HETA 87-348-2011 NIOSH INVESTIGATORS:

FEBRUARY 1990 Randy L. Tubbs, Ph.D.

ELECTRIC BOAT Thomas E. Doyle

GROTON, CONNECTICUT Thomas G. Wilcox, M.D., M.S.

 I. SUMMARY

In July, 1987, the Metal Trades Council of New London County, AFL-CIO requested that the National Institute for

Occupational Safety and Health (NIOSH) evaluate the use of pneumatic hand tools by workers employed as grinders

and welders at the Electric Boat Shipyard in Groton, Connecticut. The request reported that approximately 100 of these

workers had complained of tingling and numbness in their hands, symptoms compatible with the Hand/Arm Vibration

Syndrome (HAVS), a condition caused by excessive exposure to hand-tool vibration. 

On April 4-7, 1988, NIOSH conducted a site visit to the Shipyard. Vibration measurements were made on eleven

different commonly-used pneumatic hand tools in accordance with the method specified by the American National

Standard Institute's Guide for the Measurement and Evaluation of Human Exposure to Vibration Transmitted to the

Hand.1 The tool types investigated were a needle gun, a sand tamper, a lead caulker, and grinders and burring tools

manufactured by several different tool companies.

The vibration measurements revealed that most of the eleven tools should be limited to 4 or fewer hours of use during an

8-hour work shift to be within the 1989-90 American Conference of Government Industrial Hygienists (ACGIH)

Threshold Limit Value (TLVs) for hand/arm vibration exposure. Only the Stanley Offset Grinding Wheel, one of the

True Power Burring Tools, and the Chicago Pneumatic #3 Corner Drill had vibration levels determined in one or more

measurements that would allow usage from 4 to 8 hours per day. The other eight tools had levels of vibration measured

which would restrict their usage during an 8-hour work shift from less than 4 hours to no usage whatsoever (levels

greater than 12 meters/second2[m/sec2]). The lead caulker (pneumatic chipping hammer), sand tamper, and three of the

4 types of burring tools had vibration levels in excess of the ACGIH TLV of 12 m/sec2. 

A local occupational medical clinic reported that over 300 Electric Boat Shipyard employees had been seen because of

tingling and numbness in their hands and/or finger blanching [symptoms compatible with hand/arm vibration syndrome

(HAVS)]. Physicians at this clinic had also distributed a questionnaire to a sample of grinders, welders, and shipfitters

inquiring about symptoms compatible with HAVS. Approximately 70% of grinders, 25% of welders, and 10% of

shipfitters reported finger blanching.

Because of the small number of tools measured, it would be inappropriate to generalize these vibration

measurements to all of the tools used at the shipyard. However, because of the large number of workers seen at

the occupational medicine clinic for symptoms compatible with HAVS, because the tool measurements revealed

that restrictions in the times of use for most of the tools was warranted, and because no administrative procedure

existed to determine and implement these tool use restrictions, the NIOSH investigators conclude that a health

hazard existed at the shipyard. Recommendations to reduce vibration exposure are made in Section VII.

KEY WORDS: SIC 3731 (Shipyard), Vibrating Tools, Hand Transmitted Vibration, Hand Arm Vibration Syndrome

(HAVS), Vibration White Finger (VWF) 

This Health Hazard Evaluation (HHE) report and any recommendations made herein are for the specific facility evaluated and may not be universally

applicable. Any recommendations made are not to be considered as final statements of NIOSH policy or of any agency or individual involved.

Additional HHE reports are available at http://www.cdc.gov/niosh/hhe/reports

This Health Hazard Evaluation (HHE) report and any recommendations made herein are for the specific facility evaluated and may not be universally

applicable. Any recommendations made are not to be considered as final statements of NIOSH policy or of any agency or individual involved.

Additional HHE reports are available at http://www.cdc.gov/niosh/hhe/reports

This Health Hazard Evaluation (HHE) report and any recommendations made herein are for the specific facility evaluated and may not be universally

applicable. Any recommendations made are not to be considered as final statements of NIOSH policy or of any agency or individual involved.

applicable. Any recommendations made are not to be considered as final statements of NIOSH policy or of any agency or individual involved.

