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

• Journal of the Microelectronics and Packaging Society
• /
• v.8 no.4
• /
• pp.11-15
• /
• 2001

In this paper, hermetic sealing technology was studied for wafer level packaging of the RF-MEMS devices. With the flip-chip bonding method. this non-conductive B-stage epoxy sealing will be profit to the MEMS device sealing. It will be particularly profit to the RF-MEMS device sealing. B-stage epoxy can be cured by 2-step and hermetic sealing can be obtained. After defining 500 $\mu\textrm{m}$-width seal-lines on the glass cap substrate by screen printing, it was pre-baked at $90^{\circ}C$ for about 30 minutes. It was, then, aligned and bonded with device substrate followed by post-baked at $175^{\circ}C$ for about 30 minutes. By using this 2-step baking characteristic, the width and the height of the seal-line could be maintained during the sealing process. The height of the seal-line was controlled within $\pm$0.6 $\mu\textrm{m}$ in the 4 inches wafer and the bonding strength was measured to about 20MPa by pull test. The leak rate, that is sealing characteristic of the B-stage epoxy, was about $10^{-7}$ cc/sec from the leak test.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.10 no.2
• /
• pp.46-51
• /
• 2011

This study result is obtained by flow analysis according to opening and shutting angle of ball valve. As opening and shutting angle becomes larger, vortex flow becomes smaller and flow rate becomes increased. And the pressure drop is shown to be smaller at the inlet and outlet of ball. As this angle becomes larger, mass flow rate becomes increased. Its rate becomes increased abruptly in case of opening and shutting angle at more than $60^{\circ}$.This analysis result can be applied usefully with no leak at pipe system field by the optimum control of mass flow rate according to opening and shutting of ball valve.

• Journal of Chest Surgery
• /
• v.24 no.2
• /
• pp.161-170
• /
• 1991

Clinical results with the Mechanical cardiac valves were reviewed for 261 patients who underwent cardiac valve replacement from September, 1985 to July, 1990. of the Mechanical valves used, 156 were Carbomedics, 109 Duromedics, 52 St. Jude and 11 Bjork-Shiley. Overall hospital mortality was 14 out of 261[5,36%]: 9 out of 159[5.66%] for MVR, 1 out of 35[2.86%] for AVR and 4 out of 67[5.96%] for DVR[AVR+MVR]. Two hundred and forty seven operative survivors were followed up for a total 466.8 patient-years, ranged from 1 month to 4.9 years [a mean 1.8 years] and the follow up was 96.0%. There were 12 valve-related complications: three from thromboembolism, three from valve thrombosis, three from prosthetic valve endocarditis, two from paravalvular leak and the other one from hemorrhage. Actuarial rate free from all valve-related complication at 4.9 years was 96$\pm$1.3%. There were 11 late deaths: two from thromboembolism, one from valve thrombosis, one from prosthetic valve endocarditis, one from hemorrhage and the others 6 from non-valve-related complications. Actuarial survival rate at 4.9 years was 94$\pm$2.0%. 96$\pm$3.0% for MVR, 94$\pm$4.2% for AVR and 91$\pm$3.7% for DVR[AVR+MVR]. And there are 7 reoperations: three from paraprosthetic leak, two from prosthetic valve endocarditis and two from valve thrombosis. Actuarial rate free from reoperation at 9 years was 96$\pm$2.9%. On the basis of this 4.9 years of experience, the pyrolytic carbon mechanical valves appears to be an excellent mechanical prosthesis for cardiac valve replacement, in terms of hemodynamic performance, low mortality and low thrombogenecity.

