Condensation Induced Waterhammer in District Steam Distribution Systems

2013 ◽  
Author(s):  
Sri K. Sinha ◽  
Robert S. Vecchio ◽  
Paul M. Bruck ◽  
Thomas C. Esselman ◽  
Gregory Zysk ◽  
...  
Keyword(s):  
New York ◽  
Distribution Systems ◽  
Construction Materials ◽  
Operating Conditions ◽  
Operating Pressure ◽  
Excessive Pressure ◽  
Root Cause ◽  
Steam Pipe ◽  
Event Based ◽  
Steam System

Condensation induced waterhammer in district steam distribution systems can cause catastrophic rupture of piping and inflict severe damage to personnel, property, and environment. On July 18, 2007, a 20-in. diameter underground steam pipe in New York City ruptured at 5:56 p.m. at the intersection of 41st Street and Lexington Avenue in midtown Manhattan. At the time of rupture, the steam system was in service delivering steam to the customers at an operating pressure of approximately 160 psig and a steam temperature of approximately 370°F. The incident opened a large cavity measuring approximately 32 ft × 32 ft × 18 ft deep at the intersection of 41st Street and Lexington Avenue. The pipe rupture released steam, condensate, water, pipe insulation and various construction materials to the environment. Consolidated Edison Co. of New York, Inc. (Con Edison) and LPI (Lucius Pitkin, Inc.) investigated the event. Based on detailed metallurgical and engineering evaluations of the steam system configuration and operating conditions, it was concluded that the steam pipe ruptured as a result of excessive pressure caused by condensation-induced waterhammer. This paper presents a summary of the engineering evaluation, root cause, and conditions leading to the pipe rupture and provides measures which can be taken to reduce the likelihood of such a failure and enhance public safety.

scholarly journals Assessment of water quality modelling capabilities of EPANET multiple species and pressure-dependent extension models

2013 ◽  
Vol 13 (4) ◽  
pp. 1161-1166 ◽  
Author(s):  
Alemtsehay G. Seyoum ◽  
Tiku T. Tanyimboh ◽  
Calvin Siew
Keyword(s):  
Water Quality ◽  
Distribution Systems ◽  
Operating Conditions ◽  
Quality Analysis ◽  
Future Research ◽  
Operating Pressure ◽  
Quality Model ◽  
Water Age ◽  
First Order ◽  
Multiple Species

The need for accurately predicting water quality through models has increasingly been crucial in meeting rigorous standards and customer expectations. There are several endeavours on developing robust water quality models for water distribution systems. In this paper, two variants of the EPANET 2 water quality model have been assessed to inform future research. The models are the multiple species extension EPANET-MSX and the pressure-dependent extension EPANET-PDX. Water quality analysis was conducted on a hypothetical network considering various operating pressure conditions. Different kinetic models were employed to simulate water quality. First order, limited first order and zero order models were used for predicting chlorine residual, disinfection by-products (DBPs) and water age respectively. Generally, EPANET-MSX and EPANET-PDX provided identical water quality results for normal operating conditions with adequate pressure but different results for pressure-deficient networks. Also, a parallel first order model with fast and slow reacting components was used for chlorine decay and DBPs using the EPANET-MSX model for a network operating under normal pressure conditions.

Evaluation and Analysis of High Frequency Vibration on the Cavitating Venturi Downstream Piping

2006 ◽  
Author(s):  
Chang-Bin Jeon ◽  
Woochie H. Chun ◽  
Ju-Yeoul Lee
Keyword(s):  
Steam Generator ◽  
High Frequency ◽  
Nuclear Power ◽  
Operating Conditions ◽  
Operating Pressure ◽  
Test Results ◽  
Root Cause ◽  
Threaded Connection ◽  
Mode Vibration ◽  
Beam Mode

