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Dunn, Scott E.
Vibration level characterization from a needle gun used on U.S. naval vessels
h [electronic resource] /
by Scott E. Dunn.
[Tampa, Fla] :
b University of South Florida,
ABSTRACT: United States (U.S.) Navy sailors are exposed to a very large number of hazards, both chemical and physical. Occupational vibration from pneumatic air tools is one of the potential exposure hazards. There are very limited data as to the exposures to one type of tool, a needle gun or needle scaler, used by the sailors.The purpose of this study was to characterize the vibration levels generated by a needle gun used in the U.S. Navy. The design of the study evaluated the difference pressure had on the acceleration levels generated from the needle scaler. Five subjects were used in the evaluation of the tool. Each subject was required to hold the tool for twenty seconds activated without contact and activated on a surface and at two different pressures, 60 and 80 pound per square inch (psi). Each subject repeated each of the conditions three times for a total of 12 measurements. Each subject was also required to hold the tool in hand without the tool activated. The measurements were collected from an accelerometer on the needle gun following ISO 5349-1:2001 and ISO 5349-2:2001 methods. Significant differences were observed individually in pressure (p < 0.0001), contact (p < 0.0001)), and subjects (p < 0.001). In addition, there was a significant interaction between contact and pressure (p < 0.001). It was concluded that U.S. Navy sailors are not likely at significant risk to Hand-Arm Vibration Syndrome for lifetime exposures to hand transmitted vibration.
Thesis (M.A.)--University of South Florida, 2006.
Includes bibliographical references.
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Adviser: Thomas E. Bernard, Ph.D.
Vibration white finger.
x Public Health
t USF Electronic Theses and Dissertations.
Vibration Level Characterization from a Needle Gun Used on U.S. Naval Vessels by Scott E. Dunn 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. Steve Mlynarek, Ph.D. Andrea Spehar, D.V.M, M.P.H., J.D. Date of Approval: July 14, 2006 Keywords: hand-arm vibration, needle gun, needle scaler, percussive tool, vibration white finger Copyright 2006, Scott E. Dunn
Acknowledgments Foremost, I would like to acknowledge the United States Navy for providing the opportunity for pursuing my advanced degree. Especially, I want to thank the senior officers within the Medical Service Corps that had the confidence in selecting me for this DUINS assignment which ultimately allowed me to pursue my education interests at the University of South Florida. I would also like to thank the Naval Medical Education and Training Command staff that supported me throughout the program. I would like to thank my committee members for their time, consideration, and effort during the development and completion of my research. I would like to thank Dr. Andrea Spehar for becoming a committee member on such short notice and providing an outsider perspective on the project. Dr. Steve Mlynarek was an excellent sounding board for ideas and problem solving and kept me on track with this project and my coursework at the University of South Florida. I would especially like to thank Dr. Tom Bernard for his time, effort, and his expertise on the subject of this research. I would like to thank the commanding officer and the Operations Department personnel of the USS McInerney (FFG-8), home-ported in Mayport, Florida, for their cooperation in allowing me to conduct my research on their vessel and use the personnel to conduct the research. I would also like to acknowledge LT John Zumwalt at DESRON 14 and LCDR Tim Jirus at SERMC in Mayport for their assistance and coordination of the research on USS McInerney. On a personal level, I am grateful to my wife Beth and my children, Kathryn, Jeffrey, and Ryan that provided support, love, and understanding throughout this program. I would also like to thank the following individuals who assisted me with my research: Adam Marty, LT Charles Wilhite, and Luis Pieretti.
i Table of Contents List of Tables ii List of Figures iii Abstract iv Symbols and Abbreviations vi Introduction 1 Literature Review 5 Background 5 Health Effects of Hand-Transmitted Vibration 6 Diagnosis of Hand-Transmitted Vibration 8 Physics and Terminology 9 Occupational Standards and Guidelin es for Hand-Transmitted Vibration 14 Hand-Transmitted Vibration Measurements 20 Studies Associated with Needle Scal ers and Hand-Transmitted Vibration 22 Study Objectives 24 Methods 25 Materials & Equipment 25 Vibration Measurement Instrumentation 26 Protocol 27 Results 29 Discussion and Conclusions 31 References Cited 35 Appendix A: PCB ICP Accel erometer Specifications 39 Appendix B: Taylor Needle Scaler T-7356 Specifications 41
ii List of Tables Table 1 TaylorPelmear Stages of VWF 9 Table 2 Stockholm Workshop Scale for the Classification of Cold-Induced Raynauds Phenomenon in HAVS 9 Table 3 Stockholm Workshop Scale for the Cl assification of Sensorineural Affects of HAVS 9 Table 4 Needle Gun Vibration Measurements from HSE Contract Research Report 234/199 23 Table 5 Order Exposure 29 Table 6 Summary of a hv for All Subjects, Trials, Pressure (60 & 80 PSI), and Contact/No Contact 30
iii List of Figures Figure 1 Description of Bi odynamic and Basicentric Orthogonal Coordinate Axis Systems 12 Figure 2. Frequency Weighting Used by ANSI, ISO and ACGIH 13 Figure 3. ANSI Health Risk Zones for DEAV and DELV 17 Figure 4. Taylor Pneumatic Tool Company, Needle Scaler, Model T-7356 25 Figure 5. Illustration of Accelerometer Mounting 26
iv Vibration Level Characterization from a Needle Gun Used on U.S. Naval Vessels Scott E. Dunn ABSTRACT United States (U.S.) Navy sailors are expos ed to a very large number of hazards, both chemical and physical. Occupational vibr ation from pneumatic air tools is one of the potential exposure hazards. There are very limited data as to the exposures to one type of tool, a needle gun or needle scaler, used by the sailors. The purpose of this study was to character ize the vibration levels generated by a needle gun used in the U.S. Navy. The de sign of the study evaluated the difference pressure had on the acceleration levels genera ted from the needle scaler. Five subjects were used in the evaluation of the tool. E ach subject was required to hold the tool for twenty seconds activated without contact a nd activated on a surface and at two different pressures, 60 and 80 pound per square inch (psi ). Each subject repeated each of the conditions three times for a total of 12 measur ements. Each subject was also required to hold the tool in hand without the tool activated. The meas urements were collected from an accelerometer on the needle gun following ISO 5349-1:2001 and ISO 5349-2:2001 methods. Significant differences were obser ved individually in pressure ( p<0.0001), contact ( p<0.0001)), and subjects ( p<0.001). In addition, there was a significant interaction between contact and pressure ( p<0.001). It was concluded that U.S. Navy
v sailors are not likely at significant risk to Hand-Arm Vi bration Syndrome for lifetime exposures to hand transmitted vibration.
