Piping selection

Kiefner, J. F. and W, A. Maxey, Specifying Fracture Toughness Ranks High In Line Pipe Selection, Oil and Gas Journal, Oct. 9,1995. 

If the calculations were started by assuming a pipe size and length, determine the number of lengths from the total area calculation and surface area per length of pipe selected. 

EXAMPLE Find friction loss 6,000 ft per min (cfm) through 100 ft of 16-in. diameter pipe. Select 6,000 cfm on left scale and move horizontally right to diagonal line marked 16 in. The other intersecting diagonal shows that velocity in the pipe is 4,300 ft per min. Vertically below,the friction per 100 ft is 1.35 in. 

A simple cell design is required to reduce capital costs. The cost of the raw materials, HF and electricity, are not negligible, but they are minor. The pilot plant cell design shown in Fig. 16 is derived from the callandria cell developed for the Phillips ECF process.14 The cell body and internals are of mild steel pipe selected to be resistant to hydrogen embrittlement. Figure 17 is a horizontal section through the working part of the cell. 

The minimum thickness, T, for the pipe selected, considering the manufacturer s minus tolerance, shall be not less than tm. 

In perhaps the majority of pipe selection situations the initial purchase price of the pipe, for a given size, is a decisive factor in material selection. The selling price set by the... 

A major component of this framework is the use of nondestructive evaluation technicjues to provide information about the condition of the pijjeline. All pip>es will eventually fail, but the rate of failure will dejjend on both the pipe material and the actual exposure to environmental and ojjerational conditions. The most important feature of the framework relates to the cyclical nature of pipeline management. Each pipe in the system must be examined periodically, and its condition reassessed in order to determine what action should be taken to maintain or upgrade its condition. The entry point to the cycle is the pipe selection area labeled as "Prioritize Pipes for Analysis" in Fig. 8.3. 

Work with the pipe size and wall thickness until the flow and pressure in the pipe selected are acceptable for both... 

The total system pressure drop should not exceed the pressure rating of the thermoplastic pipe selected... 

When designing a pressurized pipe system, the pipe selected must hold the internal pressure safely and continuously. In a non-pressurized system such as a gravity flow sewer, pipe selection depends on other factors. Vacuum piping systems must use a pipe that resists collapse. The design engineer will use different design criteria and calculations for each type of installation. 

Filter Selection. A variety of product- and process-related factors govern filter selection. Considerations include the characteristics of the fluid to be filtered, ie, its chemical composition and compatibiHty with the filtration system (inclusive of the membrane, filter hardware, piping, etc), the level of bioburden present, specifications on effluent quaHty, the volume of product to be filtered, flow rate, and temperature. 

Reynolds dumber. One important fluid consideration in meter selection is whether the flow is laminar or turbulent in nature. This can be deterrnined by calculating the pipe Reynolds number, Ke, a dimensionless number which represents the ratio of inertial to viscous forces within the flow. Because... 

A.m blent Environment. The environment around the flow conduit must be considered in meter selection. Such factors as the ambient temperature and humidity, the pipe shock and vibration levels, the avadabiHty of electric power, and the corrosive and explosive characteristics of the environment may all influence flow meter selection. Special factors such as possible accidental flooding, the need for hosedown or steam cleaning, and the possibiHty of lightning or power transients may also need to be evaluated. 

Additives. Because of their versatility, imparted via chemical modification, the appHcations of ethyleneimine encompass the entire additive sector. The addition of PEI to PVC plastisols increases the adhesion of the coatings by selective adsorption at the substrate surface (410). PEI derivatives are also used as adhesion promoters in paper coating (411). The adducts formed from fatty alcohol epoxides and PEI are used as dispersants and emulsifiers (412). They are able to control the viscosity of dispersions, and thus faciHtate transport in pipe systems (413). Eatty acid derivatives of PEI are even able to control the viscosity of pigment dispersions (414). The high nitrogen content of PEIs has a flame-retardant effect. This property is used, in combination with phosphoms compounds, for providing wood panels (415), ceUulose (416), or polymer blends (417,418) with a flame-retardant finish. 

AH columns, distributors, and ancHlary hardware such as piping, valves, and pumps must be constmcted of corrosion-resistant materials, or coated with an appropriate substance. AH streams that contact the hardware during each step of the cycHc operation need to be considered in this selection. 

Design parameters as a function of temperature and design temperature limits are set forth in the ANSI/ASME B31 Piping Codes for a very broad range of materials. These codes, and the additional information available from manufacturers, vendors, and technical societies such as the National Association of Corrosion Engineers provide ample data for the selection of materials for piping systems (1—13). 

In order to select the pipe size, the pressure loss is calculated and velocity limitations are estabHshed. The most important equations for calculation of pressure drop for single-phase (Hquid or vapor) Newtonian fluids (viscosity independent of the rate of shear) are those for the deterrnination of the Reynolds number, and the head loss, (16—18). 

Pipe-Wall Thickness. Once the design pressure and temperature have been established and the pipe material and size selected, the wall thickness is calculated using the appropriate section of the code. In rare cases, a thin pipe must be made thicker to withstand handling. Occasionally the thickness is affected by external loads or vibrations. All codes prescribe essentially the same design formula for metallic hoUow circular cylinders under internal pressure ... 

A particular type of support assembly is selected according to the amount of restraint tolerable by the piping system and the movement to be allowed at each location. Support types ate classified as rigid, resiUent, and constant-effort hanging and resting are the two basic arrangements. 

Pipe attachment devices are either integral or nonintegral with the shell of the pipe. The particular type is selected according to load-carrying capacity, severity of service, and the desirability of welding directly to the pipe. 

The movement-absorbing devices used in semirigid and nonrigid piping systems are usually called expansion joints. Based on the method by which the pressure seal is effected, joints are either of the packed type or the packless or bellows type. Selection depends not only on the required movement but also on the severity of service in terms of pressure and temperature, tolerabiUty of leakage, and the number of service cycles. 

The selection and appHcation of an expansion joint is not as simple as selecting a pipe fitting or a valve and requires a sound understanding of the joint s capabihties and limitations. Improper appHcation of any type of joint can result in serious or damaging effects. However, when properly selected and integrated into the piping system, satisfactory service and safe operation can be expected. Selection and appHcation of beUows expansion joints require special attention to design and installation. 

The location of the pipe in the rack is selected to minimize the congestion and eliminate line crossing. If a process line connects two nozzles which are elevated higher than the piperack, then the upper level of the rack is used. Similarly, if the nozzles are both below the piperack, then the lower level rack is used. Other cases in which one nozzle is below and the other above use the least congested part of the piperack. Lines with valves are more easily accessed from the upper level, but require an access platform. 

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