Section 3: Ergonomics and Materials Handling

Transcription

1 Section 3: Ergonomics and Materials Handling OVERVIEW This section provides information about designing your work area and completing tasks in a way that makes you more comfortable while performing your job more efficiently. Practicing proper ergonomics and materials handling techniques can make your job safer and help to prevent injuries. Ergonomics is the science of matching the job to the worker to improve efficiency and to reduce the risk of discomfort or injury. Examples can include: restructuring or changing the work environment modifying a task materials handling training using mechanical lifting devices ERGONOMIC RISKS 1. Awkward Postures refer to positions of the body that deviate significantly from the neutral position while job tasks are being performed. Examples include bending over to lift, working with your hands overhead, and squatting or kneeling. 2. Sustained or Static Postures involve little or no movement. Even neutral postures can result in discomfort if one position is maintained for a prolonged period of time. Examples include sitting or standing in one place for long periods of time, gripping tools that cannot be put down, and elevating arms or tilting the head for extended periods. 3. Forceful Exertion is the amount of effort required by the body to perform a task or motion such as lifting, pushing, pulling, carrying, gripping, etc. Examples include forceful gripping and heavy lifting. 4. Contact Pressure occurs when a body part is compressed against a hard surface or sharp edge. Examples include using the heel of your hand as a hammer and forearms resting against the edge of a work bench. 5. Repetition refers to performing a task or series of motions over and over again with little variation. Examples include hand tool use (saw, screwdriver, or hammer) and sanding by hand. Section 3 Ergonomics and Material Handling 1 June 2013

2 6. Vibration occurs when the body is exposed to pulsation, shaking, or tremor usually produced by a vibrating object, such as a power hand tool. Examples include use of power tools, jackhammers, and operating heavy equipment. 7. Cold Temperatures can reduce the dexterity and sensitivity of the hand. Cold temperatures can also cause someone to apply more grip force to hold hand tools and objects. EXAMPLES OF RISKS AND SOLUTIONS IN SHOPS AWKWARD POSTURES A joint becomes weaker as it is moved away from its neutral position and into awkward postures. These postures place the muscles out of balance, make tasks more physically demanding, and add stress to the muscles and joints. Examples of awkward postures in the shop environment Illustration Risk Solution Working with hands above the head or with the elbows above the shoulders for prolonged periods without frequent breaks Take frequent breaks Stretch fatigued muscles Whenever possible, bring work to a height that is below shoulder level Working with the neck bent forward more than 45 If possible, raise the work to reduce neck flexion Take frequent breaks Stretch fatigued muscles Working with the back bent forward without support or frequent posture changes Bend the knees and keep the back straight Take frequent breaks Stretch fatigued muscles When possible, raise the work to waist level Section 3 Ergonomics and Material Handling 2 June 2013

3 Illustration Risk Solution Squatting or kneeling repetitively or for prolonged periods Consider using low stools to eliminate squatting or kneeling Consider using gel knee pads or closed-cell memory foam kneeling pads Take frequent breaks Alternate periods of squatting or kneeling with walking or standing Working outside of the power zone (working below the knees or above the shoulders) Use mechanical assistance to lift or move items outside of the power zone Whenever possible, reposition or store items in the power zone SUSTAINED OR STATIC POSTURES Too little movement can be as harmful as too much movement. Although there is little or no actual movement with static postures, the muscles become fatigued as a result of a sustained contraction to hold a steady position. Examples of static postures in the shop environment Illustration Risk Solution Prolonged Standing Consider using anti-fatigue mats or insoles at work areas requiring long periods of standing Alternate standing with movement or sitting Stretch fatigued muscles Prolonged Sitting Ensure that the chair provides a good fit and promotes neutral posture Alternate sitting with 3-4 minutes of movement or standing activities every hour Section 3 Ergonomics and Material Handling 3 June 2013