vi SYMBOLS AND ABBREVIATIONS a hw ( t ) instantaneous single-axis acceleration value of the ISO frequencyweighted hand-transmitted vibration at time t in meters per second squared (m/s 2 ); a hw root-mean-square (rms) single-axis acceleration value of the ISO frequency-weighted hand-transmitted vibration, in m/s 2 a hw x a hw y a hw z values of a hw in m/s 2 for the axes denoted x y and z respectively a hv vibration total value of the ISO frequency-weighted rms acceleration; it is the root-sum-of squares of the a hw values for the three measures axes of vibration in m/s 2 a hv(eq, 8h) daily vibration exposure (8-h energy equivalent vibration total value), in m/s 2 a hv(DEAV) vibration total value for a time T v other than 8 h that will result in a DEAV of 2.5 m/s 2 a hv(DELV) vibration total value for a time T v other than 8 h that will result in a DELV of 5.0 m/s 2 A (8) a convenient alternative term for the daily vibration exposure a hv(eq, 8h) DEAV or EAV Daily Exposure Action Value A(8) is equal to 2.5 m/s 2 DELV or ELV Daily Exposure Limit Va lue A(8) is equal to 5.0 m/s 2 D y group mean total (lifetime) exposure duration, in years HAVS Hand-arm vibration syndrome HTV Hand-transmitted vibration rss root sum of squares 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 a hv T 0 reference duration of 8 h (28,800 s) W h frequency-weighting characteristic for hand-transmitted vibration
1 INTRODUCTION The general United States worker may be exposed to a myriad of hazards, both physical and chemical. Occupational vibra tion is one of the many physical hazard exposures. It is found in landscaping (mowing lawn s and trimming shrubs), tree cutting, driving heavy construction equipment, or usi ng any assortment of hand power tools (i.e., jackhammers, grinders, need le guns, etc.) (NIOSH, 1989). E ight to ten million Americans are exposed to occupational vibration where two million of these are exposed to hand-arm vibration alone (Wasserman, 2001). Occupational vibration is cat egorized into hand-arm vibration (HAV) and whole body vibration (WBV). Whole body vibrati on affects the entire human body, and is usually transmitted in a sitting or standing position from a vibrating seat or platform (Wilder, D. E. Wasserman, J. Wasserman, 2002, p. 80). Hand-arm vibration focuses on the hand-arm unit alone and is transmitted to the hand via a power tool (Wilder et al., 2002). Hand-arm and whole-body vibration each elicit different health effects (Wilder et al., 2002). Whole body vibration primarily affects the lower back region (Wilder et al., 2002). The primary health effect curren tly associated with hand-arm Hand-Arm Vibration Syndrome (HAVS)(Wilder et al., 2002). Vibration white finger is also known by other names, such as vibration-indu ced Raynauds phenomenon (Pelmear, Taylor & Wasserman, 1992), secondary Raynauds phenomenon (Griffin, 1990), Raynauds Phenomenon of Occupational Origin, and vibration white finger (VWF) (Bruce,
2 Bommer, & Moritz, 2003). The prevalence and severity of HAVS usually increases with the magnitude of acceleration of the power tool and the durati on of time the tool is used (NIOSH 1989). United States Navy sailors, like their Amer ican worker counterparts, are exposed to hand-transmitted vibration (C. R. Wilh ite, personal communication, July 12, 2006). A typical example is the use of a compressed ai r power tool called a needle gun or needle scaler. The needle scalers are used to remove rust and/or coatings from the substrate, usually a steel bulkhead, deck or railing. N eedle scalers are used extensively during periods when the ship was in port. The exposure levels to these tools have not been fully characterized and the exposure levels are unknown. In 1999, Padda n, Haward, Griffin, & Palmer published some limited hand transmitted vibration data on several tools from surveys conducted around the United Kingdom. They conducted sampling on three needle scalers and found a range between 10.9 to 28.7 mete rs per second per second (m/s 2 ) (Paddan et al., 1999). Currently, the U.S. does not have a regulat ory standard for occupational vibration. However, the U.S. has three health and safety guidance documents published by: American Conference of Governmental Indus trial Hygienists (ACGIH) Threshold Limit Value (TLV) for Hand-Arm Vibration (2006), th e American National Standards Institute (ANSI) S2.70-2006 American National Standa rd Guide for the Measurement and Evaluation of Human Exposur e to Vibration Transmitted to the Hand (2006), and the National Institute for Occupational Safe ty and Health (NIOSH) Criteria For a Recommended Standard: Occupational Expos ure to Hand-Arm Vibr ation (1989). The international community also ha s published similar guidelines:
3 International Standards Or ganization (ISO) 5349-1:2001 Mechanical vibration Guidelines for the measurement and the assessment of human exposure to handtransmitted vibration (2001). European Directive 2002/44/EC On the minimum health and safety requirements regarding the exposure of work ers to the risks arising from physical agents (vibration)(2002).Member states were required to comply with the Directive by 6 July 2005. The occupational exposure limits published by most of the standards are prefaced with a disclaimer indicating th at the etiology of these disord ers is not well [understood] (ANSI S3.34-1986, 1986, p. 1). ANSIs older hand-transmitted vibration standard (1986) goes on to state that because of severa l confounding factors, Appendix B [of ANSI S3.34-1986, Latent Period for Hand-Transmitted Vibr ation] shall not be construed to be a general guide to permissible exposures to vibration transmitted to the hand (p. 1). NIOSH (1989) indicates that th ere are many variables that af fect the acceleration of the transmitted vibration to the hand and ther efore has not established a recommended exposure limit. The ISO 5349-1 (2001) publication states that the standard does not define the limits of safe vibration exposur e (p. 1) and therefore does not provide an exposure limit. The European Directive (2002), ACGI H TLV for Hand-Transmitted Vibration (2006), and the new ANSI S2.70 standard (2006) have establishe d an occupational exposure limit for hand-transmitted vibration. The European Directive for occupational vibration (2002) suggests a numerical value for vibration with the exposure action limit (EAL) of 2.5 m/s 2 (rms) and an exposure limit value (ELV) of 5.0 m/s 2 (rms). The European Directive (2002) derived these values from the ISO 5349 (1986) standard. The ANSI S2.70 (2006) standard defines the daily EAV represents the health risk threshold
4 to hand-transmitted vibration (p. 11). At the EAV and above, abnormal signs & symptoms will become prevalent. The daily ELV is considered a high health risk and the prevalence of symptoms will be more preval ent in the exposed population (ANSI, 2006). The new ANSI S2.70 standard (2006) for handtransmitted vibration has also adopted the same European Directive (2002) ELV and EAV. The current ACGIH TLV for Hand-Transmitte d Vibration (2006) is similar to the ISO 5349 (1986) hand-transmitted vibration standard. The ACGIH TLV for handtransmitted vibration (2006) is based on the do minant frequency-weighted, single axis acceleration and on a four hour exposure. The ANSI S2.70 (2006) and the European Directive (2002) vibration levels are base d on an equal energy model (root sum of squares for each of the ort hogonal axes of the hand) and standardized to an eight hour exposure.
5 LITERATURE REVIEW Background At the beginning of the 20 th century, physicians began to document health effects generated from vibrating equipment/tools. On e of the first docume nted occurrences of occupational injury from vibration app eared in 1907 when the United Kingdom Departmental Committee on Compensation for Industrial Diseases identified neurosis (p.74) in workers that was caused by vibration from pneumatic tools (Griffin, 1997). In 1911, the Italian physician, Giovanni Lori ga, identified Rayna uds phenomenon in workers that used pneumatic hammers on stone and marble (Bovenzi, 1998a). And in the United States, Alice Hamilton observed Ra ynauds phenomenon caused by vibration of pneumatic tools used in stone cutting in 1918 (Pelmear et al., 1992). In 1960, Louis Pecora et al. (1960) stated that Raynauds phenomenon of occupational origin may not be completely eradicated but that it may ha ve become an uncommon occupational disease approaching extinction in [t he United States] (p. 82). From the time occupational vibration was fi rst identified as a health hazard, more and more sources of hand-transmitted vibration have been identified. Besides vascular related adverse health effect s (e.g., VWF), other conditions have been linked to handtransmitted vibration, which include sensineura l and musculoskeletal effects (Pelmear et al., 1992). Since the turn of the twentiet h century, the scientific community has commonly assumed the vibration frequency ra nge of significance is between 8 1000 Hz (Griffin, 1990).
