Hold on pressure

The preferred types of runner system are full round or trapezoidal. However, do not make the runners too small (i.e. not less than 4 to 5mm (0.157 to 0.197in) in diameter) as this can create the need for high melt temperatures. The types of gates used for ASA are similar to those used for ABS. TTie size of the gate must be large enough to allow the application of hold-on pressure for the correct screw forward time typical gate depths of 0.6 to 0.7t (where t is the wall thickness of the component) are recommended. 

If the component cannot be readily ejected fi om the mold when using low hold-on pressures, the problem can be overcome by using a slightly stiffer grade of BDS. 

Sample All. Shows the best procedure for hold-on pressure profile. 

Sample 7. Shows flashing. The hold-on pressure was applied too late, and the filling pressure (13.8 MNm 2) was held for too long. Thus the mould overfilled and flashed. 

Sample 8. The hold-on pressure (5.5 MNm 2) is applied too soon, and filling continued at this lower pressure. The flow rate thus changed and there are tell-tale boundary marks near the weld areas. The witness marks of the welds themselves also show. The gloss and definition of the hatched lines and numbers are poor, showing too little energy in the final stage of filling. 

Conventional machine single selected hold-on pressure... 

D. The Effect of Pressure on Surface Tension The following relationship holds on thermodynamic grounds [26, 27] ... 

Path III (a) Do electrical work on the system, holding the pressure constant at 1.000 atm, until the volume /has increased to 34.33 I under these circumstances, the system also does expansion work against the external pressure. 

Dr. Blum As a further comment on pressure optimization, and as it relates to our system, I think the response of the slurry methanation system to pressure is somewhat different from that of dry methanation. It relates to the ability of the catalyst to methanate a given amount of gas. In our system, the effective pressure is the total pressure minus the vapor pressure of the liquid phase. This doesn t hold for the standard methanation catalyst in the dry system. There is a different pressure relationship so the optimum just might not work quite the same way. 

Find the first-order rate constant for the disappearance of A in the gas reaction 2A R if, on holding the pressure constant, the volume of the reaction mixture, starting with 80% A, decreases by 20% in 3 min. 

At this stage, one has to take into account the volume compressibility of the material, since upon feed-up the hold-on time of material under pressure is determined by compressibility and slow viscous flow. If the pressure of injection PQ is sufficiently high, then at this stage a liquid may be considered to be Newtonian with viscosity q ,. Keeping this in mind, we may state that the calculation given below will be applicable to various plastisols (of types I and II) with the only difference that for plastisol I q = const, while for plastisol II q = q. For the sake of simplicity, the analysis will be performed for the case of a flat mould filled through a slit runner (Fig. 10 a). 

Hold-on under pressure ( feeding-up ). As may be easily seen, the equation of piezoconductivity [Eq. (5.6)] will remain unchanged when Eqs. (3.8)-(3.10) are taken into account it will take the form ... 

Example The dew point is defined an all-vapor system except for one very small increment of liquid. Now take the feed again, and consider the fact that this is a flash-off crude still sidestream vapor at 20 psig (34.7 psia). The dew point is to be determined to set the proper sidestream stripper overhead temperature for this desired product. This problem is worked similarly to the bubble point. Simply hold the pressure (34.7 psia) constant, and vary the temperature. Note that when you find the temperature at which just a small amount of liquid is formed, the sign SYSTEM IS ALL VAPOR goes off and the flash component summary appears. Note also that the previous flash summary will remain on the screen (if you had a previous run) until you input a flash zone temperature and click on Run Prog. 

A third stream is another pseudostream, which is attached on the red arrow at the bottom of the vessel called Reactor Product (required) (see Fig. 4.22). This pseudostream represents the contents of the reactor at the end of the batch cycle. Note the blue arrow pointing out of the vessel in Figure 4.22. This can be used as a product stream that is withdrawn from the vessel during the batch cycle. For example, a pressure controller can be used to withdraw a vapor stream to hold the pressure in the reactor. Figure 4.23 shows the flowsheet with the three streams attached to the RBatch reactor. Remember that the charge and product streams are required connections for the reactor. 

The file is pressure checked and exported into Aspen Dynamics. A flow controller is installed on the feed. A pressure controller is installed that holds reactor pressure by adjusting valve V24 in the process discharge line. Figure 7.30 shows the flowsheet with these controllers installed. 

Since both the vacuum isolation foil and the target backing foil must hold a pressure difference of greater than 1 bar, relatively thick metal foils, such as 2.5 mg/cm2 Be or 1.8 mg/cm2 HAVAR, have been used. These thick foils are especially attractive when considering the mechanical stability of extremely radioactive actinide targets. Variations on the double-window target system have traditionally been used for heavy element production with actinide target materials. 

Activation volume — As in case of homogeneous chemical reactions, also the rate of heterogeneous electron transfer reactions at electrode interfaces can depend on pressure. The activation volume AVZ involved in electrochemical reactions can be determined by studying the pressure dependence of the heterogeneous -> standard rate constant ks AVa = -RT j (p is the molar - gas constant, T absolute temperature, and P the pressure inside the electrochemical cell). If AI4 is smaller than zero, i.e., when the volume of the activated complex is smaller than the volume of the reactant molecule, an increase of pressure will enhance the reaction rate and the opposite holds true when A14 is larger than zero. Refs. [i] Swaddle TW, Tregloan PA (1999) Coord Chem Rev 187 255 [ii] Dolidze TD, Khoshtariya DE, Waldeck DH, Macyk J, van Eldik R (2003) JPhys Chem B 107 7172... 

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