The Williams Companies, Inc., is an American energy company based in Tulsa, Oklahoma. Its core business is natural gas processing and transportation, with additional petroleum and electricity generation assets. A Fortune 500 company, its common stock is a component of the S&P 500.
Expanded skill sets will be needed as the coatings industry embraces new technologies.
Electric Motor Drives in the power range from 1,000 to 60,000 HP are often used to drive centrifugal compressors. One of the key reliability issues is the treatment and management of torsional vibrations. The torsional behavior impacts shaft endurance limits and operational flexibility. In this paper, a methodology used to ensure torsional integrity in standardized Electric-motor-driven gas compressor packages is described. The electric drive ("drive")may be a variable frequency drive (VFD), or a constant speed electric motor. In addition to steady-state torsional analysis, the drive harmonics from electrical sources (steady-state pulsation) and the drive's characteristics at fault-events such as phase-tophase faults (transients) are incorporated into the torsional model to perform a complete torsional analysis. Shaft stresses are evaluated over a wide range of motor frame sizes, and consequently couplings and gearboxes. Couplings and gearboxes are designed to handle the mean torque and peak transient torques as appropriate.
The use of numerical modelling in solving geotechnical problems has significantly increased in the past two decades due to its widespread acceptance by geotechnical engineers and the rapid growth in computing power. In this work the failure of a slurry wall system which was the subject of a dispute between two contractors is investigated. The failed slurry wall was part of an excavation shoring system for a power plant intake structure in Australia. The construction sequence provided by the wall designer/contractor was not followed by the main contractor. The slurry wall failed and resulted in flooding of the excavation and significant ground deformations. This was followed by extensive and costly remediation works. The main contractor believed that the adopted construction procedure was not responsible for the failure, but its inadequate design was. This paper presents the methodology and results of modelling undertaken of the slurry wall installation to determine the magnitudes of induced stresses and displacements in the wall as a result of the adjacent excavation for two scenarios, "as designed" and "as constructed". The analysis was carried out utilizing the FLAC 2D program (Itasca group) for a plane strain case, and its built-in elastic-plastic Mohr-Coulomb stress-strain model.
The work in this paper concerns the axisymmetric pipe flow of a Herschel-Bulkley fluid, with the aim of determining a relation between the critical velocity (defining the transition between laminar and turbulent flow) and the pipe diameter in terms of the Reynolds number Re-3. The asymptotic behaviour for large and small pipes is examined and simple expressions for the leading order terms are presented. Results are then compared with experimental data. A nonlinear regression analysis shows that for the tested fluids the transition occurs at similar values to the Newtonian case, namely in the range 2100 < Re-3 < 2500.
Predicting the flow behaviour, most notably, the apparent viscosity and yield stress of sludge mixtures inside the anaerobic digester is essential because it helps optimize the mixing system in digesters. This paper investigates the rheology of sludge mixtures as a function of digested sludge volume fraction. Sludge mixtures exhibited non-Newtonian, shear thinning, yield stress behaviour. The apparent viscosity and yield stress of sludge mixtures prepared at the same total solids concentration was influenced by the interactions within the digested sludge and increased with the volume fraction of digested sludge - highlighted using shear compliance and shear modulus of sludge mixtures. However, when a thickened primary - secondary sludge mixture was mixed with dilute digested sludge, the apparent viscosity and yield stress decreased with increasing the volume fraction of digested sludge. This was caused by the dilution effect leading to a reduction in the hydrodynamic and non-hydrodynamic interactions when dilute digested sludge was added. Correlations were developed to predict the apparent viscosity and yield stress of the mixtures as a function of the digested sludge volume fraction and total solids concentration of the mixtures. The parameters of correlations can be estimated using pH of sludge. The shear and complex modulus were also modelled and they followed an exponential relationship with increasing digested sludge volume fraction.
