Ergonomic Assessments of the Melni BD2HL-S Mechanical Lug Connector and the Traditional Crimped Lug Connector

Transcription

1 Ergonomic Assessments of the Melni BD2HL-S Mechanical Lug Connector and the Traditional Crimped Lug Connector August 4, 2016 Prepared for: Melni, LLC 265 Ash St. N. Twin Falls, ID Prepared by: Lee T. Ostrom, Ph.D., CSP, CPE, CTM 2811 Disney Dr Idaho Falls, ID 83404

2 Abstract In July of 2016 an ergonomic assessment of the Melni BD2HL-S mechanical lug connector (Melni connector) was conducted in a mocked up industrial setting. This report documents the ergonomic assessments performed on the traditional method of performing a lug connection for 2/0 electrical cable on an industrial panel and the Melni connector to perform the same connection. A master electrician performed two (2) connections using each methodology. The tasks were performed in the Melni laboratory area on a mocked up electrical panel simulating connection 2/0 cable to a transformer or industrial panel. The tasks were recorded using digital video and still photography. The data were analyzed using two methods: 1. Observational and video analysis was used to detail the steps in the procedure and to identify the ergonomic risk factors associated with each of the two (2) sets of tasks. 2. The Rapid Upper Limb Assessment (RULA) tool was also used to perform a postural analysis of the two (2) sets of tasks (Ref 2). The ergonomic risk factors associated with the traditional connection method were: Twisted back postures for several aspects of the task Repetition associated with crimping the lug connector High forces and duration when crimping the lug connector Compression of the thigh, shoulders, and hands when crimping It is quite apparent that using the crimping tool places great musculoskeletal stress on the user. The ergonomic risk factor associated with the Melni connector method was minimal and was the awkward posture of the electrician leaning into the panel when tightening the connector nuts and the Melni connector. The RULA scores for the traditional connection method was seven (7+) indicating a person is working in the worst posture with an immediate risk of injury from their work posture and changes should obscure immediately to prevent injury,. The RULA scores for the most stressful aspects of the Melni connector method was two (2) or less, indicating an acceptable task. According to the RULA methodology this task would be considered safe from an ergonomic perspective. The overall conclusion is that the Melni connector method has significant ergonomic benefit over the traditional method of performing connections on 2/0 electrical cable. The Melni method should replace the traditional method whenever feasible. ii

3 Table of Contents 1. Introduction and Background Analysis of the Traditional Method Analysis of Using the Melni Connector to Perform a Connection Conclusions References iii

4 1. Introduction and Background I was requested to perform an ergonomic assessment comparison of the traditional method of a 2/0 gauge aluminum cable to a mocked up industrial panel, with using the Melni BD2HL-S mechanical lug connector (Melni connector) to perform the same sort of connection. The data collection phase of this assessment occurred on July 30, The data collection consisted of a master electrician performing two (2) cable connections using the traditional crimping method and two (2) connections using the Melni connector. The Melni connector is shown in Figure 1. I observed the two tasks and recorded video, along with still photographs. These tasks were performed in a mocked up industrial setting, simulating connecting the cables to a transformer or industrial panel. Figure 1: Melni Connector 1

5 The electrical panel was 48 inches tall by 36 inches wide. The bottom of the bottom simulated bus bar was 45.5 inches from the floor. The bottom of the top simulated bus bar was 55.5 inches from the floor. Figure 2 shows a photo of the panel prior to the beginning of the test. 36 inches 48 inches 45.5 inches 55.5 inches Figure 2: Test Panel I analyzed the data during the week of August 1, 2016 using two (2) methodologies. These were: 2

6 1. Using the observations, pictures and videos of the task to identify the steps in the procedure and to identify the ergonomic risk factors associated with each of the two (2) sets of tasks. The traditional ergonomic risk factors are (Ref 1): a. Force b. Posture c. Repetition d. Duration e. Vibration f. Compression 2. Using the Rapid Upper Limb Assessment (RULA) evaluation tool to perform a postural analysis of the two (2) sets of tasks (Ref 2). This report discusses the results of the assessments. Section 2.0 discusses the analysis of the traditional cable connection task and Section 3.0 discusses the analysis of using the Melni connector to perform the task. 2. Analysis of the Traditional Method For this test the cable was already stripped of insulation at the required distance for the two types of connectors. Therefore, the equipment The equipment used for the traditional task is: Wire Crimp connectors Crimping tool Battery drill motor Adjustable wrench The basic steps I observed for performing the traditional connection of 2/0 gauge wire were: 1. Adjusting the crimping tool for the correct connector 2. Inserting an end of the wire into the end of the butt connector 3. Ensuring the crimping tool is adjusted correctly for the connector 4. One worker holds wire while the second worker holds the crimping tool 5. Crimp the connector using the crimping tool 6. Rotating the wire 90 degrees 7. Crimp the connector 3

