Vacuum Cleaning
Design & Task Analysis - Spring 2019
Overview
Janitors performing vacuuming task are under risk because of the long working duration, the energy required to perform the task, improper postures, repetitive motions, and unsuitable vacuum cleaners. From four ergonomics aspects, the vacuuming task and three kinds of vacuum cleaners (Oreck ® U2000RB-1, ProTeam Super CoachVac, & Sanitaire SC3683B) are examined. The analysis considers engineering anthropometry, human strength, work-rest cycles, and work factors for repetitive motion injuries. The result shows that the Sanitaire SC3683B commercial canister vacuum cleaner should be selected from the three models.
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Note: Full analysis and details aren't shown on this page. For more detailed analysis, please refer to the project report located at the bottom of this page.
Analysis of Existing Designs
Based on several online ratings and reviews, the following three models are selected, including the three common types of commercial vacuum cleaners: upright, backpack, and canister.
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1. Engineering and Anthropometry and Anthropometrics Design
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Purpose
Determine whether the heights of the vacuum cleaners are suitable for the workers
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Data used
The “(D14) elbow rest height, standing” data from 2012 Anthropometric Survey of U.S. Army Personnel (Table A 1)
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Assumptions
(1) The vacuum cleaners shouldn’t be shorter than [elbow height – 4 in], or the workers must bend their back to reach further.
(2) The vacuum cleaners shouldn’t be higher than [elbow height + 6 in], or it would be hard for the workers to lift vacuum cleaners when cleaning stairs.
(3) The population consists of 50% of males and 50% of females.
The design criterion for vacuum height is:
Elbow Height – 4 < Vacuum Height < Elbow Height + 6
Calculate percent accommodated for females and males separately, and then calculate the average percent accommodated using equation
(Females Percent Accommodated + Males Percent Accommodated) / 2
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The vacuum height that maximizes the average percent accommodated is 43 inches. Therefore, the vacuum heights for “ProTeam Super CoachVac” and “Sanitaire SC3683B” are suitable, while “Oreck® U2000RB-1” might be too high for some workers to use it especially when cleaning stairs.
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2. Biomechanics of Work and Design for Human Strength
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Based on online videos, two vacuuming motions are considered and examined by 3DSSPP:
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Motion A
Pushing and pulling forward and backward while standing straight. This motion is assumed to be performed while vacuuming wide areas.
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Motion B
Pushing and pulling sideways while standing bent. This motion is assumed to be performed while vacuuming underneath obstacles such as tables and chairs. Only the hand that exerts more force is considered in the analysis. Assume that the right hand is the primary hand to exert force.
Both 50th percentile male & female anthropometry data is used. The postures are examined to see if they can be performed by 99% of males and 75% of females.
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The result from 3DSSPP shows that the vacuuming postures while using ProTeam Super CoachVac and Sanitaire SC3683B require less strength and are safer for the workers. The motion that rocks back and forth and the motion that bends and twists the torso should be avoided.
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3DSSPP analysis example 2. Bending pull motion using ProTeam Super CoachVac
3DSSPP analysis example 1. Bending push motion using Oreck® U2000RB-1 for males
3. Work-Rest Cycles and Energy Expenditure Rate
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Assumptions
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The workers are average healthy females weighing 60 kg and healthy males weighing 70 kg.
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The workers are in their thirties and forties.
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The workers vacuum three hours a day (based on the research by Suzanne Teran and Evan vanDommelen-Gonzalez (2017)).
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During rest periods, the workers perform light works that require 2 kcal/min.
Calculations
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Table 3-1 is used to determine the maximum aerobic capacity (V ̇ O2) for different workers.
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E ̇ max is calculated using the equation E ̇ max = 5 V ̇ O2.
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For a three-hour work, PWC = 0.37E ̇ max.
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The energy expenditure rates (E ̇ Task) when using different kinds of vacuum cleaners are determined based on Table 3-2.
