Technologies HAV Pro personal vibration sampler was used for the data collection of all four pneumatic tools. The HAV Pro sampling package comes with a small, cube-like, tri-axial, integrated circuit piezoelectric (ICP) accelerometer manufactured by PCB Group, Inc. (Triaxial PCB ICP Model 356A67) to measure handarm vibration. The accelerometer was attached on the pneumatic tool as closely as possible to the hand deemed to have the highe st potential for vibra tion exposure. This hand was generally considered the one that cons tituted a complete grasp of the tool likely to have a higher probability of receiving the greatest vibration load.
30 The mounted Â“XÂ” axis was the (percussive) axis, the mounted Â“YÂ” was the basicentric coordinate perpe ndicular to the X axis in the horizontal plane and the mounted Â“ZÂ” axis was perpendicular to the X axis in a vertical plane orientation. (a) (b) (c) Figure 11 Mechanical Filter, Accelerometer an d Hand Placement. (a) Photo of mounted mechanical filter, accelerometer placement and hand grasp. (b) Photo of accelerometer mounted onto angle grinder. Please note, X axis runs parallel to tool handle and would be considered the Y (percussive) axis on the basicentric coordinate system. (c) Photo of 3-D axes: X, Y, and Z as depicted on the ICP accelerometer. A mechanical filter was added to the sa mpling apparatus as suggested by the ISO 5349-2 standard and Dong, et al. (2003) in order to prevent a DC-shift which could potentially prevent the HAVP ro from obtaining reliable vibra tion data. The mechanical filter consisted of three 1/16Â” rubber gasket s which were placed between the pneumatic tool, the accelerometer, and the hose clamp. First, two rubber gaskets were stacked on top of one other and placed between the t ool and the accelerometer. The accelerometer was then placed on top of these two gaskets; the third gasket was placed over the top and sides of the accelerometer. The hose clamp was th en slide over the top of the third gasket Yaxis Z axis
31 to secure the mechanical f ilter to the accelerometer and th e tool (Figure 11a-b). The specifications of the pneumatic tools used in this study are provided in Appendix B-E. The accelerometer was connected to the HAV Pro instrument via a small electrical cable. The cable was taped to both the pneuma tic tool and the air hose to prevent and/or reduce a triboelectric effect (Figure 6a). The HAV Pro meets requirements of the ISO 8041:1990(E), Human response to vibration Â– Measuring instrument ation, ISO 8041, 5349-1:2001, and 5349-2:2001 vibration sampling standards. Protocol Five Sailors used three pneumatic tools on two different surface orientations (e.g., horizontal and vertical) and an additional fourth tool sole ly on the horizontal surface. The following were the conditions of the study concerning surface orientation and handarm vibration characterization: 1) sitti ng or kneeling on the deck (ground) while removing paint/rust from shipÂ’s deck (horizontal surface) 2) standing, removing paint/rust from the bulkhead (vertical surface) at chest level. The tools were measured for vibration levels in three conditions: 1) idle, in hand, 2) acti vated, in hand, and 3) activated on the shipÂ’s steel deck or steel bulkhead. Th e idle condition was conducted one time for each test subject with each tool for twenty seconds. Each of the other two conditions was conducted for twenty seconds and each condition was repeated three times. This procedure was repeated for al l four tools under stu dy except the vertical surface for the fourth tool as shown below in Table 7. The fourth tool could not be used on the bulkhead of the ship because it w ould damage the thin metal walls.
