Bypass Pipe Research Articles

Combining self-lift and gas-lift: A new approach to slug mitigation in deepwater pipeline-riser systems

Recent slugging studies have identified the need to develop new and optimal slug mitigation strategies as the key gap in slugging studies. This paper focused on combining the self-lift and gas-lift slug mitigation strategies for slugging mitigation in deepwater scenarios.The Self-Lift Slug mitigation Strategy is a novel approach that involves tapping off gas via a by-pass pipe along the pipeline upstream of the riser. The gas is then re-introduced into the riser column via an injection point on the riser, to break the liquid slugs within the riser and mitigate severe slugging.This research investigated the performance of the Self-Lift Strategy when adapted to a deepwater oil field case scenario via OLGA simulation. An alternative scenario of combining self-lift and gas lift was also investigated.The approach for this study involved a robust methodology of firstly validating the field data by comparing pressure field data with OLGA simulation of the input data from the field. The field case consists of a 2712 m pipeline section and a 1513 m riser section. In this study, the severe slugging scenario was first run at the following flow conditions: well X1 was set up at 72.2 °C temperature and mass flow of 3.25 kg/s, well X2 was set up at 70.5 °C and 12.13 kg/s mass flow rate and the outlet section set up at 65.5 °C and pressure 20 bara.Self-lift was able to reduce holdup within the riser column, however pressure behaviour at the riser column was observed to be over 20 bara which is the design pressure for the inlets of the separator. Further studies involving a combination of Self-lift and gas lift at 8 kg/s and 2 inches by-pass internal diameter, indicated that the pressure at the riser column was reduced to 20 bara, allowing for stable flow into the separator.

Optimal Design of Bypass Line for an Industrial-Scale 8-Leg Polyolefin Loop Reactor to Manage Slurry Dispersion Using Hydraulic and CFD Simulations

The pump power oscillation caused by slugs in slurry phase polymerization reactors limits production capacity. A bypass line connecting two locations of a loop reactor is suggested in patent literature to dissipate slugs. The optimal design of such bypass lines is studied through a hierarchy of modeling approaches applied to an industrial-scale reactor. In the design process, 1D hydraulic calculations guide the selection of optimal bypass pipe sizes to maximize slurry velocity. 2D CFD simulations provide data on slug dissipation processes. 3D simulations guide selection of optimal installation angle to maximize solid intake into the bypass line. By combining these approaches, a bypass line connecting the second and sixth legs by 6 in. pipes at a 45° angle is found to be optimal for reactor considered here. Such designs achieves high slurry velocity in the bypass line while maximizing slug dissipation, and the approach is applicable for other loop reactor configurations.

Numerical investigation of a looped-tube traveling-wave thermoacoustic generator with a bypass pipe

In this paper, based on the recent development of looped-tube thermoacoustic engine with a bypass pipe, we propose and numerically demonstrate a travelling wave thermoacoustic electric generator using this configuration. It essentially employs a one wave-length travelling-wave acoustic resonator which has low acoustic losses. The engine branch consists of a compliance, a inertance tube, an engine core, and an alternator. An ultra-compliant alternator (i.e., a sub-woofer) is installed in the acoustic compliance section where the local acoustic impedance is relatively low but the cross sectional area is big. The numerical simulations demonstrate its working principle, and show that it can potentially achieve comparable performance as other types of travelling wave thermoacoustic electric generators.

