Industrial ERG

CHAPTER 16 CASE STUDIES

The following section includes a number of ergonomic case studies where hazards were recognized and evaluated and recommendations made to reduce the extent of the exposure.

REPAIR PROCESS

The repair process consists of the following steps:

· Disassembly

· Send out for cleaning

· Painting process

· Reassembly

· Release mechanism test

· Load test

· Quality check

· Storage.

These steps and the related ergonomic issues are discussed below.

Disassembly

The disassembly task takes approximately 30 min/unit. The steps to perform the disassembly are as follows:

· Remove unit from storage rack.

· Place into support jig on workbench.

· Disassemble rack.

Figure 16.1  shows a technician preparing to perform the disassembly. Note that his elbows are at approximately 135°angle. This task would be considered light work, so the angle of the elbow joint should be no more than 100–110°.  Figure 16.2  shows the typical posture of a technician while disassembling the device. Notice that he has his legs wide apart so that he can get low enough to work on the device without bending his back.

Figure 16.1  Disassembly task – 1 (Graphic by Lee Ostrom)

Figure 16.2  Disassembly task – 2 (Graphic by Lee Ostrom)

Simple hand tools are used to take the device apart. These are shown in  Figure 16.3 .

Figure 16.3  Hand tools

Cleaning and Painting

Once the device is disassembled, it is sent out for cleaning. There is a 1-day turnaround time for this step. The device is then painted. There is a half-day curing time for the paint. A cleaning device was purchased but has not been installed. The new device can clean five racks at a time and will save considerable turnaround time in this process.

Reassembly

The device is reassembled and this process takes approximately 45 min. The device is placed on a supportive rack during parts of the process.  Figure 16.4  shows this step. The reassembly process is considered easier because it requires less force to accomplish. The same workstation is used for reassembly as that of disassembly.

Figure 16.4  Reassembly (Graphic by Lee Ostrom)

Mechanism Test

This step is accomplished by a technician using electronic test equipment. It is a simple step, taking a few minutes. However, as  Figure 16.5  shows, the technician is slightly bent forward while he performs this test. The table height is approximately 38 in.

Figure 16.5  Release mechanism test (Graphic by Lee Ostrom)

Load Test

The most difficult step in this process is the load test. The steps involved in the load test are as follows:

· The device rack is placed on a steel load test machine at a height of 32 in.

· The safety cage is 46 in. high.

· Technician has to climb into the cage to place the device on the tester.

· Technician has to move in and out of the cage 13 times to accomplish one test.

· Technician is bent over at the waist 90° each time he enters the cage.

When the device is placed in the cage, the technician has to kneel down to make the initial connections. The technician's knee is placed onto the horizontal cross assembly, and the lower leg is compressed on that sharp cross member. This process causes the compression on the soft tissues and causes fatigue to the opposite leg.  Figure 16.6  shows this step.

Figure 16.6  Connecting device to test machine (Graphic by Lee Ostrom)

In the process of performing this test, the technician enters the cage multiple times to check if the device is connected appropriately.  Figure 16.7  shows the posture the technician must attain to do this step.

Figure 16.7  Checking connection to test equipment (Graphic by Lee Ostrom)

Next the technician closes the cage and begins the test by using a hand-pumping hydraulic pump. The technician kneels on the floor to pump the handle ( Figure 16.8 ).

Figure 16.8  Hand-pumping hydraulic pump (Graphic by Lee Ostrom)

The technician enters the cage up to four more times to complete the test.  Figure 16.9  shows the posture he must assume to accomplish this.

Figure 16.9  Entering cage (Graphic by Lee Ostrom)

Quality Check and Storage

Finally, a quality check is performed on the reassembled device, and the device is stored on racks as shown in  Figure 16.10 .

Figure 16.10  Storage racks (Graphic by Lee Ostrom)

Recommendations

1. An adjustable height fixture should be developed so that the device can be maintained at an appropriate work height for each technician. If this cannot be provided, then an adjustable height work bench should be provided. There are a wide variety of choices in adjustable height work benches, ranging from simple hand-crank models as shown in  Figure 16.11  to electrically adjustable models as shown in  Figure 16.12 . The cost of these benches ranges from $800 on up.

2. Redesign the load test cage. There are several options to redesigning the cage. The first is to build a cage of 7 ft tall and 4 ft wide so the technician can enter and exit the cage in an upright posture and have unobstructed access to the test article. The second would be to add lockable roller casters to the load test machine and remove the lower cross member of the cage so the tech can roll the test machine in and out of the cage and place the device onto the machine from an unrestricted posture outside the cage. This is an extremely ergonomically stressful task and should be modified at the earliest opportunity.

