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Lubrication of Distribution Electrical Equipment
Published in Bella H. Chudnovsky, Electrical Power Transmission and Distribution, 2017
Viscosity is a measure of flowability. It is the resistance to flow caused by internal friction between the lubricant molecules. This characteristic helps determine the load-carrying capacity, thickness of the lubricating film, and operating temperature. In selecting a lubricant for a particular application, definition of the required viscosity level at start-ups and during operation conditions is critically important to ensure optimum lubricant performance. Viscosity can be expressed as the number of seconds required for a measured volume of oil to flow through a specified orifice in standard conditions. In the United States viscosity is usually measured and specified between 100°F and 210°F (~40–100°C).
Properties of bulk materials
Published in D.V. Subba Rao, The Belt Conveyor, 2020
The flowability is determined by material characteristics such as size and shape of the fine particles and lumps, roughness or smoothness of the surface of the material particles, proportion of fines and lumps present, and moisture content of the material.
Sprayed concrete systems in the Gotthard base tunnel
Published in Erik Stefan Bernard, Shotcrete: More Engineering Developments, 2004
The spraying robot for this task was part of the shaft boring machine. The only economically practicable solution for supplying the concrete to the pump installed on the shaft boring machine was supply through a downpipe. In the most extreme case, the concrete falls 800 m before it is fed to a pump via an energy dissipator. The loss of consistency suffered by the concrete during the fall is very high. Because remixing at the bottom of the shaft is out of the question due to restricted space availability, the freshly mixed concrete must start with a spread size of at least 64m (Flowtable test, EN 12350-5 1999) in order to be sufficiently fluid for pumping upon arrival at the bottom. Achieving such high fluidity while still maintaining the specified low w/c ratio calls for flowability-friendly additives. Fly-ash in combination with silica fume was again shown to be the most efficient workability aids. Super-plasticisers specially developed for sprayed concrete and designed for improving flowability are necessary for achieving the required flowability characteristics. The mix design for the sprayed concrete conveyed by downpipe to the transfer station was as follows: Cement:475 kg/m3 slag cement,Holcim Gottardo 310Aggregate:Granitic aggregate Sedrun, mica removed20% 0–1 mm45% l–4 mm35% 4–8 mmAdditives:25 kg/m3 silica fume, SikaFume-AT 4225 kg/m3 fly-ashAdmixture:1.4% SikaTard-AT73
Effect of bentonite on the stability of fresh cement slurry
Published in Journal of Sustainable Cement-Based Materials, 2022
Ping Zhang, Lin Chen, Ruishi Xie, Lixian Song, Jun Jiang
High-flow cement-based materials, such as cementitious grout, self-consolidating concrete or mortar, have been rapidly developing and widely using in many countries for different applications and structural configurations [1, 2]. Two primary properties, flowability and stability, must be considered in the mix design and application of these cement-based materials [3, 4]. Specifically, flowability is the ability to deformation or flowing under its self-weight, and another property is to remain homogeneous while cement-based material owns a good flowability under fresh state. Usually, good flowability can be achieved easily according to suitable water to powder ratio and water reducing admixtures [5, 6]. At the same time, the stability of fresh cement-based materials is also ensured, and the approaches routes contain introducing viscosity modifying admixtures (VMAs) and increasing the content of powder [7–9]. However, high powder content is not the best choice for achieving the designed stability anymore due to the environmental problems and high CO2 emission in the world; Furthermore, the strategy is not also suitable for low-strength cement-based materials owing to the possible strength surplus. Currently, incorporating VMA into cement-based materials is becoming the most popular method for achieving good stability [10, 11].
Use of novel pour point depressant synthesized from vegetable oil for waxy crude oil
Published in Petroleum Science and Technology, 2020
Anas Azeem, Rahul Kumar, Biswadeep Pal, Tarun Kumar Naiya
Any material that is present with a crystallizing compound as it crystallizes can influence crystallization (Sangwal 1996). In crude oil, these materials include the solvent (generally shorter chain hydrocarbons) where crystallization is taking place, naturally present material such as asphaltenes, resins and water and artificially added materials such as inhibitors and flow improvers. These materials can influence the thermodynamics and kinetics of crystal growth as well as the solubility of the crystal (Sangwal 1996; Fang et al. 2012). Crystallization is the first step of the deposition mechanism, meaning that changes in crystallization will influence deposition and gelation. Additionally, some materials that do not influence crystallization are capable of influencing the fluid flow, gelation and/or deposition of the wax crystals (Bacon et al. 2010; Taraneh et al. 2008). Petroleum companies have dedicated a significant portion of time and money to exploit these issues in attempt to mitigate wax deposition. Additives aid in flowability by a number of different ways: lowering the cloud point of the system, modifying the crystal size and shape to retard gel formation by preventing the formation of large wax crystal lattices, reducing the oil viscosity and modifying the surface of the pipe wall to prevent deposition (Ashbaugh et al. 2002).