Through-holes

Wider passages are provided for vapours and the comparatively narrow tubes, which are usually fitted through holes bored in cork or rubber stoppers, are absent this considerably diminishes danger in violent reactions and also tends to give better results in distillation under reduced pressure as well as diminishing the hazard of choking. ... 

Fig. 8. Protection of a plated through-hole in a PWB during etching by using a tenting dry-film photoresist.

Sir Joseph Swan, as a result of his quest for carbon fiber for lamp filaments (2), learned how to denitrate nitrocellulose using ammonium sulfide. In 1885 he exhibited the first textiles made from this new artificial sHk, but with carbon fiber being his main theme he failed to foUow up on the textile possibihties. Meanwhile Count Hilaire de Chardoimet (3) was researching the nitrocellulose route and had perfected his first fibers and textiles in time for the Paris Exhibition in 1889. There he got the necessary financial backing for the first Chardoimet silk factory in Besancon in 1890. His process involved treating mulberry leaves with nitric and sulfuric acids to form cellulose nitrate which could be dissolved in ether and alcohol. This collodion solution could be extmded through holes in a spinneret into warm air where solvent evaporation led to the formation of soHd cellulose nitrate filaments. 

After exiting the economizer, the feedwater is directed iato the boilet s cylindrical steam dmm via a common header pipe that penetrates the dmm s wall and distributes the water evenly within the dmm through holes drilled ia the upper side of the distribution pipe. Because the distribution pipe is located axially below the waterline ia the lower section of the steam dmm, the incoming feedwater mixes thoroughly with the water ia the dmm and prevents any significantly uneven temperature distributions within the dmm. 

Newer variations of the normal asphaltic subbase include a permeable version (4) which allows rainwater to trickle through holes punched into the underpad and to drain away through the asphaltic subbase to a pipe grid system under the base (Fig. 4). 

In duidized-bed roasters (19), the concentrate is suspended in an upward-moving air stream. The vessel is a refractory-lined steel shell with air entering through holes in a refractory-lined plate at the base. The sulfur dioxide concentration of the exit gas is 10—15%. 

Fig. 2. Press-Fit pias of A, soHd B, crescent or C, spHt-beam (compHant) design, are forced iato through-holes of priated circuit boards where they...

Fig. 2. Multilayer printed circuit board composite. Constmction is multiple layers of epoxy—glass and foil copper. Foil copper outermost layer and drilled through-holes are sequentially plated with electroless copper, electrolytic copper, electroless nickel, and electroless gold.

Yullj Additive Method. No electrolytic plating step is used ia the fully additive process. The copper circuit is formed directly on the board without a continuous copper film. Heavy-build electroless coppers are used to iacrease the final thickness of the entire circuit. This process is much more difficult to control than the others. Additive processiag is becoming increasingly important ia high aspect ratio, very small diameter through-holes that caimot be easily electrolyticaHy plated. 

Pellet Mills Pellet mills operate on the principle shown in Fig. 20-92. Moist, plastic feed is pushed through holes in dies of various shapes. The friction of the material in the die holes supplies the resistance necessary for compaction. Adjustable knives shear the rodlike extrudates into pellets of the desired length. Although several designs are in use, the most commonly used pellet mills operate by applying power to the die and rotating it around a freely turning roller with Fixed horizontal or vertical axis. 

Vapor cloud explosions can result if clouds of flammable vapor in air are formed. It is important to understand how hquids and gases flow through holes in equipment and how resulting vapor or gas clouds are dispersed in air. 

In the constant-strain method, the specimen is stretched or bent to a fixed position at the start of the test. The most common shape of the specimens used for constant-strain testing is the U-beud, hairpin, or horseshoe type. A bolt is placed through holes in the legs of the specimen, and it is loaded by tightening a nut on the bolt. In some cases, the stress may be reduced during the test as a result of creep. In the constant-load test the specimen is supported horizontally at each end... 

The air enters the annular spaee between the liner and easing, and is admitted into the spaee within the liner through holes and slots beeause of the pressure differenee. The design of these holes and slots divides the liner into distinet zones for flame stabilization, eombustion, dilution, and provides film eooling of the liner. 

This combustion product is diluted with air entering through holes on the liner to make the temperature appropriate for blade material and to have enough volume-flow in the dilution zone. Air is jet-penetrated mainly because of converging clearances and creates high local pressure. 

Transverse baffles support the tubes that pass through holes in the baffle. The transverse baffle cannot go all the way across the cro.ss-section of the shell, because the fluid that is in the. shell has to be able to come... 

In a later paper, Brasie (1976) gives more concrete recommendations for determining the quantity of fuel released. A leak potential can be based on the flashing potential of the full amount of liquid (gas) stored or in process. For a continuous release, a cloud size can be determined by estimating the leak rate. For a combined liquid-vapor flow through holes of very short nozzles, the leak rate (mass flow per leak orifice area) is approximately related to the operating overpressure according to ... 

Vapor rises through holes (Ke- to 1-in.) in tray floor and bubbles through liquid. At the same time liquid head forces liquid countercurrent through these holes and onto tray below. Liquid flow forms random patterns in draining and does not form continuous streamlets from each hole. See Figures 8-67D and 8-68A... 

Holes and Smaller With Water or High Surface Tension Liquids > om= Minimum Vapor Velocity Through Holes, ft./sec. 

Vpt, B = vapor velocity through holes, open balance point, ft/sec... 

Tower shells may be ferrous, non-ferrous, stainless alloys or clad (such as monel-clad-steel). The trays are usually light gage metal consistent with the corrosion and erosion problems of the system. The velocity action of vapors flowing through holes and slots accentuates the erosion-corrosion problems, and often a carbon steel tower will use... 

The NTTD s are quite often used with structured packing where it may be desired to have an overflow sheet of liquid onto the packing and (rather than through holes) oriented at 90° to the top structured layer [131]. 

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