Core vents

The venting is incorporated only in one mold half This type of venting can be used on all sizes of molds. When certain areas of the mold cavity are prone to trap air, core vents as shown in Figure 24 can be used. 

The vent opening will pass through a boss in the baffle to the back or outside of the mold. In machined molds, care must be taken so that vents miss the drilled cooling channels. When core vents cannot be used because the slots mark on the blown part will show, small drilled holes can be used. The effect of the size of hole on the surface of the part is shown in Figure 26. 

Slotted nozzles and core vents are available in various diameters. The open cross section of the slotted nozzles is a little bit larger than the one of the core vents. Slotted nozzles are more sensitive during installation and operation. 

Well-designed molds are vented, as entrapped air in the mold prevents good contact between the parison and the mold cavity surface. When air entrapment occurs, the surface of the blown part is rough and pitted in appearance. A rough surface on a shampoo bottle, for example, is undesirable because it can interfere with the quality of decoloration and can detract from the overall appearance. Molds are easily vented by means of their parting line, with core vents and with small holes. A typical mold parting line venting system is shown in Fig. 13.23. 

Pipe and fittings remain a significant market for ABS, particularly in North America. ABS foam core technology allows ABS resin to compete effectively with PVC in the primary drain-waste and vent (DWV) pipe market. 

A long evolving use of PSA was for Anticipated Transients without Scram (ATWS) which extended over 15 years to culminate in NUREG-0460 which was upset by the Salem failure-to-scram incident and the subsequent SECY Letter 83-28. Other special studies have been (a) value-impact analysis (VIA.) studies of alternative containment concepts (e.g., vented containment, NUREG/CR-0165), (b) auxiliary feedwater studies, (c) analysis of DC power requirements, (d) station blackout (NUREG/CR-3220), and (e) precursors to potential core-damage accident.s (NUREG/CR-2497), to name a few of the NRC sponsored studies. 

After venting of the elongated bubble, the region of liquid droplets begins. The vapor phase occupies most of the channel core. The distinctive feature of this region is the periodic dryout and wetting phenomenon. The duration of the two-phase period, i.e., the presence of a vapor phase and micro-droplet clusters on the heated wall, affects the wall temperature and heat transfer in micro-channels. As the heat flux increases, while other experimental conditions remain unchanged, the duration of the two-phase period decreases, and CHF is closer. 

As the blackpowder core of a safety fuse bums, it produces gases which must escape. At the same time the heat of the combustion melts the bitumen and plastic and thus produces side venting through the textile layers. This results in the production of an increased but constant gas pressure, determined by the equilibrium between gas generation and gas lost sideways. As the rate of burning of blackpowder depends markedly on the pressure, it is this process of equilibration which determines the speed of burning of the fuse. 

As the exploration of the biosphere has continued, environments on Earth have been discovered that are quite different from and alien to human-like life. Nevertheless, where an environment has been found to contain a chemical disequilibrium, if liquid water is also present and the temperature does not exceed the upper limit for covalent bonding of core biomolecules, life is present. Active life has been found in deep-ocean thermal vents at temperatures in excess of 112°C. Life has been found in Antarctica where liquid water exists only transiently. It has been found 5 km below Earth s surface in mine shafts, and in the effluents of mining operations at Rio Tinto, Spain, that are as acidic as dilute sulfuric acid. Several of those environments are summarized in Table 3.1. 

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