Investigation of Leakage Rates in Pressure Retaining Piping

2017 ◽  
Author(s):  
Fabian E. Silber ◽  
Xaver Schuler ◽  
Stefan Weihe ◽  
Eckart Laurien ◽  
Rudi Kulenovic ◽  
...  
Keyword(s):  
Power Plants ◽  
Leak Detection ◽  
Operating Conditions ◽  
Leak Rate ◽  
Test Facility ◽  
Experimental Investigations ◽  
Two Phase ◽  
Detection Systems ◽  
Test Loop ◽  
Calculation Models

Within the break preclusion concept, leak-before-break (LBB) behavior must be demonstrated for safety relevant pressure retaining piping systems in nuclear power plants (NPP) [1]. This requires leak detection systems in NPP with the capability to detect leak rates below the maximum allowable leak rate calculated by the LBB assessment according to nuclear standards, like the German KTA rule 3206 or the U.S. Standard Review Plan (SRP). An important part of the LBB assessment is the availability of accurate calculation models to predict the leak rate under normal operating conditions for postulated through wall cracks. Current leak detection systems in NPP are capable of reliably detecting liquid leak rates 0.05 kg/s. However, most of the available experimental leak rate data published in literature focus on the range between 0.2 kg/s and 2 kg/s, which is significantly above the detection limit. Therefore, additional experimental investigations are necessary to develop and verify leak rate calculation models for smaller leaks. In order to investigate such types of leaks, a modular test facility (fluid-structure-interaction test loop) has been developed and installed at MPA University of Stuttgart within the framework of a research project sponsored by the German Ministry of Education and Research (BMBF). The test rig includes a leakage piping module which includes artificially machined slits and fatigue through-wall cracks. It allows the variation of the significant influencing parameters such as crack size, surface roughness and the system parameters pressure and temperature up to 75 bar and 280 °C and also the measurement of the pressure gradient across the crack surface at two locations. This is important to develop a better understanding of the two-phase flow and pressure drop across the leak channel. A first test series has been performed and the results were used to evaluate existing leak-rate models. Within this paper an overview of the test facility, the testing procedure, and the results of the investigations will be presented and discussed.

Experimental Inverstigations On the Pressure Fluctuations in the Sealing Gap of Dry Gas Seals with Embedded Pressure Sensors

2021 ◽  
Author(s):  
Jingjing Luo ◽  
Dieter Brillert
Keyword(s):  
High Speed ◽  
Gas Flow ◽  
Static Pressure ◽  
Pressure Sensors ◽  
Operating Conditions ◽  
Test Facility ◽  
Experimental Investigations ◽  
Mechanical Seals ◽  
Process Gas ◽  
Sealing Gap

Abstract Dry gas lubricated non-contacting mechanical seals (DGS), most commonly found in centrifugal compressors, prevent the process gas flow into the atmosphere. Especially when high speed is combined with high pressure, DGS is the preferred choice over other sealing alternatives. In order to investigate the flow field in the sealing gap and to facilitate the numerical prediction of the seal performance, a dedicated test facility is developed to carry out the measurement of key parameters in the gas film. Gas in the sealing film varies according to the seal inlet pressure, and the thickness of gas film depends on this fluctuated pressure. In this paper, the test facility, measurement methods and the first results of static pressure measurements in the sealing gap of the DGS obtained in the described test facility are presented. An industry DGS with three-dimensional grooves on the surface of the rotating ring, where experimental investigations take place, is used. The static pressure in the gas film is measured, up to 20 bar and 8,100 rpm, by several high frequency ultraminiature pressure transducers embedded into the stationary ring. The experimental results are discussed and compared with the numerical model programmed in MATLAB, the characteristic and magnitude of which have a good agreement with the numerical simulations. It suggests the feasibility of measuring pressure profiles of the standard industry DGS under pressurized dynamic operating conditions without altering the key components of the seal and thereby affecting the seal performance.

