Straight run requirements

If a control or other throttling v ve must be installed upstream from a flow measuring instrument, the minimum straight run requirement is as shown. If... 

Rotameters require no straight runs of pipe before or after the point of installation. Pressure losses are substantially constant over the whole flow range. In experimental work, for greatest precision, a rotameter should be cahbrated with the flmd which is to be metered. However, most modern rotameters are precision-made so that their performance closely corresponds to a master cahbration plot for the type in question. Such a plot is supphed with the meter upon purchase. 

Table 41.3 shows a performance comparison of Pt/Pd TUD-1 with a commercial Pt/Pd catalyst (26). The feedstock is a typical straight run gasoil ( SRGO ), a distillate precursor to diesel fuel. Under identical test conditions, the TUD-1 catalyst achieved 75% aromatics saturation versus 50% for the same volume of commercial catalyst. This superior result is particularly interesting because the TUD-1 catalyst had a much lower density than the commercial material, so that less catalyst by weight was required in the reactor. 

Stress intensification factors for branch connections are based on tests with at least two diameters of straight run pipe on each side of the branch centerline. More closely loaded branches may require special consideration. 

Studies have been made thruout the refining industry in an effort to utilize selected stocks for the production of jet fuels. Basically, this would amount to determining the stability of many stocks, for example, straight run gasolines, distillates, kerosines, alkylate bottoms, and whatever else is available from refinery streams. Those with best heat stability, by laboratory test, could then be blended into jet fuels meeting required... 

Straight-pipe run requirements as a function of upstream disturbance. (Courtesy of Endress+Hauser, Inc.)... 

The swirl meter operates in most of the same applications as the vortex-shedding flowmeter but has the advantage that, because flow conditioning is done at the inlet and outlet of the meter body, virtually no upstream or downstream straight run is required for optimal installation. 

The disadvantages are that (1) they are not suitable for services that are dirty, abrasive, viscous, or mixed-flow (gas with liquid droplets, liquid with vapor bubbles), or that have low Reynolds numbers (below 20,000) (2) the available choices in materials of construction are limited (3) the pulse resolution (number of pulses per gallon or liter) drops off in larger sizes (4) the pressure drop is high (two velocity heads) and (5) substantial straight runs are required, both upstream and downstream. 

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