6 Health Effects of Hand-Transmitted Disorders The ANSI S2.70 standard (2006) defines hand-transmitted vibration as the mechanical vibration that, when transmitted to the human hand-arm system, may entail risks to worker health and safety, in particular vascular, bone or joint, neurological and muscular[disorders] (p. vi). Hand-transmitted vibration is vibration that is transmitted to the hand by some type of rotating and/or pe rcussive hand held tool (Bovenzi, 1998a). Workers that use rotating and/or percu ssive tools are found in mining, construction, forestry, shipbuilding, and landscap ing, among others (ISO 5389-1, 2001). The target organs for hand-transmitted vibration using hand-held power tools include the skin vasculature of the fingers, sensory nerves of the hand, and components of the locomotor apparatus of the hand-arm sy stem" (Pelmear et al., 1992). The primary health effect currently associated with hand-transmitted vibration is vibration white finger (VWF), Raynauds phenomenon of occupational origin, or hand-arm vibration syndrome (HAVS) (Pelmear et al., 1992). The prev alence of hand-arm vibration syndrome (HAVS) in the U.S. for worker populations th at use vibrating tools ranges from 6 to 100% with an average of about 50% (NIOSH 1989). There are also other disorders associated with hand-transmitted vibration from different types of tools other than vascular disorders (VWF). Griffin separates the disorders into five separate categories: vascular disorders, bone and joint disorders, peripheral neurological disorders, muscle disorders, and other disorders (e.g., of the whole-body and central nervous system) (Griffin, 1990). Vibration white finger is the commonly know n health effect associated with handtransmitted vibration. Environm ental factors can incr ease the prevalence of this disorder.
7 Bovenzi (1998b) demonstrated that different geographic areas are more or less susceptible to VWF based on temperature. Colder climat es had a higher prevalence of VWF compared to warm climates (Bovenzi, 1998b). Symptoms associated with VWF include tingling, numbness, blanching of the fingers, cyanosis (a bluish or purplish discoloration due to deficient oxygenation of the blood) and gangrene (Griffin, 1990). The actual HAVS mechanisms caused by hand-transmitted vibration are not clear (Wilder, et al., 2002). Some of the factors that lead to the deve lopment of HAVS are characteristics of the vibrating tool (vibra tion magnitude, direction and frequency; and duration of tool use), the type and condition of the tool, environmental factors, biodynamic factors, ergonomic factors, and i ndividual factors (ISO 5349-1, 2001). There has been extensive research conducted on vascular disorders associated with vibrating tools. NIOSH published a document in 1997 that provided a critical review of epidemiological evidence associated with Hand Arm Vibra tion Syndrome (Bernard, 1997). From 20 epidemiological studies, Bernard conclude d that there is subs tantial evidence that as intensity and duration of exposure to vibrating tools increase, the risk of developing HAVS increases (1997, p. 5c-9). In addition to VWF, Carpel Tunnel S yndrome (CTS) has also been linked with exposures to hand-transmitted vibration, how ever, not by itself (Bernard, 1997). Mild numbness and tingling is common in both HAVS and CTS. But the vascular injury to the hand in hand-transmitted vibration is different than the nerve compression in CTS (Pelmear & Leong, 2000). Disorders associated with hand-transmitte d vibration are not only linked to the vascular system of the hand but also there is evidence with chronic problems with bone and
8 joints, peripheral neurological system, muscular system of the hand, among other disorders (Griffin, 1990). The mechanisms for each of the disorders is also not clearly understood (Pelmear et al., 1992). Diagnosis of Ha nd-Transmitted Vibr ation Disorders There is no definitive, objective diagnos tic test for the vascular disorders associated with hand transmitted vibrati on (NIOSH, 1989). Physicians rely on the subjective report from the worker. This ma kes the diagnosis and classification difficult for the physicians (NIOSH, 1989). Although non e of the diagnostic tests for vascular disorders due to hand transmitted vibration are considered the gold standard, some of these tests can be useful in the assessment in conjuncti on with the subjective medical evaluation (Griffin, 1990, p. 592). Some of the di agnostic tests include: Doppler studies, plethysmography, finger systolic pressure measurements. There are also similar diagnostic tests for sensineural effects (Physical and Biological Hazards, Wilder, 2002). The medical community has devised assess ment methods to determine the degree of HAVS once it is diagnosed. In 1968, Taylor and Pelmear devised a classification system that was used until 1986 when their classification system wa s modified by the Stockholm Scale (Wasserman, 2001). The Stockholm Scale separated vascular and sensineural effects and also evaluated both hands (Pelmear, et al., 1992). The three scales are found in Tables 1 through 3.
9 Table 1. TaylorPelmear Stages of VWF (Pelmear et al., 1992, Table 3-1, p. 28) 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 Raynauds Phenomenon in HAVS (Pelmear et al., 1992, Table 3-2, p. 29) Stage Grade Description 0 No attacks 1 Mild Occasional attacks affecting on ly the tips of one or more fingers 2 Moderate Occasional attacks affec ting distal and mi ddle (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 Sensorineural Effects of HAVS (Pelmear et al., 1992, Table 3-3, p. 29) 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 Physics and Terminology In order to understand how vibratio n affects the body and how vibration is measured, it is important to understand so me of the physics and terminology involved with vibration. For the purposes of this discussion, vibration is the oscillatory movement of a solid or tool; the motion can be peri odic (sinusoidal) or random, and either
10 intermittent or continuous (Soule, 1973). The simplest form of periodic vibration is called pure harmonic motion which is a function of time and that can be represented by a sinusoidal curve (Soule, 1973, p. 339). Three co mponents are related mathematically to pure harmonic motion: displacement from an equilibrium position, velocity or rate of change in displacement, and acceleration or vect or quantity expressed as rate of change in velocity (Bruce et al., 2001). Acceleration is the critical component when considering occupational vibration measurement since it be lieved that the force from the acceleration is responsible for adverse h ealth effects (Bruce et al., 2001). Equation 1 represents acceleration mathematically. a = 2 X sin(t) = a peak sin(t) (1) Where: a = acceleration (m/s 2 ) a peak = maximum acceleration f = frequency (Hz or cycles/s) t = time (s) = angular frequency or 2 f X = maximum displacement (m) adapted from The Industrial Environment: Its Evaluation and Control, NIOSH, 1974, p. 339 Vibration is defined as a vector qu antity; it has magnit ude and direction (Wasserman, 2001). Describing occupational vibrat ion exposure levels is difficult. Peak vibration levels are useful when the wave form is purely sinusoidal; however, most occupational vibrations are not pure sinus oid waveforms and are complicated with varying frequencies (Bruce et al., 2003). Root-mean-square (rms) values are the primary unit for occupational vibration because the rms values are proportional to the energy content of the vibration (Soul e, 1973). Root-mean square values were the preferred method to describe severity of HTV exposur es; it was a common measure in engineering fields and was a convenient term for meas urement and analysis (Griffin, 1990). Root-