3. The storage shelves for the racks should be modified so that the top shelf is no more than 60 in. in height. The bottom shelf should be at approximately 30 in. and the middle shelf can be placed approximately in between the two. This will reduce the ergonomic stress of placing the devices in and out of storage.

4. The cleaning device that was purchased should be placed in service. This will better optimize the process.

Figure 16.11  Manual adjustable height work bench (Photo with permission from Pro-Line)

Figure 16.12  Electric height adjustable work bench (Photo with permission from Pro-Line)

ERGONOMIC RECOMMENDATIONS FOR BACKPACK WELDER APPARATUS

Introduction

In a review of the design of a backpack welding/cladding system from an ergonomic perspective, there were only two pieces of physical dimensions of the proposed backpack welding/cladding system found when reviewing the information. This was that it would weigh between 40 (18 kg) and 60 lb (27.2 kg) and be approximately 29 in. (73.7 cm) in diameter. The exact design of the backpack was not available to review. Therefore, in this regard, ergonomic guidelines were provided from a variety of sources for the design of the backpack.

Weight of Load

There are not good guidelines for weight of the load that can be carried on the shoulders. Mil Std 1472F states that for a mixed population of males and females the maximum weight should be 42 lb (19 kg) and weights should only be carried 33 ft (10 m) (Mil Std 1472F, 1999). For a male-only population, the weight can be up to 82 lb (37.2 kg), with carry distances being again 33 ft. However, military backpacks infantry soldiers carry are much heavier. A NATO commissioned study puts the maximum weight for backpacks for a strong person at 95 lb (43 kg). The question is, of course, “what is a strong person?” (Ros).

Snook's tables (Liberty Mutual Insurance Company) for carrying loads in front of a person show that 90% of the male population can carry 41 lb (18.6 kg) 28 ft (8.5 m) every 5 min (hand height 33 in.) and 57% of the female population can carry 40 lb (18 kg) every 5 min (hand height 31 in.). The tables also show that 69% of the male population, and less than 10% of the female population would find an approximately 60-lb (27.2 kg) load acceptable (same hand heights). From all these sources, it appears that a 40-lb backpack would be acceptable to 90% of the male population and over 50% of the female population. A 60-lb backpack would limit the population that could perform this task.

Strap and Belt Configuration

Wide, padded straps should be used that distribute the weight over the widest area possible. Though we could not find good guidance, a survey of quality mountaineering backpacks shows the approximate width to be 2.5 in. (6.3 cm). A sternum strap helps to prevent the straps from slipping off the shoulders. The load must be symmetrical or divided equally on each shoulder (Mil Std 1472F, 1999; Healthworks Medical Group, 2015).

Most modern mountaineering backpacks are also contoured to the back.

A hip belt should be provided. The weight of the load should be distributed one-third on the shoulders and two-thirds on the hips (Ros).

Center of Mass

Most all studies found concerning the biomechanics of loads concern lifting and carrying in front of a person and not carrying in the back. There are some on children's book bags, but these are not applicable to this application. However, the center of mass of the backpack should be as close to the body as possible. The further the center of mass is away from the user's back, the greater the movement there would be to try to topple the person backward.  Table 16.1  shows these movements. Note that these movements are calculated from the back and not from the core. If calculated from the center of the user's core, the movement would be even higher.

Table 16.1  Center of Mass and Moments

Center of Mass from Body (in.)	40 lb Weight (ft-lb)	60 lb Weight (ft-lb)
6	20	30
12	40	60
18	60	90
24	80	120

Figure 16.13  from an Aarn backpack advertisement shows the comparison of a large load in which the center of mass is solely on the back and one in which the load is spread from back to front. Note that the posture of the person with a standard backpack is inclined forward. The user would be even more inclined forward if the center of mass of this backpack was farther back. A hip belt might help counter the effect of the center of mass not being very close to the body. However, it will not eliminate it.

Figure 16.13  Comparison of the center of mass from a standard backpack and an Aarn backpack (Permission from Aarn)

Using a backpack weighing 40 lb (18 kg) with the center of mass 12 or more inches (30.5 cm) from the user would possibly cause a smaller individual great difficulty navigating stairs and small hatchways. In fact, there are no guidelines for how much weight a person can carry up- and downstairs. Keep in mind that if the backpack is 29 in. in diameter (73.7 cm) and the user is large, the combined measurement from the front of the person to the back of the backpack could be 45 or more inches (114 cm). The hatchway openings would have to be large enough to allow access. Also, it might actually be difficult to descend certain staircases face forward if the slope of the stairs is at a high angle. The back of the backpack might snag on the stair risers as the person descends them. There also might be a situation where an emergency develops, and a person has the backpack on. The person must be able to exit the emergency area with the backpack on. Also, the straps should allow the person to drop the backpack easily (quick release) ( Figure 16.14 ).