4 Illustration Risk Solution Stretch fatigued muscles Adjust tools and work area so that hands and wrist maintain neutral postures Holding tools for long periods of time Alternate between right and left hands Take frequent breaks or rotate tasks Stretch fatigued muscles Work that requires looking down for longer periods of time (prolonged head and neck flexion) Set up the work area to minimize the amount of forward bending of the neck Take frequent breaks or rotate tasks Stretch fatigued muscles FORCEFUL EXERTIONS Shop work requires various types of forceful exertions, including forceful gripping and muscular stress associated with lifting and carrying tasks. The table below depicts examples involving forceful hand exertion. (Lifting, carrying, pushing, and pulling are covered in the Safe Materials Handling section of this document.) Examples of forceful hand exertions in the shop environment Illustration Risk Solution Gripping an unsupported tool or object weighing 10+ pounds per hand, or gripping with a force of 10+ pounds per hand for more than 3 hours per day. Use balances, articulating arms or tool holders Consider the overall weight when evaluating or considering tools or equipment Take frequent breaks or rotate tasks Section 3 Ergonomics and Material Handling 4 June 2013

5 Illustration Risk Solution Holding and operating a hand tool weighing 2 pounds or more for more than 3 hours per day. Pinching with a force of 4 pounds or more (comparable to using a pair of pliers or hammer) for more than 3 hours per day. Use tools holders when possible Maintain neutral wrist posture to maximize grip and pinch strength Consider the grip or pinch force requirements when evaluating or purchasing hand tools Take frequent breaks or rotate tasks CONTACT PRESSURE Contact pressure results from occasional, repeated, or continual contact between unprotected body tissue and a hard surface or sharp edge. The pressure can lead to reduced blood flow, nerve conduction, or muscle function. Examples of contact pressure in the shop environment Illustration Risk Solution Using the hand (heel/base of palm) as a hammer Use rubber mallet, hammer or other appropriate tools Kneeling on hard or firm surfaces Use gel knee pads Use closed-cell foam kneeling pads Take frequent breaks Alternate positions Tool handles pressing into the palm Select tools with softer grips and handles When appropriate, wear gloves with gel or padded palms After-market tool handle wrap or sleeve Section 3 Ergonomics and Material Handling 5 June 2013

6 Illustration Risk Solution Leaning on the edge of a work bench Pad the edge of work bench with foam Padded sleeves along the forearm REPETITION Motions that are repeated with little variation may cause fatigue and overuse of the muscles, tendons, and joints that are involved in the movement. Overuse can lead to strain and inflammation. The longer these repetitive motions are performed, the greater the risk of injury due to overuse and lack of adequate recovery time. The following table shows the frequency of repetition that is considered high risk of injury in repetitive motion jobs: Body Part Shoulder Upper arm/ Elbow Forearm/wrist Finger *Adapted from Kilbom, 1994 Frequency >2.5 per minute >10 per minute >10 per minute >200 per minute The risks identified in the table above elevate to very high risk when combined with other factors such as forceful exertion, awkward postures, lack of training, or extended periods of repetitive work. Examples of repetition in the shop environment Illustration Risk Solution Use power tools whenever possible Rotate repetitive tasks with Use of hand tools such as other activities to provide an screwdrivers, hammers, saws, adequate rest period for and wrenches muscles Take short, frequent breaks Stretch fatigued muscles Section 3 Ergonomics and Material Handling 6 June 2013

7 Illustration Risk Solution Use a power sander whenever possible Rotate repetitive tasks with Hand sanding or grinding other activities to provide an adequate rest period for muscles Take short, frequent breaks Stretch fatigued muscles VIBRATION Localized vibration occurs when a specific part of the body comes into contact with vibrating objects (power tools, equipment). Whole-body vibration occurs when standing or sitting in vibrating environments (driving a truck over bumpy roads) or when using heavy vibrating equipment that requires whole-body involvement (jackhammers). Examples of vibration in the shop environment Illustration Risk Solution Pulse tools generate less vibration than impact tools Consider vibration-dampening tool wraps or gloves Use of power tools Purchase/use equipment with lower vibration levels Limit daily exposure with frequent breaks and task rotation Avoid tight grips on vibrating tools Ensure proper and regular maintenance Jackhammer use Consider vibration-dampening tool wraps or gloves Consider low vibration levels when selecting equipment Limit daily exposure with frequent breaks and task rotation Avoid tight grips on vibrating tools Ensure proper and regular maintenance Section 3 Ergonomics and Material Handling 7 June 2013