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The percent rest required is calculated using the equation %Rest = (PWC - E ̇ Task)/(ERest - E ̇ Task)
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Some of the energy expenditure rates exceed the PWC. For those cases, rest is required. The rest required is shown in Table 3-3. The result shows that all three vacuum cleaners aren’t suitable for females to operate for three hours. If the company requires all workers to vacuum about three hours per day, the “Sanitaire SC3683B” should be selected.
Table 3-2. Energy Expenditure Rate Benchmark
Table 3-1. Maximum Aerobic Capacity for Different Population
Table 3-3. Percent rest required for a 3hr vacuuming task for different vacuum cleaners
4. Work Factors for Repetitive Motion Injuries
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The ACGIH TLV for Hand Activity and the Strain Index are used to evaluate the risk of repetitive vacuuming task. The three vacuum cleaner models are ranked respectively based on the rating scales. The calculated results are compared with the recommended values to determine if the current tasks are hazardous.
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ACGIH TLV for Hand Activity
The ratios for all three models are all between the action limit (AL) and the threshold limit value (TLV), but Oreck® U2000RB-1 has a higher ratio compared to the other two models.
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Strain Index
The result shows that using Oreck® U2000RB-1 is hazardous, while using the other two models pose some risk to the workers.
ACGIH TLV for Hand Activity Evaluation
Example of Strain Index Evaluation: Strain Index Evaluation for a 3hr vacuuming task using Oreck® U2000RB-1
Proposed Design & Analysis
Proposed Vacuum Cleaner Design
Based on the analysis in the last section, the canister vacuum cleaner “Sanitaire SC3683B” is recommended to be used. This model has the following advantages:
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A suitable height that accommodates 93.9% of workers, which is close to the maximum possible percentage.
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The vacuum tube is light. And both hands can be easily used when cleaning underneath objects such as tables and chairs to avoid twisting the body and overextending the primary arm.
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Since the workers don’t need to carry a motor on their back or push and pull a heavy vacuum cleaner, the energy expenditure rate for Sanitaire SC3683B is the lowest among the three models. More workers can operate the vacuum cleaner for three hours without getting fatigued.
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The strain index is lower than the Oreck® U2000RB-1.
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Although the ProTeam Super CoachVac isn’t the recommended model, its tube shape helps clean underneath objects. In addition, the adjustable wand can accommodate more workers to perform the task comfortably.
The image below shows the vacuum cleaner design with a bendable tube. This kind of vacuum cleaners can help people clean underneath objects even more easily.
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Either the special tube shape of ProTeam Super CoachVac or bendable tubes, and adjustable vacuum heights are recommended to be added to the Sanitaire SC3683B model. The adjustable vacuum heights should at least cover the 41 to 45 inches range to maximize the percent accommodated for females and males respectively.
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Task Design
Considering the task design, the vacuuming duration should be shortened to prevent fatigue. When the duration is shortened to two hours, males in their forties only need 3% rest even if they’re using the Oreck® U2000RB-1, which is the model that requires the most energy. When the duration is shortened to one hour, females in their thirties can perform vacuuming task without fatigue when using ProTeam Super CoachVac and Sanitaire SC3683B; females in their forties only need a short resting period when using Sanitaire SC3683B, the recommended model.
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In addition, if the task duration is reduced, the Strain Index can also be decreased. When vacuuming for one to two hours using Sanitaire SC3683B, the Strain Index is 4.5, which is a little higher than the safe value 3. When vacuuming for less than one hour using Sanitaire SC3683B, the vacuuming task becomes safe for the workers.
Percent rest required for a 1hr vacuuming task for different vacuum cleaners.
Strain Index for less-than-1- hour vacuuming task using Sanitaire SC3683B.
Implementation & Benefits
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Companies can purchase new vacuum cleaners to help workers perform vacuuming tasks with less stress on their bodies.
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Work shifts can be arranged or more workers can be hired to reduce the vacuuming time per worker.
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Although there will be more expense in the short term, it would be less likely for the workers to get injured and can reduce workers’ compensation and avoid lost workdays in the long term. Both productivity of vacuuming and the health of the workers can be improved.