• Journal of Chest Surgery
• /
• v.29 no.9
• /
• pp.964-970
• /
• 1996

One hundred eight patients (Feb.'86, through Jan.'96) underwent 53 mitral(MVR), 20 aortic(AVR), )5 double(DVR) valve replacement with SJM prosthesis. There were 55 males and 53 females whose mean age was 36.3 $\pm$ 10.4 years. We used 143 valves in mitral(88), aortic(54), and tricuspid(1) sites. The size and number of valves were 31 mm(32). 33inm(23), 29mm(20), 27mm(10), 25mm(2), and 35mm(1) in mitral site; 2)mm(21), 21mm(1 S), 19mm(7), 25mm(5), 27mm(2), and 33mm(1) in aortic site; and Blmm(1) in tricuspid site. Preoperative NYHA functional classes were II(14), III(73) and IV(21), and which were improved into I(89) and II(16) postoperatively. Early postoperative complications occurred in 15 cases(13.9%) in which LOS was the most common one(5 cases; 4.6%). fatly hospital death occurred in 3 cases(2.8%) due to LOS(1) and sudden cardiac arrest(2) he cummulative total follow-up period was 437.6 pl-yr with a mean of 4.1$\pm$2.9 years. There were 5 events of valve related'complications (2 TE, 1 paravalvular leak, 1 TE+paravalvular leak, 1 PVE) with the occurrence rate as 1.14%/pt-yr. Reoperation was performed in 2 cases and there were 2 cases of valve related death due to one PVE and one paravalvlllar leak. The complication free rate was 91.4$\pm$ ).4% at 10 years. Actuarial survival rate was 93.6 $\pm$ 3.1 % at 10 years.

• Journal of Chest Surgery
• /
• v.25 no.3
• /
• pp.296-306
• /
• 1992

A 6 year experience with the bileaflet St. Jude Medical valve is reported. Between Feb. 1986 and Dec. 1992, 68 patients received 87 such valves[36 mitral, 13 aortic, and 19 double mitral-aortic valve replacements]. The results are summarized as follows 1. There were 35 male and 33 female patients ranging in age from 17 to 55 years the mean age of 35.3 $\pm$ 9.7 years. 2. The mean aortic clamp time[ACT] of the MVR, AVR and DVR groups were 91.5$\pm$16.4, 117.2$\pm$28.7 and 165.5$\pm$24.1 minutes. The mean total bypass time [TBT] of the MVR, AVR and DVR groups were 112.8$\pm$19.5, 134.7$\pm$31.4 and 192.2$\pm$28.5 minutes. 3. Eighty seven valves were used [55 mitral site, 32 aortic site]. 31mm[20], 33mm[15], 29mm[15], 27mm[2], 25mm[2] and 35mm[1] were used in mitral site and 23mm[13], 21mm[8], 19mm[7] and 25mm[4] were used in the aortic site. In the DVR, there were valve combinations such as 4 cases of M[29mm]-A[19mm], 4 of M[31mm]-A[23mm], 3 of M[33mm]-A[23mm] and others. 4. Preoperative NYHA functional classes were II [3 cases], III [46 cases], IV[19 cases] and improved to I [52 cases] and Il [13 cases] postoperatively. 5 Early postoperative complications were occurred in 15 cases[2Z.l%] and there were LOS in 5 cases[7.4%], arrythmia [3 cases], wound infection [2 cases], hepatitis [2 cases], sudden cardiac arrest [2 cases] and postoperative bleeding [1 case]. The early hospital death was occurred in 3 cases[4.4%] with LOS [1 case] and sudden cardiac arrest [2 cases]. 6. Mean follow-up time of survival cases[65 cases] was 31.3$\pm$21.9 months and the total follow-up time was 169.8 patient-years. Late postoperative complications were occurred in 4 cases[2 thromboembolism, 1 paravalvular leak, 1 thromboembolism br paravalvular leak, 1 valve endocarditis] with the occurrence rate as 2.35% per patient-years. Reoperation was performed in 2 cases [1 paravalvular leak, 1 left atrial thrombus] and there was one [1.5%] late valve related death. Therefore the 6 year complication free rate was 90.6% and 6 year actuarial survival rate was 98.3$\pm$1.7%. On the basis of this experience and the results, SJMvalve appears to be one of the best performing mechanical prosthesis currently available, in terms of both hemodynamics and lower complications with warfarin antioagulation.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.24 no.5
• /
• pp.553-560
• /
• 2015