저층수 배사관 내 유입된 사석 배출능력에 대한 연구

국내 중소하천의 횡단구조물인 보 또는 낙차공은 대부분 고정식 콘크리트 구조물이며, 저층수의 배제가 쉽지 않다. 횡단구조물로 인해 유사가 퇴적되며, 유사에 흡착한 오염물들이 그대로 하천의 바닥을 오염시키고 있다. 이에 저층수 및 퇴적유사에 대한 관심이 증가하고 있는 실정이며, 이러한 대안의 하나로 횡단구조물 상류와 하류를 하상 아래로 연결시키는 구조물로써, 보 상류 저층의 물 및 유사 배제를 목적으로 저층수배출관을 설치하는 방안이 있다. 그러나 사석이 유입되고, 배제 되지 않을 경우 효율성이 크게 저하될 가능성이 있다. 이에 본 연구에서는 저층수 배출관 내 사석을 배제할 수 있는 능력에 대한 연구를 수행하였다. 사석과 거동이 유사한 유사(sediment)의 한계조건(critical condition) 중 한계전단력(critical shear stress) 유도과정과 달랑베르의 원리(d'Alembert principle)를 응용하여 이동 중인 사석이 배제될 수 있는 조건(<TEX>${\tau}_c{^*}$</TEX>)을 유도하였다. 그러나 저층수 배출관 내 유입된 사석은 정지상태가 아닌 이동 중이므로, Lagrangian 기법을 활용하여 수리실험에서 도출된 유속으로 상대속도(relative velocity)를 제시하였다. 수리실험은 축척효과(scale effect)를 최소화하기 위해 폭이 5.0 m이고, 높이가 1.0 m인 광폭 개수로를 제작하였으며, 사용된 사석은 가공된 완전 구형을 사용하였다. 실험 결과 유속과 구형 입자 속도와의 비가 0.5~0.7 사이로 나타났으며, 이러한 결과를 유도된 식에 적용하여, 최종적으로 사석이 배제되는 조건을 도출하게 되었다. 구간은 입자레이놀즈수(<TEX>$Re_p$</TEX>)와 무차원 한계 전단력(<TEX>${\tau}_c{^*}$</TEX>)에 따라 크게 3가지로 구분되었다. 배제 구간(exclusion section), 확률적 배제 구간(probabilistic exclusion section), 비배제 구간(no exclusion section)이다. 본 연구결과는 횡단구조물의 저층수 배출관 설계시 유용한 기초 정보를 제공할 수 있을 것이다. There are various transversal structures (small dams or drop structures) in median and small streams in Korea. Most of them are concrete structures and it is so hard to exclude low-level water. Unless drainage valves and/or gates would not be installed near bottom of bed, sediment from upstream should be deposited and also contaminants attached to the sediments would devastatingly threaten the water quality and ecosystem. One of countermeasures for such problem is the bypass pipe installed underneath the transversal structure. However, there is still issued whether it would be workable if the gravels and/or stones would roll into and be not excluded. Therefore, in this study, the conditions to exclude the rip stone which enter into the bypass pipe was reviewed. Based on sediment transport phenomenon, the behavior of stones was investigated with the concepts from the critical shear stress of sediment and d'Alembert principle. As final results, the basis condition (<TEX>${\tau}_c{^*}$</TEX>) was derived using the Lagrangian description since the stones are in the moving state, not in the stationary state. From hydraulic experiments the relative velocity could be obtained. In order to minimize the scale effect, the extra wide channel of 5.0 m wide and 1.0 m high was constructed and the experimental stones were fully spherical ones. Experimental results showed that the ratio of flow velocity to spherical particle velocity was measured between 0.5 and 0.7, and this result was substituted into the suggested equation to identify the critical condition wether the stones were excluded. Regimes about the exclusion of stone in bypass pipe were divided into three types according to particle Reynolds number (<TEX>$Re_p$</TEX>) and dimensionless critical shear force (<TEX>${\tau}_c{^*}$</TEX>) - exclusion section, probabilistic exclusion section, no exclusion section. Results from this study would be useful and essential information for bypass pipe design in transveral structures.

On the Degradation Modes of Various Steel Grades Used in Heat Recovery Systems: An Application from the Petrochemical Industry

Various steel grades used in the piping system of a waste heat recovery system at a petrochemical plant producing hydrogen by the steam–methane process are shown to be degraded by different modes. Pipes made of low-alloy steel (grade C-1/2Mo) have developed two problems: (1) pitting and formation of a blackish powdery deposit at the internal surface of the pipe adjacent to the inlet of the reboiler, and (2) an oxide at the internal surface of the bypass pipe fitted into a 304 stainless steel pipe. Furthermore, a welded elbow made of 304 stainless steel has developed a crack in the weld seam by a fatigue mechanism. Although the results suggest that metal dusting may be related to leakage of the reformed carbonaceous gas into the piping system, a steel resistant to metal dusting with a composition defined by %Cr + 2%Si > 24 wt% may be considered for the application. On the other hand, a steel with better fatigue resistance such as one with a tempered martensitic structure may be considered as a replacement for the 304 stainless steel.