8 Driving a truck or heavy-duty equipment Properly adjust the driver weight setting on their suspension seats (where it is available) to minimize vibration Properly adjust the seat position and controls to provide adequate postural support and ease of reach for foot and hand controls Adjust vehicle speed to suit the ground conditions to avoid excessive bumping and jolting Select vehicles and machines with the appropriate size, power, and capacity for the work and the ground conditions Properly maintain vehicle suspension systems (tire pressures, seat suspension) Limit daily exposure with frequent breaks and task rotation Consider vibration-dampening seat cushions COLD TEMPERATURES Cold temperatures can cause one to apply more grip force to grasp hand tools or hold objects. Additionally, prolonged exposure to the cold can impair dexterity and cause numbness. Cold is especially a hazard when it is present with other ergonomic risk factors. The effects of other risk factors previously discussed can be exacerbated if the employee is exposed to cold while performing a task. Solutions may include proper personal protective wear or adjusting the temperature of the shop. SAFE MANUAL MATERIALS HANDLING Many tasks require frequent lifting, carrying, pushing, and pulling materials by hand. These job tasks are often referred to as manual materials handling. Staff who lift or perform other materials handling tasks may be at risk for back or other injuries. These injuries may be prevented by redesigning jobs (reducing the weight, the number of lifts, and the distance objects are moved). Additionally, safe lifting can help prevent back injuries. LAYOUT OF WORK AREA The layout of work areas should be arranged to prevent awkward postures such as bending, twisting, and over-reaching Work surfaces should be at waist height, or height-adjustable, to prevent bending Section 3 Ergonomics and Material Handling 8 June 2013

9 There should be sufficient space to pivot around and prevent twisting at the spine or joints All materials should be stored at least 8-12 off the floor, not directly on the floor Frequently used and heavy items should be stored between knee and waist height, referred to as the Power Zone (see section below S.M.A.R.T. Lifting Technique) Elevated platforms or step stools should be provided to reach items stored above chest level S.M.A.R.T. LIFTING TECHNIQUE There is really no single correct way to lift. However, there are less demanding ways to lift. The key to working safely is to determine how to lift loads in the least demanding way possible. Size up the load Assess the size, weight, and shape. Remove obstacles from the load (such as loose wrapping materials). Assess whether the load actually needs to be moved Where is the load going to be placed? Remove obstacles from your path. Determine whether mechanical or human assistance is required Move the load as close to your body as possible The whole hand should be used to ensure a firm grip Always bend your knees Maintain balance Keep feet apart and in a comfortable position Stagger your stance. This engages your leg muscles and reduces the demand on your back. Minimize bending at the waist Bend your knees to a semi squat Move Close Firm Grip Bend your knees Lift with your legs Raise the load with your legs Lift smoothly, without jerking Maintain the normal curves of your spine throughout the lift Turn your feet in the direction that you want to move the load Avoid unnecessary bending, twisting, and reaching Change direction by turning your feet and not your back To set down a load, squat down and keep your head up. Let your legs do the work. Section 3 Ergonomics and Material Handling 9 June 2013

10 THE POWER ZONE The power zone for lifting is close to the body, between midthigh and mid-chest height. Comparable to the strike zone in baseball, this zone is where the arms and back can lift with the least amount of effort. TEAM LIFTING Team lifts are appropriate if: o The load is too heavy for one person o The load is large, bulky, or oddly-shaped o If you feel uncomfortable lifting the load by yourself Whenever possible, team members should be of around the same height and build. If this is not possible, taller members should be at the back. Designate a lift leader, who: o Plans and coordinates the lift o Provides simple and clear instructions o Ensures that you lift and lower the load together. Assess the weight of the load Follow the S.M.A.R.T. lifting technique The lift leader should ensure that all team members are comfortable once the load has been lifted. If not, the load should be carefully and immediately lowered. Heavy items requiring a team lift should be clearly labeled. OVERHEAD LOADS Always use a stool or elevated platform to lift loads above chest level Test the weight of the load before removing it from the shelf Slide the object toward you, to the edge of the shelf before lifting Hold the load close to your body as you lower it AWKWARD LOADS Sometimes different lifting techniques need to be adopted to move awkward loads Over-sized or Odd-shaped In many cases, oversized loads may be light enough to carry, but block vision or may be difficult to hold. In such cases, use mechanical assistance or seek help from a coworker. Section 3 Ergonomics and Material Handling 10 June 2013