Additional HHE reports are available at http://www.cdc.gov/niosh/hhe/reports
 II. BACKGROUND

In July, 1987, the Metal Trades Council of New London County, AFL-CIO requested that investigators from the

National Institute for Occupational Safety and Health (NIOSH) evaluate the use of pneumatic hand tools by

workers employed as grinders and welders at the Electric Boat Shipyard in Groton, Connecticut. The request

reported that approximately 100 of these workers had complained of tingling and numbness in their hands,

symptoms compatible with the hand/arm vibration syndrome (HAVS), a condition caused by excessive exposure to

hand-tool vibration. 

On April 4-7, 1988, a NIOSH field team visited the Shipyard to meet with Electric Boat management personnel

and representatives from the Metal Trades Council. After proper clearances had been obtained for the NIOSH

team, an opening conference was held on April 4 to gather facts about the health and work activities of the

employees. At this time, it was explained that vibration measurements would be taken on a selected number of

pneumatic hand tools in use in the shipyard to assess the magnitude of the vibration impinging on the workers' hands. 

A walk-through tour of the areas where these tools were used was then conducted. Beginning on April 5, vibration

measurements were made over the next two and one-half days.

 III. METHODS

Vibration measurements were conducted at the work site using hand tools which had been checked out of the tool

crib by the employees. To the extent possible, these measurements were obtained with the employee using the tool

on the ship's hull in his normal work routine. Information on the vibration levels was obtained from eleven different

pneumatic hand tools. The tool types investigated were a needle gun, a sand tamper, a lead caulker, and grinders

and burring tools manufactured by several different tool companies. The vibration data measurement runs were

generally collected for durations of two minutes and were repeated at least once if permitted by the work task. There

were also two instances where the same model-numbered tool from the same manufacturer was measured in

different locations, operated by different workers.

Measurements were made in accordance with the orthogonal direction definitions specified by the American

National Standard Institute's Guide for the Measurement and Evaluation of Human Exposure to Vibration

Transmitted to the Hand (ANSI S3.34-1986).1 According to the standard, a triaxial configuration of measuring

transducers is mounted onto the tool handle. A basicentric coordinate system uses the head of the third metacarpal

bone as the origin and defines the Z-axis as the longitudinal axis of the bones of the arm. The X-axis is perpendicular

to the palm of the hand ("up and down") when the palm faces forward. The Y-axis passes through the origin and is

perpendicular to the X-axis ("side to side"). This coordinate system for the hand is shown in Figure 1. 

Three Columbia Research Model 6064 piezoelectric accelerometers were fixed in a small metal cube welded to a

hose clamp in the triaxial fashion referred to above. The clamp and accelerometers were tightened onto the handle of

the pneumatic tool being measured. The triaxial accelerometer assembly was connected through a 20-ft. charge

cable to a tape recorder where the acceleration signals from these three transducers were converted to voltages,

amplified by individual charge amplifiers, integrated in the FM tape recorder, and recorded on their respective data

channels. The data were recorded on a Bruel & Kjaer Model 7006 FM instrumentation recorder and stored for

later analysis on 1/4" instrument grade magnetic recording tape. The recorder has four-channel capability, allowing

for the simultaneous acquisition of data from all three orthogonal axes, as well as a timing channel. A time code was
placed on the tape with a Datum Model 9300 Time Code Generator/Reader. Using a tape speed of 1.5 in/sec, a

frequency range from 0.5 Hz to 1600 Hz was obtained.

Before and after data collection, the three piezoelectric accelerometers were dynamically calibrated according to the

manufacturer's instructions using a Bruel & Kjaer Model 4291 Accelerometer Calibrator. As measurements were

being made, a monitoring oscilloscope (Tektronix Model 321) was observed to insure that only true vibration data

was being recorded and that no signal overloading (clipping) was occurring.

The analysis of the tape-recorded acceleration data was performed with a Hewlett-Packard Model 3561A

Spectrum Analyzer. This analyzer is capable of doing real-time frequency analyses of the 1/3 octave band center

frequencies of 6.3 Hz to 1250 Hz. Because of the long integration times necessary to reliably analyze the lower

frequency bands, usually only 2-4 continuous samples were included in each of the spectral analyses. This number of

samples, however, incorporates about 50-100 seconds of real-time continuous vibration data.