Figure 16.14  Aarn bodypack and standard backpack (aarnpacks, 2015)

The guidance we can provide for the center of mass is keep it as close to the body as possible. Also, a backpack 29 in. in diameter (73.7 cm) might be problematic for negotiating small hatchways and stairways.

Lifting and Lowering the Backpack

We recommend that the backpack be positioned on a stand so the user can back into the backpack in a standing posture and then snap on the straps and hip belt. The same setup should be positioned where the device is used. This would eliminate the need to pick up the backpack and swing it into position on the back. Another option would be to have a second person always help the user put the backpack on and remove it.

Summary of Guidance and Recommendations

1. The backpack should not be more than 40 lb.

2. The shoulder straps should be 2.5 in. wide and padded. The backpack should be contoured to the back.

1. There should be a hip belt and sternum strap.

2. The weight of the backpack should be divided one-third on the shoulders and two-thirds on the hips.

3. The load must be symmetrical.

4. The center of mass of the backpack should be as close to the body as possible.

5. The diameter of the backpack must be small enough to fit through a hatchway with a large individual.

6. The straps should be quick release.

7. A stand should be used to help the person put on and take off the backpack, and/or a second person should always help the user put on and take off the backpack.

BEAD-BLASTING OPERATION CASE STUDY

Purpose and Introduction

The purpose of this case study is to document the findings from an ergonomic assessment of the aircraft bead-blasting facility. Also, to present alternative potential solutions to alleviate the musculoskeletal stressors associated with these sorts of decoating operation.

This decoating operation uses modern, safer plastic beads and recovers and reuses the decoating material. The impurities and spent beads are captured in a bag house and disposed of appropriately.

The workers who are tasked with performing this task are motivated and wish to have the task optimized. Several of the workers have experienced musculoskeletal injuries. The most common injury report is carpel tunnel syndrome (CTS). The workers are required to wear heavy coveralls with a disposable synthetic suit over the top. They also wear vinyl gloves, a cotton gauntlet type glove over the vinyl gloves, and a supplied air hood with apron and hearing protection. The supplied air hood can provide cooled or heated air, depending on the time of year.  Figures 16.15  and  16.16  show workers preparing for the decoating task.

Figure 16.15  Decoating (Graphic by Lee Ostrom)

Figure 16.16  Decoating 2 (Graphic by Lee Ostrom)

The air hoods the workers use sit on the head via head band webbing. On the day the assessment was conducted, the workers did not wear knee pads. The workers might perform this task from between 2 h a day up to 6 h a day. This is the actual time the workers spend suited up and spraying decoating material. The task constraints are listed below:

· The workers have to suit up in the protective gear.

· The workers have to have the ability to get away from a broken hose.

· The task requires that the workers articulate their wrists in several deviated postures to direct the spray of decoating beads under the edges of floor beams and angled/bent structural members.

· Potentially all surfaces of the aircraft must be decoated.

Ergonomic Assessment Procedures

The ergonomic assessment of the decoating was conducted in the following manner:

· Introduction to the tasks

· Observation of the workers

· Interviews with the workers

· Ergonomist suited up and participated in the decoating operation

· Evaluated alternative potential solutions.

Findings

Figures 16.17  show aspects of the decoating task. This task has all the attributes of a very stressful task. It requires the workers to wear several layers of protective gear. The task requires the workers to use the equipment with their wrists in deviated postures, and the task requires the workers to attain several stressful postures. The workers have to grip the nozzle and depress a dead-man lever to allow the stream of decoating beads to exit the nozzle. However, the actual grip on the lever, once it is depressed, is relatively light. Though, a grip has to be maintained on the lever or it will stop the stream. The grip required on the nozzle barrel to hold and direct it to the surface to be decoated varies from a relatively high level to a relatively low level depending on where the stream is being directed. For instance, the worker can brace the hose against their shoulder and maintain a lighter grip if they are spraying directly in front of them. However, this posture is not possible if they are directing the spray alongside of a floor beam. Also, the nozzle is a smooth and somewhat polished finish. Therefore, a stronger grip has to be maintained on it to prevent the nozzle from slipping through the hand ( Figures 16.17 – 16.22 ).

