New at PipingDesign.com: 25 October 2000

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A Review of Butterfly Valve Components and Operation Chemical Processing Magazine

<<Many different types of valves are used in flow control. They are used
for a variety of reasons, such as phase (liquid or gases), pressure, piping restrictions and solids content. Other valves are chosen for their capability to open and close in a quarter turn. Of all the valve types, the butterfly valve is used as a control device for many reasons including some or all of the above.This article explains the workings of a butterfly valve and its operation. The butterfly valve offers many advantages that include quarter-turn, openness for less plugging and good control capabilities. Both manual and control versions are used.>>

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How to Compare Heat Exchangers
Chemical Processing Magazine

<<Life's a little easier for anyone buying a heat exchanger because the
manufacturers have agreed to standards that make comparisons easy.The guidelines, laid down by TEMA (the Tubular Exchanger Manufacturers Association), establish style and set tolerances for machining and assembly. The three major TEMA classes are: TEMA C or general service; TEMA B for chemical service; and TEMA R for refineries. TEMA R is the most restrictive, and TEMA C is the least stringent. TEMA B and TEMA R are similar. TEMA R includes the requirement for confined joints where recesses must be machined in the flanges and tubesheets. Spiral-wound gaskets with a ring construction also meet that TEMA R requirement. TEMA R also calls for greater minimum thickness for some components. TEMA designations refer to the construction of the heat exchanger: front head design, the shell design and the rear head design. For example, a TEMA Type BEM has a Type-B front head, a Type-E shell and a Type-M rear-head design. TEMA types are chosen depending on the application. With high vapor flows, high pressure and temperature crossing, a combination of special TEMA features is advantageous. For example, Type-K shells allow for proper vapor disengagement in reboilers. Type-J and Type-H shells accommodate high vapor flow. >>

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Understanding Relief Valves and Pressure Regulators Chemical Processing Magazine

<<Thermoplastic pressure-relief valves are multifunctional, normally
closed valves available in a wide selection of designs and materials for specialized applications. Pressure-relief valves are often confused with pressure regulators (pressure-reducing valves), which may have a similar shape and appearance, but which perform totally different functions. Pressure-relief valves perform functions such as protecting equipment against pressure surges, preventing pumps from dead-heading and maintaining necessary backpressure in closed loop systems. Their most common function is protecting piping systems and other equipment from excess pressure. In this application, the normally closed valve is set (adjusted) to a specific pressure and will open (relieve) gradually when the pressure exceeds that value. The resulting flow across the valve varies with the amount of pressure above the set pressure. The valve will reclose when the pressure falls below the set value. Thermoplastic pressure regulators are normally open valves manufactured in a variety of styles, sizes and materials. They are one of the most indispensable valves used in process systems, but are also one of the most misunderstood and misapplied. Often called "the protectors," they protect expensive, sensitive, downstream instruments, filters and tools against overpressure damage. They also regulate to the correct pressure range so the flow system or equipment operates safely and effectively.>>

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Pre-Installation Planning Critical to Laying Marlin Lines Pipe-Line.com

<<Detailed planning was critical to the successful installation of
subsea crude oil and natural gas export pipelines for BP Amoco's Marlin Development Project in the Gulf of Mexico. The project, formerly Amoco Marlin, involved laying a 10-in. oil line along with a 14-in. gas line from a Tension Leg Platform (TLP) in Viosca Knoll 915 to facilities located in Main Pass 260 and 225. Water depths along the route ranged from 3,240 ft at the TLP to 300 ft at the Main Pass location. By design, the lines were laid parallel to each other at a nominal separation of 200 ft from the TLP steel catenary riser until they diverge in the northwestern quadrant of Viosca Knoll 738. The 10-in. line measures 21.8 mi and the 14-in. line is slightly shorter at 18.6 mi. To minimize risk and maximize economic considerations, early planning and engineering for the pipelines were undertaken in 1996, 20 months ahead of pipelaying.>>

Minimizing Piping Friction Losses In Low-Pressure Regulating Valves Control Engineering

<<One common type of installation for a pressure regulating valve is
where the pressure is reduced to a very low value to supply or pressurize the system downstream of the valve. In the case of gas blanketing systems, system pressure could be reduced to as as much as one inch of water column. Liquid system losses may be several pounds per square inch. While these systems perform different functions, they have one feature in common--reduced pressure. Fluids flow by means of a pressure differential. If the system is to function, the backpressure must be less than the pressure being controlled at the valve. When designing and installing such a system, the engineer must specify the downstream piping and components that will keep the fluid resistance low. In no case can the valve be set for a pressure less than the backpressure created by the downstream.Backpressure from downstream piping and components is usually not an issue with systems operating at higher outlet pressures. But, it can be a problem with systems operating below 10 psi. As the pressure decreases, the potential for piping system-induced problems increases.>> Received on Wed Oct 25 13:42:00 2000