 IV. EVALUATION CRITERIA

Hand-Arm Vibration Syndrome (HAVS) can affect workers who have extensively used vibrating hand tools.2

Loggers who use gasoline-powered chain saws, foundry workers who use pneumatic air hammers and grinding

wheels, and miners who use pneumatic drills have been the occupational groups most extensively studied. Usually

the first symptoms experienced by affected workers consist of numbness and tingling of the hands and fingers similar

to that reported by people with carpal tunnel syndrome. After a variable period of tool use (depending on the

intensity of the vibration produced by the tool), workers will notice that one or more finger tips become white and

numb when the workers are exposed to cold. The worker may also notice decreased hand dexterity and impaired

sense of touch in the hands. If vibration exposure continues, symptom severity can increase to the point where all

fingers of both hands frequently experience local vasospasm and finger blanching upon even mild cold exposure. 

Occasionally tissue necrosis in the fingers can occur. The Hand-Arm Vibration Syndrome is more extensively

discussed in NIOSH Current Intelligence Bulletin Number 38.2

The criteria used in the evaluation of hand-arm vibration exposure are twofold: 1) The American National Standard

Institute's Guide for the Measurement and Evaluation of Human Exposure to Vibration Transmitted to the Hand

(ANSI S3.34-1986),1 and 2) American Conference of Government Industrial Hygienists (ACGIH) Threshold

Limit Values (TLVs) and Biological Exposure Indices for 1989-90.3

1. The ANSI standard specifies the recommended method for the measurement, data analysis, and reporting of

human exposure to hand-arm vibration. The standard format for reporting the vibration spectral data is to

analyze the root mean square (rms) acceleration levels in meters per second squared (m/sec2) in one-third

octave bands in the frequency range from 5.6 Hz to 1400 Hz. This format is followed for each of the three

orthogonal directions of vibration.

Additionally, the ANSI standard contains three appendices, which are not part of the standard, but do

provide information on the assessment of exposure to hand-arm vibration for each center frequency of the

discrete one-third octave bands analyzed.
Figure 2 is reproduced from the standard and is based on regular daily exposures extending over many

years. Occasional days of exposure to vibration levels higher than that shown in the reported exposure zones

is not necessarily harmful. The time values given in the zones are for the actual length of tool use and not the

length of the work day.

2. The ACGIH Threshold Limit Values (TLVs)3 state that the magnitude of the vibration of the tool in each

direction (X, Y, Z) during normal operation shall be expressed by the rms value of the frequency-weighted

component accelerations, in units of m/sec2. The direction with the largest rms acceleration forms the basis for

the exposure assessment. If the total daily vibration exposure in a given direction is composed of several

exposures of different rms accelerations, the equivalent frequency-weighted component acceleration in that

direction shall be determined by using a time-weighted average.

In this investigation of pneumatic tool assessment, linear integration of the tool's acceleration for the time period

during which each tool was measured (1-2 minutes) was assumed to be representative of the daily work task. 

If these work conditions are unchanged for the entire work day, then the measured acceleration levels are

compared to the daily exposure TLV for hand-arm vibration (Table 1) to assess the exposure limits.

When one compares the two vibration exposure standards, it should be noted that they are not directly

comparable. The ACGIH TLV is a single number which represents the summed power values for each of

the 1/3 octave bands after each band has been weighted according to the filter characteristics given in the

TLV. The ANSI standard, however, considers each of the 1/3 octave bands separately as it compares them

to the exposure time zones. Thus, there may be instances where the overall ACGIH acceleration value may

limit tool usage to less than 1 hour per day while the individual 1/3 octave band values from the same tool may

only reach the 1-2 hour line of maximum tool usage. This difference is due entirely to the manner in which the

two different evaluation criteria are calculated. 

Information for both evaluation standards is based on available knowledge about the latent intervals (time

between first using vibrating tools and the first appearance of finger blanching) associated with vibration

exposure of various magnitudes. Considering the available knowledge and confounding factors such as grip

force, grip orientation, ergonomics, intermittent exposures, temperature, etc., it is not possible to provide

precise guidelines for each exposure condition. Therefore, the tables and graphs of vibration assessment

present "zones" of daily exposure time. These criteria are based on relatively uninterrupted vibration

exposures. They also assume a good coupling of the worker's hand to the tool. For any other hand-arm

vibration conditions, this assessment may be overly conservative, that is, the hazard may be less.

The ACGIH TLVs were formulated as guidelines to be used in conjuction with anti-vibration tools,

anti-vibration gloves, proper work practices, and a conscientiously-applied medical surveillance program to

protect workers from the adverse affects of hand-arm vibration exposure. The tool acceleration levels and

durations of exposure in the ACGIH guidelines represent conditions under which it was believed that most

workers could be exposed without progressing to severe signs of HAVS (episodes of extensive blanching of

all fingers and definite interference with activities at work and home). 