Figure 16.17  Nozzle (Graphic by Lee Ostrom)

Figure 16.18  Standing posture (Graphic by Lee Ostrom)

Figure 16.19  Standing posture 2 (Graphic by Lee Ostrom)

Figure 16.20  Kneeling posture (Graphic by Lee Ostrom)

Figure 16.21  Another required posture (Graphic by Lee Ostrom)

Figure 16.22  Aircraft to ground clearance (Graphic by Lee Ostrom)

The ergonomist who performed the assessment found that they started with their right hand, shifted to their left hand when their left hand became fatigued, then used both hands.

Since the air hood helmet sits on the head via head band webbing, it tends to want to slip off the head in any posture, other than standing/kneeling/sitting straight up. The task requires all postures, so a part of the effort of this task is trying to keep the hood in place so one can see the part they are decoating.

The easiest way to perform the task is in an upright, standing posture. However, this is not possible because all postures are required.

Evaluation of Solutions and Recommendations

Table 16.2  defines the different levels of controls for hazards related to ergonomics.

Table 16.2  Levels of Hazard Control

1. Elimination – A redesign or procedural change that eliminates exposure to an ergonomics risk factor; for example, using a remotely operated soil compactor to eliminate vibration exposure 2. Engineering controls – A physical change to the workplace; for example, lowering the unload height of a conveyor 3. Substitution – An approach that uses tools/materials/equipment with lower risk; for example, replacing an impact wrench with a lower-vibration model 4. Administrative – This approach is used when none of the above is practical to implement. Administrative controls are procedures and practices that limit exposure by control or manipulation of work schedule or the manner in which work is performed. Administrative controls reduce the exposure to ergonomic stressors and thus reduce the cumulative dose to any one worker. If you are unable to alter the job or workplace to reduce the physical stressors, administrative controls can be used to reduce the strain and stress on the work force. Administrative controls are most effective when used in combination with other control methods; for example, requiring two people to perform a lift

Using this table as a guide, the possible controls that can be used to reduce the stress related to this task are discussed below:

· Supplying workers with a better fitting helmet

· Improve gripping:

· Modifying the nozzles so they have a better gripping surface

· Purchasing nozzles with a better gripping surface

· Finding a glove with a better gripping surface.

· Parking the aircraft on the grating, using jacks to elevate the aircraft, and using a creeper to better access the underside of the aircraft

· Using coveralls with integral kneepads.

The most thorough, long-term hazard reduction strategy modifications to the facility should be considered. It is speculated that a considerable time savings would occur with reduced processing and clean-up times associated with facility modifications.

In the event all other recommendations are not implemented, then a worker rotation schedule should be developed.

PROTECTION FROM BAD VIBRATIONS

This case study is adapted from a US Navy Case Study on Hand Arm Vibration (US Navy public website, Navy, 2015).

Some potentially serious occupational hazards in Navy workplaces, such as noise-induced hearing loss and heat stress, are well known, heavily reported, and well documented ( Figure 16.23 ). However, certain other workplace hazards, some of which can produce serious, irreversible, and unsuspected diseases, are not as widely recognized. One such hazard is hand arm vibration, which can cause Raynaud's syndrome or hand arm vibration syndrome (HAVS).

Figure 16.23  Sailor grinding a handrail

Raynaud's syndrome/HAVS is a medical condition that can lead to permanent disability. HAVS is caused by people's hands being exposed to chronic vibration, which damages the nerves, blood vessels, and bones. Exposure to cold temperatures also increases the probability of acquiring HAVS and the likelihood of exhibiting symptoms.

Most occurrences of HAVS affecting Navy personnel involve workers who use gasoline, pneumatic, hydraulic, or electric vibratory tools, such as grinders used for surface preparation, or rivet guns and bucking bars for airframes maintenance. These tools are common in Navy shipyards, aircraft-maintenance shops, and other environments such as construction sites and foundries.  Table 16.3  lists tasks in the US Navy and the vibrating tools associated with the tasks.

