V notch

Fig. 10. Stream flow over (a) a broad-crested, rectangular weir (b) a cross-current view of the rectangular and CipoUetti weirs (c) a trape2oidal-notch or CipoUetti weir (d) a sharp-crested, triangular, or V-notch weir (e) a cross-current view of the V-notch and hyperboHc-notch weirs and ( a...

Materials selection for low-temperature service is a specialized area. In general, it is necessaiy to select materials and fabrication methods which will provide adequate toughness at all operating conditions. It is frequently necessaiy to specify Charpy V-notch (or other appropriate) qu fication tests to demonstrate adequate toughness of carbon and low-aUoy steels at minimum operating temperatures. 

Notched outlet weirs (usually 60° V-notch) are only used for low liquid flow rates, and the head over this type of weir with notches running full [13]. 

Because the liquid flow is low also, K-in. v-notched weirs should be used to ensure uniform flow and level across the tray. The bottom of the notches should be 2.5 in. above the tray floor. 

Height of liquid crest over flat weir or measured from weir (straight or circular) or from bottom of notches (v-notch weir), in. 

The use of V-notches in a trough wall for overflow is more sensitive to leveling problems than the other designs, and for the same %- to Me-in. level tolerance produces a more severe non-uniform flow distribution. The quality of distribution from a V-notch is poor compared to the other types of trough distributor, but does have advantages in slurry systems [131]. It should not be used for critical distillation applications, but is good for heat transfer and where solids are in the system. 

Figure 9-9. Liquid maldistribution is a function of opening, shape, and liquid head over the opening for a /s-in. out-of-level distributor. The openings were 3-in. dia. orifice, 3-in. slot, and 22.5° V-notch. Used by permission of The American Institute of Chemical Engineers, Bonilla, J. A., Chemical Engineering Progress, V. 89, No. 3 (1993) p. 47, and with special permission from Fractionation Research, Inc., all rights reserved.

V-Notch Accomodates Moderate Liquid Flow, or for Draining after Washout. Size to Suit Flow. This is Not Recommended for Horizontal Condensers. 

Fig. 3.13 Impact strengths (Charpy V -notch) at various temperatures for several stainless...

V-notch impact tests, such as the Charpy test, are used to test the susceptibility of materials to brittle failure see Wells (1968) and BS 131. 

In addition to rectangular weirs, V-notch or triangular weirs are commonly used with a cross-sectional flow area as shown in Figure 8.9. In... 

Cross-sectional flow area in a V-notch weir... 

Equation 8.37 gives the volumetric flow rate Q through a V-notch weir when there is no friction in the system. 

V-notch weirs are particularly useful for measuring flow rates that vary considerably. 

Calculate the volumetric flow rate in m3/s through a V-notch weir when the height of liquid above the weir is 0.15 m given that the notch angle 6 = 20° and the discharge coefficient Cd - 0.62. 

Minimum Required Charpy V-Notch Impact Values. ... 

Lateral Expansion Requirements. Other carbon and low alloy steels having specified minimum tensile strengths equal to or greater than 656 MPa (95 ksi), all bolting materials, and all high alloy steels (P-Nos. 6, 7, and 8) shall have a lateral expansion opposite the notch of not less than 0.38 mm (0.015 in.) for all specimen sizes. The lateral expansion is the increase in width of the broken impact specimen over that of the unbroken specimen measured on the compression side, parallel to the line constituting the bottom of the V-notch (see ASTM A 370). 

All pressure retaining steels applied at a specified minimum design metal temperature (2.11.4.5) below -30°C (-20°F) require a Charpy V-notch impact test of the base metal and the weld joint unless they are exempt in accordance with the requirements of paragraph UHA-51 in Section Vlll, Division 1 of the ASME Code. Impact test results shall meet the requirements of paragraph UG-84 of the Code. 

Table V. Notched Izod Impact Strength (ft-lbs/inch) of Polyblends at 20 and 30% Substrate Levels...

Almost never take a person s word for the water recirculation rate. Check the number of pumps available and the number operational, read the pump plate, use pump curves, read the pump manual, measure using pitot tubes (measures the total pressure and hence indirectly the velocity), orifice plates, V-notch weirs, and distribution deck levels, or calculate based on amperage draw and the discharge pressure, to confirm the volume of water actually circulating in the system. 

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