Pipe Sizing Considerations

Because of the reciprocating action of the piston, care must be exer-ci.sed to size the piping to minimize acoustical pulsations and mechanical vibrations. As a rule of thumb, suction and discharge lines should be sized for a maximum actual velocity of 30 ft/.sec (1,800 ft/min) to 42 ft/sec (2,500 ft/min). Volume 1 contains the necessary formulas for determining pressure drop and velocity in gas piping. 

To minimize pipe vibrations it is necessary to design pipe runs so that the acoustic length of the pipe run does not create a standing wave that 

The end of a pipe run can be classified as either open or closed. Typically, closed ends are where the pipe size is dramatically reduced, as at orifice plates and at short length flow nozzles. A typical open end is where the pipe size is dramatically increased. 

Where the pipe run contains similar ends (closed-closed or open-open), prohibited pipe lengths are  

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Outlet Pipe Sizing - Outlet piping is sized according to minimum diameter and exit velocity considerations, as follows ... 

For the first kind of application, the focus is on certain elements of the HVAC component under consideration. The simulation is used to study and optimize design-specific aspects such as the pipe size and spacing or wetted area and fin geometry in a heat exchanger. This kind of modeling requires detailed knowledge on many input parameters and the related physical processes. 

Oil fuel pipeline systems transfer oil from storage to the oil burner at specified conditions of pressure, viscosity, temperature and rate of flow. There can be considerable variety in the choice of system, but its design (particularly correct pipe sizing and temperature control) is most important if it is to function satisfactorily. 

Both pipe sizes give reactors that are satisfactory from the standpoint of pressure drop and effluent temperature. Although the 4-in. reactor must be longer to achieve the desired conversion, it requires significantly less volume, and this is an important consideration in the design of a pyrolysis furnace. The 6-in. pipe has... 

Most every flow control valve is sized 1 to 2 pipe sizes less than the pipe run the valve serves, because the valve restriction opening is considerably smaller than the connected pipe size. We size flow control on the basis of C (see Table 6.2). Most every valve vendor publishes C values for each valve they make. For good control tolerance choose a valve with a maximum C value at least 1.3 times greater than the calculated maximum flow C value. This means the designer should try 3 or more C values before setting a recommended size for the control valve. 

The determination of the economic choice for pipe size and insulation thickness has been discussed by many authors (9,10,11 12). Most piping systems are designed on the basis of simple rules-of-thumb in which the primary factor is a velocity or a pressure gradient. Often times the pipe is sized prior to any consideration of insulation thickness, which is in turn selected... 

The pressure drop allowed through the inlet and discharge lines is unlimited as long as the capacity of the line is adequate for the relief requirements. That is, at the required flow rate the vessel pressure must not exceed the maximum allowable accumulated pressure. In sizing a safety disc, it is usually assumed that the entrance loss at the nozzle is the governing restriction insofar as capacity is concerned. Thus the effective orifice area is considerably larger than the effective orifice area of a safety valve of the same pipe size. Consequently,... 

In Eqs. (10.1)-(10.3) Dl denotes the diameter of the leak in mm (a circular leak geometry is assumed) and DN is the nominal diameter (occasionally called nominal bore) of the pipe (approximately equal to the internal diameter in mm). Equation (10.3) is the only one to estabhsh a relationship between leak size and its expected annual frequency of occurrence h. The latter refers to a length of 1 m and must therefore be multiplied by the length of the pipe under consideration. Equation (10.3) is based on evaluations for steel pipes in the process and petrochemical industries. 

A pipe break need not be assumed if a successful qualification for leak before break, for break preclusion or for low probability of failure has been performed for the piping under consideration, resulting in a sufficiently low frequency of the occurrence of a spontaneous break In general, a fracture mechanics analysis should be performed to calculate the leak size. In lieu of such an analysis, a subcritical crack corresponding to a leak size of 10% of the flow cross-section should be postulated The leak detection system should be shown to have a sensitivity that is adequate to detect the minimum leakage from a crack that is just subcritical. 

Production experience and considerable investment in accelerated testing are necessary to determine the maximum acceptable production rates for any given polymer and pipe size. This is one of the main causes of the high production costs in obtaining high performance pressure pipes to meet strict quality specifications. 

In order to refer the pump specifications back to tank requirements, this loss must be added to the NPSH requirement of the pump itself. It must be appreciated that the values of the loss coefficient are quite low and require careful consideration of the suction piping design. This curve shows the importance of the choice of piping size in the suction and illustrates the very large pipe sizes required if pumping from a vented tank. 

Other considerations for both heated and unheated delivery/header systems include modularity for system configuration or redesign, backup temperature sensors, hose and pipe sizing, ease of maintenance, and routing of hoses on the robot with regard to its movements during robot cycles and for robot maintenance. 

The designer must use proper judgment to select pipe sizes that best meet the project conditions. The following considerations may be helpful ... 

Materials for piping should be selected from an economic viewpoint however, strength based on the pressure-temperature rating against corrosion resistance should be satisfied. Where high alloy or non-ferrous material is employed, special consideration should be given to decide the economical limits of the pipe size for which a clad or sohd design is to be adopted. 

Contingent upon the final mission, the overall service life was identified as a minimum of 12 years to a maximum of 20 year of maintenance free operation while maintaining functional performance and mechanical integrity. Based on pipe size, operational environment, and ambient environment this is a challenging requirement. Typically, a spacecraft design would include redundant valves, operators or systems to ensure that critical functions could be performed for this duration. Redundancy must be balanced against mass and space considerations for the overall spaceship. 

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