Table 16.3  Tasks and the Vibrating Tools Associated with the Tasks

Potential HAV Exposures and Tasks Relevant to US Navy
Task	Type of Tools	Remarks
Dismantlement of ships, particularly submarines	Electric and pneumatic cutting tools, grinders, and electric saws	The presence of hazardous materials often prevents use of torch cutting to dismantle vessels. This forces the use of hand tools to cut metal sections. Significant vibration exposures have been associated with this work because of duration, tool size, and substrate and work postures
Paint removal/surface preparation	Hand grinders, needle guns, hydroblast nozzles, and abrasive blast nozzles	Heavy metal lead exposure can also affect peripheral nerve conduction and may have an additive neurological effect
Preparation of welding surfaces – precleaning or smoothing after welding	Hand grinders
Foundry cleaning departments. Removal of burrs and projections on newly cast work	Grinders, chippers	Improved quality control can reduce need for finishing and cleaning. Silica exposure also may be an issue
Sheet metal and fiberglass work	Hand grinders, orbital sanders, and polishers
Road repair	Jackhammers	Much of the noise and vibration are associated with air-blow off and escape post tool impact. Devices controlling exhaust and recoil control exposure with minimal or no effect on productivity
Forestry (chain saw use)	Chain saws	Tool maintenance increases safety while reducing vibration. Cold is an additional hazard to hands

Historically, there has been inconsistent and often limited progress in eradicating or even recognizing the HAVS problem. Puget Sound Naval Shipyard & Intermediate Maintenance Facility (PSNS & IMF) in Bremerton, WA, was one of the first Navy activities to look at issues involving HAV. Early in the 1990s many of the jobs at PSNS & IMF that used handheld power tools were labor intensive. The safety office evaluated some of these jobs by slow motion videotaping workers using power tools, since vibration measuring instruments were not available at the time. As a follow-on effort, PSNS & IMF made a considerable effort to evaluate the ergonomics of handheld tools and the benefits of antivibration gloves ( Figure 16.24 ).

Figure 16.24  Builder from Naval Mobile Construction Battalion Four Zero breaks apart the asphalt with a jackhammer on a road repair project

Mindful of the need for further study, the Defense Safety Oversight Council (DSOC) initiated a project in 2007 to address the root causes of HAVS. The Council collaborated with the General Services Administration (GSA) and the National Institute for Occupational Health and Safety (NIOSH) to provide guidelines for low-vibration and other ergonomics characteristics in procurement criteria for new power hand tools. A concurrent effort worked to identify and incorporate International Organization for Standardization (ISO) 10819 and American National Standards Institute (ANSI) S2.73 certified vibration absorbing gloves into the federal procurement process.

A working group with Department of Defense (DoD)/GSA/NIOSH and US Coast Guard members was formed. The Navy was recognized as a leader within DoD in identification of HAVS having a focused effort within several fleet concentration areas. PSNS & IMF, Naval Base San Diego, and the Navy Fleet Readiness Center, East (Cherry Point, NC), provided leadership and technical support in their areas of expertise for this project. Procurement criteria for vibration absorbing gloves, low-vibration tools, and third-party certification guidelines were developed.

As a result of the DSOC project in September 2009, several lower vibration tools were introduced into the federal supply system ( Figure 16.25 ).

Figure 16.25  Operations specialist wears certified antivibration gloves while using a needle gun to chip paint off a bulkhead

With input from Navy subject matter experts, GSA is continuing to incorporate low-vibration and other ergonomics characteristics into procurement criteria for new and updated power hand tools.

Collaboration with the Navy Clothing and Textile Research Facility in Natick, MA; the Defense Logistics Agency; and support from the office of the Secretary of Defense for Manpower, Personnel and Readiness (see OSD MPR Memo of December 15, 2009; Prevention of Vibration-Induced Hand and Arm Injury) resulted in the introduction of certified vibration absorbing gloves into the federal supply system.

Only full-finger protected gloves are tested since HAVS always begins at the fingertips and moves toward the palm (Finger-exposed “half-finger” gloves are not recommended). Using certified antivibration gloves alone will not solve the HAV problem, and the Navy recommends that the gloves be used in combination with low-vibration tools such as the ones listed above, worker education, and appropriate work practices.

The Navy, in conjunction with the US Army Center for Health Promotion and Preventive Medicine, has also developed guidelines for workers and supervisors on the use of low-vibration tools and antivibration gloves to protect Navy workers from hand arm vibration exposures as shown below:

Guidelines to protect Navy workers from harm vibration exposures:

· Workers and their supervisors should ensure use of appropriate work practices and protective equipment. These include the following:

· Use of certified ANSI S2.73/-ISO 10819 (third-party tested) vibration absorbing gloves. (Many models are now available within the federal supply system.)

· Use power tools with reduced-vibration characteristics.

· Keep fingers, hands, and the body warm.

· Do not smoke. (Nicotine in tobacco constricts the blood vessels and can reduce circulation in the fingers.)