The ACGIH vibration exposure guidelines will not necessarily prevent the development of all hand morbidity

associated with vibration exposure. Extrapolation of data presented in Appendix A of the ANSI vibration
standard suggests that after 4 hours of daily use of a vibrating tool with a frequency weighted acceleration of 4

m/sec2 for a period of about 17 years, 50% of a workforce cohort so exposed could be expected to have

experienced episodes of at least initial finger blanching. If the tool used had a weighted acceleration of 6

m/sec2, 50% of the workforce could be expected to have experienced finger blanching after about 11 years. 

For a tool with a weighted acceleration of 12 m/sec2, 50% of the workers could have such symptoms after

working only 5 to 6 years. 

 V. RESULTS

Acceleration data were collected from eleven different types of pneumatic hand tools. For this report, the tools will be

grouped as follows:

A. Grinders Group

1. Dresser Cleco 6000 Grinder, Model 15GL60RA (2 tools)

2. Chicago Pneumatic "Whirlybird" Grinder/Vertical Sander,

 Model CP 9122 (2 tools)

3. Stanley Grinder/Offset Wheel, Model G30LA2

B. Burring Tools Group

1. Chicago Pneumatic Large Straight Burr, Model 9113G

2. Stanley Offset Burring Tool, Model G30LA2

3. Dresser Cleco Burring Tool, small, Model 11GLF250

4. True Power "Welder's Burr" Burring Tool, Model AP-210 (2 tools)

 C. Other Pneumatic Tools

1. Von Arx Offset Needle Gun, Model MDP-1

2. Chicago Pneumatic Caulking Gun/Chipping Hammer, Model CP 4112

3. Chicago Pneumatic Corner Drill, Model CP 3450

4. Dresser Cleco Sand Tamper, Model AT 6874

The data were tape recorded while the operator was performing real work on a particular task in construction (one

task was simulated). The tasks were varied, ranging from grinding external weld beads, to using the grinding wheel

edge to grind slots by holding the wheel perpendicular to the work face. The ergonomic positions were quite varied,

with workers standing, sitting, bending, or even lying prone at the work site. Some workers, while sitting, would

brace their forearm against their knees. In some situations, the grinding or burring was done at a higher than head

level, with the arms raised.

All operators observed in the vibration tests (three females and eight males) wore work gloves of some type. Some

of the gloves had leather palm areas, but many wore "Impact-o-Gloves", a cotton work glove lined with Viscolast

ER 505 which is a material advertised to decrease the transmission of vibration to the hand. Workers told NIOSH

investigators that the operators would order the smallest size vibration glove available in order that the glove would fit

tightly over the palm, so as not to "bunch up" and cause discomfort in the palm area.
The acceleration data collected for the three groupings of pneumatic tools are presented in Tables 2-4. Each Table

indicates the kind of tool measured, the dominant axis of vibration based on the weighted rms acceleration value, the

range of acceleration levels in m/sec2 for the dominant axis over the repeated measurements of the tool, a comparison

of the low and high acceleration value to the ACGIH TLV for hand-arm vibration, and a brief description of the

worker's activity during the recording period. Additionally, a spectral plot of the three axes of vibration of the

measurement of the tool for the high and low range acceleration values is given for each tool listed in the tables. These

plots are included in Appendix A. 

Overlayed on the spectral plots in this report's Appendix A is the upper limit of the time zones referred to in the ANSI

standard's Appendix A. Thus, if the dark spectral line is below the first solid line, the worker can use the tool for the 4

- 8 hour time zone. If the spectral line crosses into the next layer, the worker is allowed a 2 - 4 hour usage period. A

crossing into the next higher layer is the 1 - 2 hour zone, and a spectral plot which crosses all three zone boundaries

may be in excess of the ANSI appendix to the standard. It should be noted that the ANSI document does allow for

a 1/2 - 1 hour zone, but that has not been included in the spectral plots presented in this report. This was done for

clarity and simplicity in the plotting of these data.

Generally, the vibration measurements revealed that most of the eleven tools should be limited in their usage during an

8-hour work shift. Only the Stanley Offset Grinding Wheel, one of the True Power Burring Tools, and the Chicago

Pneumatic #3 Corner Drill had vibration levels determined in one or more measurements that would allow usage

from 4 to 8 hours per day. The other eight tools had levels of vibration measured which would restrict their usage

during an 8-hour work shift from less than 4 hours to no usage whatsoever (levels greater than 12 m/sec2). The

majority of the burring tool measurements were in excess of the ACGIH TLV of 12 m/sec2. The True Power

"welder's burr" was the only burring tool which did not exceed an acceleration of 12 m/sec2 on any measurement.

