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Excerpts from OSHA Ergonomic Report (con920518)
SIC 29 - Petroleum Refining and Related Industries
REPLACEMENT OF VALVES

Potential Hazards and Possible Solutions

Removal of Parts For Cleaning

The employees must remove various parts from refinery processes for cleaning and/or replacement. This involves removing bolts from the flanges which hold the parts together. This is accomplished by loosening the securing nut from the bolt with a pneumatic nut driver or with a closed or open end wrench. All nuts are put back on the bolt by hand and the part is lifted away by an overhead crane after all bolts have been removed.

  • Employees have frequent and forceful pinch grips and muscle exertions while in awkward postures. Frequent pinch grips and forceful muscle exertions are consistent with the development of musculoskeletal injuries. While it is not possible to say that a certain number if repetitions of a particular action is hazardous, it is possible to say that the more times an action is performed the greater the chance of injury. Engineering controls for these hazards will be mentioned in subsequent sections as well as some proposed remediation strategies. Administrative procedures that can be implemented to reduce the hazard are mentioned below.
  • Jobs should be classified as to the nature and extent of exertion and a rotation schedule should be created that allows for as much variation as possible in the distribution and frequency of musculoskeletal activity.
  • Work-rest schedules should be enforced. Generally, a minimum of a 15 minute rest break at least every two hours is required.
  • The employees are frequently required to work with their elbows abducted and their hands above shoulder height. Working with the elbows abducted and the hands above shoulder height constricts the neurovascular bundle and can impede the blood and nutrient circulation to the tendons, ligaments, and muscles of the arm. This situation slows muscle recovery, limits duration of activity, and makes the muscle, tendon, ligament system more susceptible to injury. In addition repeated and prolonged overhead work can lead to wear and tear, and thickening of the unsheathed tendons and bursa of the shoulder which is consistent with the development of frozen shoulder syndrome and rotator cuff injuries.
  • Educate the employee on the basics of body biomechanics and the importance of maintaining the body in an ergonomically neutral position. While it may be difficult to perform the task without reaching above shoulder height, education will enable the employee to recognize the hazard and provide him with the skills to minimize it. Generally, the hands should remain below the mid chest level and the elbows should remain in close to the body.
  • Redesign as many areas as possible to ensure better access. Investigate the possibility of changing the position of frequently replaced items to ensure greater access and to minimize the use of awkward positions and excessive forces.
  • Develop and use extensions for the impact wrench and other tools. This will allow the employee to access and loosen many of the nuts while keeping the elbows and hands in a lower position. Use ratcheting tools whenever possible to speed up the operation and reduce the amount of time the employee is in hazardous positions.
  • Employees are frequently required to assume awkward postures while performing strenuous pushing, pulling, and lifting actions. The employee frequently has no leverage in these positions and is often subject to isolated and repeated strains of the musculoskeletal system. These strains are consistent with the development of over exertion injuries to the shoulder, hand, neck, low back, and herniation of various muscle groups.
  • Educate the employee on the basics of body biomechanics and the importance of maintaining the body in an ergonomically neutral position. While most of the body positions available to the employees are not ideal education will enable the employee to recognize a hazard and provide the knowledge to minimize it.
  • Redesign as many areas as possible to ensure better access. Investigate the possibility of changing the position of frequently replaced items to ensure greater access and to minimize the use of awkward positions and excessive forces.
  • Provide power assist tools where possible such that force requirements by the employees body is minimized.
  • The employee has forceful and repetitive gripping to activate the channel lock pliers while separating nuts from their bolts. Grasping large objects, such as the channel locks handle, when they are not correctly sized, requires the PIP joint (middle joint) to be maintained relatively straight while the DIP joint (end joint) is flexed. This puts excessive strain on the flexor and extensor tendons of the fingers and is a recognized cause of UECTDs such as carpal tunnel syndrome. Use of forceful repetitive flexing of the finger tendons, as depicted on the video documentation, during the process of removing nuts from bolts is consistent with the development of tendinitis and tenosynovitis as well as muscle strain. Grasping the channel lock pliers requires a great deal of force to maintain the nut in the stationary position. This stretches the tendons and stresses the small muscles of the hand which without adequate rest and recuperation can become inflamed and irritated. Mechanical abrasion is also possible by continued use of channel locks as the handle is pressed against the palm of the hand compressing the nerves and tendons located close to the surface. This creates additional inflammation and swelling and can lead to reduced blood flow, nerve conduction and eventual deterioration of the musculoskeletal system.
  • The use of channel locks should be restricted to only very light use requirements. When they are used train the employees to adjust the handle to the proper grip width. Generally, the grip distance from the thumb to the four fingers should not exceed 2.5 to 3.5 inches and the DIP and PIP joints should both be flexed and the hand should form the shape of a "C".
