Orifice purging

The safety advantages of these devices can be seen in the release rates of a compressed gas from cylinders under pressure. The orifice is an effective, inexpensive, and easy to use safety device which should be used more often to mitigate the consequences of catastrophic gas release. Almost all compressed gases, with the exception of low vapor pressure materials, such as chlorine and boron trichloride, may be used successfully with a limiting orifice. 

---

A small hole has been deliberately placed in a vessel near the top to provide a controlled vent for a nitrogen purge/blankeL The hole is 0.2-inch diameter witli the vessel operating at 150 psig at 100°F. Determine the flow through this vent hole. Assume it acts as a sharp edged orifice. 

Once the unit is running well, it is often assumed that the aeration system is sized properly, but changes in the catalyst physical properties and/or catalyst circulation rate may require a different purge rate. It should be noted that aeration rate is directly proportional to catalyst circulation rate. Trends of the E-cat properties can indicate changes in the particle size distribution, which may require changes in the aeration rate. Restriction orifices could be oversized, undersized, or plugged with catalyst, resulting in over-aeration, under-aeration, or no aeration. All these phenomena cause low pressure buildup and low slide valve differential. 

Improperly designed, eroded, or even missing restriction orifices used for steam purge or aeration nozzles could cause catalyst attrition. Catalyst attrition is also caused by broken air and stripping steam distributors. 

Confirm that the restriction orifices used for instrument purges are in proper working condition and that the orifices are not missing. 

Early modern experiments in anatomy confirmed and intensified interest in the ear as a permeable orifice. In 1564 the anatomist Bartolomeo Eustachio identified the passage now known as the eustachian tube. As an open passage, the eustachian tube represents the ear s ability to transmit matter in or out of the body. As Eustachio commented, Knowledge of this passage will be very useful to physicians for the correct use of medicaments, because now they will know that even thick material can be expelled or purged from the... 

A-FEED GAS CYLINDER B-ORIFICE C-AP TRANSMITTER D-P.T.AP RECORDER E-MANOMETER F-SOLENOID VALVE G-N2 PURGE SYSTEM H-REACTOR BY-PASS LINE J-PREHEATER K-REACTOR L-MAGNETIC DRIVE M-SPEED CONTROL AND TACHOMETER N-CONDENSER P-KNOCKOUT POT Q-LIQUID COLLECTING TANK R-LIQUID LEVEL CONTROL... 

Simplified versions of the Fig. 5.8d arrangement are common some are described elsewhere (68). In some cases, the purge lines split downstream of a shared rotameter and needle valve. An even simpler system replaces the pressure regulator, rotameters, and needle valves by a restriction orifice in each line. Although the simplified systems save capital and can be made to work, the simplifications are achieved at the expense of more troublesome operation, and the author would not recommend them. 

Include high pressure water purge for both forward and reverse flow at velocity > 1 m/s. Avoid dead ends and pockets. Arrange for flushing of the line with water place nozzles on the top of the primary loop. Avoid flow restrictions, including orifices. 

These cabinets are automated-purge cabinets with redundant safety features such as excess-flow sensors, reduced-flow orifices, and system-failure shutdown protocols. They utilize high-turbulence constmction with high exhaust flow—200 cubic feet per minute at 0.02 inches of water pressure differential. These are monitored by automated sensors and manometers with a visual readout at the cabinet location. All cabinets contain fire sprinklers (Figures 8.15 and 8.16). 

Drains, purges, and bypass and isolation valves are properly installed. Orifices and accessories conform to specifications and are properly installed and oriented. 

---