Pressure observations during emptying

The lowest pressure cell, A, is the first to register pressure (at 2 min), and the pressure rises rapidly towards the Janssen asymptote. The other cells progressively start to register 

One must not be too unkind to the researchers who reported these experiments. The instrumentation is very expensive, so most tests were conducted with relatively few pressure cells. Faced with the challenge of where to place their few cells, most experimentalists were persuaded by the above theories that placement down a vertical line on the side of the silo would deliver the pattern of pressure to be expected, naturally a constant value at each level. Consequently, the information concerning variation of pressure at a particular level is rather sparse. 

A further reason for using only one pressure cell at each level was that the simple theory used to translate pressures into forces in the structure (Equations (3.9) and (3.10)) implied that only the largest pressure needed to be found, and presumably that large pressure might well pass by every point at a particular level, even if not quite simultaneously. 

The consequences of unsymmetrical pressure patterns are noted further in Section 3.5. 

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The proper method to control drum foamovers during a rapid switchover is to control coke drum pressure by pinching back on the outlet vapor valve to maintain the pressure in the full coke drum. While the operator at the switch valve is diverting the feed to the empty drum, he observes the full coke drum pressure. As this pressure falls during the switch, he closes off the vapor outlet valve from the full drum to hold the pressure within 5 psig of normal operating pressure. Using this technique, the switchover can be accomplished in about 20 minutes. 

Once accumulator injection began, injection cycles were predicted to continue until the accumulators were empty at 23,772 s. From Figure 7, it is seen that the same pressure response during accumulator injection was observed for Sequoyah as was observed for Surry. The delay in emptying the accumulators relative to Surry is related to the smaller PORV in the Sequoyah analysis. 

Dining interaction at ambient temperature in a bomb to produce poly (carbon monofluoride), admission of fluorine beyond a pressure of 13.6 bar must be extremely slow and carefully controlled to avoid a violently exothermic explosion [1], Previously it had been shown that explosive interaction of carbon and fluorine was due to the formation and decomposition of the graphite intercalation compound, poly (carbon monofluoride) [2], Presence of mercury compounds prevents explosion during interaction of charcoal and fluorine [3], Reaction of surplus fluorine with graphite or carbon pellets was formerly used as a disposal method, but is no longer recommended. Violent reactions observed when an exhausted trap was opened usually involved external impact on the metal trap, prodding the trap contents to empty the trap, or possibly ingress of moist air... 

Movements of liquid water within porous solids have been experimentally observed. Haines studied the movement of liquid water within porous media during drying [26, 27]. He observed rapid movements of water elements in the porous system (Haines jumps). The capillary pressure transports water to narrow pores at the surface. Larger volumes surrounded by narrow pores can be rapidly emptied, and smaller volumes can be filled when the water is removed out of the narrow... 

When switching feed out of a full coke drum into an empty drum,. the pressure on the full drum will drop. Experienced operators carefully observe the pressure on the full drum during a switch. Allowing the pressure to drop too rapidly will start a foamover. A drop of 1 or 2 psi every five minutes is about right. The top gamma-ray level indicator will show when a foamover starts during the feed switchover. To stop this foamover, the vapor valve on the full drum should be pinched closed until the drum pressure rises a few psi. 

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