Numerical Simulation of Transient Pressure Control in a Pumped Water Supply System Using an Improved Bypass Pipe

The use of a bypass pipe in a pump system is an economical and simple method of preventing water hammer surges to control the extreme transient pressures induced by pump failure. Currently, conventional bypass pipes (CBPs) have certain limitations in engineering applications. To overcome these limitations, in this study, a CBP is modified to create an improved bypass pipe (IBP). Unlike that of a CBP, the control valve in an IBP system is a hydraulic control valve that uses a controller on an uninterruptible power source (UPS) to turn the valve on or off. This modification enables the hydraulic control valve to be precisely controlled and facilitates the prevention of water hammer surges. To study the transient control effect of the IBP using the method of characteristics (MOC), a mathematical model of a complex system that includes an IBP, a check valve, and a water pump is established. Using MATLAB software, a water supply system in an industrial zone is used as an example for numerical simulations of the transient process experienced by this pump after it fails. The extreme pressure variations and the envelope of the pipe pressure in a typical section of the pumped water supply system are analysed and compared. The results show that an IBP can effectively reduce the maximum extreme pressure in a pumped water supply system.

Gas–solid flow behaviour prediction for sand in bypass pneumatic conveying with conventional frictional-kinetic model

Bypass pneumatic conveying is an alternative way to convey material which does not have dense phase transport capability. The computational fluid dynamics based commercial software Fluent 6.3 is used to investigate the pressure drop as well as the gas–solid flow behaviour in a bypass pneumatic conveying system. The conveyed material was sand with a mean particle size of 378µm and the solid loading ratio was in the range of 10–123. The conventional frictional-kinetic model combining frictional and kinetic stresses simultaneously was applied for pressure drop prediction. The simulation results were then compared with experimental results from bypass pneumatic conveying tests. Selected image results from the computational fluid dynamics simulations were utilised and compared with images captured from high speed camera. In addition, a test case with low air mass flow rate and high solid loading ratio 82.49 was chosen as an example to show detailed gas–solid flow behaviour in the simulation of highly dense flows. It was found that conventional frictional-kinetic model with modified packing limit and friction packing limit has greatly improved the pressure drop prediction result compared with kinetic theory without friction. The detailed analysis for the selected test case showed how the full bore dune formation and deformation of sand and bypass flutes interact. High amplitude fluctuations and variation in pressure and gas velocity were observed. The gas velocity vectors indicate a high degree of air penetration from the flute into the bypass pipe. This behaviour provides an aeration mechanism which is what makes the bypass system work and allows non-dense phase material to be conveyed in a dense mode of flow.

Numerical investigation of a looped-tube travelling-wave thermoacoustic engine with a bypass pipe

A new configuration (“a looped-tube with a bypass pipe”) was recently proposed for low temperature travelling wave thermoacoustic engines and a prototype using atmospheric air as the working gas achieved an onset temperature difference as low as 65 °C. However, no further research has been reported about this new configuration to reveal its advantages and disadvantages. This paper aims to analyse this type of engine through a comprehensive numerical research. An engine of this type having dimensions similar to the reported prototype was firstly modelled. The calculated results were then qualitatively compared with the reported experimental data, showing a good agreement. The working principle of the engine was demonstrated and analysed. The research results show that an engine with such a bypass configuration essentially operates on the same thermodynamic principle as other travelling wave thermoacoustic engines, differing only in the design of the acoustic resonator. Both extremely short regenerators and a near-travelling wave resonator minimise the engine's acoustic losses, and thus significantly reduce its onset temperature difference. However, such short regenerators likely cause severe heat conduction losses, especially if the engine is applied to heat sources with higher temperatures. Furthermore, the acoustic power flowing back to the engine core is relatively low, while a large stream of acoustic power has to propagate within its resonator to maintain an acoustic resonance, potentially leading to low power density. The model was then applied to design an engine with a much longer regenerator and higher mean pressure to increase its power density. A thermoacoustic cooler was also added to the engine to utilise its acoustic power, allowing the evaluation of thermal efficiency. The pros and cons of the engine configuration are then discussed.

