Depressurization time

Average depressuring rate used to determine depressuring time... 

The SC-CO2 drying procedure was as follows Steel containers were loaded onto a metallic support that was put into the high-pressure vessel, which was then closed and filled from the bottom with SC-CO2. When the required pressure and temperature were obtained (200 bar and 35 °C), drying was performed for 4 h with an SC-CO2 flow rate of about 1 kg/h, which corresponded to a residence time inside the vessel of about 4 min. The depressurization time of 20 min was allocated to bring the system back to atmospheric pressure [65]. 

Microporous PVB membranes could be prepared by supercritical C02-induced phase separation (31). Characterization be SEM indicated that the process parameters, such as the concentration of PVB in the casting solution, the CO2 pressure, and also temperature and depressurization time, had significant effects on the structure of the membrane. 

An increase of the PVB concentration decreases the pore size. The top surface of the membrane becomes dense, when temperature and CO2 pressure is increased. An increase of the depressurization time, causes a porous top surface (31). 

In this chapter, microcellular foaming of low-Tg biodegradable and biocompatible polycaprolactone (PCL) in supercritical CO2 will be described. The effects of a series of variable factors, such as saturation temperature, saturation pressure, saturation time and depressurization time on the foam structures and density were studied through measurement of density and SEM observation. The experimental results show that higher saturation temperatures lead to a reduction in bulk densities and that different saturation pressures result in different nucleation processes. In addition, saturation time has a profound effect on the structure of the product. Both X-ray diffraction (XRD) and differential scanning calorimetry (DSC) results show that the foaming treatment widi supercritical CO2 increased the crystallinity of PCL. 

Foams were prepared in a glass tube (<1>15 mm x 50 mm) inside the reactor to facilitate removal of the foamed samples. PCL was placed into the tube and the PCL and tube were then placed in the reactor together. The closed reactor was preheated in a bath to a set temperature, and flushed for a few minutes with CO2. The cell was then filled to the desired pressure. At this pressure the resin was exposed to supercritical CO2 for a prescribed period of time. Finally, the valve of the reactor was opened and the pressure was released to the atmosphere. The depressurization time was recorded in order to quantify its influence on the final product. The system was maintained at zero pressure for approximately half an hour so that the bubbles could mature completely. 

Density of the bulk foams as a function of depressurization time. (Temperature = 40 >C, pressure = 10 MPa, saturation time =2h.)... 

A series of experiments were carried out at 40 °C and 10 MPa using a number of different depressurization rates. The experimental results are given in Fig. 18.12 and show that the bulk foam density increases with increasing depressurization time. It may be deduced that prolonging the depressurization time ensured the cells more time to contract at fixed sites, thus decreasing the bulk volume. Hence the bulk density increases with depressurization time. 

Locate leaks Apply soap solution to tape bleed holes and threaded connections depressure when tests are done. Block in N2 and check for loss of pressure. Check all connections. Same as in Step 1. Tag flanges to identify leaks tighten or repair leaks each time a system is pressurized, drain condensate at low-point bleeds. 

Fit an emergency depressuring valve so that the pressure in the vessel can be reduced to one fifth of design in ten minutes to reduce the strain on the metal [13]. The time can be increased to 30 minutes if the vessel is insulated and to one hour if, in addition, the ground is sloped. 

The costs of a wrong decision are loss of production, on the one hand, and failure to respond to a real emergency on the other. In order to improve his or her decision basis, the control room worker will usually dispatch others to the source of the emergency signal to declare whether it is spurious (false alarm) or whether it is real, but it is containable without need for depressurizing. This takes up valuable time, during which the situation could escalate dangerously. 

Activation of the blowdown, however, will not depressurize a system fully for a considerable length of time. One of the reasons for considering retaining the possibility of human intervention was that the automated blowdown system was not considered completely reliable at the time because of the limitations of the fire and gas detection hardware. This would have the effect of resulting in increasing the likelihood of spurious blowdown production losses. 

A mixture of the arylsulfonyl chloride (5 mmol), benzene (2.56 mol), NaN3 (5 mmol), NaHCO, (20 mmol), and methyltrioctylammonium chloride (0.5 mmol), under N2 in an autoclave, was stirred al 40 C for 3 h. The mixture was then heated slowly to 125 C and maintained at this temperature for another 3 h, during which time the pressure in the vessel rose to 31 -54 atm. The mixture was allowed to cool and the autoclave was depressurized. The residual mass was filtered, and the residue washed thoroughly with cold H20. The benzene solution was separated from the aqueous filtrate, dried, and evaporated to give the crude product as a reddish yellow mass which was purified by column chromatography (neutral alumina, hexane/ benzene 3 2). The 1-(arylsulfonyl)-l//-azepines 16 were crystallized from light petroleum ether (bp 60-80 LC). 

The time required to stop the leak is a function of isolating points, emergency valves, depressuring systems, and other mitigation systems as appropriate. 

In theory, the application of radon barriers should be adequate to avoid elevated radon levels in houses. In practice, however, a backup radon mitigation system has been found essential for maintaining indoor radon concentrations below 4 pCi/L in most homes studied. In the recent radon-resistant residential construction projects conducted by U.S. EPA and/or private builders, several of the homes designed to be radon resistant have contained radon concentrations above 4 pCi/L. In each of those houses, a backup system consisting of an active (fan-assisted), or passive (wind-and-stack-effect-assisted), SSD system was installed at the time of construction. When mechanical barriers failed to adequately control radon, the soil depressurization methods were made operational. 

Fireproofing Reduces rate of heat input and provides additional time for depressurizing, fire fighting, etc. 1 X 1CT2 to 1 X 1CT3 1 x 1CT2... 

Depressurization and Blowdown Capabilities - A mathematical calculation of the system sizing and amount of time needed to obtain gas depressurization or liquid blowdown according to the company s philosophy of plant protection and industry standards (i.e., API RP 521). 

To overcome the possibility of a vessel rupture from a hydrocarbon fire exposure several methods are available. Depressuring, insulation, water cooling or draining are usually employed in some fashion to prevent of the possibility of a vessel rupture from it s own operating pressures. A generalized method to qualitatively determine the effect of a hydrocarbon fire on the strength of vessels constructed of steel is available. With this method one can estimate the time for a vessel to rupture and therefore the need to provide protective measures. 

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