There were two situations where the type of work being done influenced the levels of acceleration. One instance

was with the Chicago Pneumatic Whirlybird Grinder (b). The operator was working on the hull at the outer torpedo

doors. A cut had been made into the hull, and the grinder operator was smoothing the area around the cut on the

surface of the hull as well as smoothing the cut metal edge. This operation necessitated that the worker either place

the grinding wheel parallel to the surface of the hull with the majority of the wheel touching the surface (measurement

#1) or at a perpendicular orientation to the hull with only a minimal part of the grinding wheel in contact with the metal

edge of the hull (measurement #2). As can be seen in Table 2, the second work condition resulted in higher vibration

levels than the condition where a large portion of the grinding wheel was in contact with the work piece surface. This

is most likely due to the small surface area of the hull's metal edge and the need for the operator to direct the grinding

wheel into the restricted area of the cut. The second instance of the work influencing the measurements was with the

Chicago Pneumatic #3 Corner Drill. The operator made two different drill holes during the measurement period. 

For the first measurement, a brace which attached to the drill was used. In the second instance, the brace was

removed and the drill was hand held by the operator. The former situation resulted in an acceleration level of 1.1

m/sec2, and the latter work practice yielded a 12.5 m/sec2 acceleration value. Obviously, the additional support from

the brace reduced the amount of vibration being emitted by this rather large drill.

During the course of the site visit, the NIOSH investigators were given the opportunity to use some of the

pneumatic tools in the work place. The group of burring tools were the most difficult to operate for the untrained

user. They would have a propensity to grab into the surface and "run away" from the user as he hung onto the tool. 

Workers said that a great deal of strength was needed to control the tool as it did its work. The strength needed to
operate the grinders and the other types of tools, which were larger and heavier, was to lift and hold them, rather than

control them during operation.

It must be emphasized that the measurement conditions under which the Chicago Pneumatic Chipping Hammer

(lead caulker) was tested were simulated to try to mimic the typical workplace conditions. This was necessary

because of the inaccessibility of work areas where lead was being used. A square piece of steel was placed into a

square wooden box and the caulker was used to spread lead into the seam formed between the steel block and

wooden box. This proved to be less than an adequate simulation of actual worksite practices. The metal block and

wooden box had a great deal of play in the way in which they fit together. This would cause the work piece to rattle

around as the operator attempted to caulk lead into the seam between the block and box. The actual work

performed on the ship would not cause this kind of extraneous movement of the work piece. These less than perfect

conditions most likely affected the acceleration levels measured on this pneumatic tool.

 VI. DISCUSSION AND CONCLUSIONS

Because of the complicated nature of the measurement scheme and the limited time available, the number of tools

measured during the site visit is small when compared to the hundreds of pneumatic hand tools used at Electric Boat. 

It necessarily takes a great deal of time to correctly make these kind of measurements. Because of the small number

of tools measured, it is impossible to generalize these measurements to all of the tools used at the facility. 

Nevertheless, the measurements, which were made at the work site under actual work conditions, are at least

indicative of the magnitude of acceleration levels which can be obtained with pneumatic hand tools of the types

studied. Because the majority of the acceleration measurements revealed that a restriction in the time of use of the

tools was warranted, Electric Boat should be aware of the potential for excess hand-arm vibration exposure in

workers who must routinely use these kinds of tools in performing their jobs.

Workers reported that chipping hammers had formerly been used to clean many of the weld sites, but that

gradually burring tools had been substituted for the chipping hammers to perform the rough removal of metal. The

acceleration levels recorded for burring tools revealed that the current ACGIH TLV was exceeded in the majority of

cases. It appears that the objective of quickly removing metal from the hull may be the reason for the high levels of

vibration. Doing a lot of work in a short period of time yields high levels of vibration, and burring tools require extra

effort to hold them in place on the work piece surface to keep them from radically moving along the surface. If one

would slowly remove the metal, then the higher peak acceleration levels would be reduced, thus reducing the

integrated vibration per hour of tool use. It will take additional time to remove metal with a grinder; however, the

vibration levels from this class of tool is less than the accelerations found in the burring tools.

