Case Studies

Latest Case Studies and white papers

Centrifugal pump vibration caused by super-synchronous shaft instability

Centrifugal pump vibration caused by super-synchronous shaft instability

Donald R Smith, Stephane M Price and Friedrich K Kunj

Many centrifugal pump vibration problems are due to synchronous phenomena such as vane-pass frequency energy and running speed energy. To address such problems, guidelines have been developed to assist with their identification and to evaluate their severity. However, nonsynchronous phenomenon such as recirculation, stage-stall, and shaft instabilities can also cause vibration problems. These types of problems are more difficult or diagnose, since the excitation mechanisms are less obvious. Discussed herein are field measurements and computer analysis that were done to analyze and solve supersynchronous shaft vibration problem on a two-stage horizontal centrifugal coke crusher pump and a vertical single-stage centrifugal water pump. These pumps were marginally stable at low discharge pressures, but were unstable at high discharge pressures. Field tests indicated that the shaft instability vibrations of both pumps could be removed by installing vanes on the back side of the impellers (“pumpout” vanes). Although the pumpout vanes were very effective in eliminating the destabilizing forces on these pumps, the exact effects of the pumpout vanes on the rotor instabilities are not clearly understood. The authors feel that additional analytical and experimental work should be conducted to fully understand the effects of the pumpout vanes.

Friction Stir Welding-What is it?

Friction Stir Welding-What is it?

TWI Global

Friction stir welding was invented by Wayne Thomas at TWI in 1991, with patents filed in Europe, the USA, Japan and Australia. Further work to study the process was undertaken at TWI in 1992 with the project titled, ‘Development of the New Friction Stir Technique for Welding Aluminum.’ Industrial production using FSW was in progress by the mid-1990s, making it one of the shortest time periods for any welding process to go from invention to widespread use. The non-consumable tool, with a profiled probe and shoulder, is rotated and plunged into the interface between two work pieces. It then traverses along the joint line, causing the material to heat and soften. The shoulder also acts to contain this plasticized material, which is mechanically mixed to create a solid phase weld.

COMPARISON BETWEEN CREEP FAILURE ANALYSIS AND MAGNETIC BARKAHUSEN NOISE RESULTS

COMPARISON BETWEEN CREEP FAILURE ANALYSIS AND MAGNETIC BARKAHUSEN NOISE RESULTS

Jonhson D. ANGELO, Linilson R. PADOVESE, Manuel ALBERTERIS, Eduardo R. BERNASCONNI

The Barkhausen effect is a name given to the noise in the magnetic output of a ferromagnet when the magnetizing force applied to it is changed. Discovered by German physicist Heinrich Barkhausen in 1919, it is caused by rapid changes of size of magnetic domains (similarly magnetically oriented atoms in ferromagnetic materials).
On this work authors have compared the results obtained after a conventional creep failure analysis and magnetic Barkhausen noise. They chose one region without creep damage that was named as standard. Two other regions with creep damage were named as T1 and T2. The sample T1 after optical metallographic analysis has presented level A and B of creep damage according the method of Neubauer to estimate the rest life of creeping by replicas. The sample T2 after optical metallographic analysis has presented level C and D of creep damage according the same method. Based on the failure analysis, they evaluated MBR analysis and compared the results.
Creep damage is the root causes of many failure equipments on heavy industries that work at non conventional temperature, specially boilers and furnaces. It's very difficult detect regions with creep damage by others conventional NDT methods. Replicas are the most used NDT technique to detect creep damage but this technique is based on result of discrete point; may not cover the entire surface of tubes. The electromagnetic techniques are sensible to micro structural change that modifies the magnetic permeability of the material. The authors have emphasized these promising techniques - remote field and magnetic Barkausen noise. The details of the write-up may be downloaded clicking the blue rectangle below;

Axial Thrust calculation in High Pressure Centrifugal Compressors

Axial Thrust calculation in High Pressure Centrifugal Compressors

Leonardo Baldassarre, Andrea Bernocchi, Emanuele Rizzo, Michele Fontana, Francesco Maiuolo
Florence, Italy