During hot functional test (HFT) of the auxiliary feedwater (AFW) system of a nuclear power plant, high vibration and noise occurred in the downstream of the cavitating venturi (CV), which caused severe damages, such as the disengagement of internal parts, failure of threaded connection to the temperature gauge located nearby downstream piping, relaxation of fastening nuts for pipe clamp and damaged socket weld connection. The objective of this paper is to evaluate the venturi downstream piping vibration in accordance with the ASME OM 3 requirements and identify the characteristics of the high frequency piping vibration. The vibration test was performed for the steam generator-operating pressure range to confirm whether the amplitudes of the vibration are within the acceptable limits to assure that no piping failures would occur due to cyclic loads. In addition to the vibration evaluation from the fatigue standpoint, the root cause of piping vibration is investigated. From the test results, the characteristics of vibration are acoustically coupled with vortex-shedding and cavitations, which results in a frequency range from 2,000 to 5,000 Hz. During the test, the vibration and noise were severer at the steam generator pressure of 40 kg/cm2 rather than at the atmospheric pressure, or even at 82 kg/cm2. It was also detected that degrees of cavitation and locations where the collapse occurred varied depending on operating conditions. Due to the high frequency characteristics, the shell mode vibration was more dominant than the lateral beam mode vibration.

Analysis Approach on DMOS Transistor Vth Mismatch Due to Trapped Charges

2015 ◽  
Author(s):  
Hashim Ismail ◽  
Ang Chung Keow ◽  
Kenny Gan Chye Siong
Keyword(s):  
Failure Analysis ◽  
Threshold Voltage ◽  
Gate Oxide ◽  
Analysis Approach ◽  
Test Results ◽  
Root Cause ◽  
Switching Event ◽  
Output Transistor ◽  
Event Based ◽  
Trapped Charge

Abstract An output switching malfunction was reported on a bridge driver IC. The electrical verification testing revealed evidence of an earlier over current condition resulting from an abnormal voltage sense during a switching event. Based on these test results, we developed the hypothesis that a threshold voltage mismatch existed between the sense transistor and the output transistor. This paper describes the failure analysis approach we used to characterize the threshold voltage mismatch as well as our approach to determine the root cause, which was trapped charge on the gate oxide of the sense transistor.

Pseudo-Dynamic Fault Isolation Technique Using Backside Emission Microscopy – Case Study, Where All Other Methods Fail

2002 ◽  
Author(s):  
Yoav Weizman ◽  
Ezra Baruch ◽  
Michael Zimin
Keyword(s):  
Failure Analysis ◽  
Process Variations ◽  
Fault Isolation ◽  
Operating Conditions ◽  
Detection Sensitivity ◽  
Isolation Technique ◽  
Root Cause ◽  
Emission Microscopy ◽  
Failure Location ◽  
Noisy Background

Abstract Emission microscopy is usually implemented for static operating conditions of the DUT. Under dynamic operation it is nearly impossible to identify a failure out of the noisy background. In this paper we describe a simple technique that could be used in cases where the temporal location of the failure was identified however the physical location is not known or partially known. The technique was originally introduced to investigate IDDq failures (1) in order to investigate timing related issues with automated tester equipment. Ishii et al (2) improved the technique and coupled an emission microscope to the tester for functional failure analysis of DRAMs and logic LSIs. Using consecutive step-by-step tester halting coupled to a sensitive emission microscope, one is able detect the failure while it occurs. We will describe a failure analysis case in which marginal design and process variations combined to create contention at certain logic states. Since the failure occurred arbitrarily, the use of the traditional LVP, that requires a stable failure, misled the analysts. Furthermore, even if we used advanced tools as PICA, which was actually designed to locate such failures, we believe that there would have been little chance of observing the failure since the failure appeared only below 1.3V where the PICA tool has diminished photon detection sensitivity. For this case the step-by-step halting technique helped to isolate the failure location after a short round of measurements. With the use of logic simulations, the root cause of the failure was clear once the failing gate was known.