In the shipyard, tools are normally checked out of a tool crib by the employee at the beginning of the shift or when a

particular tool is needed. Workers reported that tools were only repaired when they failed completely and could thus

perform no work. One of the burring tools measured during the study had a shaft with a very noticeable amount of

play. This tool, whose shaft would wobble back and forth when the tool was moved in the operator's hand, had a

measured acceleration ranging from 7.9 to 8.7 m/sec2. The looseness of the shaft probably added to the high

vibration level being emitted by this tool. The same model of pneumatic burring tool measured at another shipyard

worksite had the lowest acceleration of any tool measured (1.0 to 2.7 m/sec2). A program of routine preventative

maintenance for pneumatic tools is needed. Routine inspection of the defective burring tool following usage may have

identified it as one needing repair or one which should have been removed from the tool crib.
The observation of reduced vibration in the #3 corner drill through the use of an additional brace is a work practice

which should be encouraged and continued. This type of tool should not be used as a hand-held tool. The practice

of using a brace should be pursued to see if other tools would lend themselves to this use condition. There may be

situations where mechanical supports could be used in jobs which require a lot of tool usage. The operator would

have less contact with the tool, and the vibration levels may be reduced during the periods where the tool must be

directed.

The majority of the tool measurements made in the NIOSH survey had frequency-weighted vibration levels in the

range of 6 to 12 m/sec.2 As discussed in Section III, workers exposed to vibrating hand tools producing a

frequency-weighted acceleration in the range of 6 to 12 m/sec2 could be expected to have a median latent interval

(the time between beginning such tool use and first experiencing finger blanching) of 6 to 11 years. If employees were

using a tool of much higher acceleration (e.g., the burring tool measured at 79 to 88 m/sec2) symptoms could begin

much earlier. 

In the last 4 years, over 300 employees from Electric Boat who used vibrating tools in their work have been

evaluated at a local occupational medical clinic because of numbness and tingling in their hands and/or finger

blanching. It is of interest that the average latent interval to initial finger blanching was about 8 to 10 years for affected

workers, but some workers experienced symptoms after only 2 to 3 years. 

At the time of the NIOSH site visit, the majority of vibrating tools were used by grinders and welders. 

Approximately 500 workers were employed as grinders, whose primary tasks involved using grinding tools, such as

large and small pneumatic grinding wheels, or smaller burr tools. The approximately 800 welders performed

"incidental grinding", mostly using small burr tools 1 or 2 hours per day. In 1988, the local occupational medicine

clinic distributed a questionnaire to a sample of grinders, welders, and shipfitters. Seventy percent of the grinders and

25% of the welders reported experiencing finger blanching. Ten percent of the shipfitters (who use vibrating tools less

frequently) reported experiencing finger blanching. 

The reported fact that over 300 workers have been medically evaluated for symptoms compatible with the

hand/arm vibration syndrome, and NIOSH's tool vibration survey results indicate that additional measures to lower

hand/arm vibration exposures and to medically monitor employees at Electric Boat are necessary. The following

recommendations are made to help achieve those goals. 

 VII. RECOMMENDATIONS

1. Electric Boat should make every effort to ensure the use of pneumatic grinding and burring tools that have been

designed to minimize the amount of vibration energy transmitted to the users' hands and arms. 

2. The company has recently improved its ability to measure the vibration levels of hand-held vibrating tools. The

tool models found to have markedly high vibration levels in the NIOSH survey (the chipping hammer, sand

tamper, and several of the burr tools) should be carefully evaluated by the company regarding their vibration

characteristics. If the excessive tool acceleration levels found in the NIOSH survey are representative of those

tool models, those tool models should be replaced with anti-vibration tools as soon as possible. The remaining

vibrating tool classes used in the shipyard should then be systematically evaluated to determine their vibration

characteristics. Until all vibrating tools in use at the shipyard produce levels of vibration less than 4 m/sec2, a

program should be instituted to restrict the time of use of tools exceeding that level to time periods well within

those allowed by the ACGIH TLV. 
3. The present tools should receive corrective and periodic maintenance to the manufacturers specifications to

minimize their vibration energy during operation. If these tools become so worn that they cannot be repaired

(e.g., damaged bearings, bushings, etc.), the tool should be replaced immediately. 

4. Some of the air-powered tools have an air exhaust that causes the tool and the user's hand to become cold

when the tool is in use, sometimes even developing frost on the metal surface and handles. Since affected

workers may have "white finger" attacks precipitated by this cold exhaust air, tool modifications to redirect this

air exhaust away from the user's hands should be considered.