The main difficulty of axial thrust calculation lies in the correct prediction of the static pressure distribution over the external surface of the impeller hub and shroud. This distribution depends on a large set of parameters, including rotor geometry, operating conditions, properties of the process gas, leakages flows across the rotor-stator seals. A detailed fluid-dynamic model of the gas in the cavities between impeller and diaphragm was developed and applied first to stage model tests and then to high-pressure centrifugal compressors, and its predictability was assessed by direct comparison with experimental data. The compressors were tested in full load conditions, with thrust bearing pads equipped with load cells, and the thrust values were recorded for several points across the operating envelope.

A Case Study on Design of Ammonia Condenser: Effect of Independent Variables

A Case Study on Design of Ammonia Condenser: Effect of Independent Variables

Ronak Patel, Sanjay Patel and Raju Mewada, Nirma University

Shell and tube heat exchangers are widely used in process industries for exchange of heat from one fluid to another by indirect means. Design of heat exchanger is lengthy and iterative procedure and overall cost of heat exchanger depends upon various independent variables. Here in present study, we have considered ammonia condenser for study purpose. As ammonia is produced widely in urea manufacturing industries. In present study, we have studied effect of various independent variables like tube outside diameter, tube length and baffle spacing on heat transfer coefficient and pressure drop.
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Shycocan: Hypercharge Corona Canon air-purifier is intended to disable air and surface-borne coronaviruses

Shycocan: Hypercharge Corona Canon air-purifier is intended to disable air and surface-borne coronaviruses

by Rajah Vijay Kumar, D.Sc. Bangaluru

Scalene Hypercharge Corona Canon (SHYCOCAN™), is intended for realtime attenuation and disabling of certain viruses, including coronaviruses - the virus associated with COVID-19, and the elimination of expected viral loads of Influenza B. This device is a simple, portable, and sensitive methodology intended to disable air and surface borne coronaviruses. Exposure to atmospheric and surface contamination of SARS-CoV-2 can randomly occur. The SHYCOCAN technology is intended to inactivate coronaviruses in the air and on surfaces. The negative charge-seeking guidance mechanism of the virus’ Spike Protein can be disabled and neutralized by trillions of electrons generated per second by the SHYCOCAN™. High-intensity discharge of electrons relies on precision design and geometry of the proprietary Photon-Mediated Electron Emitters (PMEE) in the device. This unique and innovative device can be readily and cost-effectively manufactured to meet demand.

Application of Nanosize Zeolite Molecular Sieves for Medical Oxygen Concentration

Application of Nanosize Zeolite Molecular Sieves for Medical Oxygen Concentration

Mingfei Pan, Hecham M. Omar and Sohrab Rohani, University of Western Ontario,
ON N6A 5B9, Canada;

The development of a portable oxygen concentrator is of prime significance for patients with respiratory problems. This paper presents a portable concentrator prototype design using the pressure/vacuum swing adsorption (PVSA) cycle with a deep evacuation step (−0.82 barg) instead of desorption with purge flow to simplify the oxygen production process. The output of the oxygen concentrator is a ~90 vol % enriched oxygen stream in a continuous adsorption and desorption cycle (cycle time ~90 s). The size of the adsorption column is 3 cm in diameter and 20 cm in length.
A Li+ exchanged 13X nanosize zeolite is used as the adsorbent to selectively adsorb nitrogen from air. A dynamic model of the pressure and vacuum swing adsorption units was developed to study the pressurization and depressurization process inside the microporous area of nanosized zeolites. The describing equations were solved using COMSOL Multiphysics Chemical Engineering module. The output flow rate and oxygen concentration results from the simulation model were compared with the experimental data. Velocity and concentration profiles were obtained to study the adsorption process and optimize the operational parameters.
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Failure Mechanisms and Material Degradations at High Temperatures in Ammonia Plants

Failure Mechanisms and Material Degradations at High Temperatures in Ammonia Plants

Dr. Jürgen Korkhaus
BASF Aktiengesellschaft and Dr. Rainer Feser
BASF Aktiengesellschaft