11 Long, but light weight, objects Support the load on your shoulder Keep the front end higher than the rear PUSHING AND PULLING Keep your back straight, avoiding excessive bending or twisting Use your legs to push or pull Keep the load as close to your body as possible When using mechanical aids to push and pull, the handles should be positioned at a height between the shoulder and waist When pushing on a slope or ramp, ask for assistance whenever necessary. Keep in mind that the incline can significantly increase the forces required. Uneven loads may also require increased push and pull forces MECHANICAL LIFTING DEVICES THE SAFEST LIFT IS NO LIFT AT ALL! The best way to avoid a back injury is to minimize the number of lifts you execute. Hand trucks, pushcarts, lifts, and other devices are great engineering controls that reduce your exposure to lifting hazards. Before operating any mechanical lifting devices, be sure you have been properly training and/or certified. EXAMPLES OF MECHANICAL LIFTING DEVICES Illustration Equipment Applications Carts Transporting tools and materials to/from job sites Hand Trucks Transporting boxes and other heavy loads Section 3 Ergonomics and Material Handling 11 June 2013

12 Scissor Lift Carts The height can be adjusted to allow the user to slide the load off the cart to storage, rather than lifting and lowering Can also be used as a heightadjustable work surface Hoists Lifting large, bulky, and very heavy items Pallet Jacks/ Fork Lifts Moving pallets Mechanical or Platform Lifts Similar to a scissor lift, often has a smaller platform and greater height range WHAT ABOUT BACK BELTS? Back belts are sometimes prescribed or used when recovering from a back injury. However, many experts have questioned the effectiveness of back belts in preventing back injuries. There is little scientific evidence that back belts reduce the possibility of injury during lifting. Back belts do not increase strength or lifting ability and they are not a substitute for proper body mechanics and common sense. They will not prevent back injuries, especially if you do not use proper lifting techniques or good judgment when deciding to lift. For additional information on back belts, refer to the University of California Back Belt Information and Guidance document. Hyperlink to document. In addition, the Shop Manager s Safety Management Tool Kit has guidance for managers on back belt use by subordinates. Section 3 Ergonomics and Material Handling 12 June 2013

13 SETTING UP A SAFE WORK ENVIRONMENT Avoiding exposure to work hazards such as awkward postures, repetition and high forces is the best way to avoid discomfort and injury. Here are some ways that you can set up your work environment to avoid such hazards. Reach Zone Distance Tasks Items should be placed no further than 10 from edge or Tools and materials that are Primary work surface handled frequently Reach distance should be no Secondary greater than 15 Items should be placed no further than 20 from edge or work surface Reach distance should be no greater than 24 Tools and materials that are handled occasionally RECOMMENDED REACH DISTANCES Reach Zones Precision Work (with elbows supported) WORK SURFACE HEIGHT RECOMMENDATIONS Different tasks require different work surface heights. Light Work (exerting 10 pounds or less) Heavy Work (exerting greater than 10 pounds OR large upward/downward forces) 4 above elbow height Slightly below elbow height At hip level (4 below elbow height) Section 3 Ergonomics and Material Handling 13 June 2013

14 HAND TOOL CONSIDERATIONS The design of a hand tool can affect your working posture and the force required to operate the tool. To minimize risk of injury, refer to the table below to match your tool selection to the task you must complete. For tasks requiring a POWER GRIP DOUBLE-HANDLE TOOLS SINGLE-HANDLE TOOLS Open Grip Span = < 3 ½ Closed Grip Span = > 2 Handle Diameter= 1¼ to 2 For tasks requiring PRECISION SINGLE-HANDLE TOOLS DOUBLE-HANDLE TOOLS Handle Diameter= ¼ to ½ Open Grip Span = <3 Closed Grip Span = >1 GUIDELINES FOR HAND TOOL SELECTION Select tools with smooth, non-slippery, padded handles. Avoid tools with finger grooves, hard plastic handles, sharp edges, and small or large diameter handles. Use grips or tape to build up small diameter tools, especially if you need to use them with a power grip. Better still, select tools with larger diameter handles (1¼ -2 ) and soft grips. Use tools with longer handles (screwdrivers, wrenches) for better leverage BEST PRACTICES FOR HAND TOOL USE Avoid gripping or pinching tools with your wrist in awkward positions Take frequent breaks to stretch and rest hands Alternate hand tools use with other activities frequently throughout the day Use vises, clamps, or jigs to stabilize objects to avoid prolonged forceful gripping with the hand. Section 3 Ergonomics and Material Handling 14 June 2013