mean-square acceleration for an ISO frequency-weighted, single axis is defined in Equation 2 below: dttaTaTrmshwhw02)(1 (2) Where: a is the rms single axis acceleration of the ISO frequency-weighted hand-transmitted vibration in m/s 2 t is time in seconds T is the measurement time period. *from ANSI S2.70-2006,(2006, Eq. 3, p. 4) The direction component of vibration transmitted to the hand is described in three directions (x, y, and z) of an orthogonal coordinate system. Additionally, vibration is also transmitted through rotational axes: pitch, roll and yaw. The linear axes (x, y, and z) are used and explained by two coordinate systems typically associated with hand transmitted vibration: biodynamic and the basicentric coordinate systems. The biodynamic system is referenced from the third metacarpal of the hand and defines motions in x, y, and z axes (Wilder et al., 2002). Measurements for occupational vibration are not traditionally obtained directly from the hand but are taken from the tool handle, making the tool the reference point for the basicentric coordinate system (See Figure 1). It is an approximation of the biodynamic coordinate system. 11
Figure 1. Description of Biodynamic and Basicentric Orthogonal Coordinate Axis Systems (diagram from ANSI S2.70-2006, Figure 1(a), p. 6) In 2001, the ISO 5349 (1986) was revised to change reporting requirements from a dominant, ISO frequency-weighted, single axis acceleration to a root sum of squares acceleration (a hv ) (ISO 5349-1, 2001). The European Union Directive (2002) followed by requiring the measurement and reporting criteria of the ISO 5349 (2001). In 2006, ANSI updated their 1986 standard for hand-transmitted vibration to meet the measurement and reporting criteria of the ISO 5349 standard (2006). The current ACGIH TLV (2006) and the NIOSH Criteria Document (1989) for hand-transmitted vibration both still use the dominant, ISO frequency-weighted, single-axis measurements. The vibration generated by the tool has direction and is quantifiable, but the direction and magnitude also vary with the frequency component of the vibration transmitted to the hand. The vibration frequency unit is expressed in Hertz (Hz). A frequency weighting has been used in several vibration standards and is based on subjective sensations tolerated at varying frequencies (Griffin, 1997). The frequencies 12
evaluated ranged between 10 and 300 Hz for hand-transmitted vibration (NIOSH, 1989). The frequency weightings currently used in ANSI, ACGIH, and ISO have been extrapolated from the vibration sensations and are not health based (Griffin, 1997). The frequency range for each of the standards (ISO 5349-1, 2001; ACGIH, 2006; & ANSI S2.70, 2006) is between 5.6 and 1400 Hz. The composite frequency weighting used for hand-transmitted vibration by ANSI, ISO and ACGIH has not been linked to any one specific disorder; however there are certain frequencies have been linked to specific disorders (Griffin, 1990). The frequency weighting is illustrated below in Figure 2. Figure 2. Frequency weighting used by ANSI, ISO, and ACGIH (From ISO 5349-1:2001(E), Figure A.1, p. 9). The NIOSH Criteria Document for HAV (1989) disagreed with the frequency weighting and suggested that it underestimates the health effects produced from the high frequencies (NIOSH, 1989). NIOSH (1989) also goes on to state that unweighted frequency acceleration values provides a better means of assessing health risk with hand13
14 transmitted vibration. Bovenzi (1998b) indicated that there is not enough evidence to support the theory that unweighted accelerati on values are a more representative measure of risk for vascular disorders than the ISO frequency-weighted accelerations. Another topic important to the understa nding of occupational vibration is the concept of resonance. Wasserman (2001) de fines resonance as the tendency of a mechanical system (or the human body) to act in concert with externally generated vibration and to internally amplify the input vi bration and exacerbate its effects (Chapter 105, Section 1.6, para. 1). The maximum acceleration can be transmitted to the handarm system at its resonant frequency. Th e resonant frequency range of the hand-arm system is between 150 300 Hz (Bruce et al., 2003). Since the acceleration leve ls are gathered from the tool, an important question must be answered: how much is energy is ab sorbed by the hand? Several factors affect how the vibration is transmitted to the ha nd and fingers which includes the vibration magnitude, direction, and frequency, hand coupling to the tool, hand-arm posture, environmental conditions, and duration of expos ure (Griffin, 1990, p. 609). There is still a tremendous amount information that must be discovered to fully understand how vibration causes injury. Occupational Standards and Guidelines for Hand-Transmitted Vibration Several organizations have put forth hea lth and safety standards or guidelines for the control of the vibration produced by pow ered hand tools. The United States has published the following guidance on hand-transmitted vibration: ACGIH TThreshold Limit Value for Hand-Arm Vibration, 2006,
15 ANSI S2.70-2006 American National Standa rd Guide for the Measurement and Evaluation of Human Exposure to Vibration Transmitted to the Hand and, NIOSH Criteria For a Recommended Sta ndard: Occupational Exposure to HandArm Vibration, 1986. The U.S. Occupational Safety and H ealth Administration (OSHA) has not developed regulatory standard s for the control of HAV. The American Conference of Governmental Industrial H ygienists (ACGIH) developed a threshold limit for hand-transmitte d vibration that ACGIH believes that will protect nearly all workers from progressing to Stage 1 of the Stockholm Workshop Scale for the Classification of Cold-Induced Raynauds Phenomenon in HAVS (see Table 2)(ACGIH, 2006). The ACGIH guideline require s that measurements be collected in accordance with ISO 5349 (1986) or ANSI S3.3 4 (1986). Both the ISO 5349 (1986) and the ANSI S3.34 (1986) standards are based on the dominant axis, frequency-weighted, rms accelerations. Both the ISO and ANSI standards have been revised in 2001 and 2006, respectively considers root sum of squa res for each of the three basicentric or biodynamic axes. Guidance for hand-transmitted vibration in the United States Navy sailors is found in OPNAV Instruction 5100.23G (2005) The U.S. Navy guidance document instructs personnel to refer to the ACGIH TLV for Hand-Arm Vibr ation (2006) for two exposure scenarios. The first is for high vibr ation tools, such as, percussive-type tools (impact wrenches, carpet strippers, chain saws ), percussive tools (jack hammers, needle scalers/guns, riveting or chi pping hammers), and other high vibration tools where the usage exceeds 30 minutes total per day. The se cond is for moderate vibration tools such as, grinders, sanders, jigsaws, where th e usage exceeds 2 hours total per day.
16 ANSI recently updated the standard for hand-transmitted vibration in May 2006: American National Standard Guide for th e Measurement and Evaluation of Human Exposure to Vibration Transmitted to the Hand, ANSI S2.70-2006. The ANSI standard is very similar to the current ISO 53 49 (2001) and European Commission (2002) standards in that it requires the determinati on of the root sum of squares, frequencyweighted, rms acceleration ( a hv ). The ANSI S2.70 standard (2006) also identifies both parts of the ISO 5349 (2001) and ISO 8041 (2005) (Human Response to Human Vibration Measuring Instrumentation) as i ndispensable for the application of the ANSI S2.70 standard. One difference betw een the ISO 5349 (2001) and the ANSI S2.70 standard (2006) is that new ANSI standard prescribes a Daily Exposure Action Value (DEAV) and a Daily Exposure Limit Value (DELV) Each of the values are based on an eight hour work day where the DEAV is equal to 2.5 m/s 2 and the DELV is equal to 5.0 m/s 2 The DEAV represents a point at whic h symptoms of HAVS ma y begin to appear and the DELV are expected to be at high risk for developing HAVS (ANSI, 2006). The ANSI standard (2006) also presen ts a plot, Figure 3, which il lustrates the location of the health risk zones based on duration of tool use and the root sum of squares acceleration value (a hv ).