32Table 7 Tool Trials by Surface: Horizontal and/or Vertical Tool type Horizontal Surface Vertical Surface Grinder X X Needle Scaler X X Wire Wheel X X Knuckle Buster X A total of 49 measurements were collect ed for each of the 5 Sailors for 245 measurements for the entire study. The HAV Pro instrument was setup to average in 1second intervals for the x, y, z axes and the root sum of squares ( ahv). Prior to each measurement, the instrument was allowed to stabilize for approximately twenty seconds. The data was stored electronically onto the HAV Pro Â’s electronic data collection software and recorded manually on paper. The manual recording was transferred onto a Microsoft Excel spreadsheet for future data analysis. The data from the Microsoft Excel spreadsheet was formatted for analysis by using the HAV ProÂ’s calculated root-mean-square (rms) values obtained onboard the USS SIMPSON (Equation 2.) The acceleration values for the root sum of squares ( x, y, and z axes ) were then analyzed with the JMP IN 5 statistical software (SAS Institute, Cary, NC) obtaining measures of va riance, an analysis of va riance (ANOVA) and a TukeyÂ’s Honestly Significant Difference (HSD) test. Significant differences were considered to exist when the probability of a Type I error was less than 0.05. A multiple comparison procedure, TukeyÂ’s Honestly Significant Difference (HSD) test, was used to determine where differences might exist.
33 Results The major objective of this study was to assess whether there was a difference in hand-arm vibration levels while working on one of two surface orientations (e.g., horizontal and vertical) among different pneumatic tools wh ile cleaning or not cleaning (i.e., contact with the surface). Five Sailors participated completing the protocol for all seven combinations of tool and orientation. The following tables (8 -15) are the acceleration data collected for each pneumatic tool and posture corresponding as the means and standard deviations. Table 8. Summary of Needle Gun ahv for All Subjects, Trials, and Idle/Contact/No Contact on Vertical Surface Subject Trial # No-Contact, ahv (m/s2) Contact, ahv (m/s2) Idle, ahv (m/s2) #1 1 14.6 9.3 2 12.4 10.2 3 13.6 9.68 0.22 #2 1 1.65 2.63 2 1.62 2.53 3 1.61 2.58 0.22 #3 1 3.45 3.96 2 3.38 4.02 3 3.31 4.33 0.165 #4 1 11.7 9.27 2 12.1 10.4 3 11.8 10 0.3 #5 1 3.41 3.98 2 3.4 4 3 3.31 4.31 0.16 Mean 6.76 6.08 0.21 Standard Deviation 5.11 3.22 0.06
34Table 9. Summary of Needle Gun ahv for All Subjects, Trials, and Idle/Contact/No Contact on Horizontal Surface Subject Trial # No-Contact, ahv (m/s2) Contact, ahv (m/s2) Idle, ahv (m/s2) #1 1 17.6 9.09 2 16 8.4 3 16.9 9.17 0.304 #2 1 1.6 2.2 2 1.45 2.29 3 1.4 2.25 0.07 #3 1 2.28 4.08 2 2.33 3.89 3 2.96 4.49 0.18 #4 1 12.5 11 2 12.3 8.85 3 12.6 9.17 0.419 #5 1 1.65 3.58 2 1.72 3.16 3 1.71 2.88 0.052 Mean 7.00 5.63 0.21 Standard Deviation 6.64 3.19 0.16 Table 10. Summary of Wire Wheel ahv for All Subjects, Trials, and Idle/Contact/No Contact on Horizontal Surface Subject Trial # No-Contact, ahv (m/s2) Contact, ahv (m/s2) Idle, ahv (m/s2) #1 1 2.66 9.59 2 2.48 9.33 3 2.54 8.46 0.068 #2 1 13.7 12.2 2 13.5 12.1 3 13.4 12.5 0.32 #3 1 1.21 2.31 2 1.18 2.04 3 1.31 2.17 0.215 #4 1 1.93 10.6 2 1.99 10.7 3 2.05 10.6 0.332 #5 1 15.7 9.68 2 15.9 9.7 3 15.3 10.1 0.06 Mean 6.99 8.81 0.20 Standard Deviation 6.47 3.61 0.13
