Liquid seals

The main stem of the nitrometer widens into a bulb and then narrows to form a graduated tube. The usual graduation is of 8 ml. in o o2 ml. divisions. The graduations continue to the tap Tj at the top of the stem. Above Tj there is a small reservoir H to prevent splashing of the concentrated alkali when gas is expelled from the nitrometer and also to ensure that a small excess of potash is left as a liquid seal above the tap T ,. 

FIG. 26-27 Some special arrester designs (a) liquid seal arrester (h) Linde hydraulic seal arrester (c) wetted packed-bed acetylene decomposition arrester. (Howai d, 19S2.)... 

An effeetive way of preventing vent loss is to use one of the many types of variable-volume tanks. These are built under API Standard 650. They may have floating roofs of the double-deek or the single-deek type. There are lifter-roof types in whieh the roof either has a skirt moving up and down in an annular liquid seal or is eonneeted to the tank shell by a flexible membrane. A fabrie expansion ehamber housed in a eompartment on top of the tank roof also permits variation in volume. 

Gas compressors operating on highly toxic or flammable gases may require redundant systems to assure no leakages. In many applications, such as refrigeration gas, buffer seals are required with the liquid-buffered face seal. A popular technique is to use a buffered labyrinth seal with a liquid seal. 

Check gravity decanters for liquid seal and vapor equalizing line (syphon breaker). 

The top pressure controller varies the level of liquid in the condenser, so it, like the reboiler, must have extra surface for the derating required for control. Many other control methods also require some control surface. If noncondensibles are present, a vent should be provided. Otherwise, they collect at the liquid seal. With large amounts of noncondensibles, another type of system should be considered. 

In a 2-1. three-necked, round-bottomed flask fitted with a liquid-sealed mechanical stirrer, a dropping funnel, and an efficient reflux condenser are placed 720 g. (226 cc., 4.5 moles) of bromine (Note i) and 1.5 g. of sulfur (Note 2). A glass tube is connected to the top of the condenser to carry the evolved hydrogen bromide to a gas trap (Org. Syn. 14, 2). Sixty-nine grams (69 cc., 0.52 mole) of dry paraldehyde (Note r) is added slowly, with stirring, over a period of about four hours. The reaction proceeds under its own heat during the addition of the paraldehyde subsequently the mixture is heated externally for two hours at 60-80°. The solution is distilled and a fraction collected over the range 155-175° (Note 3). 

About half of the sodium ethylate solution is poured into a 3-]. round-bottomed, three-necked flask provided with a liquid-sealed stirrer and a reflux condenser the other half is kept warm by a small flame. The first half of the solution is allowed to... 

In a i-l. round-bottomed, three-necked flask fitted with an efficient reflux condenser, liquid-sealed stirrer, and dropping funnel is placed t3 g. (0.53 gram atom) of magnesium turnings. A few cubic centimeters of a solution of 60 g. (41.4 cc., 0.55 mole) of pure ethyl bromide in 50 cc. of absolute ether is added and the stirrer started (Note i). When the bromide begins to react 200 cc. of absolute ether is added, and then the balance of the bromide solution is run in as fast as the refluxing permits (about one-half hour). After allowing fifteen minutes for the completion of the reaction, a solution of 40 g. (0.42 mole) of 2,4-dimethyl-pyrrole (Org. Syn. 15, 20) in 100 cc. of absolute ether is added in the course of twenty minutes (Note 2) and the mixture is refluxed for one-half hour on the steam bath. 

In a 3-I. round-bottomed, three-necked flask fltted with a liquid-sealed mechanical stirrer, a thermometer, and a 500-cc. separatory funnel are placed 1700 cc. of dry ben2ene and 160 g. (1.2 moles) of powdered, anhydrous aluminum chloride (Note i). The mixture is cooled to 10° by means of an ice-water bath and maintained at 10-20 during the addition of a solution of 120 g. (0.58 mole) of benzalacetophenone (Note 2) (Org. Syn. Coll. Vol. I, 71) in 300 cc. of dry benzene. This addition requires about thirty minutes. The cooling bath is then removed and stirring continued at room temperature until all the dense, yellow precipitate formed at first has gone into solution (Note 3). The reaction is complete after stirring for an additional hour. 

Pressure Safety Design Practices Liquid Seals... 

Although liquid seals are relatively simple, reliable, and inexpensive, they are of limited application, because of the difficulty in meeting all of the criteria listed above. Also, they may not be too practical where vacuum conditions are encountered. 

On open drain piping leaving buildings, a liquid seal should be installed as further protection to assure that gases flashing from liquids from other locations in the drain system will not exit the system in the building. 

The NAO design uses a perforated (bubbler) plate with a skirt and bypass gap in case the bubble holes (about A-inch in diameter) get plugged. The design includes a minimum of 6 inches of liquid seal above the bubbler plate, and the gas superficial velocity is limited to 1 to 3 ft/s. 

Deflagration and detonation flame arresters should be inspected annually until operating experience indicates otherwise. Also, the need for frequent inspection and maintenance may affect the selection of one type of flame arrester over another type for a specific application. For example, a hydraulic (liquid seal) flame arrester may be more suitable than a dry, fixed-element, flame arrester if the latter requires frequent inspecdon and maintenance because of persistent plugging problems. 

Some designs of hydraulic (liquid seal) flame arresters have been sric-cesshilly tested for hydrogen service. NAO has designed and snccessfully tested and provided a hydraulic flame arrester for hydrogen-air applications (Straitz 1999). This design is for detonations and has dual liquid seal chambers with shockwave breakers. Rao (1980) also provides information... 

Acetylene may propagate decomposition flames in the absence of any oxidant above certain minimum conditions of pressure, temperature, and pipe diameter. Acetylene, unlike most other gases, can decompose in a detonative manner. Among the different types of flame arresters that have proven successful in stopping acetylene decomposition flames are hydraulic (liquid seal) flame arresters, packed beds, sintered metal, and metallic balls (metal shot). 

Elydranlic (liquid seal) flame arresters require attention on a regular basis similar to that for dry-type flame arresters. It is critical to ensnre that the liquid level is at the required height, and level instmmentation with alarms is recommended. Automatic addition of makeup liquid (to replace evaporation and entrainment losses) is desirable. Temperatnre instrumentation is also recommended to monitor the occurrence of sustained burning (a stabilized flame). See Section 5.3.18 for more details. 

A vacuum pump seal drum design which provides a liquid seal (hydraulic flame arrester) to mitigate flame propagation backward into the vacuum system. The seal liquid is an organic stream (mostly Cg aromatics) that comes from the vacuum pump discharge drum overflow. 

Q In-Line Deflagration FA Q End-of-Line Deflagration FA Q Hydraulic (Liquid Seal)... 

Dodge, F. T., White, R. E., and Bankler, T. 1998. Risk Assessment of Liquid Seals in Marine Vapor Control Systems. Final Report, SWRl Project No. 04-8954, Southwest Research Institute, San Antonio, TX (June 1998). 

Liquid Seal A device for preventing the passage of flame by passing the gas mixture through a suitable liquid. See Hydraulic Flame Arrester. 

The compound MgGa204, when activated by divalent impurities such as Mn +, is used in ultraviolet-activated powders as a brilliant green phosphor. Another very important application is to improve the sensitivity of various bands used in the spectroscopic analysis of uranium. Minor uses are as high-temperature liquid seals, manometric fluids and heat-transfer media, and for low-temperature solders. 

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