![]() Prior to the determination of the mast length, the distance between the inner edge of the mast and the centerline vertical to rail level, namely mast gauge is determined. Length of the mast depends on the design of the connection between mast and foundation and is determined during the system design. In many cases, the additional cost of an external flush or dual pressurized seal was justified on the basis of past plant mechanical seal maintenance history and the loss of revenue when the standby pump was under maintenance and the operating pump failed.ġ, Single cantilever mast 3, 4, dual cantilever mast 5, midpoint mast 6, midpoint anchor mast 8, anchor mast. A contingency recommendation where a clean external flush was not available was to use a dual pressurized seal. This best practice has been used since the 1990s to thoroughly investigate, with the process engineers, the possibility of using a clean external flush source in services where solid particles were contained in the seal fluid. Eventual modification to a clean external flush or a dual pressurized seal has significantly increased seal MTBFs (greater than 48 months). Lessons Learnedįlush line strainers and cyclone separators have been the cause of low seal MTBFs (less than 12 months) in many applications where the seal fluid contains solid particles. Using an external clean flush, if available, or a dual pressurized seal arrangement will eliminate the need for flush line strainers and cyclone separators and ensure optimum mechanical seal MTBFs. In services where the pumped fluid can contain solids, API 610 and API 682 both offer the option of using flush line strainers or cyclone separators.įlush line strainers can become blocked resulting in immediate seal failure.Ĭyclone separator effectiveness is dependent on the relative density difference between the fluid and solid particles and the flush line piping (adequate slope for the debris drain line back to the pump suction). Mechanical seal reliability is significantly affected by the operational characteristics of the flush system and its components. Both dry and resin systems will ultimately catch the projectile via re-orientation of the yarns and drawing, a net catching analogy is commonly used, but is related to excessive shearing of the ply and scissoring of the yarns.Īvoid the use of flush line strainers and cyclone separators in dirty services, and use an external flush or a dual pressurized seal to optimize mechanical seal MTBFs: When using a unidirectional (UD) yarn architecture, which potentially can yield a very high volume of fiber up to 85% in the composite system, a resin is usually employed to “bond” the ply layers together, typically in a 0/90 configuration. The pull-out of the yarns, during the impact, provides an energy dissipating mechanism and relaxes the contact forces, and hence forces within the yarns. ![]() However, woven architecture with little or no resin are commonly used in bullet proof vest. The ideal ply architecture would have straight fibers to prevent dispersion of waves at fiber or yarn cross-over points in a woven ply architecture. This would result in a very high longitudinal and transverse wave speed along the fiber, thus engaging more material and allowing greater dissipation of energy. The ideal fiber would have a very high stiffness and strength with a very low density and yarn dtex, but also a high melting temperature. The fundamental design selection in a protective system is the fiber type, and thus the yarn. Lorenzo Iannucci, in Comprehensive Composite Materials II, 2018 8.16.1.1 Design Concepts This chapter provides guidance on the selection of an appropriate foundation scheme: (1) to contribute to the reduction of total construction costs (2) tailored to the foundation load, landform, and geological conditions to ensure the safe and stable operation of the line and grid (3) where the advantages of each foundation are fully utilized so as to reduce the volume of earthworks and minimize the effect of construction activities on the environment. The type of tower foundation selected needs to take into account such factors as tower structure type, terrain and relief characteristics, geological conditions at the tower position, construction, and transport conditions. The type selection and optimization design of tower foundations, as well as construction techniques and technical schemes of foundations, are of decisive importance to the construction costs, safety, stability, environmental protection, and soil and water conservation of transmission line projects. In UHV Transmission Technology, 2018 Abstract
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