35Table 11. Summary of Wire Wheel ahv for All Subjects, Trials, and Idle/Contact/No Contact on Horizontal Surface Subject Trial # No-Contact, ahv (m/s2) Contact, ahv (m/s2) Idle, ahv (m/s2) #1 1 2.43 5.8 2 2.57 5.27 3 2.67 5.88 0.31 #2 1 18.7 11.6 2 15.2 12.6 3 15.1 13.2 0.44 #3 1 1.37 2.04 2 1.33 1.86 3 1.29 1.95 0.24 #4 1 2.58 12.8 2 2.02 12.1 3 2.16 11.6 0.3 #5 1 14.5 15.9 2 16.8 12.4 3 15.6 12.3 0.25 Mean 7.62 9.15 0.31 Standard Deviation 7.14 4.79 0.08 Table 12. Summary of Angle Grinder ahv for All Subjects, Trials, and Idle/Contact/No Contact on Vertical Surface Subject Trial # No-Contact, ahv (m/s2) Contact, ahv (m/s2) Idle, ahv (m/s2) #1 1 1.78 2.42 2 1.79 2.38 3 1.73 2.56 0.176 #2 1 2.83 4.1 2 2.42 4.97 3 2.27 4.32 0.175 #3 1 12.7 9.45 2 13.1 8.5 3 12.9 8.69 0.23 #4 1 2.03 2.25 2 2.25 2.62 3 2.23 2.01 0.289 #5 1 2.18 7.53 2 2.25 8.11 3 2.3 8.25 0.21 Mean 4.32 5.21 0.22 Standard Deviation 4.45 2.86 0.05
36Table 13. Summary of Angle Grinder ahv for All Subjects, Trials, and Idle/Contact/No Contact on Horizontal Surface Subject Trial # No-Contact, ahv (m/s2) Contact, ahv (m/s2) Idle, ahv (m/s2) #1 1 1.83 3.49 2 1.82 3.38 3 1.88 2.98 0.158 #2 1 2.24 8.55 2 2.55 7.6 3 2.43 7.62 0.09 #3 1 13 10.5 2 11.7 10.1 3 12.3 9.91 0.142 #4 1 2.16 1.9 2 2.23 1.94 3 2.18 1.91 0.277 #5 1 2 10.1 2 2.01 9.7 3 2 7.23 0.199 Mean 4.16 6.46 0.17 Standard Deviation 4.24 3.43 0.07 Table 14. Summary of Knuckle Buster ahv for All Subjects, Trials, and Idle/Contact/No Contact on Horizontal Surface, (accelerometer next to hand closest body) Subject Trial # No-Contact, ahv (m/s2) Contact, ahv (m/s2) Idle, ahv (m/s2) #1 1 21.8 20.1 2 21.6 20.5 3 21.5 20.6 0.195 #2 1 21.3 17 2 20.9 17.1 3 21 18.3 0.071 #3 1 20.4 21.2 2 20.7 21.1 3 20.8 21.3 0.268 #4 1 21 16.7 2 21.5 18.4 3 21.4 16.9 0.279 #5 1 21.2 18.1 2 21.2 17 3 21.1 17.3 0.212 Mean 21.16 18.77 0.21 Standard Deviation 0.37 1.81 0.08
37Table 15. Mean Summary ahv and P-value Data for Vertical Surface vs. Horizontal Surface, No Contact vs. Contact Excluding Knuckle Buster. Tool Vertical Surface Horizontal Surface No Contact, ahv (m/s2) Contact, ahv (m/s2) No Contact, ahv (m/s2) Contact, ahv (m/s2) Needle Scaler 6.76 6.08 7.0 5.63 Grinder 4.32 5.21 4.16 6.46 Wire Wheel 6.99 8.81 7.62 9.15 P-Value 0.64 Comparison Mean Values of Pneumatic Tools: Cleaning vs Not Cleaning0 5 10 15 20 25 GrinderNeedle ScalerWire WheelKnuckle Buster Pneumatic Tools, 1-4Acceleration, (m/s^2) Cleaning Not Cleaning Figure 12 Comparison Mean Values of Pneumatic Tools in Horizontal Orientation: Cleaning vs. Not Cleaning A three-way ANOVA (subjects by tool, conditio n and orientation with replicates (not including idle conditions ) was conducted on the data. The analysis included the main effects and the interact ion of tool and condition. Th e Sailors were treated as a blocking variable. All the main effects and the interaction were significant at p <0.0001 except for surface orientation p<0.6396.
