• Journal of the Korean Solar Energy Society
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• v.36 no.3
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• pp.25-31
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• 2016

Gaskets are usually used for the sealing of flange joints. The joint is usually composed of two flanges, a ring gasket and clamping bolts. The metal ring gasket is suitable for pipe flanges, pumps and valve joints in high temperature and high pressure environments. A very high surface stress is developed between a ring type joint gasket and the flange groove when the ring type joint is bolted up in a flange. The dimensions of flanges and ring joint gaskets for the pipe sizes that are in common use are specified in the ANSI codes. However, sometimes it is necessary to make a new design for the flange joint which is not specified in the codes, as the equipment is getting larger and larger in size. This paper presents the contact behavior of Class 600 ring joint gaskets with oval and octagonal cross sections. Five different sizes of gaskets are employed in the analysis, and one of them is newly designed on the basis of analysis results obtained from existing models. Three load steps are used to find the stress, stain and contact pressure etc., and to compare the contact characteristics among the models due to the bolt clamping force and the working surface pressure. ANSYS Workbench version15 is used to conduct the finite element analysis.

• Tribology and Lubricants
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• v.15 no.4
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• pp.297-303
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• 1999

O-rings in automotive engines are important components such as a coolant pipe, engine oil circulating lines and fuel injector for sealing that makes efficient performance of the engine. Life cycle of O-rings is effected in environments of the O-ring seal, like that applied pressure, working temperature, precompressed ratio and materials. It is related in extrusion, expansion and fatigue failure of O-rings. In this paper, an pressurized, compressed elastomeric O-ring inserted into a rectangular groove is analysed numerically using the nonlinear finite element method. The calculated FEM results showed that extrusion ratio and contact stress are strongly related to the gap clearance and edge radius of the groove.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.1
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• pp.34-41
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• 2018

A flange joint is a pipe connection used to prevent the leakage of high-pressure fluids by inserting a gasket and tightening the bolts. Among several kinds of gaskets available, metal ring type joint gaskets are most widely used in conditions that require high-temperature and high-pressure fluid flow, such as oil pipelines, gas pipes, pumps, valve joints, etc. The purpose of this study is to investigate the contact pressure and stress characteristics closely related to the sealing performance of Class 900 flange joints used in high temperature and high pressure environments. The dimensions of flange joints with five different nominal pipe sizes were determined with reference to those specified in ASME 16.5. The metal ring gaskets inserted in the joints were octagonal and oval gaskets. The bolt tensile forces calculated from the tightening torques were input as the bolt pretension loads in order to determine the contact pressure and stress levels after fastening. Loading was composed of three steps, including the fastening step, and different amounts of applied pressures were used in each analysis to investigate the effect of fluid pressure on the contact force of the joints. A general-purpose software, ANSYS 17.2, was used for the analysis.

• 한국가스학회:학술대회논문집
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• 2007.04a
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• pp.85-91
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• 2007

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.10
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• pp.182-188
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• 2016

A decoy is a weapon system that can protect vessels from an enemy's torpedo. Thus, the decoy should be able to operate in the field without any failure. Because the decoy can be inoperable once its sealing is broken and water permeates inside the system, the hermetic sealing capability considering the operational environment is mandatory. To be hermetically sealed, a rubber-type O-ring is generally used in a decoy system. The sealed performance of rubber-type products, however, tends to age and deteriorate with time. Therefore, the O-ring needs to be maintained or changed periodically. This paper proposes a method to estimate the proper maintenance period using the hardness and elongation percentage, which represents the performance of the O-ring product and test data from Accelerated Life Test (ALT) of the product. The O-ring used in this paper is a NBR type, and the temperature was chosen to be the main accelerating factor as referenced in many studies. The criteria for the failure of the O-ring was set for the product to be 50% degraded compared to the initial performance. In addition, the Korean standard KS M 6518 was adopted and referenced for the preparation of test samples and the calculation of estimates. The O-ring's predicted life was simulated by analyzing the test results from a computer program, and the optimized maintenance period for the product was determined.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.12 no.1
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• pp.49-55
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• 2016

This paper analyzed a root cause of abnormality in the temperature and vibration at generator-side bearing of motor generator set (MG Set), which is a power supply system to control element drive mechanism (CEDM) of nuclear power plants (NPPs), and modified the design of roller-type and sealing method to improve the abnormalities. From the inspection of MG Set and analysis of temperature variation during service, it was found that the abnormal temperature transition was basically associated with original design of generator-side bearing, whose roller was axially restrained by inner race, and that the abnormal vibration level was caused by inserting small chips of cage and V-ring, which were generated due to the abnormal temperature transition at roller bearing. Type of bearing and sealing method were modified based on these analyses. The temperature and vibration level measured at roller bearing showed that the modifications clearly improved the operational stability of MG Set.