Figure 3. ANSI Health Risk Zones for DEAV and DELV (ANSI S2.70-2006, Figure A.1, p. 12) In the international community, the International Organization for Standardization (ISO) has developed a consensus standard for hand transmitted vibration: ISO 5349-1:2001 Mechanical vibration Measurement and evaluation of human exposure to hand-transmitted vibration General Requirements ISO 5349-2:2001 Mechanical vibration Measurement and evaluation of human exposure to hand-transmitted vibration Practical guidance for measurement at the workplace The ISO 5349 (1986) was changed in 2001 to measure the root sum of squares for the x, y, and z axes acceleration values instead of reporting the rms acceleration of the dominant axis. The new ISO 5349 standard (2001) recognized that not all power tools are dominated by a single direction of vibration magnitude. The current ISO standard for exposures to hand-transmitted vibration, ISO 5349 (2001), is divided into two parts. Part 1 provides information on the health effects related to hand-transmitted vibration, the relationship between vibration exposure and effects on 17
health, factors likely to influence the effects of human exposure to hand-transmitted vibration in working conditions, and specific guidance on preventative measures for hand transmitted vibration. Part 2 gives specific guidelines on how to measure vibration on hand-held vibrating and percussive tools. This standard takes into consideration the frequency of the vibration, magnitude, duration of exposure per day and the cumulative exposure to date (ISO 5349-1, 2001). However, the ISO 5349 (2001) standard does not prescribe a safe limit for hand-transmitted vibration exposures. The standard does indicate that the information it provides should protect the majority of the workers against serious health impairment associated with hand-transmitted vibration (ISO 5349-1, 2001, p. vi) Although the ISO 5349 standard does not provide occupational exposure limits, it does provide a way of predicting 10% prevalence of HAVS in a population that uses vibrating hand tools. The ISO 5349 standard (2001) indicates that Equation (3) below can be used to define exposure criteria designed to reduce the health hazard of hand transmitted vibration in a group of occupationally exposed persons (p. 16). For example, an eight hour daily exposure of 10 m/s 2 would indicate that 10% of that particular exposed group would develop finger blanching or HAVS in 2.77 years. 06.1)8(8.31ADy (3) Where A(8) is the daily vibration exposure and D y is the group mean total (lifetime) exposure in years *from ANSI S2.70(2006, Eq. A.4, p. 13) 18
The ISO 5349-2 standard describes guidance on the measurement methods and data collection. Both the ANSI S2.70 standard (2006) and the NIOSH Criteria Document (1989) provide information regarding measurement and data collection. The Europeans have recently taken a step forward in setting a regulatory health standard for hand-transmitted vibration that includes exposure limits. All countries part of the European Commission were required to comply with the requirements set forth in the European Directive 2002/4/EC (2002) regarding the minimum requirements for protecting the health of workers from hand transmitted vibration by July 6, 2005. The European Directive prescribes a daily Exposure Action Value (EAV) and a daily Exposure Limit Value (ELV). Both the EAV and the ELV consider time of exposure. The 8-hour acceleration value for the EAV is 2.5 m/s 2 and for the ELV it is 5.0 m/s 2 (European Directive, 2002). The equations for calculating the EAV and the ELV based on time are described below with Equation (4) and (5), respectively (Griffin, 2004). 21haction85.2ta (4) 21hlimit80.5ta (5) Where t h is the exposure duration express in hours. The ELV and EAV have also been adopted by the new ANSI S2.70 Standard (2006). The European Directive requires measurements to be collected in accordance with ISO 5349-1 (2001). Griffin (2004) and the new ANSI S.2.70 (2006) standard use an equation from ISO 5349, Equation (3) above, to predict HAVS in 10% of a population exposed to 19
20 vibration of the hand for the EAV and the ELV values of the European Directive. There is a 10% chance of HAVS for an ELV exposed worker in 5.8 years and 12 years for the EAV. Hand-Transmitted Vibr ation Measurements The test tool for the study was a compre ssed air-powered needle gun. The needle gun is considered a percussive tool and measurement challenges are associated with these types of tools. The ISO 5349-2 standard (20 01) gives practical guidance in measurement collection. The ISO 5349-2 standard (2001) suggest s the following considerations when collecting measurements with percussive tools: proper selection of accelerometer, proper placement of the accelerometer, proper connections between the vibration instrument and the accelerometer, and placement of the cable The ISO 5349-2 st andard (2001) also suggests that a mechanical filte r be used with percussive t ools that should not alter the frequency response characteristics of the instrume ntation. The filter is to be used to reduce high frequencies and prevent mechanical overloa ding of the integrated circuit piezoelectric accelerometer (ISO 5349-2, 2001). ISO 5349-2 (2001) suggests that the selecti on criteria for the accelerometer should allow it to tolerate the range of anticipat ed vibration magnitudes and have stable characteristics. The accelerometer should also be stable in the environment (i.e., temperature, humidity) tested and the weight should not interfere with the vibration characteristics of the tool. Placement of the accelerometer is also important and can vary. The ISO 5349-2 standard (2001) recommends that placement of the accelerometer be at or near the surface
21 of the hand near the vibration entry point of the hand or near the middle of the palm. In most practical cases, the accelerometer canno t be placed on the hand without interfering with the workers grip on the tool. The accelerometer should be placed near either side of the hand from the grip position (ISO 5349-2, 2001). There are also various ways to mount th e accelerometer to the tool. The most common method is to securely tighten a clam p around the accelerometer and tool. There are other ways of securing the accelerometer on the tool as well: screwed or welded mountings, glue or adhesive mountings, cl amp mountings, hand-held adaptors (ISO 53492, 2001). Another important aspect in the meas urement of hand-transmitted vibration concerns the cable between the accelerometer and the instrument. If the cable is not secured to the vibrating surface near its conn ection, this may cause in terference with the measurement. Additionally, improper or faulty connections between the cable, acceloremeter, and the instrument can also contri bute to unreliable acceleration values (ISO 5349-2, 2001). Other possibilites for measur ement error include DC-shi fts. Griffin (1990) describes this phenomenon as an erroneous instantaneous change in the DC signal produced by some accelerometers and their sign al conditioning in response to mechanical shock (p.811). The ISO 5349-2 standard (2001) states that the DC-shift can occur in the accelerometer and cause a mechanical overloadi ng of the piezoelectric electronics. The ISO 5349 standard for hand-transmitted vibration indicate that a mechanic al filter should be used between the accelerometer and the percu ssive tool. The ISO 5349-2 standard (2001) cautions the user that the m echanical filter may increase th e accelerations of the non-
22 percussive axes. Smeatham, Kaulbars, and Hewitt (2001) suggest that a thin sheet of resilient material will suffice to reduce the DC-shift with lightweight accelerometers; less than two grams. Studies Associated with Needle Sc alers and Hand-Trans mitted Vibration There are few studies on th e characterization of needle scalers with regard to vibration. The British Human Factors Research Unit, Institu te of Sound and Vibration Research, and Medical Research Council evaluated vibration associated with several different types of tools in 199 9 (Paddan, Haward, Griffin, & Palm er). This study evaluated vibration by using a finger ring th at was held securely against the tool and fitted with three separate accelorometers to meas ure each of the mutual orthog anol axes (Paddan et al., 1999). The researchers sampled for a five se cond period and used the ISO 5349 (1986) frequency-weighting for the measurements. Th e study gathered 10 triaxial measurements from three needle scalers. The dominant axis was determined to be the y axis (percussive axis) for all but one measuement from the ne edle scalers. This study also included a spectral analysis of the acceleration across th e frequency range evalua ted. Pressure from the compressor supplying air to the tool was not noted in the survey. The researchers calculated the root sum of squares (rss) for all ten measuremen ts. The mean rss accelerations for tools 1 and 2 in the cl eaning modes wa s approximately 17 m/s 2 The results of this study are summarized below in Table 4. The rss values in Table 4 for the x y and z axes were not part of the report; but were calculated for comparison purposes to the data collected for th is research study.