· Let the tool do the work, grasping it as lightly as possible, consistent with safe work practices.

· Keep tools well maintained.

· For pneumatic tools, keep the cold exhaust air away from fingers and hands.

· Take breaks from tool use for at least 10 min/h to allow circulation to recover.

· Wear hearing protective equipment as appropriate. (Most operations producing significant hand arm vibration are also noisy.)

· Have vibration exposure evaluated by a professional if they feel they are exposed to high levels of vibration.

· If signs and symptoms of HAVS appear, seek medical help.

· Work with your supply points of contact and process managers (engineers, shop supervisors, and technical authorities) to specify and order suitable low-vibration tools and certified antivibration gloves. The continued and expanded availability of these products will depend on user demand.

· Report concerns and worker complaints to the appropriate industrial hygiene and occupational health professionals through their safety office. Specialized assistance such as that provided by the Navy and Marine Corps Public Health Center may be beneficial.

· Review the process specification and technical manuals. If they feel that low-vibration tools and/or antivibration gloves might be considered for the relevant processes, use the comment sheet, typically on the last page of nearly every DoD/Navy technical manual to describe potential issues and concerns.

The Navy faces the continual challenge of finding better and improved vibration-reducing materials and technologies that meet ANSI/ISO guidelines and standards and can be incorporated into ships and shore facility designs during the acquisition process. Because Navy leadership is concerned about the safety and health of its military and civilian workers, they are working hard to address HAVS as an under-recognized occupational health problem through acquisition of safe, cost-effective, and performance-improving designs and equipment.

HEAVY CABLE HANDLING

Introduction

Ship–to-shore cable handling is common on cruise ships, commercial vessels, and navy ships.

There are two ends of the cable, the ship end and the shore end. Before a ship arrives in port, electricians perform additional tests in conjunction with the ship's crew to again ensure the ship-to-shore cables and outlet assemblies meet the minimum requirements for delivering power to the vessel.

After testing, the head of the ship-to-shore cable is installed into the outlet assembly. Several other cables may also be installed into the outlet assembly, depending on the power requirements of the particular ship. In some instances, one outlet assembly might be used to supply part of the power and another outlet assembly might be used to supply the remaining power. The shore end of the cable is heavy, weighing approximately 25 lb with each foot of the attached cable weighing approximately 12 lb.

In general, the electricians do not handle the ship end of the cable, unless they are performing a specific test. The ship end weighs approximately 44 lb.

The ship's crew normally removes both the ship end and shore end of the cables when they are readying to leave port. In many cases, the ship's crew leaves the cables in a disorganized pile.

The discussion section of this report addresses these tasks in additional detail and describes the hazards associated and methods to abate the hazards.

Approach

To obtain an understanding of actual operations, the following was included in the site visit:

· Observing the process and procedures

· Meetings with task performers, a supervisor, and an industrial hygienist

· Identifying, evaluating, and discussing the physical workplace risk factors and possible ergonomic solutions.

The ergonomic assessment report was prepared by the following:

· Evaluating the severity of the exposure to the physical workplace risk factors

· Identifying ergonomic solutions for controlling the hazards that fit within the constraints of the tasks

· Performing cost-benefit trade-off analyses for proposed solutions

· Providing recommendations for the most advantageous control measures as well as the related cost impacts and ergonomic benefits for each.

Hazard Control Options

Ergonomic recommendations developed to mitigate the identified physical workplace risk factors were evaluated against each other in a cost-benefit trade-off analysis.

There are four basic approaches to controlling risk from eliminating the hazard to using administrative controls.  Table 16.4  includes a full description of the hazard control options in order of highest to lowest priority.

Table 16.4  Levels of Hazard Control for Implementing Ergonomic Improvements

Hazard Control Hierarchy

1. Elimination – A redesign or procedural change that eliminates exposure to an ergonomic risk hazard; for example, using a remotely operated soil compactor to eliminate vibration exposure 2. Engineering controls – A physical change to the workplace; for example, lowering the unload height of a conveyor 3. Substitution – An approach that uses tools/material/equipment with lower risk; for example, replacing an impact wrench with a lower-vibration model 4. Administrative – This approach is used when none of the above can be used or are impractical to implement. Administrative controls are procedures and practices that limit exposure by control or manipulation of work schedule or the manner in which work is performed. Administrative controls reduce the exposure to ergonomic stressors and thus reduce the cumulative dose to any one worker. If you are unable to alter the job or workplace to reduce the physical stressors, administrative controls can be used to reduce the strain and stress on the work force. Administrative controls are most effective when used in combination with other control methods; for example, requiring two people to perform a lift