  • Supply the employees with adequate ratcheting wrenches to eliminate the use of repeated hand flexions for activating the channel locks currently used to maintain the nut position during the removal process. Proper wrenches and socket tools should eliminate the need for channel lock type devices which require frequent and excessive hand gripping.
  • Employees are required to move through a maze of pipes, valves, and walkways to gain access to the parts which need maintenance or replacement. Because of space and access restrictions the employees often have to work in less than ideal postures. Employees spend considerable time working with; their hands above shoulder height, with extreme torso flexions, lifting and supporting loads and tools away from the body, and pulling and pushing with considerable force while having poor mechanical leverage because of inadequate access. All of these problems are consistent with the development of UECTDs such as musculoskeletal injury of the shoulder and arm as well as low back injury.
  • Educate the employee on the basics of body biomechanics and the importance of maintaining the body in an ergonomically neutral position. While most of the body positions available to the employees are not ideal education will enable the employee to recognize a hazard and provide the knowledge to minimize it.
  • Redesign as many areas as possible to ensure better access. Investigate the possibility of changing the position of frequently replaced items to ensure greater access and to minimize the use of awkward positions and excessive forces.
  • Employees are wearing large bulky cotton gloves during the operation which create resistance to finger movement. In addition, poorly fitting cloth gloves require more force production by the fingers and hands to overcome decreases in friction and tactile sensitivity. Increases in the force required for a task will significantly increase the chance of UECTDs of the hand and wrist such as carpal tunnel syndrome.
Make sure gloves fit properly, offer minimal resistance to finger movement, and do not decrease the tactile sensitivity. Gloves should be made of a material which increases the coefficient of friction between the hand and the load surface. This will reduce the hand and finger force required to perform a particular repetitive task.
  • Impact wrenches are heavy and have only a single handle for activation and control. The tool appears to have a metal case with a low coefficient of friction. The employee is more apt to use only one hand when operating the tool if it has a handle with only one hand position. This increases the chance of fatigue and injury in the support arm and increases the amount of instability over a tool which has support mechanisms for two handed use. Fatigue created by one handed use is consistent with the development of UECTDs such as shoulder and arm pain and injury. In addition, one handed use and a handle with a low coefficient of friction increases the amount of finger force required to maintain control of the tool. Exertion of long term finger force often with a deviated wrist is consistent with the development of UECTDs such as carpal tunnel syndrome and tendinitis
  • Provide an impact wrench with an additional side control handle or with a "T" handle to facilitate two handed usage of the power tools. Calculations indicate about a 30% reduction in force requirements on the shoulder when two hands can be used to perform the task as compared to single hand operation.
  • Either purchase tools, or retrofit existing tools, with handles which have a high coefficient of friction to facilitate tool control without exertion of extreme finger force.
  • The impact wrench is pneumatically powered and equipped with a metal handle. Pneumatically driven tools generate vibrations which can desensitize the hands thus increasing the grip force required to control the tool. Metal handles have a poor coefficient of friction which also increases the grip force necessary. Pneumatic tools can blow cool air onto the hands causing further desensitization. Desensitization of the hand and fingers requires the use of additional finger force to maintain adequate control of the tool. High grip force requirements with wrist deviations are consistent with the development of hand pain and UECTD's such as carpal tunnel syndrome.
  • Provide vibration dampening material for the tool handle that will also increase the coefficient of friction thus decreasing the grip force required to control the tool.
  • Ensure that exhaust air does not blow across the hands.
  • Provide tools with handles that allow for two handed operation thus reducing finger force requirements and shoulder stress.
  • Hand tools such as open and box end wrenches are frequently used to perform the bolt removal operations. These require frequent and forceful repetitions of actions generally above shoulder height. This increases the amount of time spent with the hands in an elevated position because of the slow process of positioning, tightening/loosening, and repositioning the wrench for each turn. Extended time with the hands in an elevated position is consistent with the development of UECTDs such as shoulder and upper arm fatigue and pain.
Provide ratcheting tools which can reduce the amount of time required to remove the nut from a bolt.
  • Employees often use channel lock pliers to hold a nut or bolt stationary while performing tightening or loosening operations. This requires extended periods of forceful hand gripping often with the wrist in a deviated position and creates significant pressure on the palm of the hand which can compress the nerves, tendons, and blood vessels located there. These actions and postures are all consistent with the development of UECTDs of the hand and wrist such as tendinitis and carpal tunnel syndrome.
  • Discontinue use of channel lock pliers in situations where extreme force is required keep a section of the bolt stationary.
  • When channel locks are used make sure the employee adjusts them properly. Generally the hand should be in the shape of a "C" and the distance from the thumb to the four fingers should be no more than 2.5 to 3.5 inches. In addition the handles of the pliers should be padded such that the musculoskeletal constituents located in the palm of the hand are not compressed or injured.

 

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