• Tribology and Lubricants
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• v.24 no.6
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• pp.285-290
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• 2008

The purpose of this paper is to present the case study of tribological failure analysis on the gear damages, oil leakage, and sealant sealing in a manual transmission of front engine and front wheel drive vehicle. The manual transmission is to change the speed range and direction of the engines depending on the driving conditions by friction driving forces with input and output gear system. The material property and surface roughness of the gears are strongly related to the gear noise and micro-vibration, oil leakage and wear, which may decrease the real contact area of the gear and the strength of the oil film thickness between the driving gear and driven one. The O-ring damage of speedometer driven gear and bad sealant sealing of oil pan may produce oil leakage through the contact surfaces, which cause the oil shortage and seizure on the sliding surfaces of the transaxle gears. In the failure case study, the proper repair working and good lubrication are very important for the long life of the transaxle without any tribological failures and oil leakage.

• Tribology and Lubricants
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• v.27 no.5
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• pp.240-248
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• 2011

Mechanical face seal installed in primary heat transport pump used for heavy water reactor prevents leakage of working fluid using thin working fluid film between primary seal ring and mating ring. If the leakage of working fluid exceeds the allowable volume, serious accident can be happened by the trouble of primary heat transport pump. The thinner fluid film exists between primary seal ring and mating ring, the less working fluid leaks out. On the other hand, if the thickness of fluid film is not enough, the life of mechanical face seal will be reduced by friction and wear. Therefore appropriate design is necessary to maximize the performance and life of mechanical face seal. In this study, numerical analysis using finite volume method was conducted to investigate the performance of mechanical face seals which have same deep straight groove and 11 different net coning values. As results, equilibrium clearance between primary seal ring and mating ring, leakage volume of working fluid, friction torque on sealing surface and stiffness of working fluid film were obtained. With increasing net coning value, equilibrium clearance and leakage volume increase, and friction torque and stiffness of fluid film decrease.

• Journal of the Korean Institute of Gas
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• v.11 no.1 s.34
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• pp.23-28
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• 2007

This paper presents an experimental investigation on the sealing defects and cracks of O-rings and a valve packing of a gas valve for a LPG cylinder. O-ring in which stops a gas leakage of a liquefied petroleum gas is very important for a LPG valve safety. Valve packing is to open and close a gas flow port for supplying and charging a LPG fuel. The sealing performance of two sealing units ism related to the leak safety and long lift of a gas valve. The investigated results show that most of O-rings was failed due to a circumferential crack in which is caused by partial press bonding failure near the partition zone and an excess compression rate. Some of the O-ring failure was originated by an extrusion of an excessive leak pressure of a LP gas. Thus, this paper strongly recommends a tight quality control and a safety guarantee system of O-rings and valve packing to guarantee a leak safety and to extend a service lift of a gas valve. At the end, a warranty policy of the sealing units should be adopted for increasing a product quality and safety of a gas valve.

• Elastomers and Composites
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• v.53 no.1
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• pp.13-18
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• 2018

A face seal comprising a metal ring and acrylonitrile butadiene rubber (NBR) was installed in the driving part and suspension unit. The seal serves as a bearing and simultaneously prevents entry of foreign matter from external environment as well as internal oil leakage. Subsequently, the rubber-rod ring generates axial pressure owing to rubber elasticity (hardness), performs static sealing function between housing details and outer diameter of seal, and transmits rotational torque to the rotating support ring. In order to improve the durability of NBR, which performs the above tasks, and to effectively use it in tracked-vehicle applications at extreme temperatures, this study reports a mixing design approach to enhance cold and oil resistances of NBR.