38 Discussion and Conclusions The major objective of this study was to assess whether there was a difference in hand-arm vibration levels while working on one of two surface orientations (e.g., horizontal and vertical) among di fferent pneumatic tools while cleaning or not cleaning. Significant differences in vi bration were noted with different pneumatic tools while cleaning or not cleaning vertical and horiz ontal surfaces (Figure 12). This finding replicated previous studies of individual tool vibration acceleration levels conducted while cleaning by others (Dunn, 2006: HSE, 2005: EU, 2002). The vibration acceleration levels of each i ndividual pneumatic tool were averaged for each surface and compared to the HSE accel eration chart data (Figure 8) and Dunn (2006) data. The HSE chart indicates the acceleration range between the 25th and 75th percentile points for a needle scaler to be 4.75 Â– 7.0 m/s2. This study found a needle scaler to average 5.63 m/s2 on a horizontal surface and 6.08 m/s2 on a vertical surface (Figure 12). In 2006, Dunn noted needle scal er acceleration levels ranging from 10.7 Â– 12.3 m/s2 at 60 psi and 12.5 Â– 14.1 m/s2 at 80 psi, and was higher than this study. The needle scalers were different models which might explain the difference. Additionally, DunnÂ’s research utilized test subjects that had no prior expe rience with pneumatic tools. Dale et al., (2006) compared production workers with non-production workers, (e.g., no previous pneumatic tool experience) and noted the non-production workers experienced higher vibration acceleration levels because they physically forced the tool to do the work
39 versus guiding the tool and allowing it to do the work. This study used experienced workers and this might also explain the lowe r vibration acceleration le vels noted in this study. The pneumatic grinder is a tool that produces vibration via a rotational motion rather than percussive and is commonly used onboard Navy ships. The HSE acceleration chart suggested 3.5-7.0 m/s2 vibration acceleration values in the 25th to 75th percentile range. This study noted a pneumatic grinderÂ’ s average vibration acceleration values to range from 5.21 m/s2 on a vertical surface to 6.46 m/s2 on a horizontal surface. Again, this data concurred with the HSE, 2005 vibr ation acceleration data (Figure 8, Tables 6 and 17). The pneumatic wire wheel is another rota tional motion tool that is used by the U.S. Navy to remove paint and corrosion from metal. The pneumatic wire wheel toolÂ’s average vibration acceleration values were from 8.81 m/s2 for a vertical surface and 9.15 m/s2 for a horizontal surface. The NavyÂ’s unique Â“knuckle busterÂ” is a percussive tool that generated the highest vibration acceleration levels noted in this study. The knuckle buster produced vibration acceleration values of 16.9 Â– 21.3 m/s2 with a mean of 18.77 m/s2 (while cleaning). It was similar to the demolition hammerÂ’s 25th to 75th percentile vibration acceleration data ranges from 13 18.2 m/s2 and the rammerÂ’s at 22.5 Â– 37.2 m/s2 (Figure 8 and 12, Table 14: HSE 2005). There is no significant difference in handarm vibration levels when comparing horizontal and vertical surfaces alone, p< 0.6396 (Table 17). Additionally, there was vague evidence that percussive pneumatic tools have higher rms values when not
40 cleaning vs. cleaning as compared to rotati onal pneumatic tools which have higher rms values when cleaning vs. not cleaning (Figure 12). In 2006, Dunn noted that U.S. Navy Sailors were not likely to have significant risk for Hand-Arm Vibration Syndrome fo r lifetime exposures to hand transmitted vibration (Dunn, 2006). He suggested that Â“if a sailor were exposed at the 80 psi level of 13.1 m/s2 for four hours per day, the daily exposure vibration level, A (8), would be 9.3 m/s2. Based on the ANSI group mean total (lifetime) exposure equation, it would take 3 years or 650 working days for this exposure group to present ten percent prevalence of HAVS. It does not likely a ppear that HAVS would be prev alent in sailor populations because it is not likely that they will use the needle gun for four hours per day for 650 days in their career.Â” In repeating DunnÂ’s conditions listed above for the tools studied in this research, the knuckle buster at 120 psi and a daily exposure vibration level, A (8), of 13.3 m/s2 for four hours per day equated to a lifetime expos ure of 2.0 years to pr esent a potential ten percent prevalence of HAVS in Sailors (Fig ure 6). The wire wheel at 120 psi, A (8), of 6.5 m/s2 and work duration of 4 hours per day eq uates to a lifetime exposure of 4.4 years to present a potential ten per cent prevalence of HAVS. The gr inder and needle scaler at 120 psi, A (8), of 4.6 and 4.3 m/s2 and a work duration of 4 hours per day produced lifetime exposures of 6.3 and 6.8 years, respectf ully (Figure 6). However, if any of the pneumatic tools in this study were used for gr eater than 1-4 hours, the Sailor will enter into the ANSI Â“Health Risk ZoneÂ” based on vi bration dose and duration of work (Figure 5; ANSI 2006).
