• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.20 no.5
• /
• pp.564-569
• /
• 2011

The current establishment of city gas piping polyethylene (PE) tube used as bonding state or part of the health or safety of fusion is very important. A part of these fusion methods to determine the soundness of the short-term trials and long-term tests can be largely classified. Typical tests include short-term strength, tensile strength, impact strength, compressive strength, resiliency and compression. Polyethylene (PE) pipes installed in the domestic terms of overall penetration rate of 45% has been used. However, polyethylene (PE) pipes have reliability problems, and these occurs mostly in part by defective welding. Therefore, the test is necessary for safety. Non-destructive methods (ultrasonic testing) are difficult to be used. Therefore, Polypropylene copolymer (PP-C), polypropylene homopolymer (PP-H), and polyethylene (PE) pipe are used. Fusion of these materials is necessary in these field however, its technical, and basic research has not been studied well. In this research, short-term strength of welding parts, its tensile strength, hardness, fatigue, and microstructure have been analyzed to find the optimum process conditions to improve mechanical properties.

• Journal of Power System Engineering
• /
• v.7 no.1
• /
• pp.82-85
• /
• 2003

This study is to look at the effect for deformation of Polyethylene, on the wave forms produced by tensile test. Signals collected were then classified visually into three types according to their shapes in the time and frequency domain. Each type should contain signals which could be correlated to a certain micro failure mechanism that occurs during the tensile process. The result showed that the acoustic emission method could be effectively used for analysis of fracture mechanism in Polyethylene structures.

• Journal of Korean Society of Water and Wastewater
• /
• v.32 no.5
• /
• pp.435-443
• /
• 2018

Most of aged water supply pipes have been replaced by the open cut method. However, this method has some limitations because water pipes, in many cases, are buried together with other underground facilities or are buried in the middle of high-traffic roads or in narrow alleyways where boring machines cannot be used. This research developed a pipe bursting device for small diameter pipes that enables pipe replacement without excavating the ground, by the busting of existing buried pipes followed by the traction and insertion of new pipes. As a results of examining the field applicability of the developed device, PE pipes and PVC pipes required the tractive force of 413.65~665.69 kgf and 457.43~791.35 kgf respectively, plus an additional 30 % tractive force per elbow. The proper number of bursting head was demonstrated that the connection of more than 2 heads could secure a stable bending radius of 15D. The developed device can be improved through field experiments involving various pipe types and pipe diameters, as well as presence/absence of elbow, so as to be utilized regardless of diverse variables according to the conditions of the soils surrounding existing pipes.

• Fire Science and Engineering
• /
• v.27 no.6
• /
• pp.44-49
• /
• 2013

As the polyethylene of high strength and ductility stabilized chemically has been mass-produced, it is spreading widely as material of industrial piping and water service piping. Recently, High density polyethylene (HDPE) pipe has been used even in water supply system of plant as buried pipe instead of cast iron pipe in domestic, but HDPE pipe has a probability of occurrence of damage if plant design and operating conditions are not considered. As a result of reviewing with respect of system design engineering based on operating conditions and verification test results, the specific design criteria for the use of HDPE piping in fire water supply system need to be established because of the possibility of crack damage due to water hammer.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2023.05a
• /
• pp.288-288
• /
• 2023

도로, 철도 등의 횡단통로, 오폐수관로, 지하배수관 등 연약지반에서 상재하중과 부등침하에 의한 파괴 위험을 줄이기 위해 구조적인 안전성과 내구성이 개선된 다양한 관로들이 활용되고 있다. 관은 매설특성에 따라 콘크리트관, 도관, 합성수지관, 덕타일 주철관, 파형강관, 유리섬유 강화 플라스틱과 폴리에스테르수지 콘크리트관 등의 종류로 구분된다(환경부, 2017). 수리설계 시 이러한 관의 단면 규모 결정 및 흐름 특성을 파악하기 위해 관수로 유량측정에 이용되는 Manning의 경험식을 이용하고 있으며, 관로의 주요 재질에 따른 다양한 조도계수가 제시되어 있다. 새로운 재질을 이용하여 제작된 관은 수리실험을 통해 조도계수를 결정하는 것이 바람직하지만, 조도계수 실험은 대규모의 실험시설과 유량공급이 요구되기 때문에 여러 한계가 있다. PE관의 경우, 미국의 ASTM 표준에 의해 저밀도 폴리에틸렌(LDPE), 선형 저밀도 폴리에틸렌(LLDPE), 고밀도 폴리에틸렌(HDPE) 등으로 분류되는데 본 연구에서는 HDPE 재질의 서로 직경이 다른 다중벽관 PE관을 대상으로 조도계수를 결정하기 위한 현장 실규모 수리실험을 수행하였다. 본 실험에서는 식생, 수로의 불규칙성, 수로노선, 침전과 세굴, 장애물, 계절적 변화, 부유물질과 소류사는 무시되며 표면조도, 관의 크기와 형상, 수위와 유량이 조도계수에 영향을 미치는 주요 인자라고 할 수 있다. 수리실험은 실물모형(Prototype)으로 한국농어촌공사 농어촌연구원의 대형수리모형실험장에서 수행되었으며. 길이 24 m, 직경 150 mm의 PE 관은 고정식 개수로, 직경 800 mm의 관은 대형유사순환수로에 각각 설치되었다. 관로의 전면에 차폐막을 설치하여 상류부 수위를 안정시킨 상태에서 실험을 수행하였고, 차폐막으로부터 하류방향으로 약 7 m(측정기준지점), 11 m, 13 m, 15 m, 17 m 떨어진 곳에서 각각 수위와 유속을 측정하였다. 실험 결과, φ150관은 직경대비 수심이 클수록 조도계수가 감소하는 경향이 나타났고, φ800관은 직경대비 수심의 변화에 따른 조도계수의 경향이 크게 드러나지 않았다. 결론적으로 PE관의 조도계수는 수심별로 변화하는 것으로 나타났으며, 특정 수심을 지나면 조도계수가 다시 감소할 것으로 판단된다.