scholarly journals Leak rate testing in the range of leak detection systems

2021 ◽  
Vol 372 ◽  
pp. 111000
Author(s):  
S. Schmid ◽  
F.E. Silber ◽  
K. Heckmann ◽  
R. Kulenovic ◽  
E. Laurien ◽  
...  
Keyword(s):  
Leak Detection ◽  
Leak Rate ◽  
Detection Systems ◽  
Rate Testing

scholarly journals Current Advances in Ejector Modeling, Experimentation and Applications for Refrigeration and Heat Pumps. Part 2: Two-Phase Ejectors

Inventions ◽  
2019 ◽  
Vol 4 (1) ◽  
pp. 16 ◽  
Author(s):  
Zine Aidoun ◽  
Khaled Ameur ◽  
Mehdi Falsafioon ◽  
Messaoud Badache
Keyword(s):  
Heat Pumps ◽  
Operating Conditions ◽  
Industrial Processes ◽  
Experimental Investigations ◽  
Mixing Enhancement ◽  
Data Generation ◽  
Two Phase ◽  
Wide Range ◽  
Potential Applications ◽  
And Performance

Two-phase ejectors play a major role as refrigerant expansion devices in vapor compression systems and can find potential applications in many other industrial processes. As a result, they have become a focus of attention for the last few decades from the scientific community, not only for the expansion work recovery in a wide range of refrigeration and heat pump cycles but also in industrial processes as entrainment and mixing enhancement agents. This review provides relevant findings and trends, characterizing the design, operation and performance of the two-phase ejector as a component. Effects of geometry, operating conditions and the main developments in terms of theoretical and experimental approaches, rating methods and applications are discussed in detail. Ejector expansion refrigeration cycles (EERC) as well as the related theoretical and experimental research are reported. New and other relevant cycle combinations proposed in the recent literature are organized under theoretical and experimental headings by refrigerant types and/or by chronology whenever appropriate and systematically commented. This review brings out the fact that theoretical ejector and cycle studies outnumber experimental investigations and data generation. More emerging numerical studies of two-phase ejectors are a positive step, which has to be further supported by more validation work.

Experimental Investigation of the Flow in the Pipe Diffuser of a Centrifugal Compressor Stage Under Selected Parameter Variations

2009 ◽  
Author(s):  
Uwe Zachau ◽  
Reinhard Niehuis ◽  
Herwart Hoenen ◽  
David C. Wisler
Keyword(s):  
Centrifugal Compressor ◽  
Measurement Techniques ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Test Facility ◽  
Experimental Investigations ◽  
Pressure Side ◽  
Compressor Stage ◽  
Diffuser Flow ◽  
Parameter Variations

On a centrifugal compressor test facility various experimental investigations have been carried out contributing a valuable gain in knowledge on the fundamental flow physics within passage type diffusers. An extensive measurement series using various steady, unsteady and laser optical measurement techniques has been performed to detect the unsteady, highly three dimensional diffuser flow under various realistic operating conditions. Zachau et al. [1] presented the test facility and the results gathered under nominal conditions. As a follow-up the results of investigated parameter variations are now presented, covering bleed variations, impeller tip clearance and impeller-diffuser misalignment studies. The data is compared to the benchmark created from the nominal baseline data sets and evaluated with respect to the compressor stage performance. Zachau et al. [1] found that under nominal conditions the flow in the pipe diffuser separates on the pressure side in the first half of the pipe. In the last 30% of the pipe hardly any deceleration of the flow takes place. From this, special attention is given to the investigated parameter variations regarding a first proposal for a diffuser design change, which consists in shortening the diffuser. The results for each parameter variation are evaluated in detail in direct comparison to the nominal baseline configuration underlining the conclusion made earlier that the diffuser flow always separates on the pressure side with negligible deceleration in the last third of the diffusing pipe.