41 U.S. Navy Sailors have a greater risk of HAV exposure while using a percussive pneumatic tool versus a ro tational pneumatic tool (Fi gure 5 & 7; ANSI, 2006; HSE 2005). The average HAV exposure time is gene rally less than one-hour for a Sailor to complete a typical paint removal task (Schiermeier 2007). Based on the ANSI, 2006 standard, (Figure 6) Sailors exposure leve l to HAV would not place them in the ANSI Â“Health Risk Zone,Â” (Figure 5, ANSI 2006). It was interesting to note that the type of tool class produced similar results throughout the study. The rotational tools such as the grinder and wire wheel had higher vibration acceleration levels while cleaning versus not cleaning. Conversely, the percussive tools had higher vibration accel eration levels while not cleaning versus cleaning. This relationshi p is shown in Figure 12. In conclusion, 1. There was a significant difference in hand-arm vibration levels among different pneumatic tools while clea ning or not cleani ng vertical and horizontal (bulkhead or deck) surfaces, 2. There was no significant difference in hand-arm vibration levels when evaluating surface orientation alone, 3. Some evidence demonstrated percussi ve pneumatic tools have higher rms values when not cleaning as opposed to rotational pneumatic tools which have higher rms values when cleaning.
42 REFERENCES CITED American Conference of Government al Industrial Hygienists (2006): 2006 TLVs and BEIs. Threshold Limit Values for Chem ical Substances and Physical Agents and Biological Exposure Indices Hand-Arm (Segmental) Vibration. (pp. 120Â–123). Cincinnati, OH: ACGIH. ANSI S2.70 2006. American National Sta ndard Guide for the measurement and evaluation of human exposure to vibr ation transmitted to the hand. (2006). Melville, NY: Acoustical Society of America. Brammer, A. J., et al., (1982). Vibration Effects on the Hand and Arm in Industry John Wiley & Sons, Inc., New York, Chiche ster, Brisbane, Toronto, Singapore. Bureau of Labor Statistics. (2004). W orkplace Statistics. U.S. Department of Labor. Retrieved April 11, 2007 from http://www.bls.gov/iff/oshw c/osh/case/in2004_nature.pdf Coffman, J. D., (1989). RaynaudÂ’s Phenomenon, Oxford University Press, New York Dale, A. M., et al. (2006). Challenges and Uncertainties in Designing Field Studies to Measure Hand Vibration Washington University School of Medicine, St. Louis, MO. Dear, J. A., (1994) Remarks by Assistant Secretary Dear via Satellite GovernorÂ’s Industrial Safety and Health C onference Spokane Convention Center Retrieved February 27, 2007 from http://www.osha.gov/pls/oshaweb/owad isp.show_document?p_table=SPEECHES &p_id=189 Dong, R. G. (2003). An Evaluation of the Standardize d Chipping Hammer Test Specified in ISO 8662-2. Ann. Occup. Hyg Vol. 48, No. 1, pp. 39-49, (2004). British Occupational Hygiene Society: Published by Oxford University Press. Dong, R. G. (2004). Measurement of Hand-Transmitted Vibration Exposures. Proceedings of the 10th International Conference on Hand-Arm Vibration, Las Vegas, USA, 2004.