Effect of operating conditions on rejection of anionic pollutants in the water environment by nanofiltration especially in very low pressure range

1996 ◽  
Vol 34 (9) ◽  
pp. 149-156 ◽  
Author(s):  
C. Ratanatamskul ◽  
K. Yamamoto ◽  
T. Urase ◽  
S. Ohgaki
Keyword(s):  
Water Environment ◽  
Chloride Ions ◽  
Operating Conditions ◽  
Transmembrane Pressure ◽  
Operating Pressure ◽  
Nanofiltration Membranes ◽  
Single Solution ◽  
Crossflow Velocity ◽  
Membrane Type ◽  
New Generation

The recent development of new generation LPRO or nanofiltration membranes have received attraction for application in the field of wastewater and water treatment through an increasingly stringent regulation for drinking purpose and water reclamation. In this research, the application on treatment of anionic pollutants (nitrate, nitrite, phosphate, sulfate and chloride ions) have been investigated as functions of transmembrane pressure, crossflow velocity and temperature under very much lower pressure operation range (0.49 to 0.03 MPa) than any other previous research used to do. Negative rejection was also observed under very much low range of operating pressure in the case of membrane type NTR-7250. Moreover, the extended Nernst-Planck model was used for analysis of the experimental data of the rejection of nitrate, nitrite and chloride ions in single solution by considering effective charged density of the membranes.

scholarly journals A Numerical Investigation into the PAT Hydrodynamic Response to Impeller Rotational Speed Variation

2021 ◽  
Vol 13 (14) ◽  
pp. 7998
Author(s):  
Maxime Binama ◽  
Kan Kan ◽  
Hui-Xiang Chen ◽  
Yuan Zheng ◽  
Daqing Zhou ◽  
...  
Keyword(s):  
Rotational Speed ◽  
Distribution Systems ◽  
Water Distribution ◽  
Production Efficiency ◽  
Operating Conditions ◽  
Energy Regulation ◽  
Speed Increase ◽  
Energy Field ◽  
Long Run ◽  
Study Results

The utilization of pump as turbines (PATs) within water distribution systems for energy regulation and hydroelectricity generation purposes has increasingly attracted the energy field players’ attention. However, its power production efficiency still faces difficulties due to PAT’s lack of flow control ability in such dynamic systems. This has eventually led to the introduction of the so-called “variable operating strategy” or VOS, where the impeller rotational speed may be controlled to satisfy the system-required flow conditions. Taking from these grounds, this study numerically investigates PAT eventual flow structures formation mechanism, especially when subjected to varying impeller rotational speed. CFD-backed numerical simulations were conducted on PAT flow under four operating conditions (1.00 QBEP, 0.82 QBEP, 0.74 QBEP, and 0.55 QBEP), considering five impeller rotational speeds (110 rpm, 130 rpm, 150 rpm, 170 rpm, and 190 rpm). Study results have shown that both PAT’s flow and pressure fields deteriorate with the machine influx decrease, where the impeller rotational speed increase is found to alleviate PAT pressure pulsation levels under high-flow operating conditions, while it worsens them under part-load conditions. This study’s results add value to a thorough understanding of PAT flow dynamics, which, in a long run, contributes to the solution of the so-far existent technical issues.

scholarly journals Configurations, Power Topologies and Applications of Hybrid Distribution Transformers

Energies ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1215
Author(s):  
Alvaro Carreno ◽  
Marcelo Perez ◽  
Carlos Baier ◽  
Alex Huang ◽  
Sanjay Rajendran ◽  
...  
Keyword(s):  
Distribution Systems ◽  
Power Converter ◽  
Operating Conditions ◽  
Distribution Transformer ◽  
Nonlinear Loads ◽  
Electric Vehicle Charging ◽  
Distribution Transformers ◽  
Alternative Systems ◽  
Charging Stations ◽  
Hybrid Distribution