Passage of downstream migrant American eels through an airlift-assisted deep bypass

Traditional downstream guidance and bypass facilities for anadromous fishes (i.e., surface bypasses, surface guidance structures, and behavioral barriers) have frequently been ineffective for anguillid eels. Because eels typically spend the majority of their time near the bottom in the vicinity of intake structures, deep bypass structures with entrances near the bottom hold promise for increased effectiveness, thereby aiding in the recovery of this important species. A new design of a deep bypass system that uses airlift technology (the Conte Airlift Bypass) to induce flow in a bypass pipe was tested in a simulated intake entrance environment under controlled laboratory conditions. Water velocities of 0.9–1.5ms−1 could be generated at the bypass entrance (opening with 0.073m2 area), with corresponding flows through the bypass pipe of 0.07–0.11m3s−1. Gas saturation and hydrostatic pressure within the bypass pipe did not vary appreciably from a control (no air) condition under tested airflows. Migratory silver-phase American eels (Anguilla rostrata) tested during dark conditions readily located, entered, and passed through the bypass; initial avoidance rates (eels approaching but not entering the bypass entrance) were lower at higher entrance velocities. Eels that investigated the bypass pipe entrance tended to enter headfirst, but those that then exited the pipe upstream did so more frequently at lower entrance velocities. Eels appeared to swim against the flow while being transported downstream through the pipe; median transit times through the bypass for each test velocity ranged from 5.8 to 12.2s, with transit time decreasing with increasing entrance velocity. Eels did not show strong avoidance of the vertical section of the pipe which contained injected air. No mortality or injury of bypassed eels was observed, and individual eels repeatedly passed through the bypass at rates of up to 40 passes per hour, suggesting that individuals do not avoid repeated entrainment through the bypass. Airlift technology appears to be a viable method for increasing passage effectiveness for American eels through a deep bypass system.

A new approach for measuring the permeability of shale featuring adsorption and ultra-low permeability

Based on the critical issues associated with shale permeability measurements, a new experimental approach by modifying the traditional pressure-pulse decay method was developed. In order to reduce the measurement error caused by the pore volumes of the traditional method, we made a new design that the upstream and downstream reservoir volumes can be changed, In addition, we added a by-pass pipe to measure the bidirectional permeability instantaneously, which can reduce the total test time significantly. Except for nitrogen or helium, methane was utilized to measure the shale permeability in this work, which can be more practical and better understand the real gas transport mechanisms in shale. Furthermore, we modified the conventional interpretation model of permeability measurements by incorporating the physical mechanism of gas adsorption. We also performed a series of experimental measurements and data analyses using different cores from pure shale, sand shale, to sandstone, which are from the Ordos basin (Chang 7 section) in China. The results show that: (1) the error caused by the pore volume errors of the traditional method is decreased by nearly half if variable reservoir volumes are used. The total test time is reduced by around 7 h by adding the by-pass pipe on the apparatus. The value of permeability measured with methane is higher than that measured with nitrogen while lower than that measured with helium. (2) The effective gas adsorption porosity increases with the increasing Langmuir pressure and decreasing pore pressure. If without considering gas adsorption, the measured permeability value will be underestimated, especially under lower pore pressure, higher adsorption capacity, and higher Langmuir pressure. (3) The total error is less than 10% using this new apparatus and the modified permeability interpretation method. The measured permeability values are reliable by comparing the measurements using the new apparatus and the standard instrument of ProPDP-200 under the same condition. (4) The influence of gas adsorption on permeability measurement in shale cannot be ignored, and the permeability is underestimated by up to 97% in pure shale while by only 7.5% in sandstone if the gas adsorption is not taken into account.