43 Dong, R. G. (2006). Proceedings of the First Americ an Conference on Human Vibration (DHHS/CDC/NIOSH-June 5-7, 2006) Morg antown, WV. NIOSH-Publications Dissemination. Cincinnati, OH. The European Parliament and the Council of the European Union. (2002). On the minimum health and safety requirements regarding the exposure of workers to the risks arising from physical agents (vibration). Directive 2002/44/EC. Official Journal of the European Communities, L177, 13-19. Retrieved April 11, 2007 from http://europa.eu.int/eurlex/pri/en/oj/dat/2002/l_075/l_07520020316en00440045.pdf European Union. (2002). Guide to Good Practice on HAV, Retrieved February 26, 2007 from http://www.humanvibrati on.com//eu/bibguide/hav.pdf Giancoli, D. C. (1985). Physics, Principles With Applications, Prentice hall, Inc. Englewood Cliffs, New Jersey, 07632 Griffin, M. J. (1997). Measurement, ev aluation, and assessment of occupational exposures to hand-transmitted vibration. Occupational and Environmental Medicine, 54 73Â–89. Griffin, M. J. (2006). Proceedings of the First American Conference on Human Vibration (DHHS/CDC/NIOSH-June 5-7, 2006) Morgantown, WV. NIOSHPublications Dissemination. Cincinnati, OH. Health and Safety Executive, (1999). Hand-transmitted vibration: Occupational Exposures and their health effects in Great Britain Medical Research Council, University of South Hampton Health and Safety Executive. (2005). Control the risks from hand-arm vibration (HSE Books, leaflet INDG24(rev1)). Caerphilly Business Pa rk, Caerphilly. Retr ieved February 26, 2007 from http://www.hse.gov.uk/vibration. Health Safety Executive, (2005). The Control of Vibrati on at Work Regulations. Crown Copyright, QueenÂ’s Printer of Acts of Parliament. Retrieved February 26, 2007 from http://www.opsi.gov.uk/si/si2005/20051093.htm Howard, J. (2006). Proceedings of the First Americ an Conference on Human Vibration (DHHS/CDC/NIOSH-June 5-7, 2006) Morg antown, WV. NIOSH-Publications Dissemination. Cincinnati, OH. ISO 5349-1:2001(E). Mechanical vibration Measurement and evaluation of human exposure to hand-transmitted vibration Part 1: Ge neral guidelines. (2001). Geneva, Switzerland: International Organization for Standardization.
44 ISO 5349-2:2001(E). Mechanical vibration Measurement and evaluation of human exposure to hand-transmitted vibrati on Part 2: Practical guidance for measurement at the workplace. (2001). Geneva, Switzerland: International Organization for Standardization. ISO 8041:2005(E). Human response to vibratio n Measuring instrumentation. (2005). Geneva, Switzerland: International Organization for Standardization. ISO 8662-14:1996 (E). Hand-held portable power tools Measurement of vibrations at the handle Part 14: Stone-working tool s and needle scalers. (1996). Geneva, Switzerland: Internat ional Organization for Standardization. National Institute for Occupational Safety and Health. (1983). Current Intelligence Bulletin 38, Vibration Syndrome Cincinnati, OH. Retr ieved February 26, 2007 from http://www.cdc.gov/niosh/pubs.html National Institute for Occupational Safety and Health. (1989). Criteria for a recommended standard: Occupational exposure to hand-arm vibration (DHHS (NIOSH) Publication No. 89-106). Cinc innati, OH. Retrieved April 11, 2007 from http://www.cdc.gov/niosh/89-106.html National Institute for Occupational Safety and Health. (1997). Hand/wrist