• 한국안전학회지
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• 제36권5호
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• pp.36-42
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• 2021

Portable ladders are widely used as ascend and descend pathways and platforms for works at height at residential and industrial sites. In the last 10 years, 267 fatalities and 36,571 accidents related to portable ladders have been reported, suggesting a need to develop countermeasures to prevent such accidents. In this study, an in-depth focus group interview (FGI) was conducted with various stakeholders of portable ladders to survey the current usage and requirements for improving work safety. A new portable ladder called active platform ladder was developed based on the requirements suggested by the FGI. A stability test confirmed that the developed ladder is more stable than conventional ones, suggesting that it can reduce the fall accidents.

• 대한안전경영과학회지
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• 제23권1호
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• pp.9-15
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• 2021

The leading source of occupational fatalities is a portable ladder in Korea because it is widely used in industry as work platform. In order to reduce victims, it is necessary to establish preventive measures for the accidents caused by portable ladder. Therefore, this study statistically analyzed injury death by portable ladder for recent 10 years to investigate the accident characteristics. Next, to monitor wearing of safety helmet in real-time while working on a portable ladder, this study developed an object detection model based on the You Only Look Once(YOLO) architecture, which can accurately detect objects within a reasonable time. The model was trained on 6,023 images with/without ladders and safety helmets. The performance of the proposed detection model was 0.795 for F1 score and 0.843 for mean average precision. In addition, the proposed model processed at least 25 frames per second which make the model suitable for real-time application.

• 한국안전학회지
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• 제35권5호
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• pp.86-94
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• 2020

Portable ladders are normally used both as an access tool for ascending and descending and as a platform for high place work. Though convenient, such usages make the portable ladders vulnerable to fall accidents. For this reason, many safety systems such as regulations and certifications are implemented to prevent fall accidents of portable ladders. However, nevertheless of those safety systems in Korea, annual death tolls of ladder fall accidents has remained high, and which suggests modification and improvement of the portable ladder related safety systems in Korea. The aim of this study is to propose directions for improving safety systems to effectively prevent fall accidents of portable ladders. To this end, comparative analysis on safety systems implemented in Korea and other countries including Japan, USA and UK are conducted to investigate the problems of Korean safety systems. Based on the analysis, limitations of Korean safety systems to prevent ladder fall accidents are discussed and tasks to overcome the limitations are proposed. Once implemented, the proposed tasks would contribute to prevent ladder fall accidents effectively.

• 한국안전학회지
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• 제39권2호
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• pp.44-53
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• 2024

In addition to being used for ascending and descending to work locations, portable ladders are widely used as a substitute for work platforms when working at heights in homes and industrial sites. However, accidents continue to occur in industrial sites owing to structural instabilities of ladders and the negligence of safety measures by users. To prevent accidents involving workers using portable ladders, it is important to encourage workers to use them correctly through laws and regulations; however, establishing effective preventive measures that go beyond regulations can increase acceptance in industrial sites and maximize the effect of reducing industrial accidents. Therefore, this study conducts a fact-finding survey and portable safety ladder product analysis and collects stakeholder opinions to develop a Korean-style safety ladder that can replace step ladders with a high risk of accidents.

• 한국안전학회지
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• 제36권3호
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• pp.50-59
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• 2021

The main purpose of accident analysis is to identify the causal factors and the mechanisms of those factors leading to the accident. However, current accident analysis techniques focus only on finding the factors related to the accident without providing more insightful results, such as structures or mechanisms. For this reason, preventive actions for safety management are concentrated on the elimination of causal factors rather than blocking the connection or chain of accident processes. This greatly reduces the effectiveness of safety management in practice. In the present study, a technique to model the correlational structure of accident risk factors is proposed by using the co-occurrence keyword network analysis technique. To investigate the effectiveness of the proposed technique, a case study involving a portable ladder fall accident is conducted. The results indicate that the proposed technique can construct the correlational structure model of the risk factors of a portable ladder fall accident. This proves the effectiveness of the proposed technique in modeling the correlational structure of accident risk factors.