Waste Load Allocation Using Machine Scheduling: Model Application

A novel approach for waste load allocation, namely, waste load scheduling, following the concept of machine scheduling has been developed and applied to a case study. The conceptual development and mathematical formulation for the waste load scheduling model has been discussed in the companion paper. The focus of this paper is to identify a suitable solution technique for solving the waste load scheduling model and then apply it to a case study river system in Tamil Nadu, India. The mathematical formulation for the waste load scheduling model was developed by treating it in an analogous way to a machine scheduling problem (as explained in the companion paper). Dynamic programming (DP) has been used by several researchers for solving such machine scheduling and sequencing problems and thus the same method is adopted here for solving the proposed waste load scheduling problem. To demonstrate the practical application of the proposed method, the model was applied to a real case study river system, namely, Thambraparani river system, which is located in the southern part of the Tamil Nadu state in India. The results from the waste load scheduling model proved that the method is very effective in reducing the total waste load discharge into the river and thereby achieving a high level of river water quality. Comparing the results of waste load scheduling (WLS) model with SEDP (Seasonal Effluent Discharge program) and EBP (Effluent By-Pass Piping) model shows that the proposed WLS model satisfies all the three water quality management goals (i.e., cost minimization, minimizing overall inequity, and minimizing total waste load discharge into the river) to a greater degree when compared to SEDP and EBP models.

Decentralized substations for low-temperature district heating with no Legionella risk, and low return temperatures

To improve energy efficiency and give more access to renewable energy sources, low-temperature district heating (LTDH) is a promising concept to be realized in the future. However, concern about Legionella proliferation restricts applying low-temperature district heating in conventional systems with domestic hot water (DHW) circulation. In this study, a system with decentralized substations was analysed as a solution to this problem. Furthermore, a modification for the decentralized substation system were proposed in order to reduce the average return temperature. Models of conventional system with medium-temperature district heating, decentralized substation system with LTDH, and innovative decentralized substation system with LTDH were built based on the information of a case building. The annual distribution heat loss and the operating costs of the three scenarios were calculated and compared. From the results, realizing LTDH by the decentralized substation unit, 30% of the annual distribution heat loss inside the building can be saved compared to a conventional system with medium-temperature district heating. Replacing the bypass pipe with an in-line supply pipe and a heat pump, the innovative decentralized substation system can reduce distribution heat loss by 39% compared to the conventional system and by 12% compared to the normal decentralized substation system with bypass.

菜種エステルを用いたMR流体ダンパ

In this paper magneto-rheological fluid was newly developed by using rapeseed ester. The fluid is magnetic colloidal fluid which comprises carrier and small iron particle with surfactants. Hydrocarbon oil was usually used for carrier, but rapeseed ester such as natural oil was used in this study. It was comparatively valuable for environmental protection. For purpose of applying to mechanical device using the fluid, a test MR fluid damper which was composed of a cylinder, piston, bypass pipe and electromagnets was designed and manufactured. Three types of new MR fluid, which were packed together with 30, 50 and 80 % of particle weight, were filled into the damper, respectively. A conventional MR fluid was also used for comparing with new ones. To estimate dynamic performance as damper using new MR fluid, vibration tests were carried out. Resisting force characteristics and rising time of the damper were measured under magnetic fields when the electromagnets applied current constantly. Finally, the dynamic capability of damper was confirmed experimentally.