Musculoskeletal Disorders (Carpal Tunnel Syndrome, Hand/Wrist Tendonitis, and Hand-Arm Vibration Syndrome): Evidence for Work-Relatedness. (DHHS (NIOSH) Publication No. 97-141). Cinci nnati, OH. Retrieved February 26, 2007 from http://www.cdc.gov/niosh/97-141.html. National Institute for Occupational Safety and Health. (2000). Alice Hamilton, M.D. Cincinnati, OH. Retrieve d February 26, 2007 from http://www.cdc.gov/niosh/alice.html#person#person OPNAV Instruction 5100.19D, CH-1. (2001) NAVOSH Program Manual for Forces Afloat. U.S. Department of the Navy. Retrieved April 11, 2007 from http://www.safetycenter.navy.mil OPNAV Instruction 5100.23G. (2005). Navy safe ty and occupational health program manual: Ergonomics program. U.S. Depart ment of the Navy. Retrieved July 11, 2006, from http://neds.daps.dl a.mil/Directives/5100.23G.pdf Pelmear P. L., Taylor, W., Wasserman D. E. (1998). Hand-arm vibration A comprehensive guide for occ upational health professionals. New York: Van Nostrand Reinhold. Rand, Ingersoll. (2007). Corporate Information Retrieved February 26, 2007, www.ingersollrand.com
45 Wasserman D. E., et al., (1998). Hand-arm vibration A comprehensive guide for occupational health professionals. New York: Van Nostrand Reinhold. Wasserman, D. E., Hudock, S. D., Wasserma n, J. F., Mullinix, L., Wurzelbacher, S.J., Siegfried, K. V. (2002). Hand-arm vibra tion in a group of ha nd-operated grinding tools. Human Factors and Ergonomics in Manufacturing Vol. 12 (2) 211-226. Weeks, James L., et al., (1991) Preventing Occupational Disease and Injury. American Public Health Association, Washington, D.C.
46 APPENDIX A: PCB ICP ACC ELEROMETER SPECIFICATIONS
48 APPENDIX B: DOTCO 12L12. SERIES, SPECIFICATIONS
50 APPENDIX C: VIKING V364 MIDSIZED ANGLE HEAD DIE GRINDER SPECIFICATIONS
51 Viking, V364 Mid Size Angle Head Die Grinder Technical Details V364 Mid Size Angle Head Die Grinder is sligh tly larger than our mini version and has more torque Light weight 15,000 RPM design with heavy wei ght durability. Full one year warranty. Collet Size: 1/4", Free Speed: 15,000rpm, Overa ll Length: 6-3/4", Net Weight: 1-1/3lb. Air Inlet Thread NPT: 1/4", Air Hose ID Size: 3/8" ---------------------------------------------------------------------------Product Description Product Description The new V364 Mid Size Angle Head Die Grinder is slightly larger than our mini version and has more torque for those tougher applications. Light weight 15,000 RPM design with heavy weight durability. USA-made. Fu ll one year warranty. Specifications: Collet Size: 1/4", Free Speed: 15,000rpm, Overall Le ngth: 6-3/4", Net Weight: 1-1/3lb., Air Inlet Thread NPT: 1/4", Air Hose ID Size: 3/8" ---------------------------------------------------------------------------Product Details Shipping Weight: 4.00 pounds ASIN: B000KL54MS Amazon.com Sales Rank: None This page was created by a seller.
52 APPENDIX D: DAYTON 4CA41 NEEDLE SCALER SPECIFICATIONS
53 DAYTON 4CA41 SCALER NEEDLE 16C FM 4.0 CFM AVERAGE AIR FLOW 2 1/2 IN STROKE Item Needle Scaler Type General Duty Average CFM @ 15 Second Run Time 3.6 CFM @ Full Load 14.5 Stroke (In.) 2 1/4 Blows per Minute 2850 Min. Hose (In.) 3/8 Air Inlet NPT (In.) 1/4 Required Pressure (PSI) 90 Length (In.) 14 1/2 Handle Type Pistol For Use With 6W206, 6W207 Includes Needle Set No. 6W207
54 APPENDIX E: DESCO DECK CRAWLE R (KNUCKLE BUSTER) SPECIFICATIONS