Fracture mechanics analysis for cracked pipes is essential for applying the leak-before-break (LBB) concept to nuclear piping design. For LBB assessment, crack instability and leak rate should be predicted accurately for through-wall cracked pipes. In a nuclear piping system, elbows are connected with straight pipes by circumferential welding; this weld region is often considered a critical location. Hence, accurate crack assessment is necessary for cracks in the interface between elbows and straight pipes. In this study, the stress intensity factor (SIF) and elastic crack opening displacement (COD) were estimated through detailed 3D elastic finite element (FE) analyses. Based on the results, closed-form solutions of shape factors for calculating the SIFs and elastic CODs were proposed for circumferential through-wall cracks in the abovementioned interfaces under internal pressure. In addition, the effect of the elbow on shape factors was investigated by comparing the results with the existing solutions for a straight pipe.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.30 no.2
• /
• pp.110-115
• /
• 2010

This study was conducted to estimate the feasibility using thermal image measurement that is applicable to internal leak diagnosis for the power plant valve. Abnormal heating of valve surface associated with high temperature steam f10w toward valve outlet side in the condition of low temperature is a primary indicator of leakage problems in high temperature and pressure valves. Thermal imaging enables to see the invisible thermal radiation that may portend impending damage before their condition becomes critical. When steam flow in valve outlet side in the condition of low temperature is converted into heat transmitted through the valve body due to the internal leakage in valve. The existence of abnormally increasable leakage rate in the valve will result in abnormally high levels of heat to be generated that can be quickly identified with a thermal image avoiding energy loss or damage of valve component. From the experimental results, it was suggested that the thermal image measurement could be an effective way to precisely diagnose and evaluate internal leak situation of valve.

• Journal of Chest Surgery
• /
• v.56 no.3
• /
• pp.179-185
• /
• 2023

Background: Assessments of air leaks are usually performed subjectively, precluding the use of air leaks as an evaluation factor. We aimed to identify objective parameters as predictive factors for prolonged air leak (PAL) and air leak cessation (ALC) from air flow data produced by a digital drainage system. Methods: Flow data records of 352 patients who underwent lung lobectomy were reviewed, and flow data at designated intervals (1, 2, and 3 hours postoperatively [POH] and 3 times a day thereafter [06:00, 13:00, 19:00]) were extracted. ALC was defined by flow less than 20 mL/min over 12 hours, and PAL was defined as ALC after 5 days. Cumulative incidence curves were obtained using Kaplan-Meier estimates of time to ALC. Cox regression analysis was performed to determine the effects of variables on the rate of ALC. Results: The incidence of PAL was 18.2% (64/352). Receiver operating characteristic curve analysis showed cut-off values of 180 mL/min for the flow at 3 POH and 73.3 mL/min for the flow on postoperative day 1; the sensitivity and specificity of these values were 88.9% and 82.5%, respectively. The rates of ALC by Kaplan-Meier analysis were 56.8% at 48 POH and 65.6% at 72 POH. Multivariate Cox regression analysis revealed that the flow at 3 POH (≤80 mL/min), operation time (≤220 minutes), and right middle lobectomy independently predicted ALC. Conclusion: Air flow measured by a digital drainage system is a useful predictor of PAL and ALC and may help optimize the hospital course.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
• /
• 2003.10a
• /
• pp.328-331
• /
• 2003

In this study, the experimental study based on calorimetry for terminal cryostat has been performed and evaluated. The experiments performed here were divided into two types, those are test without and with current lead. The former is intended for the evaluation of feasibility and precision of our calorimetry, the later for the application to terminal cryostat of our study. As a result, it was found that the calorimetry performed in this study could predict well the heat transfer rate into the terminal cryostat.