15 POWER TOOL CONSIDERATIONS Ergonomic Risk Static Loading The use of power tools often requires long periods of static postures, without break or movement The static postures are often coupled with static muscle force Both static postures and static force can lead to early fatigue Awkward Posture When work is not oriented properly, non-neutral postures can result Contact Stress Creates points of pressure on the hand and/or fingers Vibration Impacts circulation in the hand Frequencies between Hz can cause the most problem NIOSH has concluded that frequencies as high as 4,000Hz can present a risk Tool Weight Heavy tools cause increased fatigue Trigger Force High force causes over loading on fingers Low force can be a safety hazard Recommendation 1. Consider using tool balancers, tool holders, or articulating arms to hold the tools 2. Add a swivel to air tools between the tool and air hose 3. Ensure the appropriate tool is used for the application 1. Choose handles based on the orientation of the work surface (see pictures below) 2. Adjust the height of the work surface or use platforms 1. Avoid grooved handles 2. Ensure sufficient clearance for the hand 1. Consider impulse tools vs. impact tools 2. Vibration dampening tool wraps or gloves 3. Use air dampening percussion tools 4. Select tools with low vibration levels 5. Limit exposure to vibration 6. Avoid a tight grip 1. Should be able to easily hold the tool in one hand 2. For precision operations, the tool should weigh less than 1 pound (0.45 kg) 3. Regardless of weight, consider a balance arm for all precision tools 4. Power tools greater than 6 pounds, should be placed on a balance arm at the center of gravity 5. The tools center of gravity should be aligned with the center of the grasping hand 6. Consider tools with an extra handles to allow 2-handed gripping (or add a handle) 7. Suspend air hoses from above 8. Suspend tools with a balancer 1. Use 2-3 fingers for tools with high trigger force 2. Allow the use of alternative fingers 3. Maximum grip force should not exceed 4 pounds 4. Trigger length should be 1 minimum Section 3 Ergonomics and Material Handling 15 June 2013

16 Temperature Cold temperatures can decrease circulation to the hands and fingers Impaired circulation can cause reduced grip strength 1. Select tools with wooden, plastic or rubber handles that insulate the hand from extreme temperatures Note: gloves (often worn for heat) may actually increase grip force requirements and cause early fatigue RECOMMENDED HANDLE CHOICE, BASED ON WORK SURFACE ORIENTATION HEALTHY WORK HABITS ROTATE TASKS Alternate tasks with other activities that involve different muscle groups and body positions. This allows you to remain productive while avoiding muscular fatigue. TAKE FREQUENT REST BREAKS Frequent 3-4 minute breaks are an opportunity for blood flow and oxygen to fatigued muscles, allow time for muscles to recover WARMING UP AND STRETCHING Pre-shift: Warming up and stretching before you start your shift increases blood flow to cold muscles and improves flexibility. Section 3 Ergonomics and Material Handling 16 June 2013

17 Stretch breaks throughout the day: Stretching tired muscles can improve your endurance throughout the day and help avoid injury Listen to your Body! REFERENCES Eastman Kodak Company. (2004). Kodak s Ergonomic Design for People at Work, 2 nd Edition. Hoboken, New Jersey: John Wiley & Sons, Inc. Sanders, Mark S. and Ernest J McCormick. (1993) Human Factors in Engineering and Design, 7 th Edition. New York: McGraw-Hill. ErgoMatters Standing Workstation Guidelines, Volume 1, Number December Thompson, Norman. Mechanical Lifting Equipment. Workplace Safety Advice- August 30, Section 3 Ergonomics and Material Handling 17 June 2013

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19 QUIZ ERGONOMICS AND MATERIAL HANDLING Supervisor / Shop Manager May use this quiz as evidence of safety training. Print Trainee Name Date Trainee Signature Supervisor Signature 1. Ergonomic controls can include which of the following: a. Restructuring or changing the work environment b. Changing work tools c. Using a mechanical lift for heavy loads d. All of the above 2. True or False? You should try to keep your work materials, supplies and tools close to the body and between mid-thigh and mid-chest level. 3. True or False? One way to reduce exposure to risks, such as awkward postures, repetition and force, is to change work tasks and working positions throughout the day. 4. The lifting Power Zone is defined as the area: a. Below knee height b. Above shoulder height c. Between knee and shoulder height d. None of the above 5. True or False? One of the best ways to apologize to your body after hard work is to perform periodic stretches to help your muscles breathe. Section 3 Ergonomics and Material Handling 19 June 2013

20 * Quiz Answers: 1. D 2. True 3. True 4. C 5. True Section 3 Ergonomics and Material Handling 20 June 2013