Tanks open/closed

NOTE. The plug can be removed from the housing during operation, provided the cock in the conduit from the tank is closed first. The plug must not be removed for more than 3 minutes, as otherwise the bowl might open. 

For the meaningful deviations identified by the procedure described above, the possible causes for triggering the deviation are systematically searched. As an example, possible causes for no flow may be an empty feed tank, a closed valve, an inadvertently open valve to another direction, a pump failure, a leak, and so on. In this context, it may be useful to indicate the logical relationship between the causes, such as where simultaneous failure of several elements is required in order to trigger the deviation. This is of great help for the assessment of the probability of occurrence. 

A flowmeter-based system is an alternative to the metering pumps system and the scale tank system in the emulsion preparation. Flowmeter-based systems can also be automated through computer control covering automatic start/stop of feed pumps, opening/closing of valves, registration of raw materials consumption, etc. 

The outside operator checked and found the manual valves at the tank open. The outside operator also saw no indication of flow on the flow meter and made an effort to visually verify that there was no flow. He then began to open and close the valves manually to try to fix the problem. He reported to the control room operator that he heard a clunk that may have cleared an obstruction, and the control room operator tried opening the valve remotely again. Both operators stUl saw no flow on the flow meter. The outside operator at this time got a call to deal with a problem in a different part of the plant and left. He did not make another attempt to visually verify if there was flow. The control room operator left the valve in the closed position. In retrospect, it appears that the tank level at this time was approximately 77 feet. 

The objective is to have the vacuum surge tank as close as possible to the forming station and the vacuum control valve. Use of flexible vacuum hose with connections eliminates elbows, tees, and tubing reducers. All valves must be capable of operation at the full open position. To utilize fully the rapid vacuum capability provided by the surge tank, the mold must be able to take advantage of all vacuum pressure available. Vacuum holes should be drilled as large as possible, and a maximum number should be used. 

The correct operation of a PD pump includes correctly lining up the pump from the suction tank to the discharge tank. This includes opening all the suction and discharge valves on the flow path to the destination tank and closing any valve that is not on that flow path. Adequate liquid level is required on the suction side to operate the pump, and space should be available in the destination tank. A positive displacement pump is not dependent on NPSH or liquid level however, adequate suction is required. Vented and nonvented tanks respond differently during product transfers and should be carefully monitored. 

Now add a controller for the tank outlet temperature. The controller should manipulate the steam rate to the heater between 0 and 1 xlO kJ h (direct Q). The PV range should be 0 to 100°C, and the set point should be 70°C to match the steady-state conditions. Set the controller gain to 1.0, but leave the integral time and derivative time blank. Make sure that you correctly specify whether your controllers are direct acting or reverse acting so that the controller will open/close the valve when required, and not vice versa. Finally, set the controller to automatic. 

Apparatus— The thief shall be designed so that a sample can be obtained within 1.25 cm (Vz in.) of the bottom of the tank car or tank. A closed-core type thief is shown in Fig. 6. This type of thief has a projecting stem on the valve rod which opens the valves automatically as the stem strikes the bottom of the tank. The sample enters the container through the bottom valve, and air is released simultaneously through the top valve. The valves snap shut when the thief is withdrawn. Use only clean, dry cans, or glass bottles as sample containers. 

Batch Extractors. Coarse soHds are leached by percolation in fixed or moving-bed equipment. Both open and closed tanks (qv) having false bottoms are used, into which the soHds are dumped to a uniform depth and then treated with the solvent by percolation, immersion, or intermittent drainage methods. 

Fig. 11. Diaphragm-box systems, open and closed types, used where pressure gauges cannot be located at the minimum tank level.

Diked or Unitized Secondary Containment. Small tanks can have a secondary-containment dam built integrally into the tank. This is essentially within a steel box. These tanks may be either vertically or horizontally oriented in both cylindrical and rectangular shapes. The secondary-containment dikes may be open or closed. Closing the dikes makes access to the primary-containment tank more difficult, but keeps out rainwater. 

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