• Elastomers and Composites
• /
• v.46 no.4
• /
• pp.335-342
• /
• 2011

The virgin and recycled polyethylene composites with various ratio of fly ash were manufactured by using a fully intermeshing co-rotating twin screw extruder for the reuse of fly ash from power plant and post-consumed polyethylene. Fly ash were blended with virgin HDPE and recycled polyethylene at the weight fraction of 0 to 40 wt.%. Mechanical properties such as yield strength, abrasion resistance, and slow crack resistance were measured with ISO and ASTM standards. The experimental results for the various composites showed that the elongation at break and the yield stress of the composites decreased with increasing fly ash contents. Generally, the abrasion resistance of PEs decreased with increasing sandpaper grits but the abrasion resistance of the composites increased with fly ash content at finer abrasive surface. The slow crack growth resistance of virgin HDPE, recycled JRPE and the JRPE composite showed higher slow crack growth resistance up to 50% of load at notch depth of 20% and 30%, but KRPE and the KRPE composite showed much lower resistance than virgin HDPE, JRPE and the JRPE composite. Time to break, measured with NCLS test method, of all PEs and the composites satisfies the regulation of Korean Industrial Specification for sewer pipe and support application.

• Corrosion Science and Technology
• /
• v.3 no.1
• /
• pp.20-25
• /
• 2004

In order to clarify the durability of protective coatings for maritime steel structures, various anti-corrosive organic coated steel samples were exposed for twelve years in semitropical marine environment at Miyakojima Island, Okinawa, JAPAN. Samples were various organic coated steel pipes, 4.0 m in length and 150 mm in diameter. While the bare steel pipe entirely corroded in 4.5 mm thickness in four and half years, these organic coated steel pipes exhibited protective appearances after twelve-year-exposure except for the defect in the coatings. Polyethylene (PE) lining pipe exhibited a good protective performance. Urethane painted pipe was also good but some barnacles stuck to its surface. A combination of petrolatum tape and FRP cover showed sufficient corrosion resistance for steel surface. The correlation in results between exposure and laboratory acceleration test was examined. It was found that salt spray test (SST) results corresponded to rusted area of scratched portion and that adhesion change of coating layer corresponded to the rotating immersion test result. Among the on-site measured data, volume resistivity is utilized for the index of corrosion protection performance of organic coating.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.25 no.2
• /
• pp.237-243
• /
• 2019

Floating platforms made of PE (PolyEthylene) are often located in shallows of seas, rivers or lakes. They are widely used for marine pensions, marine pontoons, marine bridges, etc. These products are characterized by good flexibility, recyclability, chemical resistance and weatherability with corrosion resistance. Existing PE floating platforms have a simple structure in which one pipe is fastened to one bracket, but this has limited application, even if a user modifies the arrangement. Therefore, we developed a structure that allows buoyancy pipes of various sizes to be fastened to one bracket and verified the structural safety of the product using the finite element method. From the results of structural analysis for buoyancy pipes of different diameters, the maximum stress ratio was 0.78 compared with allowable criteria of 1.0, which represented sufficient safety for a model with 500 mm diameter pipes. Based on the results of this study, further research to evaluate the structural safety of various floating platforms can be carried out in the further; it will also be necessary to establish related evaluation criteria.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.56 no.6
• /
• pp.149-158
• /
• 2014

The effects of spot cooling on growing ever-bearing strawberry in hydroponic cultivation during summer by spot cooling system was estimated in plastic greenhouse located in Pyeongchang. The temperature of cooling water was controlled by heat pump and maintained at the range of $15{\sim}20^{\circ}C$. Cooling pipes were installed in root zone and very close to crown. Spot cooling effect was estimated by applying system in three cases which were cooling root zone, crown plus root zone, and crown only. White low density polyethylene pipe in nominal diameter of 16 mm was installed on crown spot, and Stainless steel flexible pipe in nominal diameter of 15A was installed in root zone. Crown and root zone cooling water circulation was continuously performed at flowrates of 300 ~ 600 L/hr all day long. Strawberry yields by test beds were surveyed from Aug. 1 to Sep. 30. The accumulated yield growth rate compared with a control bed of crown cooling bed was 25 % and that of crown plus root zone cooling bed was 25 % and that of root zone cooling bed was 20 %. The temperatures of root spot in root zone cooling was maintained at $18{\sim}23.0^{\circ}C$ and that of crown spot in crown cooling was maintained at $19{\sim}24^{\circ}C$. Also, the temperatures of root spot in crown plus root zone cooling bed was maintained at $17.0{\sim}22.0^{\circ}C$ and that of crown spot was maintained at $19{\sim}25^{\circ}C$.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.15 no.1
• /
• pp.55-62
• /
• 2011

In this study, we tried to improve the thrust control performance through the thrust control combustion experiment of the hybrid rocket. We constructed the system which controls the oxidizer flow by combining a needle valve with a stepping motor and controlling the stepping motor drive according to the thrust control command order. Gas oxygen was used as the oxidizer for two different propellants, PE(Polyethylene), PC(Polycarbonate), respectively. To improve the slow response time and the oscillation phenomenon in the beginning stage of the thrust control combustion experiment, we measured and analyzed the change of the flow speed of the propellant pipe. The revised thrust control combustion experiment showed that the thrust was stably controlled with the margin or error from the thrust command within ${\pm}1$ N.