Fluid inertia damper using MR fluid with a long spiral bypass pipe

Fluid inertia damper using MR fluid with a long spiral bypass pipe

Experimental investigations of flow distribution in coolant system of Helium-Cooled-Pebble-Bed Test Blanket Module

This paper deals with investigations of flow distribution in the coolant system of the Helium-Cooled-Pebble-Bed Test Blanket Module (HCPB TBM) for ITER. The investigations have been performed by manufacturing and testing of an experimental facility named GRICAMAN. The facility involves the upper poloidal half of HCPB TBM bounded at outlets of the first wall channels, at outlet of by-pass pipe and at outlets of cooling channels in breeding units. In this way, the focus is placed on the flow distribution in two mid manifolds of the 4-manifold system: (i) manifold 2 to which outlets of the first wall channels and inlet of by-pass pipe are attached and (ii) manifold 3 which supplies channels in breeding units with helium coolant. These two manifolds are connected with cooling channels in vertical/horizontal grids and caps.The experimental facility has been built keeping the internal structure of manifold 2 and manifold 3 exactly as designed in HCPB TBM. The cooling channels in stiffening grids, caps and breeding units are substituted by so-called equivalent channels which provide the same hydraulic resistance and inlet/outlet conditions, but have significantly simpler geometry than the real channels. Using the conditions of flow similarity, the air pressurized at 0.3MPa and at ambient temperature has been used as working fluid instead of HCPB TBM helium coolant at 8MPa and an average temperature of 370°C. The flow distribution has been determined by flow rate measurements at each of 28 equivalent channels, while the pressure distribution has been obtained measuring differential pressure at more than 250 positions.The measured data have shown that critical for flow distribution in manifold 2 are grid/cap channels attached to the manifold regions adjacent to the first wall. In these regions high velocity jets exiting from the first wall induce low pressure at the channel inlets and, therefore, lower flow supply. Making resistance to high velocity streams from the first wall the perforated penetrations of horizontal grid plates which divide the manifold 2 into chambers are crucial for pressure homogenizing and reasonable flow distribution among channels attached to the central part of manifold 2. In the major part of manifold 3 very small differential pressures were measured except for some breeding unit inlets where strong pressure peaks were recorded. Nevertheless, no dramatic differences were found between experimentally determined flow rates in individual breeding unit channels.

The efficiency of Pontederia Cordata in nitrogen removal from landscape water under varying flow rates

The Green Origio biological system, a two-stage, solar-powered constructed wetland mesocosm situated in Shanghai Jiao Tong University's plant park was used for nitrogen removal in the institution's landscape water. Whereas the first tank was anaerobic, the second tank containing fully grown Pontederia cordata was operated under aerobic conditions. The system was designed with an overflow by-pass pipe to prevent hydraulic overloading. Pump discharge values of 53, 74, 112, 120, 205 and 270 m3/day were recorded during the study. However, the corresponding flow rate values into the tanks were 16.25 m3/day, 29.47 m3/day, 36.79 m3/day, 50.57 m3/day, 71.38 m3/day and 80.52 m3/day, respectively. Experiments conducted between August and October, 2013 revealed a significant concentration decrease for total nitrogen (TN), ammonia (NH3-N), nitrate (NO3-N), nitrite (NO2-N) and total organic carbon (TOC). Whereas the Multi N/C 3100 Analyzer was used for simultaneous analysis of TN and TOC, the nitrogen fractions were analyzed using spectrophotometric methods. The TN, NO3-N, NH3-N, NO2-N and TOC removal rates under a flow rate of 16.25 m3/day were 55.65%, 75.19%, 74.03%, 95.43% and 29.87%, respectively. TN and NO2-N removal efficiencies of 4.92% and 83.64%, respectively, were observed under a flow rate of 80.52 m3/day. Concentration increase in the effluent caused by washout of accumulated concentrations was noted for NO3-N, NH3-N and TOC.

EPANET Simulation of Control Methods for Centrifugal Pumps Operating under Variable System Demand

Pump operation control under variable system demand is obtained either by throttling the discharge pipe, by using by-pass pipes, by modifying the rotor speed, or by separating the pump and the demand by means of a pressurized tank. We try to assess the efficiency of pump operation control by using a numerical model created in EPANET for a 24hours period. To avoid the demand driven algorithm used by EPANET, the network model consists of a throttle control valve followed by an emitter. Pump or valves parameters are modified using control statements. Results are consistent with the general theory.

