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Maintaining Commercial Roofs
Published in Ryan Cruzan, Manager’s Guide to Preventive Building Maintenance, 2020
Roof fasteners are used to secure roofing materials to the roof deck. Flashing is the rain-proof transitions between horizontal and vertical surfaces, between the roof and roof penetrations, and around roof mounted equipment.
Wind versus Storm Surge—Hurricane Irma Experience
Published in Syed Mehdi Ashraf, Structural Building Design: Wind and Flood Loads, 2018
Section 1503.2 of the 2015 International Business Code (IBC) requires that flashing be installed at the intersection of walls and roofs, at gutters, at locations of change of slope, and around roof openings such as vents, skylights and turbines to prevent moisture penetration into the building. Flashings are the most vulnerable areas that permit moisture penetration inside the building, which results in damage to the interior finishes. Wind-driven rain during hurricane-type events will result in an exacerbation of a pre-existing condition, resulting in a larger amount of water intrusion.
Monolithic bearing walls — masonry, stone, concrete
Published in Mayine L. Yu, Skins, Envelopes, and Enclosures, 2013
Flashing is a waterproof, formable material such as metal (stainless steel, copper, zinc, etc.); waterproofed woven fiber, felt, plastic; or man-made rubber. In monolithic walls, flashing installed in stepped configuration through brick courses can drain moisture to the exterior if small holes are installed in the outer wythe to permit moisture to drip out through weep holes. There are many options and products to further improve weep holes: plastic tubes can be used to set a minimum width, or sometimes can be a full brick high, a long oval, set into the head joint. If too large, pests and insects are liable to obstruct the opening, so the manufactured weep tubes are sometimes given a filler material. Cotton rope was used historically to conduct moisture out, like a wick, and can also be offered as weep filler.
The square root rule – a case study of a scaling factor for machines with dynamic similitude
Published in Mechanics Based Design of Structures and Machines, 2020
Robert E. Farrell, Jiradech Kongthon
According to SPI statistics reported in December 2016, the apparent U.S. consumption of plastics goods is expected to top $300 billion. In the injection molding process, plastics pellets of thermoplastic material are melted in an injection unit by a plasticizing screw turning inside a heated barrel. This results in a charge of thermoplastic material in a molten state (referred to as melt). After the mold is closed and clamped with high force, the melt is then injected at pressures as high as 138 MPa (20,000 psi) into the mold. The melt is forced through a runner system and gated to each cavity in the mold. After the parts have cooled, the mold is opened, and the parts are ejected. The mold is closed again and the process repeats. Because plastic melt pressure can be as high as 138 MPa, considerable clamping force must be applied to keep the mold from flashing.
Stability Tests and Analysis of a Low-Pressure Natural Circulation Loop with Flashing Instability
Published in Nuclear Technology, 2023
Taiyang Zhang, Caleb S. Brooks
During the transition from single-phase to two-phase operation, the natural circulation system first crosses a threshold for flashing to occur at the hot-leg top and then soon approaches a H-S stability boundary where the ratio in Eq. (45) is mainly controlled by for the following reasoning. Around the operational threshold for flashing to occur, the steady-state void fraction at chimney outlet becomes highly sensitive to the flashing region length, as shown in Fig. 11 by the steep profile slope near the flashing boundary. As the operation further increases enthalpy in the chimney and elongates the flashing region, therefore experiences a rapid increase from zero to a noticeable finite value. Meanwhile, steady-state flow velocity only slowly increases from a nonzero base previously established by single-phase natural circulation. Consequently, the RHS ratio in Eq. (45) exhibits a steep increase dominated by the trend of , indicating a rapid introduction of destabilizing feedback from two-phase gravitational pressure drop overwhelming the stabilizing hydraulic resistance, which is still maintained relatively weak by the low flow rate. The result is a highly unstable system. This trend is also consistent with the steep decay ratio increase in the vicinity of the H-S stability boundary shown in Fig. 12. In general, the target natural circulation system typically experiences flashing instability soon after crossing the threshold for flashing to occur because the void fraction at the chimney outlet becomes sensitive to the operational parameters and experiences a rapid increase, which quickly introduces and develops a delayed two-phase gravitational feedback mechanism whose destabilizing effect cannot be defeated by inertia or hydraulic resistance under the low flow rate.