Industrial ERG

CHAPTER 12 MANUAL MATERIALS HANDLING

LEARNING OBJECTIVES

At the end of the module, students will be able to apply aspects of manual material handling. Students will review and identify the factors that affect manual material handling methods, and apply common manual material handling solutions.

INTRODUCTION

Few industries are able to avoid the need for products or raw materials to be handled manually (Marras, 2006). Manual handling includes any tasks that require a person to lift, lower, push, pull, hold, or carry any object, animal, or person (see  Figure 12.1 ).

Figure 12.1  Heavy lifting over long distances and benefit from a platform cart

MANUAL MATERIAL HANDLING AND INJURIES

Manual materials handling (MMH) has long been recognized as a contributor to back pain. The National Institute of Occupational Safety and Health (NIOSH) found evidence for a causal relationship between “heavy physical work” and back pain and strong evidence for a causal relationship between lifting and forceful movement and back pain. Other notable injuries associated with MMH include slips, trips and falls, and crushing injuries.

Strategies for Reducing MMH Injures and Increasing Productivity

Several approaches can be used to reduce all types of injuries associated with MMH:

· A system approach to material handling to reduce the amount of product handled and the use of automated transfer devices

· Teaching people to lift safely

· Selecting people for specific tasks according to their strength and endurance

· Developing the workers' strength and endurance capacity through industrial fitness and total health programs

· Redesigning the workplace, containers, and jobs to make the handling suitable for more people (The Ergonomics Group, Health and Environmental Laboratories, Eastman Kodak Company, 1989).

This module addresses the systems approach and redesigning the workplace (providing aids, containers, and jobs) to make the handling suitable for more people ( Figures 12.2 – 12.4 ).

Figure 12.2  Pallet scissor l

Figure 12.3  Tilting lift table orients work to the worker so they do not need to bend forward

Figure 12.4  Two-person lift made easy

THE SYSTEMS APPROACH TO MMH

The systems approach to MMH can best be accomplished in the planning phase of a facility or operation. As much as feasible, automated movement of bulk, intermediate, and final-stage products are incorporated into the process. A number of design principles, even in an established operation, can be beneficial.

Advantages of a systems approach:

· Reduction of in-process inventory

· Elimination of multiple remaining products

· Less delay in moving materials between workstations

· Improved control of production

· Reduced damage to product

· Less opportunity for human error.

A systems approach employs one or more of the following ( Figure 12.5 ):

· Unit size or load: Increase the quantity, size, or weight of unit loads so they must be handled with powered equipment. A large drum instead of individual bags is an example of this principle.

· Mechanization: Mechanize operations with motorized conveyors, overhead hoists between workplaces, vacuum assists, and motorized carts ( Figures 12.6  and  12.7 ).

· Standardization: Standardize handling methods as well as types and sizes of handling equipment. People are more likely to use equipment they are familiar with. Use equipment that is compatible across systems. For example, an automated stair climber can be used in place of a lift gate.

· Adaptable: Choose equipment that can perform a variety of tasks ( Figure 12.8 ).

· Dead weight: Reduce the ratio of the dead weight to the load being moved. Heavy metallic trays or cans can be replaced with a lighter suitable material.

· Gravity: Use gravity to move material. Gravity feed conveyors or canted storage units (so material flows forward). Lower materials instead of lifting them.

· Automation: Provide automation to include production handling and storage functions such as an automated stacker–retriever.

1. Redesign of Work Places and Jobs

Redesigning a workplace can eliminate the hazard or greatly reduce the risk of injury. Not all tasks lend themselves to redesign; for example, the environment in which a firefighter works cannot be changed, or others may simply be cost prohibitive to redesign. Some strategies are included below:

· Provide ways to adjust material to be handled so that less lifting and more sliding can be done. For example, a scissors lift table.

· Provide comfortable, appropriately shaped hand holds or handles on containers or objects.

· Rotate people between heavy and lighter jobs.

