Archives :: Facts At Your Fingertips
June 1, 2009
One of the most important factors to consider when evaluating a specialty metal for use in valves, fittings and instrumentation is its corrosion resistance or corrosion rate of the metal in the target media. Each material discussed here has its own niche, and depending on the processing environment and the needs of the application, the metal’s strengths and weaknesses may or may not be suitable. In...
May 1, 2009
Technology Requirements [ 1] Control architecture Does the solution provide an integrated automation platform? New systems should manage process knowledge through a combination of advanced technologies, industrial domain expertise, and Six Sigma methodologies. Choose an open, scalable control system that is fully redundant, includes robust control algorithms and provides on-process upgrades to minimize...
April 1, 2009
In today’s typical process plants, preventing steam loss and improving condensate return are key opportunities to make a process more energy efficient. To be the most effective, steam generally needs to be dry (such as for process usage), or superheated (for instance, for use in turbines). These requirements dictate utility-system operating procedures for generating the highest quality steam...
March 1, 2009
Membrane polymers are packaged into a configuration, commonly called a device or an element. The most-common element configurations (figure) are tubular, capillary fiber, spiral wound, and plate and frame. Tubular Made from ceramic, carbon, stainless steel or a number of thermoplastics, tubular elements have inside diameters from ¼ in. up to about 1 in. Typically, the membrane is coated on the...
February 1, 2009
Friction Factor Fluid flowing through pipes experiences resistance due to viscosity, turbulence and roughness of the pipe surface. The Darcy-Weisbach Equation (1) is commonly used for the analysis of steady-state, Newtonian-fluid flow inside pipes. It summarizes the relations between frictional head loss, fluid properties, pipe geometry and discharge. For laminar flow (Re < 2,100), the friction factor...
January 1, 2009
Here, we present criteria needed for the intelligent, effective specification of trays for a distillation or stripping column. Among the key parameters and accessories during specification are column diameter, tray spacing, number of trays, number of passes, type of downcomers, weir heights, provision of downcomer backups, tray pressure drops, design of bottom seal pan, column bottom arrangement, and...
December 1, 2008
Laminar Pipe Flow For steady flow in a pipe (whether laminar or turbulent), a momentum balance on the fluid gives the shear stress at any distance from the pipe centerline. In Equation (1), Φ = P + ρ gz. The volumetric flowrate Q can be related to the local shear rate by doing an integration by parts of Equation (2). Newtonian fluid. For a Newtonian fluid, τ rx = µY rx, which gives the...
November 1, 2008
Biodiesel can be produced from vegetable oils by three types of reactions: base catalyzed transesterification of the oil; direct acid-catalyzed transesterification of the oil; and conversion of the oil to its fatty acids, and then to biodiesel. Biodiesel is typically produced by a base-catalyzed reaction (Figure 2). This method of production has several advantages, including the following: low temperature...
October 15, 2008
Pumps Centrifugal pumps with cast or forged steel casings are typically appropriate for systems with large flowrates Positive displacement pumps frequently can handle smaller flowrates of less than 100 gal/min Sealless pumps (canned motor or magnetic drive) avoid the installation of mechanical seals A typical centrifugal pump can be expected to deliver operational head of about: where g is gravitational...
September 15, 2008
Crystallization is a method of solid-fluid separation in which pure chemical crystals are formed. Crystallization kinetics consists of three major phenomena: nucleation (the birth of a crystal), transfer of the solute from the supersaturated solution to the crystal surface, and a reaction during which the solute becomes incorporated into the crystal. Supersaturation In order to drive the process of...
March 15, 2008
Separation by a membrane is achieved by creating a boundary between different bulk gas or liquid mixtures. As different solvents and solutes flow through a membrane at different rates, separation is achieved. Here, we will focus on three filtration techniques: microfiltration (MF), ultrafiltration (UF) and nanofiltration (NF). These processes are characterized by the size of the particle that can be...
February 15, 2008
The failure of a device or of a group of components can lead to overpressurization and subsequent adverse events, such as fire, explosion, spill or release. The most common causes of overpressurization are listed below. Understanding the circumstances surrounding overpressurization will help an engineer to avoid these failures. External Fire According to API RP 520 and 521 standards, a fire-exposed area is...
December 15, 2007
Seals are assemblies of elements that prevent the passage of a solid, liquid, gas or vapor from one system to another. When a seal allows leakage of material, failure has occurred. This guide provides an overview of common seal types and a discussion of seal failure to aid in choosing the most effective seal and avoiding future failure. Seal Types Seals types can be classified within two broad categories...
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