Setup of the Supercritical CO2 Test Facility “SCARLETT” for Basic Experimental Investigations of a Compact Heat Exchanger for an Innovative Decay Heat Removal System

2018 ◽  
Vol 4 (3) ◽  
Author(s):  
Wolfgang Flaig ◽  
Rainer Mertz ◽  
Joerg Starflinger
Keyword(s):  
Heat Exchanger ◽  
Supercritical Co2 ◽  
Nuclear Power ◽  
Power Plants ◽  
Heat Removal ◽  
Test Facility ◽  
Experimental Investigations ◽  
Decay Heat ◽  
Heat Removal System ◽  
Removal System

Supercritical fluids show great potential as future coolants for nuclear reactors, thermal power, and solar power plants. Compared to the subcritical condition, supercritical fluids show advantages in heat transfer due to thermodynamic properties near the critical point. A specific field of interest is an innovative decay heat removal system for nuclear power plants, which is based on a turbine-compressor system with supercritical CO2 as the working fluid. In case of a severe accident, this system converts the decay heat into excess electricity and low-temperature waste heat, which can be emitted to the ambient air. To guarantee the retrofitting of this decay heat removal system into existing nuclear power plants, the heat exchanger (HE) needs to be as compact and efficient as possible. Therefore, a diffusion-bonded plate heat exchanger (DBHE) with mini channels was developed and manufactured. This DBHE was tested to gain data of the transferable heat power and the pressure loss. A multipurpose facility has been built at Institut für Kernenergetik und Energiesysteme (IKE) for various experimental investigations on supercritical CO2, which is in operation now. It consists of a closed loop where the CO2 is compressed to supercritical state and delivered to a test section in which the experiments are run. The test facility is designed to carry out experimental investigations with CO2 mass flows up to 0.111 kg/s, pressures up to 12 MPa, and temperatures up to 150 °C. This paper describes the development and setup of the facility as well as the first experimental investigation.

Experimental Investigation of Steam Bubble Condensation in Flowing Subcooled Water With Two Different Injection Nozzle Geometries

2013 ◽  
Author(s):  
Suleiman Al Issa ◽  
Patricia B. Weisensee
Keyword(s):  
Test Section ◽  
High Speed ◽  
Nuclear Power ◽  
Power Plants ◽  
Bubble Diameter ◽  
Large Diameter ◽  
Low Pressure ◽  
Test Facility ◽  
Experimental Investigations ◽  
Subcooled Water

A multiphase flow test facility was built at the Department of Nuclear Engineering at the Technical University Munich. The main goal of this facility is to investigate the condensation of steam bubbles injected into a vertical large diameter pipe (104 mm) with flowing subcooled water (6–15 K) at low pressure conditions (1.1–1.45 bar). Current experimental investigations will contribute to a better understanding of subcooled boiling at low pressures, accidental conditions in nuclear power plants and low-pressure research reactors and correlations for the validation of CFD codes. The test section is a 1 m long transparent pipe that is surrounded by an 18×18 cm rectangular “aquarium” filled with distilled water for refraction correction. High-speed camera (HSC) recording was used to gather data about condensing bubbles including bubble diameter, shape and rising velocity. Steam was injected via two different vertical injection nozzles with an inner diameter of 4 and 6 mm, respectively, directly into the center of the test section. The present experiments were carried out at three different steam superficial velocities, water superficial velocities and water temperatures leading to bubble diameters up to 50 mm and bubble relative velocities around 1 m/s. The measurements enabled the calculation of bubble Reynolds and Nusselt numbers and comparison with correlations given in literature. Even though significant differences could be observed between the two injection nozzles with respect to the bubble’s diameter and velocity, the Nusselt and Reynolds numbers are in the same range of values. The bigger bubbles of the 6 mm with respect to the 4 mm nozzle are almost neutralized by the lower rising velocities.

scholarly journals Temperature Compensation for Conductivity-Based Phase Fraction Measurements with Wire-Mesh Sensors in Gas-Liquid Flows of Dilute Aqueous Solutions