The long history of ammonia production at BASF started with the development of the process in the early 20th century by Fritz Haber and Carl Bosch. In September 1913 in Ludwigshafen, Germany the first plant went into service with a capacity of 30 t (66 000 lbs) ammonia per day. Today BASF operates two plants in Ludwigshafen (Ammonia 3: conventional steam reforming plant, 1971, Ammonia 4: Braun purifier
plant, 1982) and one plant in Antwerp/Belgium (Uhde design, 1990). From the early days until now the limitation of material degradation processes at high temperatures to a tolerable scale was always a demanding task for the maintenance and operating staff in the plants to assure a safe and economic ammonia production. Read More..by downloading : click the blue rectangle

Accelerated Curing of M30 Grade Concrete Specimen Using Microwave Energy

Accelerated Curing of M30 Grade Concrete Specimen Using Microwave Energy

T.R. Neelakantan, S. Ramasundaram and R. Vinoth

Compressive strength of concrete mainly depends on the composition, size of the components, water content ratio, curing conditions etc. The 28 days strength is usually taken as reference strength. To find this, a moist curing of concrete specimen for 28 days is required. For economical construction, the 28 days strength is required well in advance and accelerated curing techniques are helpful to some extent. In the conventional accelerated curing, conduction of heat takes place from surface to the core of the concrete specimen and hence there exist a temperature gradient, leading to thermal stress in concrete. In this study, microwave radiation energy is used for accelerated curing in which the temperature change is uniform through out the concrete. The concrete cubes were cured with microwave energy after 6, 18 and 24 h of delay time of M30 grade concrete. Different microwave energy levels (360, 540, 720, 900 W) and microwave curing durations (20, 30, 40, 50 min) were used. The compressive strength developed after the microwave curing is compared with the 28 days strength estimated with the usual procedure. The results obtained were suitably plotted as graphs so that the graphs can be used to estimate the 28 days strength from the early strength obtained by microwave curing. The results of the study show the potential and scope for further research with different grade of concrete

Factors Affecting Thermal Stress Resistance 
of Ceramic Materials

Factors Affecting Thermal Stress Resistance
of Ceramic Materials

W. D. KINGERY

Susceptibility of ceramic materials to thermal stresses has been recognized for a long time. More than one hundred years ago equations for thermal stresses are arising from temperature gradients in a cylinder were derived by Duhamel (1838).‘ Since that time, about thirty papers have appeared which mainly consider the calculation of thermal stresses in an infinite cylinder subjected to temperature gradients. It is apparent that thermal stresses are not a new or uninvestigated phenomenon.
New attempts have been made to define and to measure a material property which can be called “resistance to thermal stresses.” Although these attempts have not been completely successful in a quantitative way, they have led to a much improved understanding of the factors that contribute to thermal stress resistance. It is the purpose of the present paper to consider these factors and their effect on thermal stress resistance.

Why all the hoopla about hydrogen?

Why all the hoopla about hydrogen?

ROB NIKOLEWSKI

Hydrogen’s simplicity and versatility can be applied to reduce greenhouse gas emissions across an ever-growing number of manufacturing and power segments, while also advancing the adoption and distribution of renewable energy.
The relatively high cost of adding hydrogen into the value chain has some skeptics questioning just how extensive its role will be but supporters say economies of scale — combined with a lot of government spending — will lead to an energy system at least partially infused with hydrogen. Read More following the link below

Earthing guide for surge protection

Earthing guide for surge protection

Eaton Electric Ltd., UK

A lightning flash is caused by an electrical current flowing in the
atmosphere. Moist air currents interacting with ice particles within a cloud lead to the formation of concentrations of electric charges at different heights. Very large voltage differences, of the order of many millions of volts, develop between the charge concentrations and the base of the cloud and the surface of the earth. When this voltage difference becomes sufficient to overcome atmospheric resistance, a lightning stroke occurs. Most lightning strokes take place cloud-to-cloud but some are cloud-to-ground. As a result of cloud to ground lightening, installations which are prone to attract lightening and get damaged due to high current need to be well protected.
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