• 한국안전학회지
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• 제24권6호
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• pp.136-143
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• 2009

The injuries as a result of fall accidents is the one of the most common kind of injuries in Korea, especially fall from height is the top most common kind for fatal injuries. Futhermore, the number of fall injuries in manufacturing industry has been steadily increasing from 2000 to 2007. In 2007 the number of fall fatal injuries increased 10.6 % in comparison with the number in 2006. These numbers are 6~17 times higher than those for foreign countries such as the U.K and the USA. So, it is needed to make a study to reduce these numbers for manufacturing industry. To get the goals, we did research as followings. First, this study analyzed statistics by industry, by fall height, by common agent and so on to gain an insight into real aspect of fall injuries. It showed that ladder is the commonly cited agent for manufacturing industry, and 3 risky activities ; the ladder work, the load/unload work, and the maintenance work. Secondly, this study made a survey of manufacturing workers for their understandings of the most 3 risky activities. It showed that 'tendency to work easily' and 'difficulty of applying measures due to inherent working conditions' are main reasons for workers not to implement the preventive measures against the fall accidents. Thirdly, this study tested the slip characteristics of ladder base and lungs. The tests were done based on ANSI standard and KS. In addition to the standard condition, this study performed slip tests in wet and sandy conditions and compared the results with the those of standard condition. It showed that friction coefficient is standard condition > wet condition > sandy condition, and the friction coefficient of ladder for sandy condition is measured to be reduced by 63.9% compared with that for standard condition. Finally, this study developed safety work models for using of portable ladders in consideration of the safety standards of foreign countries such as the U.K, the USA, and the Australia.

• 한국조경학회지
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• 제51권5호
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• pp.1-12
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• 2023

본 연구는 조경시공 및 관리분야에서 수목관리, 전지 등과 같은 고소부위 작업을 위해 주로 사용하는 삼각지지형 이동식 사다리의 전도 안정성을 평가한 것이다. 산업현장에서 사용 빈도가 높은 이동식 사다리에 포함되는 삼각지지형 이동식 사다리는 작업 특성에 따라 바닥지지 형태가 일반적인 A형의 사면지지가 아닌 삼각지지 방식이고, 작업 높이도 이동식 사다리와 비교하여 2배 이상 높기 때문에 떨어짐과 함께 작업자의 안전을 위협하는 전도 발생 가능성이 매우 높다고 할 수 있다. 따라서, 국내에서 사용되고 있는 삼각지지형 이동식 사다리를 대상으로 관련 기준인 ANSI-ASC A14.7과 EN 131-Part 7에서 규정하고 있는 전도 안정성 평가를 기반으로 하여 작업 높이에 따른 전도모멘트와 저항모멘트를 계산할 수 있는 수식을 각각 유도하여 계산한 후, 이 값을 상호 비교하여 전도에 대한 안전율 및 전도 방향에 따른 안정성을 평가하였다. 각 기준에 따른 전도 안정성 평가 결과, EN 131-Part 7의 규정을 적용하면 후면방향 8단과 측면방향으로 6단 이상의 삼각지지형 이동식 사다리는 전도에 대해서 불안정한 것으로 평가되었으나, ANSI-ASC A14.7의 규정에 의하면 방향에 상관없이 모든 단수에서 전도에 대한 안정성을 확보하고 있는 것으로 평가되었다.

• Journal of Electrical Engineering and Technology
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• 제8권4호
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• pp.872-878
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• 2013

In industrial control systems, flow measurement is a very important issue. It is frequently needed to calculate how much total fluid or gas flows through a cross-section. Flow volume measurement tools use simple sampling or rectangle methods. Actually, flow volume measurement process is an integration process. For this reason, measurement systems using instantaneous sampling technique cause considerably high errors. In order to make more accurate flow measurement, numerical integration methods should be used. Literally, for numerical integration method, Rectangular, Trapezoidal, Simpson, Romberg and Gaussian Quadrature methods are suggested. Among these methods, trapezoidal rule method is quite easy to calculate and is notably more accurate and contains no restrictive conditions. Therefore, it is especially convenient for the portable flow volume measurement systems. In this study, the volume measurement of air which is flowing through a cross-section is achieved by using PLC ladder diagram. The measurements are done using two different approaches. Trapezoidal rule method is proposed to measure the flow sensor signal to minimize measurement errors due to the classical sampling method as a different approach. It is concluded that the trapezoidal rule method is more effective than the classical sampling.