23 Table 4. Needle Gun Vibration Measurements from HSE Contract Research Report 234/1999 Frequency-weighted Vibr ation Accelerations (rms m/s 2 ) Tool # Operation Handle x y z rss free run main body 4.31 18.77 3.89 19.65 cleaning main body 3.99 13.35 6.48 15.37 cleaning main body 4.70 12.77 3.73 14.11 1 cleaning main body 4.05 12.64 4.94 14.16 free run main body 2.71 23.03 3.21 23.41 cleaning main body 4.81 18.62 5.78 20.08 cleaning main body 3.33 18.31 5.32 19.36 2 cleaning main body 2.49 18.21 3.90 18.79 cleaning rear 4.40 10.90 14.50 18.67 3 cleaning main body 2.50 28.70 2.60 28.93 *adopted from Paddan et al, 1999, Table B1, p. 48. This study recommended that measurements for hand-transmitted vibration should include direct measurement of vibration ma gnitudes, documentation of tool use and duration patterns, and ergonomics in the workplace (Paddan et al., 1999). Palmer, Coogon, Bendall, Kellingray, Pannett, Griffin, and Haward ( 1999), conducted a postal survey in Great Britain to determine occupational exposures to vibration. The study determined personal vibration exposures based on a hw (dominant, frequency-weigthed, single-axis) values from published and other sour ces of information. The study determined the domi nant rms single-axis accelerati on value for needle scalers was 16.0 m/s 2 Some tool manufacturers (Trelawny SPT Ltd. (2006), Chicago Pneumatic (2006), and Jet Tools (2006)) list the acceleration levels for their equipment in a specification sheet or on their web sites. The th ree listed manufacturers indicate that they us e the ISO 8662-14 standard (1996) for the measurement of their needle guns. The ISO 8662-14 is the specific guidance used in determining vibration leve ls with needle guns in laboratory-type controlled conditions. The requirements of th e ISO 5349-1 standard (2001) gives more
24 latitude as how to collect and document the vi bration levels. Trelawny SPT Ltd. (2006), Chicago Pneumatic (2006), an d Jet Tools (2006) website posted acceleration values for needle scalers can range from le ss than 10 to nearly 25 m/s 2 Study Objectives The principal purpose of this study was to assess the vibration level of a typical needle gun used by the U.S. Navy in the free and contact modes. A second objective was to examine the effects of tool supply air pressure on vibra tion. The null hypo theses for this study were: Tool supply air pressure does not affect vibration There is not a difference in vibration leve ls between contact and no contact with a surface
METHODS Materials and Equipment The test needle gun for this study was the Taylor Pneumatic Tool Company needle scaler (Model No.: T-7356). The needle scaler was borrowed from new stock of a U.S. Navy ships tool issue. The Taylor needle scaler is a cylindrical-shaped tool that is 15 inches long, weighs 6 pounds and is shown in Figure 4. The manufacturer of the needle scaler states that the tool operates at 4500 blows per minute (bpm) which can be converted to a fundamental frequency of 75 Hz. The needle scaler manufacture literature indicates that 10 cubic feet per minute (cfm) is required to operate the tool at 90 pounds per square inch (psi) and not to operate the tool above 90 psi. A 50 foot section of rubber hose was connected between the air compressor and the tool. The hose was uncoiled to prevent restrictions on air flow. A Mi-T-M Corporation single stage air compressor (Model No.: AC1-PH55-08M) was used to power the needle gun. The specifications for the air compressor indicate that 9.0 cfm of air can be delivered at 100 psi. Part of the reason for selecting 80 and 60 psi was for sustained air flow to the tool. Figure 4. Taylor Pneumatic Tool Company, Needle Scaler, Model T-7356 25
Vibration Measurement Instrumentation The Quest Technologies HAVPro personal human vibration monitor was used for the data collection. The HAVPro vibration kit comes with a tri-axial, integrated circuit piezoelectric (ICP) accelerometer manufactured by PCB Group, Inc. (Triaxial PCB ICP Model 356A67). Due to mounting limitations on the Taylor needle scaler, the tri-axial accelerometer was mounted on the tool such that the actual basicentric Y (percussive) axis was the X axis on the mounted accelerometer and illustrated in Figures 5a-c. The mounted Z axis is the X axis on the basicentric coordinate system and mounted Y is the basicentric Z axis. See Figure 1 for comparative purposes. Yaxis Z axis (a) (b) (c) Figure 6. Illustration of Accelerometer Mounting. (a) Photo of tool grip of hand and mounted accelerometer. (b) Photo of the ICP accelerometer mounted onto the needle scaler. X axis runs parallel to tool handle and would be considered the Y axis on the basicentric coordinate system, (c) illustration of all three axes on the ICP accelerometer. Two 1/16 rubber gaskets (as a double layer) were installed between the tool and the accelerometer and another 1/16 piece of rubber was wrapped around the hose clamp illustrated in Figures 5a and 5b. This provided the mechanical filter as suggested by the ISO 5349-2 standard. The filters are used to lower measurement errors by reducing the high acceleration in the higher frequencies and prevents the overloading of the 26
27 piezoelectric system (ISO 5349-2, 2001). The specifications for the PCB ICP accelerometer and Taylor needle scaler are provided in Appendix A and B, respectively. The tool-mounted accelerometer was c onnected to the Quest Technologies HAV Pro instrument by way of a shielded cable. The cable was taped to the tool and to a small length of the hose to re duce a triboelectric effect. The HAV Pro meets requirements of the ISO 8041:1990(E) Human response to vibration Measuring instrumentation. Since the HAV Pro meets the requirements for ISO 8041, the instrument is compatible with ISO Standards 5349-1:2001 and 53492:2001. Protocol Five test subjects held the needle scaler in three conditions: 1) idle, in hand, 2) activated, in hand, and 3) activ ated on a cast iron manhole cove r. The idle condition was conducted one time for each test subject. Each of the other two conditions was conducted for twenty seconds and each condition was re peated three times. Conditions #2 and #3 were repeated at two different air pressures: 60 and 80 pounds per square inch (psi). The pressures used in this research were in accordance with the manufacturers recommendations of less than 90 psi. A total of 13 measurements were collected for each subject. The HAV Pro instrument was setup to averag e in 1 second intervals for the x, y, z axes and the root sum of squares ( a hv ). Prior to each measurement, the in strument was allowed to stabilize for approximately twenty seconds. The data was stored onto the HAV Pro and then downloaded to a laptop computer which interf aced with the QuestSuite Professional, Version 1.70 software package.
28 The data from the QuestSuite were th en exported into Microsoft Excel and formatted for analysis. Each of the th irteen 20-second samples per individual was converted to a root-mean-square (rms) value by Equation 2. The rms 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) using an analysis of variance (ANOVA) and providing descriptive sta tistics. Significant differences were considered to exist when the probability of a Type I erro r was less than 0.05. A multiple comparison procedure, Tukeys Honestly Significant Difference (HSD) test, was used in a further statistical analysis.
