Pipes/ducts

Periodically flush and/or steam clean piping/ducts... 

Provide for drainage of piping/ducts (e.g., sloped, low point drains)... 

Mists and Sprays - There are numerous industrial chemical operations which involve liquid-in-gas dispersions. These operations generate mists and sprays that consist of particles in diameter ranges of 0.1 to 5,000 fim. Engineers most commonly encounter spray droplets which are particles often formed unintentionally in chemical plant operations. For example, vapors or fumes may condense onto piping, ducts, or stack walls. Under such conditions liquid films form. 

Pressure maintenance Maintenance of specified (differential) pressures in spaces or pipe/duct systems. 

Piping, Ducting, Dampers and Fans 8300-8399. .Waste Disposal and Recovery 8900-8999. .Hlace1laneoua (Wet Scrubbers) 8500-8599 -Dry Scrubbers 6550-8580. Precipitators... 

As the air or gas flows through the blower system (piping/ ducts, filters, etc.), the movement causes friction between the flowing air/gas. This friction translates into resistance to flow, whether on the inlet (suction side) or outlet (discharge side) of the system in which the blower is a part and that creates the pressure drop (see Chapter 2, V. 1, 3 Ed., of this series) which the blower must overcome in order for the air/gas to move or flow. This resistance to flow becomes greater as the velocity of flow increases, and more energy or power is required to perform the required flow movement at the required pressures. 

Solar radiation may fall on outside walls or roofs, raising the skin temperature, and this must he taken into account. Most cold stores are huilt within an outer envelope which protects them from the elements and from direct sunshine. In cases where the insulation itself is subject to solar radiation, an allowance of 5 K higher outside temperature should he taken. Heat load must he estimated through all surfaces including piping, ducts, fan casings, tank walls, etc., where heat flows inwards towards the cooled system. 

The concrete block walls of the cell housing the generator tube and associated components are 1.7 meters thick. The facility also includes a Kaman Nuclear dual-axis rotator assembly for simultaneous transfer and irradiation of reference and unknown sample, and a dual Na iodide (Nal) scintillation detector system designed for simultaneous counting of activated samples. Automatic transfer of samples between load station to the rotator assembly in front of the target, and back to the count station, is accomplished pneumatically by means of two 1.2cm (i.d.) polyethylene tubes which loop down at both ends of the system and pass underneath the concrete shielding thru a pipe duct. Total one-way traverse distance for the samples is approx 9 meters. In performing quantitative analysis for a particular element by neutron activation, the usual approach is to compare the count rates of an unknown sample with that of a reference standard of known compn irradiated under identical conditions... 

The branching of pipes/ducts in pneumatic conveying has the following two main applications in industry. 

Sprinklers are available in various temperature ratings. It is important to check for proper temperature rating of sprinklers in close proximity to hot surfaces, such as steam pipes, ducts, unit heaters, or hot equipment. For example, high temperature sprinklers should be used when located within 30 in (76 cm) vertically and 12 in (30.4 cm) to the side of a steam pipe or under skylights. 

The most common application of flow measurement in process plants is flow in pipes, ducts, and tubing. Table 10-4 lists widely used... 

Using various test devices one can differentiate between two flow forms to detect the drag reduction phenomenon the so-called external flow which includes flow over flat plates as well as around submerged bodies such as ship hulls of submarine models. The second form, named the internal flow , includes flow situations in pipes, ducts, and pumps (Fig. 7). 

Use your judgment in estimating the sampling area for non-flat surfaces where templates cannot be overlaid, such as inside the pipes, ducts, or vents. In this case, collect the surface area samples without the use of a template. 

The nature of gas flow in pipes, ducts, etc. changes with gas pressure. The type of flow is defined by the Knudsen number (Kn) ... 

The terms pipe, duct, and conduit are usually used interchangeably for flow sections. In general, flow sections of circular cro.ss section are referred to as pipes (especially when the fluid is a liquid), and flow sections of nnncircular cross section as ducts (especially when the fluid is a gas). Small-diameter pipes are usually referred to as tubes. Given this uncertainty, we will use more descriptive phrases (such as a circular pipe or a rectangular duct) whenever necessary to avoid any misunder.standings. 

Wood has also been extensively used for round and rectangular pipes, ducts and stacks for pulp mill and smelter exhaust fumes and for liquid effluent. Semicircular flumes, some with abrasion-resistant linings, have been built for the transport of mineral slurries. 

AropoL [Ashland] Theimoset polyester resins for gel coats, filled molding ctunpds., filament winding, SMC and BMC tq>piics., elec, laminates, pipe, ducts and housing, marine and transportation equipment, appliance, con-... 

MAJOR USES Used in paper products, building materials, textiles, asbestos-cement products, gaskets, valves, clutch/transmission components, molten glass handling equipment, chemical tanks, electrical switchboards, cooling tower components, roofing compositions, packaging, pipes, ducts, floor tiles, reinforced plastics and rubber, insulation, paint filler, fireproof fabrics. 

So far in this chapter and in the vast majority of problems in pipes, channels, ducts, etc., we assume that the velocity is practically uniform across the pipe, duct, or channel so that we may associate one velocity with the entire flow at one area perpendicular to the flow. In most flows of practical interest to chemical engineers, this simplification introduces negligible errors. However, there are somej very simple and common flows for which this is not the case. The simplest arid most illustrative example is the flow over a sharp-edged weir. 

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