Sensors ◽  
2020 ◽  
Vol 20 (24) ◽  
pp. 7114
Author(s):  
Philipp Wiedemann ◽  
Felipe de Assis Dias ◽  
Eckhard Schleicher ◽  
Uwe Hampel
Keyword(s):  
Temperature Effects ◽  
Temperature Compensation ◽  
Phase Distribution ◽  
Industrial Applications ◽  
Operating Conditions ◽  
Wire Mesh ◽  
Effect Of Temperature ◽  
Experimental Investigations ◽  
Fluid Temperature ◽  
Two Phase

Wire-mesh sensors are well-established scientific instruments for measuring the spatio-temporal phase distribution of two-phase flows based on different electrical conductivities of the phases. Presently, these instruments are also applied in industrial processes and need to cope with dynamic operating conditions increasingly. However, since the quantification of phase fractions is achieved by normalizing signals with respect to a separately recorded reference measurement, the results are sensitive to temperature differences in any application. Therefore, the present study aims at proposing a method to compensate temperature effects in the data processing procedure. Firstly, a general approach is theoretically derived from the underlying measurement principle and compensation procedures for the electrical conductivity from literature models. Additionally, a novel semi-empirical model is developed on the basis of electrochemical fundamentals. Experimental investigations are performed using a single-phase water loop with adjustable fluid temperature in order to verify the theoretical approach for wire-mesh sensor applications and to compare the different compensation models by means of real data. Finally, the preferred model is used to demonstrate the effect of temperature compensation with selected sets of experimental two-phase data from a previous study. The results are discussed in detail and show that temperature effects need to be handled carefully—not merely in industrial applications, but particularly in laboratory experiments.

Industrial Validation and Verification Approach for External Fiber Optic Based Leak Detection

2020 ◽  
Author(s):  
Chris Minto ◽  
Alastair Godfrey ◽  
Paul Clarkson ◽  
Alasdair Murray
Keyword(s):  
Negative Pressure ◽  
Large Scale ◽  
Pressure Pulse ◽  
Fiber Optic ◽  
Leak Detection ◽  
Probability Of Detection ◽  
Test Facility ◽  
Detection Systems ◽  
Mode Behavior ◽  
Valve Opening

Abstract External Leak Detection systems based on distributed fiber optic sensors (DFOS) offer the exciting potential to significantly reduce the overall amount of spilled product before a leak is detected and localized. Such systems are not well represented by industrial standards or recommended procedures and as a result most industrial attempts to validate the technology have been research-oriented and whilst these have contributed greatly to the knowledge base they have never been aimed at a full validation of the technology. Additionally, the lack of test facilities that can support the significant scale needed for validation (> 500 m straight line run) have led to a paucity of attempts to provide a baseline validation of such sensing technology leading to a lack of certainty over performance claims within the industrial user base and no robust method of testing such claims. With a significant customer base of deployed systems, OptaSense have developed a reproducible technology validation approach using full scale, full flow, representative leaks at the CTDUT test facility in Brazil. We have used these tests to validate 15 lpm leaks, detected and classified via their negative pressure pulse in ∼10 seconds and larger 150 lpm leaks, detected by our four modes of leak detection in ∼1 minute. Valid automated detection of a negative pressure pulse (NPP) was observed down to 1 mm holes in the pipe — representing a leak rate of only 1.5 lpm. The use of the NPP is shown to be a compelling rapid detection method. However, care is needed in testing since the use of a valve opening to stimulate a pulse is shown to be significantly inferior to burst disks due to the increased valve-opening time giving rise to a reduced amplitude pressure pulse. The conventional external leak detection signals of Orifice Noise, Ground Strain and Temperature Change can all be shown to be replicated at the large-scale test facility by these means leading to the potential to establish a valid Probability of Detection for all approaches. With validation now possible, client verification on site has also been addressed with a two-step approach being developed that replicates the validation approach detailed above. Negative Pressure Pulses are used for stand-alone leak detection and can be safely stimulated via accessible valve sites and product release via a burst disc / valve and orifice combination. To stimulate the Multiple Mode behavior (excluding Negative Pressure Pulse) a controlled fluid release injection mechanism has been developed, which can be introduced at an appropriate offset from the pipeline (mirrored from fiber offset) at any desired location with the minimum of preparation. Ground probe deployment techniques have been designed to simulate a leak event at the appropriate location resulting in the similar external signals arising on the fiber. This paper presents the benefits of large-scale validation approaches to performance bound acoustic-based leak detection systems and presents established options for in-field verification on customer owned systems.