Distribution systems are under constant stress due to their highly variable operating conditions, which jeopardize distribution transformers and lines, degrading the end-user service. Due to transformer regulation, variable loads can generate voltage profiles out of the acceptable bands recommended by grid codes, affecting the quality of service. At the same time, nonlinear loads, such as diode bridge rectifiers without power factor correction systems, generate nonlinear currents that affect the distribution transformer operation, reducing its lifetime. Variable loads can be commonly found at domiciliary levels due to the random operation of home appliances, but recently also due to electric vehicle charging stations, where the distribution transformer can cyclically vary between no-load, rated and overrated load. Thus, the distribution transformer can not safely operate under highly-dynamic and stressful conditions, requiring the support of alternative systems. Among the existing solutions, hybrid transformers, which are composed of a conventional transformer and a power converter, are an interesting alternative to cope with several power quality problems. This article is a review of the available literature about hybrid distribution transformers.

scholarly journals Modeling Bacterial Regrowth and Trihalomethane Formation in Water Distribution Systems

Water ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 463
Author(s):  
Gopinathan R. Abhijith ◽  
Leonid Kadinski ◽  
Avi Ostfeld
Keyword(s):  
Distribution Systems ◽  
Water Distribution ◽  
Mechanistic Model ◽  
Water Distribution Systems ◽  
Sensitivity Study ◽  
Operating Conditions ◽  
Growth Rate Constant ◽  
Model Parameters ◽  
Bacterial Regrowth ◽  
The Impact

The formation of bacterial regrowth and disinfection by-products is ubiquitous in chlorinated water distribution systems (WDSs) operated with organic loads. A generic, easy-to-use mechanistic model describing the fundamental processes governing the interrelationship between chlorine, total organic carbon (TOC), and bacteria to analyze the spatiotemporal water quality variations in WDSs was developed using EPANET-MSX. The representation of multispecies reactions was simplified to minimize the interdependent model parameters. The physicochemical/biological processes that cannot be experimentally determined were neglected. The effects of source water characteristics and water residence time on controlling bacterial regrowth and Trihalomethane (THM) formation in two well-tested systems under chlorinated and non-chlorinated conditions were analyzed by applying the model. The results established that a 100% increase in the free chlorine concentration and a 50% reduction in the TOC at the source effectuated a 5.87 log scale decrement in the bacteriological activity at the expense of a 60% increase in THM formation. The sensitivity study showed the impact of the operating conditions and the network characteristics in determining parameter sensitivities to model outputs. The maximum specific growth rate constant for bulk phase bacteria was found to be the most sensitive parameter to the predicted bacterial regrowth.

scholarly journals Identifying VOCs in exhibition cases and efflorescence on museum objects exhibited at Smithsonian’s National Museum of the American Indian-New York

2020 ◽  
Vol 8 (1) ◽  
Author(s):  
Alba Alvarez-Martin ◽  
John George ◽  
Emily Kaplan ◽  
Lauren Osmond ◽  
Leah Bright ◽  
...  
Keyword(s):  
New York ◽  
American Indian ◽  
Solid Phase ◽  
Construction Materials ◽  
Sampling Strategy ◽  
Sampling Technique ◽  
Direct Analysis ◽  
National Museum ◽  
Structural Adhesive ◽  
Speed Of Analysis

AbstractTwo mass spectrometry (MS) methods, solid-phase microextraction gas chromatography (SPME–GC–MS) and direct analysis in real time (DART-MS), have been explored to investigate widespread efflorescence observed on exhibited objects at the Smithsonian’s National Museum of the American Indian in New York (NMAI-NY). Both methods show great potential, in terms of speed of analysis and level of information, for identifying the organic component of the efflorescence as 2,2,6,6-tetramethyl-4-piperidinol (TMP-ol) emitted by the structural adhesive (Terostat MS 937) used for exhibit case construction. The utility of DART-MS was proven by detecting the presence of TMP-ol in construction materials in a fraction of the time and effort required for SPME–GC–MS analysis. In parallel, an unobtrusive SPME sampling strategy was used to detect volatile organic compounds (VOCs) accumulated in the exhibition cases. This sampling technique can be performed by collections and conservation staff at the museum and shipped to an off-site laboratory for analysis. This broadens the accessibility of MS techniques to museums without access to instrumentation or in-house analysis capabilities.

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