7 8. Twist the cable into place and place on mounting bolts. 9. Put washers and nuts on the bolts 10. Tighten down with the drill motor 11. Tighten to proper torque with the adjustable wrench. The total operation of these steps took approximately three minutes. However, the electrician did discuss aspects of the task as he was working which changed the time the actual task would be performed. The ergonomic risk factors identified in this procedure were: Leaning forward back postures in excess of 20 degrees for several aspects of the task Twisted back postures for several aspects of the task Repetition associated with crimping the connector High forces and duration of high forces when crimping the lug connector. The force required to begin the crimp using the tool was approximately 84 pounds determined from a previous study. Compression of the shoulder, thigh and hands when crimping the connector The steps of the process with significant ergonomic risk factors were 5, 7 and 8. The crimping steps are the most stressful and are discussed below. Figure 3 shows a photo at the start of the crimping step. The master electrician s right arm is in an awkward posture and he is beginning to put pressure on the tool handle. He is slightly leaning forward and his right wrist is deviated. He must attain this posture two (2) times each time he crimps one (1) 2/0 cable. At the midpoint of the crimping step, as shown in Figure 4 and 5, the master electrician is in a very awkward posture. His back is bent forward and twisted, his neck is twisted, and he is continuing to apply a great amount of force using his body weight and his hands. His left upper arm is abducted (away from the body) and the handle of the tool is compressing his left thigh. Figure 6 shows the end point of the crimping step. As the figure shows the Master Electrician is leaning forward more than 20 degrees and is in a twisted posture. His neck is also leaning forward. 4

8 Right upper arm approximately at shoulder height. Lower arm more than 90 degrees. Back leaning slightly forward. Figure 3: Start of Crimping Step Lower arm more than 90 degrees and abducted. Figure 4: Midpoint of Crimping Step 5

9 This is the worst posture observed. Upper arm abducted and at shoulder height. Back leaning forward and twisted. Figure 5: Second Midpoint of Crimping Step Back leaning forward and twisted. Figure 6: End Point of Crimping Step I performed RULA analysis on three of the most stressful postures associated with this task. Figure 3 shows the start of the crimping task. A RULA analysis was performed 6

10 on this posture. The completed RULA form is shown in Figure 7. The RULA score developed from this analysis was seven (7+). A seven (7+) represents the worst postural score under the RULA methodology, indicating a change needs to be made to the task. This step is performed two (2) times for each connector. Figure 4 and 5 shows the midpoint in the crimping task. The completed RULA form is shown in Figure 8 and 9. The RULA score developed from this analysis was seven (7+). A seven (7+) again represents the worst postural score under the RULA technique, indicating a change needs to be made to the task. Figure 6 shows the final phase of the crimping step and Figure 10 shows the RULA analysis. This part of the crimping task also scored a RULA score of seven (7+). Figure 7: RULA Analysis for Start of Crimping Task 7

11 Figure 8: RULA Analysis for Midpoint of Crimping Task Figure 9: RULA Analysis for Midpoint of Crimping Task 8

12 Figure 10: RULA Analysis for End of Crimping Task As stated above, a RULA score of seven (+7) is the worst postural score possible using this methodology. This score indicates that the task should be modified immediately to avoid injury. 3. Analysis of Using the Melni Connector to Perform a Connection The equipment used for the Melni connector is: The wire The Melni Connector An adjustable wrench A torque wrench 9

13 The basic steps for performing the splicing task with the Melni connector for 2/0 wire is: 1. Inserting an end of the wire into the end of the Melni connector 2. Place connector on the mounting bolts 3. Hand tightening the gripper/ seal ring on the Melni connector 4. Using an adjustable wrench to initially tighten the Melni connector 5. Use an adjustable wrench to tighten the connector and then a torque wrench to tighten the connector to 25 foot-pounds. 6. Put washers and nuts on the bolts 7. Tighten down with the drill motor 8. Tighten to proper torque with the adjustable wrench. The procedure for using the Melni connector requires three (3) fewer basic steps and the steps have many fewer ergonomic risk factors. This process took less than two (2) minutes to perform. Once again, the electrician discussed the task as he performed it, so the time to perform the task might not be accurate. From observing the task and analyzing the videos the steps with any significant ergonomic risk factors were steps 5 and 8. These factors were minimal and were that the electrician had to lean into the panel to tighten the bolts and the connector. Figure 11 shows the electrician leaning into the panel and the corresponding RULA analysis is shown in Figure 12. Figure 11: Tightening the Melni Connector 10

14 Figure 12: RULA Analysis for Melni Connector The highest RULA score for the Melni connector was 2. This score is considered acceptable. Note, the back posture will change with the height of the bus bars. 4. Conclusions The results from the analysis showed that: There were three (3) fewer steps associated with the Melni connector for performing a connection of 2/0 cable. The ergonomic hazards associated with using the Melni connector were fewer in number and, according to the RULA analyses, less stressful. The RULA scores for the three (3) parts of the crimping steps for the traditional connecting method all were seven (7+), whereas the highest RULA score for any of the steps associated with the Melni connector was two (2). The score of three (2) was due 11

15 to having to lean into the panel to tighten the connector and mounting bolts. There would be essentially no ergonomic stressors If the task were performed using the modified Melni connector with the wire at approximately elbow height. The risk of the crimping tool slipping while performing the crimping steps for a traditional connection appears to be great and could lead to an acute injury. Also, the Master Electrician reported that he suffers from bruises many times after doing a traditional lug connection. The overall conclusion is that the use of the Melni connector provides great ergonomic benefit over the traditional method of connecting 2/0 cables to transformers/industrial type panels and appears to take less time to perform. It cannot be stressed enough that the crimping tool places great musculoskeletal stress on electricians performing these tasks. It is recommended that this method be used whenever possible and the electricians should be trained on the ergonomic risk factors associated with this tasks as well as stretching techniques to reduce fatigue. 5. References 1. Stack, T., Wilhelmsen, C., and Ostrom, L., Occupational Ergonomics: A Practical Approach, publication date: May McAtamney, L. and Corlett, E.N. (1993) RULA: A survey method for the investigation of work-related upper limb disorders. Applied Ergonomics, 24 (2),