Testing and Installing Ship-to-Shore Cables

A day before a ship arrives in port, each ship-to-shore cable that will be used to supply power is tested to ensure it meets minimum standards. The test that is used is called a Megger Test. One electrician is usually required to perform the test. This test entails testing each of the leads to ensure there are no faults in the system. To do the tests, the electrician has to remove the cover on the shore end of a cable and ensure it is dry. Then the electrician maneuvers the shore end of the cable to a point where it is accessible to perform the test. The shore end weighs approximately 25 lb and each foot of cable lifted weighs approximately 12 lb. The amount of weight lifted by the electrician varies depending on how much cable must be moved or lifted with the shore end. In addition to the weight of the head and cable, there are frictional forces the electrician must overcome related to the cable sliding along the surface of the pier or the quay wall. If the cable is left in a pile, there may also be frictional forces related to disentanglement of the cable. Ships can enter the port at any time of the year, and, during winter months, the cables can be frozen to the deck of the pier or the quay wall.

Once a ship arrives in port, an electrician meets the boat and again performs tests to ensure the cables meet the minimum standards required. The shore end of the cable is then connected to the appropriate outlet on the outlet assembly. The heights of the outlets and the assemblies themselves vary from pier to pier. There are two types of outlet assemblies.  Figure 16.26  shows the type that is standard on most piers. This style of outlet assembly uses the Shore end connector.  Figure 16.27  shows the newer type of ship-to-shore cable receptacle. The newer style outlet assembly uses a Camlock style fitting for each lead and not the shore end. The Camlock style reduces many of the physical risk factors found with the shore end connector because of the lighter weight cables.  Figure 16.28  shows the height range of the outlets on the outlet assemblies.

Figure 16.26  Standard outlet assembly (Graphic by Lee Ostrom)

Figure 16.27  Newer style outlet assembly (Graphic by Lee Ostrom)

Figure 16.28  Outlet assembly measurements (Graphic by Lee Ostrom)

The weights of lift for the shore end to the various heights were measured using a handheld load cell. When the shore end was lifted 1 ft from the deck, the reading was approximately 37 lb. At the height of the racks (31 in.) the weight of lift was approximately 55 lb. At 60 in. the weight of the cable was between 75 and 85 lb. The measurements taken did not account for any additional difficulties, including freeze, friction, or tangled cables, but only assessed the weight of the cable under ideal conditions.

Two of the electricians interviewed said that the sailors always help with the connection of the shore end to the outlet assembly, whereas one former electrician who performed this task said he did it alone.

The MIL-STD 1472G states that the maximum weight of lift for a uniform load of 18 in. wide by 12 in. deep and 18 in. high to a height of 5 ft is 56 lb. The maximum weight of lift is to be reduced if the weight of load is not uniform and/or there are obstacles. The ship-to-shore cables are not a uniform package, and the weight increases as the height of lift increases. The cable handling operation does include negotiation of obstacles. Many of the heights of lift exceed 5 ft and they can be above 6 ft or more. Therefore, the maximum weight of lift should be reduced by as much as 66% to help ensure injuries do not occur.

This task clearly has a high potential to cause injury. Injuries that could occur from lifting the cables to those heights include potential for harm to the back, neck, shoulder, and lower extremities.

While connecting the Camlock-style lead connectors, the electricians have to turn the connector 180° to the left, then insert the connector, and then seat it 180° to the right, while holding the weight of lead and possible some length of the main cable.

In each current configuration, the most stressful part of this job is holding the weight of the cable and seating the connector. The possible injuries include those to the wrist, back, and shoulder. The current practice is to use two electricians to perform the task that does reduce some of the stress associated with this task but does not reduce the risk of injury.

The ship end weighs approximately 34 lb without the cap, and the cap weighs approximately 12 lb. The electricians have to sometimes persuade the cap to come loose from the ship end using a hammer.

The stressful aspects of this task are that the ship end is heavy (approximately 44 lb assembled) and the electricians have to be on their knees to perform the task. The potential injuries are primarily back, shoulder, and wrist injuries. The risk of injury is lower for this task because it is performed very infrequently.

The recommended engineering controls that should be implemented for this sort of issues are mount electric actuated jib cranes on the existing electricians' service trucks to manipulate the cables. The crane should have a capacity of at least 200 lb. Figure 16.29 shows this type of crane. The example depicted below has a capacity of 700 lb in the extended configuration.