29 RESULTS The primary purpose of this study was to characterize hand-transmitted vibration of one needle scaler used by U.S. Navy sa ilors. ISO frequency-weighted, rms (rootmean-square) acceleration levels were measured on the needle scaler with five subjects, two different pressures (60 and 80 psi), and m easurements were gathered when the tool was activated and in contact with a surface and not in contact with a surface. An additional twenty second condi tion was evaluated when the t ool was not activated in the subjects hand. The output from the HAVPro instrument provided an averaged rms acceleration level at each second for each of the three axes ( x, y, and z ) and the root sum of squares ( a hv ) of the three axes. The order of expos ures for each subject is listed below in Table 5. Subjects were measured in the orde r listed (left to right) and then from top to bottom. The rms acceleration levels for a hv from each 20-second sample and the means and standard deviations are summarized below in Table 6. Table 5. Order of Exposures Test # Subj 1 Subj 2 Subj 4 Subj 5 Subj 3 1 R R R R R 2 80NC 60C 60NC 80C 60NC 3 80C 60NC 60C 80NC 60C 4 80NC 60C 60NC 80C 60NC 5 80C 60NC 60C 80NC 60C 6 80NC 60C 60NC 80C 60NC 7 80C 60NC 60C 80NC 60C 8 60C 80NC 80C 60NC 80C 9 60NC 80C 80NC 60C 80NC 10 60C 80NC 80C 60C 80C 11 60NC 80C 80NC 60NC 80NC 12 60C 80NC 80C 60NC 80C 13 60NC 80C 80NC 60C 80NC R = tool resting in hand, not activated 60 or 80 = pressure in psi C = tool activated and in contact with surface NC = tool activated in hand, no contact with surface
30 Table 6. Summary of a hv for All Subjects, Trials, Pressure (60 & 80 PSI), and Contact/No Contact 60 PSI 80 PSI Tool Idle No Contact Contact No Contact Contact Not Activated Subject Trial a hv (m/s 2 ) a hv (m/s 2 ) a hv (m/s 2 ) a hv (m/s 2 ) a hv (m/s 2 ) 1 13.7 10.7 15.2 13.0 2 13.6 11.6 15.5 12.5 1 3 13.7 11.7 15.5 12.6 0.143 1 13.9 11.1 15.9 12.9 2 13.9 11.8 16.1 13.4 2 3 13.7 11.5 16.0 12.8 0.195 1 14.1 11.4 16.9 13.0 2 14.3 11.8 16.8 12.9 3 3 14.2 11.9 16.8 13.4 0.151 1 13.7 11.7 15.5 13.2 2 14.1 11.6 16.3 13.8 4 3 13.9 12.3 16.9 13.2 0.261 1 14.1 11.3 17.1 14.1 2 14.2 10.8 17.3 12.6 5 3 13.9 11.4 17.1 13.0 0.137 Means 13.9 11.5 16.3 13.1 0.177 Standard Deviations 0.219 0.421 0.697 0.450 0.052 A three-way ANOVA (subjects by pressure by contact) with re plicates (not including idle conditions) was conducted on th e data. The analysis included the main effects and the interaction of pressure and contact. The subjects were treated as a blocking variable. All the main effects and the interaction were significant at p<0.001. Tukeys HSD test was used to determine wh ich pairs were signifi cantly different among the interaction pairs. Each interac tion pair was significantly different at p <0.001 level. The interaction of pressure and contact s hows the amount of increase in acceleration levels from 60 to 80 psi in the contact mode is greater than the in crease in acceleration levels when the tool was not in contact with a surface.
31 DISCUSSION AND CONCLUSIONS The main purpose of this study was to provide data on vibration associated with the use of a needle gun used by U.S. Navy sa ilors. The vibration of the Taylor T-7356 needle gun was evaluated at two pressu re levels and contact conditions. Significant differences in vi bration were noted with change in pressure and between contact with a surface and no contac t. The measured mean acceleration levels for the Taylor needle gun in contac t with a surface were 11.5 and 13.1 m/s 2 at 60 and 80 psi, respectively. The mean accelerations without contact were 14.0 and 16.3 m/s 2 at 60 and 80 psi, respectively; with increased vibration over contact of 2.5 and 3.2 m/s 2 Two British reports (Palmer et al., 1999. and Paddan et al., 1999) identified differences in accelerations in the contact a nd no contact modes. The first study, Palmer et al. (1999), determined that 16.0 m/s 2 was the dominant, single-axis acceleration representative for needle guns in Great Br itain. The root sum of squares value ( a hv ) would be slightly higher than the dominant single axis value. The second study, (Paddan et al., 1999) eval uated the accelerati on levels of three needle guns used in Great Britain. The Pa ddan et al. (1999) study mean root-sum of squares (rss) accelerations for t ools #1 and #2 were 14.6 and 19.4 m/s 2 in the contact/cleaning mode and 19.7 and 23.4 m/s 2 in the non-contact mode, respectively. Tool #3 appeared to be a gun-type needle sc aler and there were two measurements (two different handles) for this partic ular tool in the cleaning mode It should be noted that neither of the two British studies indicated the tool supply ai r pressure. The acceleration levels determined by the British were higher than the values found in this research; and
32 the Paddan et al. (1999) study de monstrated similar differences between accelerations in the contact and no contact modes. Some tool manufacturers; such as Tr elawny SPT Ltd.(2006), Chicago Pneumatic (2006), and Jet Tools (2006), provided accelera tion data on their needle scalers. Trelawny SPT Ltd. (S. Jerger, personal communication, July 11, 2006) and Chicago Pneumatic (T. Wastowicz, personal communi cation, July 13, 2006) indicated they used the ISO 8662 standard for measuring acceleration levels. Jet Tools (2006) just listed the vibration acceleration levels on their web site and did not indicate what method was used to determine the acceleration levels. The ISO 8662-14 standard (1997) for needle guns requires a controlled environment for acceler ation measurements. Chicago Pneumatic had several cylindrical needle scalers in th eir inventory and the accelerations ranged from 3.7 to 16.9 m/s 2 (Chicago Pneumatic, 2006). Trelaw ny SPT Ltd. had two different cylindrical needle scalers, models 1B and 2B that had vibration acceleration levels at 8.5 and 9.3 m/s 2 respectively (Trelawny SPT Ltd., 2006). The specifications for Taylor needle scaler used in this research did not provide acceleration data. There was some lack of uniformity in currently available measurement standards, at least between the two ISO standard s, 8662-14 (1996) and 5349 (2001). Tool manufacturers use the ISO 8662-14 (1996) to pr ovide acceleration data for needle guns new tools where the ISO 5349 (2001) method is us ed for more measuring vibration levels for tools used in the workplace. Both the NIOSH Criteria Document on Hand-Arm Vibration (1989) and the work of Wasserman, D. E., Hudock, Wasserman, J. F., Mullinix, Wurzelbacher, and Siegfried (2002) suggested that newer tools will have lower
33 vibration levels than tools that have been used during normal operations over time and/or poorly maintained. One outcome that both the Paddan et al. ( 1999) or Palmer et al. (1999) studies did not evaluate was the effect of tool supply air pressure on vi bration. The current research found that increasing pressure increases vibration levels. Adjusting tool supplied air pressure to a minimum level while maintain ing tool function can be used as control measure to reduce the acceleration tran smitted to the hand. Although, reducing the pressure may increase the amount of time to complete the job w ith the tool; thereby increasing time of vibration. The current rese arch also demonstrated that the acceleration values were higher in the no-contac t mode versus the contact mode. The mean acceleration values for 60 psi, c ontact with a surface and 80 psi, contact with a surface were 11.5 and 13.1 m/s 2 Based on the means at the two pressures and with the needle scaler in contact with a surface, the EAV and ELV times for 60 psi would be 23 and 91 minutes, respectively. The E AV and ELV times for 80 psi are 18 and 70 minutes, respectively. Navy sailors may use the needle scaler, wo rst case conditions, for four to five hours in a day for a couple of months at a tim e. However, Navy use of the needle scaler changes with rank. As sailors are promoted, th e use of the needle gun either decreases or ceases. If a sailor were exposed at the 80 psi level of 13.1 m/s 2 for four hours per day, the daily exposure vi bration level, A (8), would be 9.3 m/s 2 Based on the group mean total (lifetime) exposure equation (Equation 3), it would take 3 years or 650 working days for this exposure group to present ten percent prev alence of HAVS. It does not likely appear
34 that HAVS would be prevalent in sailor populations because it is not likely that they will use the needle gun for four hour s per day for 650 days in their career. However, tool pressure can be used to decrease ac celerations to lower exposure levels. In conclusion, the principal purpose of this study was to provide vibration data on a needle gun used by U.S. Navy sailors. The results of the study revealed the following: 1. Vibration levels were higher in the no contact mode compared to the contact mode, 2. Vibration levels increased as the tool supply air pressure increased and, 3. U.S. Navy sailors are not likely at si gnificant risk for Hand-Arm Vibration Syndrome for lifetime exposures to hand transmitted vibration. Industrial workers are likely to rema in on the same job using a number of different vibrating tools longer than a U.S. Navy sailor. I ndustrial workers may likely be at higher risk to vibration-induced white fi nger due to the increased lifetime exposures.