Internal Bearing Chamber Wall Heat Transfer as a Function of Operating Conditions and Chamber Geometry

1999 ◽  
Author(s):  
Stefan Busam ◽  
Axel Glahn ◽  
Sigmar Wittig
Keyword(s):  
Heat Transfer ◽  
Operating Conditions ◽  
Chamber Wall ◽  
Test Facility ◽  
Detailed Knowledge ◽  
Wall Heat Transfer ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Dimensional Parameter ◽  
Secondary Air

Increasing efficiencies of modern aero-engines are accompanied by rising turbine inlet temperatures, pressure levels and rotational speeds. These operating conditions require a detailed knowledge of two-phase flow phenomena in secondary air and lubrication oil systems in order to predict correctly the heat transfer to the oil. It has been found in earlier investigations that especially at high rotational speeds the heat transfer rate within the bearing chambers is significantly increased with negative effects on the heat to oil management. Furthermore, operating conditions are reached where oil coking and oil fires are more likely to occur. Therefore, besides heat sources like bearing friction and churning, the heat transfer along the housing wall has to be considered in order to meet safety and reliability criteria. Based on our recent publications as well as new measurements of local and mean heat transfer coefficients, which were obtained at our test facility for engine relevant operating conditions, an equation for the internal bearing chamber wall heat transfer is proposed. Nusselt numbers are expressed as a function of non-dimensional parameter groups covering influences of chamber geometry, flow rates and shaft speed.

Field Testing of Negative-Wave Leak Detection Systems

2014 ◽  
Author(s):  
Shane Siebenaler ◽  
Eric Tervo ◽  
Paul Vinh ◽  
Chris Lewis
Keyword(s):  
Response Times ◽  
Dynamic Pressure ◽  
User Interaction ◽  
Field Testing ◽  
Leak Detection ◽  
Operating Conditions ◽  
Negative Wave ◽  
Oil Pipeline ◽  
Detection Systems ◽  
The Cost

The pipeline industry is improving its ability to detect and locate leaks through emerging technologies. There has been a variety of research in recent years aimed at further development of sensor-based technologies for leak detection. A key obstacle to retrofitting existing pipelines with leak detection technologies is the cost and risk of installing hardware, particularly those sensors that require excavation near the pipe. There are many advantages to employing leak detection systems that can leverage existing instrumentation access locations. One such technology may be negative-wave leak detection systems. Negative-wave technologies work by measuring dynamic pressure changes in the pipe. It should be noted that some negative-wave systems require line modifications to accommodate multiple transmitters. While such systems have been on the market for many years, there is insufficient data available about their performance under various pipeline operating conditions for widespread adoption. In an effort to close many information gaps on the performance envelope of negative-wave technologies, a PRCI-funded field test was performed on a 41-kilometer segment of a 30-inch diameter heavy crude oil pipeline. Products from three suppliers were installed at either end of the test segment. Actual commodity withdrawals were conducted at a remote valve site approximately 21 kilometers into the segment during various operations to test the systems’ abilities to detect the withdrawals without direct user interaction. These test points included withdrawals during steady-state flowing, pump startup, and shutdown conditions. Data were collected from each system to determine their abilities to detect leaks under various conditions, abilities to locate the leak, false alarm rates, and response times. This test provided significant insight into the performance of such systems over the range of conditions tested. The key focus of this paper is the approach for conducting such multi-vendor commodity withdrawals. This project required some unique considerations for its execution. Such considerations are also documented to provide input to others who are considering such a test.

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