5. A formal training program should be established by Electric Boat to instruct current and new employees in the

proper work practices of using vibrating hand tools. The techniques of grasping the tools as loosely as possible

consistent with safe work practices should be taught. Grasping the tools lightly will decrease the mechanical

coupling and thus the vibration energy absorbed by the hand.

6. NIOSH is releasing a Criteria Document entitled "Criteria for a Recommended Standard...Occupational

Exposure to Hand-Arm Vibration", NIOSH Publication No. 89-106, September, 1989. This document

should be available in the near future. Chapter VII is included in this report as Appendix B. This chapter,

called "Methods for Worker Protection", contains control strategies which may be quite useful for Electric

Boat's industrial hygiene and safety programs. The topics covered are engineering controls, work practices,

ergonomic considerations, protective clothing and equipment, worker training, and medical monitoring of

workers. As indicated, any effective vibration control procedures need data detailing the hazard, that is, the

"dose" to which the worker is exposed to during the workday. For vibrating tools, this would be the vibration

acceleration in m/sec2, measured in three basicentric coordinates, and the time in minutes per day the tool is

actually in use. Of utmost importance in this chapter is the discussion concerning the need of at least yearly

medical evaluation of workers using vibrating tools so that appropriate action may be taken if they begin to

experience significant signs or symptoms of HAVS.

The above measures, along with appropriate selection of ergonomically designed tools that produce the least

vibration required for the task, and proper training of workers, supervisors, and industrial hygiene/medical

professionals to recognize the very early signs and symptoms of Hand-Arm Vibration Syndrome, are a

necessary first step in reducing this occupational health problem.

As a general observation, the NIOSH field team noted that some of the grinders using vibrating tools, and also

some welders, were not using proper face and eye protection. In addition, in certain hull areas no welding

curtains were used, nor was there any notification given to adjacent personnel nearby that welding was about

to begin. The safety office should make an effort to increase employee awareness of the need to use face and

eye protection.
VIII. REFERENCES

1. American National Standards Institute. Guide for the measurement and evaluation of human exposure to vibration to

the hand. ANSI S3.34-1986, New York, New York,: Acoustical Society of America, 1986.

2. NIOSH Current Intelligence Bulletin Number 38, National Institute for Occupational Safety and Health,

Cincinnati, Ohio.

3. American Conference of Governmental Industrial Hygienists. Threshold limit values and biological exposure indices

for 1989-1990., Cincinnati, Ohio.

4. National Institute for Occupational Safety and Health. Criteria for a recommended standard: Occupational

exposure to hand-arm vibration. Cincinnati, Ohio: NIOSH, 1989. (NIOSH publication no. 89-106).

 IX. AUTHORSHIP AND ACKNOWLEDGMENTS

Report Prepared by: Randy L. Tubbs, Ph.D.

Psychoacoustician

Industrial Hygiene Section

Division of Surveillance, Hazard

Evaluations and Field Studies

*Thomas E. Doyle 

Training Instructor

Division of Training and 

Manpower Development

 Thomas G. Wilcox M.D., M.S.

Medical Officer

Medical Section

Division of Surveillance, Hazard

Evaluations and Field Studies

* Currently State of Ohio Division of Safety and Hygiene

 Field Assistance: Eugene Moss, M.S. 

Health Physicist

Industrial Hygiene Section

Originating Office: Hazard Evaluations and Technical

Assistance Branch

Division of Surveillance, Hazard

Evaluations, and Field Studies
 X. DISTRIBUTION AND AVAILABILITY OF REPORT

Copies of this report are temporarily available upon request from NIOSH, Hazard Evaluations and Technical

Assistance Branch, 4676 Columbia Parkway, Cincinnati, Ohio 45226. After 90 days, the report will be available

through the National Technical Information Service (NTIS), 5285 Port Royal, Springfield, Virginia 22161. 

Information regarding its availability through NTIS can be obtained from NIOSH Publications Office at the

Cincinnati address. Copies of this report have been sent to:

1. Metal Trades Council of New London County, AFL-CIO 

2. Electric Boat Shipyard, Groton, Connecticut

3. OSHA, Region I

For the purpose of informing affected employees, copies of this report shall be posted by the employer in a prominent place

accessible to the employees for a period of 30 calendar days.