· Alternate jobs so that the same body regions (muscle groups) are not over exposed.

· Ensure two people lift objects over a certain weight and are trained in proper lifting techniques. These objects can be tagged stating a two-person lift is required.

· Locate materials within the workers' power zone (knuckles to shoulders).

· Provide carts and handling aids to support the weight of objects carried more than a few feet.

· Provide tools to help reduce forces in the hands.

Figure 12.5  Awkward posture could benefit from a lift table

Figure 12.6  Rotating lift table used for inspection or building

Figure 12.7  Vacuum assist for lifting heavy items (Courtesy of  http://www.anver.com )

Figure 12.8  Walk behind fork truck or stacker

MMH EQUIPMENT AND SOLUTIONS

(Department of Health and Human Services, 2007)

Easier Ways to Manually Lift, Fill, or Empty Containers

Use a scissors lift, load lifter, or pneumatic lifter to raise or lower the load so that it is level with the work surface. Then slide the load instead of lifting.

Options available are as follows:

· Portable (wheels)/fixed (attached to the floor)

· Zero-clearance (can use a pallet jack or fork truck to drive on top of them)

· Powered/spring lift mechanism

· Use as workbench

· Tops:

· Lazy-Susan (top rotates 360°)

· Conveyer top

· Tilting top

· Specialized: pallet, drum, roll

Use a dolly to make things easier to push and pull.

Raise the workers so they are close to the surface they need to reach with platforms, catwalks, portable stairs, or person lifts. Work within the power zone by raising the product or the worker, or providing various working height surfaces.  Figure 12.9 shows a simple solution for keeping the work within the workers' power zone.

Figure 12.9  Manual material handling lift table

Store heavier or bulkier containers so that they can be handled within the power zone where the workers have the greatest strength. Angle the work toward the worker, also angling the product uses gravity to bring product forward. Tugging and towing equipment can be purchased and can be mated to anything that needs to be moved.  Figures 12.10  and  12.11  highlight the use of equipment to reduce the stress and strain on a worker found in a common repeatable task.

Figure 12.10  Before: Worker climbs and stretches while balancing on the ledge of a van to reach heavy ladder risking falls and soft tissue injuries

Figure 12.11  After: Worker safely removes ladder from curb side

SUMMARY

Manual material handling takes many forms and is present in all industries. Back injuries as well as caught-in or -between injuries are commonly linked to manual material handling tasks. Anticipation of overexertion, heavy, awkward lifting, and repeated lifting can lead to the proper abatement method. Manual material handling solutions do not need to be costly to be effective in accident aversion. Simple means to bring the work within the workers' power zone can reduce physical as well as physiological demands ( Figure 12.12 ). Reference the survey tools found in the  Appendix C  and  Chapter 14  for qualitative methods of manual material handling evaluation.

Figure 12.12  Arm lifts help the worker to maintain a neutral upright posture and eliminate compression on the hands (Adapted from  www.forearmforklift.com )

KEY POINTS

· Eliminate lifting from below the knees by focusing on bringing the work to the elbow height of the workers. Lifting assists such as scissor lift tables and pallet lifts are useful solutions.

· Reduce forceful pushing, pulling, and lifting by using simple transport devices such as carts or dollies.

· Use more sophisticated equipment such as powered stackers, hoists, cranes, or vacuum-assist devices for tasks that occur frequently or have a high potential for injury.

REVIEW QUESTIONS

1. What can be done to prevent manual material handling injuries?

2. What types of injuries are common in manual material handling environments?

3. What is one use for a portable scissor lift table in a manual material handling environment?

EXERCISES

See the exercise appendix.

REFERENCES

1. Marras, W. (2006). Fundamentals and Assessment Tools for Occupational Ergonomics 2nd edn. CRC Press.

2. The Ergonomics Group, Health and Environmental Laboratories, Eastman Kodak Company. (1989). Ergonomic Design for People at Work, Vol. 2. Wiley.