Figure 16.29  Truck mounted crane (Graphic by Lee Ostrom)

Other devices considered for moving the cable included a fork lift or a walk-behind forklift. However, these devices might not be effective on an icy pier and would require a higher level of maintenance.

AN ERGONOMIC IMPROVEMENT ALSO PROVIDES IMPROVED FALL PROTECTION

Naval Submarine Base Kings Bay is located adjacent to the town of St Marys in Camden County, Georgia, in southeastern Georgia, and not far from Jacksonville, Florida. Kings Bay Trident Refit Facility (TRIREFFAC) is the largest tenant command at Kings Bay and has quietly and efficiently kept a significant portion of the United States Fleet Ballistic Missile submarines at sea since 1985. TRIREFFAC provides quality industrial-level and logistics support for the incremental overhaul, modernization, and repair of Trident Submarines. It also furnishes global submarine supplies and spare parts support. In addition, TRIREFFAC provides maintenance and support services to other submarines, regional maintenance customers, and other activities as requested.

TRIREFFAC machinists were subjected to potential injuries due to ergonomic hazards while operationally testing and repairing pumps that circulate water on the Trident Submarines. These pumps support diving and surfacing operations. While being inspected and/or repaired, the pumps are placed on the test stand by a crane. The workers are required to access the entire pump (top, bottom, and sides) and were required to stand on temporary staging that was not conducive for allowing them to perform work in optimal ergonomic postures. Workers reached and extended their bodies at times as much as 4 ft, to access bolt threads, wiring, seals, and other components. They were also required to twist and bend their bodies into awkward postures for extended periods of time to perform repairs and tests. These awkward postures resulted in a higher potential for an injury. At times, workers have been observed standing on rails of the temporary staging as well as piping to access components of pumps as they disassemble/reassemble them. This was not only an ergonomic issue, but a fall protection issue as well (Figures 16.30 and 16.31). The shapes of the pumps are similar to a tower and pot belly that require the necessity for a versatile staging configuration.

Figure 16.30  Staging

Figure 16.31  Staging for pumps

These tasks are performed by three to five workers at a time and the same employees work the tasks until the entire pump repair is complete. The task duration is normally 3 days and performed 30–40 times per year.

A Mishap Prevention and Hazard Abatement (MP/HA) project was developed to provide an ergonomic solution to this issue. The project was submitted through Naval Facilities Engineering Command (NAVFAC) for ergonomic funding in March 2008 for $31,000 to design and purchase customized staging for permanent access to the pumps to eliminate the stressors created by overexertion on the workers. The Navy's MP/HA Program Team assessed the pump test stand, and the potential solution to the ergonomic issues was identified. TRIREFFAC developed a proposed design for permanent staging for the pump stand area. The design was reviewed and approved by the Building 4026 Safety Committee and Facilities Representative. Meetings were held with the potential vendor of the permanent staging, and the Navy MP/HA Team reviewed the final design of the staging. The newly acquired staging was installed by TRIREFFAC personnel (Figure 16.32).

Figure 16.32  Final staging

The completed project allows workers to work in ergonomic neutral postures, provides access to pumps in a manner that reduces the potential for injury, and reduces the potential for a life-threatening fall.

REFERENCES

1. Aarnpacks (2015). Retrieved from aarnpacks: http://www.aarnpacks.com. Accessed December 22, 2015.

2. Healthworks Medical Group (2015). Healthy Tips. Retrieved from UShealthworks: http://www.ushealthworks.com/HealthyTips_Ergonomics_BackPack.html. Accessed December 22, 2015.

3. Liberty Mutual Insurance Company (1978). Manual Materials Handling.

4. Mil Std 1472F (1999). Department of Defense Design Criteria Standard.

5. Ros, H. (2005). Prevention of Low Back Complaints. Ministry of Defense HDP/DMG/AMG, RTO-MP-HFM-124.

6. US Navy public web site, Navy (2015). http://www.public.navy.mil/comnavsafecen/Documents/SuccessStories/SuccessStories2/149_HAV.pdf. Accessed December 22, 2015

ADDITIONAL SOURCES

1. Ergonomic Guidelines for Manual Materials Handling (2007). DHHS (NIOSH) Publication No. 2007-131.

2. Gillette, J. C., Stevermer, C. A., Meardon, S. A., Derrick, T. R., & Schwab, C. V. (2009). Upper Extremity and Lower Back Moments During Carrying Tasks in Farm Children, Journal of Applied Biomechanics, 25, 149–155.

3. MIL-HDBK-759C (1995). Handbook for Human Engineering Design Guidelines.