Piping size limits

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). 

Use physical limits of pipe size, restrictive orifices, and pump sizing to limit excessive flow rates. 

Nozzles should be sized according to pipe sizing criteria, such as those provided in API RP 14E. The outlet nozzle is generally the same size as the inlet nozzle. To prevent baffle destruction due to impingement, the entering fluid velocity is to be limited as ... 

The flow of a compressible fluid through an orifice is limited by critical flow. Critical flow is also referred to as choked flow, sonic flow, or Mach 1. It can occur at a restriction in a line such as a relief valve orifice or a choke, where piping goes from a small branch into a larger header, where pipe size increases, or at the vent tip. The maximum flow occurs at... 

Figure 13-23 suggests recommended pulse level (peak-to-peak) pressure pulsations for acceptable pipe vibration. Figure 13-24 presents allowable machinery and pipe vibration at safe limits and damage levels, and Figure 13-25 presents allowable pressure pulsations for various pipe spans between rigid supports when a 5 mil peak-to-peak vibration is allowed at the center of the pipe spans for the pipe sizes noted. 

For Reynolds numbers between these two limits, in the transition zone of 2000 to 10,000, use the more conservative Eq. (6.3) or Eq. (6.5) for the case in question. For example, if the particular case has a limiting pressure drop, and the pressure drop in the pipe is critical (not too large), then consider sizing Eqs. (6.3) and (6.4) for f, as these would calculate larger pipe sizes. Otherwise, use Eq. (6.5). 

Please note that the Reynolds number has always been above the 200,000 minimum limiting value. Should any application of this methodology reveal an Re value that falls below 200,000, a smaller pipe size should be considered. If this condition applies to existing piping, then be assured of possible slug flow, and welcome to the myth. 

The size of orifice-type flow sensors is limited only by the pipe size they are installed in, and their pressure and temperature ratings depend only on the limitations of the d/p detector used. Their measurement error is the combined orifice and d/p readout error, which in a standard installation over a 3 1 range is about 2% FS, and with an intelligent and multirange transmitter it can be reduced to 1% AF over a 10 1 range. 

In 1842, Christian Doppler discovered that the wavelength of sound is a function of the receiver s movement. The transmitter of a Doppler flowmeter projects an ultrasonic beam into the flowing stream and detects the reflected frequency, which is shifted in proportion to stream velocity. The difference between the transmitted and reflected velocities is called the beat frequency, and its value relates to the velocity of the reflecting surfaces (solid particles and gas bubbles) in the process stream. For accurate readings it is important that the ultrasonic radiation be reflected from a representative portion of the flow stream. The main advantage of Doppler meters is their low cost, which does not increase with pipe size, whereas their main limitation is that they are not suitable for the measurement of clean fluids or gases. 

Pipe designei s normally work with velocities that will not create undue vibrations, and erosion in the piping. Thus velocity limits, such as those provided in the table, are used as a further critenon for optimum pressure gradients in pipe sizing. 

In many situations, it is impractical to produce a complete GHS label and attach it to the container, due, for example, to container size limitations or lack of access to a process container. Some examples of workplace situations where chemicals may be transferred from supplier containers include containers for laboratory testing or analysis, storage vessels, piping or process reaction systems or temporary containers where the chemical will be used by one worker within a short timeframe. Decanted chemicals intended for immediate use could be labelled with the main components and directly refer the user to the supplier label information and SDS. 

The type of meter used for water flow depends on the flow rate and velocity. Meter types include Venturi, propeller, turbine, and magnetic. The manufacturer of each should be consulted for their limitations, which include pipe size, up- and downstream straight pipe available at flow meter installation, minimum and maximum velocity through meter, and calibration requirements. Unfortunately, meters are usually selected by pipe size, not flow rate, so the water meter is often grossly oversized for the flow rate through it. Because most meters are least accurate at the low velocity end of their measurement range, the result is that water flow is not accurately measured. 

By measuring AB and u in one pipe size and assuming that they are independent of diameter, the friction factor of another pipe size can be obtained. However, this method gave only limited success in diameter scale-up with very small pipe sizes for polymer... 

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