DISCLAIMER

Mention of the name of any company or product does not constitute endorsement by the National Institute for Occupational

Safety and Health.
TABLE 1

ACGIH Threshold Limit Values for Hand-Arm Vibration 1989-90

Electric Boat

Groton, Connecticut

HETA 87-348

Values of the Dominant,

Total Daily Exposure Frequency-Weighted, rms

 Duration a Component Acceleration 

Which Shall not be Exceededb

 

m/s2

less than 8 hours 4

less than 4 hours 6

less than 2 hours 8

less than 1 hour 12

(a) The total time vibration enters the hand per day, whether continuously or intermittently

(b) Usually one axis of vibration is dominant over the remaining two axes. If one or more vibration axis exceeds the

Total Daily Exposure, then the TLV has been exceeded.
Table 2

Acceleration Levels in the Dominant Axis for Grinding Tools

Electric Boat

Groton, Connecticut

HETA 87-348

Dominant Acceleration Exposure Work

Tool Axis Range (m/s2) Assessment Activity

 Dresser Cleco 6000 (a) X 7.3 - 12.4 Less than 8 hours to Grinding welds on hull 

 TLV exceeded exterior

 Dresser Cleco 6000 (b) Y 5.6 - 9.6 Less than 4 hours to Grinding metal bar

less than 1 hour mounted in vise

 Chicago Pneumatic Z 6.5 - 9.8 Less than 2 hours to Grinding welds on hull

 Whirlybird (a) less than 1 hour exterior

 Chicago Pneumatic

 Whirlybird (b)

Measurement #1 Z 4.5 - 8.9 Less than 4 hours to Grinding on surface of

less than 1 hour outer torpedo doors

Measurement #2 Y 13.0 - 15.7 TLV exceeded Grinding on cut into 

hull at outer torpedo 

doors

Stanley Offset Wheel Y 3.7 - 6.7 Less than 8 hours to Grinding edge of metal

 less than 2 hours plate mounted in vise

Note: (a) and (b) refer to different measurements on the same brand of tool. Measurement #1 and #2 refer

 to different work activities using the same tool. Exposure assessments are all made with reference

 to the ACGIH criteria.
Table 3

Acceleration Levels in the Dominant Axis for Burring Tools

Electric Boat

Groton, Connecticut

HETA 87-348

Dominant Acceleration Exposure Work

Tool Axis Range (m/s2) Assessment Activity

 Chicago Pneumatic Z 10.7 - 24.2 Less than 1 hour to Cleaning & smoothing 

 Large Straight Burr TLV exceeded welds in battery well

 Stanley Offset Burr

#1) metal bit Z 79.7 - 88.1 TLV exceeded Cleaning & smoothing

#2) wire brush Y 22.6 TLV exceeded metal in torpedo room

#3) sanding disc Z 16.7 TLV exceeded

Dresser Cleco X 34.7 - 48.7 TLV exceeded Cleaning metal edge on

Small Burr on torpedo shutter

True Power Z 7.9 - 8.7 Less than 2 hours to Cleaning weld in

"Welder's Burr" (a) less than 1 hour periscope well

 True Power Z 1.0 - 2.7 Less than 8 hours Cleaning metal in

 "Welder's Burr" (b) torpedo room

Note: (a) and (b) refer to different measurements on the same brand of tool. Measurement #1, #2, and #3

 refer to different work activities using the same tool. Exposure assessments are all made with 

 reference to the ACGIH criteria.
Table 4

Acceleration Levels in the Dominant Axis for Other Pneumatic Tools

Electric Boat

Groton, Connecticut

HETA 87-348

Dominant Acceleration Exposure Work

Tool Axis Range (m/s2) Assessment Activity

Vonarx Offset Y 6.2 - 7.0 Less than 4 hours Remove paint on overNeedle Gun head beam in torpedo 

room

 Chicago Pneumatic Z 22.7 - 187.7 TLV exceeded Caulking lead; NIOSH

 Chipping Hammer measurements made in

simulated situation

with lead being spread

around metal block

placed in wooded box.

Different tamping tools

used during measurement

 Chicago Pneumatic Y 1.1 - 12.5 Less than 8 hours to Drilling holes in metal

 #3 Corner Drill TLV exceeded in torpedo room

 Dresser Cleco Sand Y 32.3 - 39.5 TLV exceeded Tamping sand around die

Tamper in wooden box

Note: Exposure assessments are all made with reference to the ACGIH criteria.