35 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. 120). Cincinnati, OH: ACGIH. ANSI S3.34 1986. American National Standard Guide for the measurement and evaluation of human exposure to vibra tion transmitted to the hand. (1986). New York: Acoustical Society of America. ANSI S2.70 2006. American National Standard Guide for the measurement and evaluation of human exposure to vibr ation transmitted to the hand. (2006). Melville, NY: Acoustical Society of America. Bernard B. P. (Ed.). (1997) Musculoskeletal disorders and wo rkplace factors: a critical review of epidemiologic evidence for wo rk-related disorders of the neck, upper extremities, and low back (DHHS (NIOSH) Publication No. 97-141, pp. 5c-1 5c-31). US Department of Health and Human Services, National Institute of Occupational Safety and Health. Bovenzi, M. (1998a). Hand-transmitted vibration. In J. M. Stellman (Ed.), Encyclopaedia of occupational health and safety (4 th ed., Vol. 2, Chap. 50). Geneva, Switzerland: International Labor Office. Retrieved July 8, 2006, from http://www.ilo.org/encyclopaedia/?d&nd=857100079&prevDoc=857000193 Bovenzi, M. (1998b) Exposur e-response relationship in the hand-arm vibration syndrome: an overview of current epidemiology research. International Archives of Occupational Environmental Health 71, 509-519. Bruce, R. D., Bommer, A. S., & Moritz, C. T. (2001). Noise, Vibration, and Ultrasound. In DiNardi, S. R. (Ed.), The occupational environment: Its evaluation, control, and management (pp. 435-493). Fairfax, VA: AIHA Press. Chicago Pneumatic. Retrie ved July 11, 2006 from http://126.96.36.199/CPIndustrialSite/Default.asp 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 July 11 2006, from http://europa.eu.int/eur-lex/pri/en/oj/d at/2002/l_075/l_075200 20316en00440045.pdf
36 Griffin, M. J. (1990). Handbook of human vibration. London: Academic Press; 1990. Griffin, M. J. (1997). Measurement, evaluation, and assessment of occupational exposures to hand-transmitted vibration. Occupational and Environmental Medicine, 54 73. Griffin, M. J. (2004). Minimum health and sa fety requirements for workers exposed to hand-transmitted vibration and whole-body vibration in the European Union; a review. Occupational and Environmental Medicine 61, 387. Griffin M., Bovenzi M., Nelson C. M. ( 2003) Dose response patterns for vibrationinduced white finger. Occupational and Environmental Medicine, 60, 16. Harris, C. M., & Piersol, A. G. (Eds.). (2002). Harris shock and vibration handbook (5 th ed.). New York: McGraw-Hill. ISO 5349: 1986. Mechanical vibration Guide for the measurement and assessment of human exposure to hand transmitted vi bration. (1986). Geneva, Switzerland: International Organizatio n for Standardization 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. 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 8662-1:1988 (E). Hand-held portable power t ools Measurement of vibrations at the handle Part 1 : General. (1988). Geneva Switzerland: Intern ational 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: International Organization for Standardization. Jet Tools. Jet air tools catalog. Retrieved July 11, 2006 from http://www.wmhtoolgroup.com/bro chures/Ind06_8Airtools.pdf
37 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). Cinci nnati, OH. Retrieved July 11, 2006 from http://www.cdc.gov/niosh/89-106.html. 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 Paddan, G.S., Haward, B.M., Griffin, M.J ., Palmer, K.T. (1999). Hand-transmitted vibration: Evaluation of some common sources of exposure in Great Britain; Final report by the Health and Safe ty Executive. CRR/234/1999-HSE Books. Palmer, K., Coogon, D., Bendall, H., Kellingr ay, S., Pannett, B., Griffin, M., and Haward, B. (1999). Hand-transmitted vi bration: Occupational exposures and their health effects on Great Britain; Final report by the Health and Safety Executive. CRR/232/1999-HSE Books. Pecora L. J., Udel M & Christman R. P. ( 1960). Survey of current status of Raynaud's phenomenon of occupational origin. Industrial Hygiene Journal 21 80-83. Pelmear P. L., Taylor, W., Wasserman D. E. (1992). Hand-arm vibration A comprehensive guide for occ upational health professionals. New York: Van Nostrand Reinhold. Pelmear, P. L. & Leong, D. (2000). Review of occupational standard s and guidelines for hand-arm (segmental) vibration syndrome (HAVS). Applied Occupational and Environmental Hygiene, 15 (3), 291-302. Smeatham, D., Kaulbars, U., Hewitt, S. (2004, September). Triaxial hand-arm vibration measurements on percussive machines. Presented at the 39 th United Kingdom Group Meeting on Human Response to Vibration, Ludlow, Shropshire, England. Soule, R. D. (1973). Vibration. In NIOSH: The industrial environment: Its evaluation and control. (DHHS (NIOSH) Publication No. 74-117), National Institute for Occupational Safety and Health. (197 3). Washington, D.C.: United States Government Printing Office. Trelawny SPT Ltd. Retrieve d July 11, 2006 from http://www.trelawnyspt.com/needle_scalers_technical.htm
38 Wasserman, D. E. (2001). Occupational Vibr ation: Hand-Arm Vi bration. In Bingham, E., Cohrssen, B., Powell, C. H. (Eds.), Patty's Toxicology: Vol. 8, Physical Agents, Interactions, Mixtures, Popu lations at Risk, United States and International Standards (5 th ed.). John Wiley & Sons. Online version available at: http://www.knovel.com/knovel2/Toc .jsp?BookID=706&VerticalID=0 Wasserman, D. E., Hudock, S. D., Wasserman, J. F., Mullinix, L., Wurzelbacher, S.J., Siegfried, K. V. (2002). Hand-arm vibration in a group of ha nd-operated grinding tools. Human Factors and Ergonomics in Manufacturing Vol. 12 (2) 211-226. Wilder, D. G., Wasserman, D. E., Wasserman, J. (2002). Occupational Vibration Control. Wald, P. H., Stave, G. M. Eds., Physical and biological hazards of the workplace (2 nd ed.)(pp. 79-104). New York: John Wiley and Sons, Inc.
APPENDIX A: PCB ICP ACCELEROMETER SPECIFICATIONS 39
APPENDIX B: TAYLOR NEEDLE SCALER T-7356 SPECIFICATIONS 41