J1010501 電磁誘導を用いた流体式ダンパに関する研究 : ハルバッハ磁石列を用いた場合([J101-5]制振(1))

The authors proposed a unique type of semiactive damper that utilizes electromagnetic induction of a fluid in previous paper. But it was not enough to act an effect of electromagnetic induction because of a weak magnetic flux density. In this paper Halbach magnetic arrays is used for the damper in order to improve the effect. The damper consists of a cylinder, a piston, a by-pass pipe, tubes, tube couplings, electrodes, and trapezoid rare-earth magnets. A high conductive polymer fluid is filled in the cylinder, the by-pass pipe and the tube. Two electrodes are fixed inside the by-pass pipe, and faced. Eight magnets are set up as an octagonal Halbach array around the by-pass pipe, and each array units are installed in series. The magnetic field of the by-pass pipe is analyzed by FEM, and measured. The maximum magnetic flux density inside the by-pass pipe is about 0.9 T, and larger than the previous type. Resisting force characteristics of the damper acting the Lorenz force are measured when a voltage of the electrodes is applied in cross at the magnetic flux. Finally the effect of the electromagnetic induction is confirmed experimentally.

초고층 건축물 연결송수관 설비의 효과적 활용에 관한 실험 연구

최근 해외뿐만 아니라 국내에서도 건축물이 초고층화 되고 있으며 다양한 복합건물의 건축이 진행되고 있다. 초고층 건축물은 물리적 특성상 공간의 수직적 분포로 인하여 화재발생 시 화재확산의 위험이 크고 이에 따른 소방 활동상에 어려움을 동반하게 된다. 연결송수관 설비에서 정전되거나 펌프고장이 발생한 다면 소방차로부터 급수된 소화용수는 정지된 펌프의 임펠러를 통과하는데 장애가 발생 수 있을 것으로 예상된다. 본 연구에서는 소화활동설비 중 연결송수관설비를 화재 시 소방대원이 효과적으로 활용하기 위하여 실험을 통하여 기존 연결송수관시스템의 문제점을 확인하고 개선사항을 제안하였다. 실험 결과 중간가압펌프를 통과한 경우와 바이패스배관을 통과한 경우 유량 및 방사압력에 현격한 차이가 발생함을 확인하였고, 이러한 결과를 토대로 중간가압펌프 정지 시를 대비하여 중간가압펌프 토출측에 직접 연결되는 바이패스 배관을 추가로 설치하여야함을 제안하였다. Recently, the building has been higher and more complicated. High-rise buildings are more dangerous when fire occurs because of fast fire spreading through vertical space. This makes difficulty for fire fighter's moving when they suppress fire. The pump impeller will be obstacle when fire water is supplied from fire department connection, if the power is failure or the pump is breakdown. This study identifies the defect of fire department connection system and compensates that. It is verified the difference of flow rate and pressure in the case through pump impeller and in the case through bypass piping by test. Based on the result of this study, it suggest that the installation of bypass piping at the discharge side of pressurization pump have to be prepared in case of pressurization pump stopping.

Failure analysis on abnormal wall thinning of heat-transfer titanium tubes of condensers in nuclear power plant Part II: Erosion and cavitation corrosion

In Part I of the failure analysis on abnormal wall thinning of heat-transfer titanium tubes used in condensers in nuclear power plant, we analyzed the causes and mechanisms of abnormal thinning that commonly happened at the contact part between the tubes and the support plates. This kind of failure was the mainstream failure type in our case and the main causes were found to be eccentric contact wear and three-body contact wear rooted in processing defect of internal borings, corrosion products deposit and sagging, and foreign particles. However, there were still some individual failure tubes with different failure sites and modes and were located under the bypass pipes at the shoulder of the tube tower instead of in its lower part, obviously telling another failure story. In Part II of the failure analysis, material analysis, metallographic examination, mechanical performance tests, macro- and microstructure analysis and composition analysis were conducted. The failure causes were found to be erosion and cavitation corrosion and the synergetic effect of them. Finally, corresponding countermeasures were suggested.