Open tanks

Fig. 10. Pressure gauge, caHbrated in terms of Hquid height, for measurement of level in open tanks.

If an ethyl ether fire occurs, carbon dioxide, carbon tetrachloride, and dry chemical fire extinguishers meeting National Eire Prevention Association Code 1 and 2 requirements may be used successhiUy (23). Water may also be effectively appHed (see Plant safety). Hose streams played into open tanks of burning ethyl ether serve only to scatter the Hquid and spread the fire. However, ether fires may be extinguished by a high pressure water spray that cools the burning surface and smothers the fire. Automatic sprinklers and deluge systems are also effective. 

Open Tanks These may be used to store materials that will not be harmed by water, weather, or atmospheric pollution. Otherwise, a roof, either fixed or floating, is required. Fixed roofs are usually either domed or coned. Large tanks have coned roofs with intermediate supports. Since negligible pressure is involved, snow and wind are the principal design loads. Local building codes often give required values. 

Types of Jigs A jig is essentially an open tank filled with water and provided with a horizontal screen on the top and a hutch compartment fitted with a spigot (Fig. 19-27 ). A layer of coarse, heavy particles, known as ragging, is placed on the top of the screen onto which the feed slurry is introduced. The feed moves over the ragging and the separation takes place as the bed is pulsated by a different mechanical device. The heavy particles are collected into the hutch compartment and removed through the spigot while the hghter particles are made to overflow from the top or the tank. 

Now let s consider Figure 2-2. This is a pump in suction lift draining an opened tank that s 8 feet below the pump centerline. This pump is installed high on a mountain at 7,000 feet above sea level. The Ha is 26.2 feet. The Hsj is -8.0 feet. The water temperature is 50° F, so the Hvp is 0.411. The Hf is 1 foot and the Hi is 2.0. According to the information ... 

The feed water in the d-a tank normally runs about 190°F in an open tank. Then we have ... 

Portable or fixed mixers up to 5hp normally use propellers and run at either direct drive speeds of 1,150 or l,750rpm or at single reduction gear drive speeds between 300 and 420 rpm. They may either be clamped on the rim of open tanks or mounted with a fixed assembly for open or closed tank operation. These mixers are the most economical and are usually used in tanks without baffles. They are rugged and long-lasting. 

Avoid open tanks, even if only loose lids practicable Provide barriers... 

Emission from an open liquid face (e.g., open tanks, liquid spills on the floor surface) can be evaluated using equations based on criteria relations and empirical data. Assuming that the heat and mass transfer processes can be described using similar differential equations, the criteria equation describing the evaporation process will be similar to one describing the heat transfer ... 

The term F in equation 8.59 may be calculated directly for the flow of liquid through a uniform pipe. If a liquid is pumped through a height Az from one open tank to another... 

Water discharges from the bottom outlet of an open tank 1.5 in by 1 m in cross-section. The outlet is equivalent to an orifice 40 mm diameter with a coefficient of discharge of 0.6. The water level in the tank is regulated by a float valve on the feed supply which shuts off completely when the height of water above the bottom of she tank is I m and which gives a flowrate which is directly proportional to the distance of the water surface below this maximum level. When the depth of water in the lank is 0.5 m the inflow and outflow are directly balanced. 

Our senses tell us that molecules escape from a liquid. The red gas phase above the liquid bromine in Figure 11-4 shows that bromine molecules are in both phases. The evaporation of a rain puddle in the sunshine shows that water molecules escape from the liquid into the gas phase. The smell of gasoline around an open tank informs our noses that gasoline molecules escape from the liquid phase into the gas phase. 

The programs for the open tank (CONFLOl), for the closed isothermal tank (C0NFL02) and for the closed adiabatic tank (C0NFL03) are given below. 

CONTINUOUS OPEN TANK FLOW PROBLEM OF RAMIREZ... 

Aqueous cyanide effluent containing a little methanol in a 2 m3 open tank was being treated to destroy cyanide by oxidation to cyanate with hydrogen peroxide in the presence of copper sulfate as catalyst. The tank was located in a booth with doors. Addition of copper sulfate (1 g/1) was followed by the peroxide solution (27 1 of 35 wt%), and after the addition was complete an explosion blew off the doors of the booth. This was attributed to formation of a methanol vapour-oxygen mixture above the liquid surface, followed by spontaneous ignition. It seems remotely possible that unstable methyl hydroperoxide may have been involved in the ignition process. 

When an open tank with a free surface is stirred with an impeller, a vortex will form around the shaft. It is important to prevent this vortex from reaching the impeller, because entrainment of air in the liquid tends to cause foaming. The shape of the free surface depends upon (among other things) the fluid properties, the speed and size of the impeller, the size of the tank, and the depth of the impeller below the free surface. 

A pump that is taking water at 50°F from an open tank at a rate of 500 gpm is located directly over the tank. The suction line entering the pump is a nominal 6 in. sch 40 straight pipe 10 ft long and extends 6 ft below the surface of the water in the tank. If friction in the suction line is neglected, what is the pressure at the pump inlet (in psi) ... 

It is desired to siphon a volatile liquid out of a deep open tank. If the liquid has a vapor pressure of 200 mmHg and a density of 45 lbm/ft3 and the surface of the liquid is 30 ft below the top of the tank, is it possible to siphon the liquid If so, what would the velocity be through a frictionless siphon, 1 /2 in. in diameter, if the exit of the siphon tube is 3 ft below the level in the tank ... 

Consider the tank on wheels shown in Fig. 5-P66. Water is draining out of a hole in the side of the open tank, at a rate of 10 gpm. If the tank diameter is 2 ft and the diameter of the hole is 2 in., determine the magnitude and direction of the force transmitted from the water to the tank. 

You want to siphon water from an open tank using a 1 /4 in. diameter hose. The discharge end of the hose is 10 ft below the water level in the tank, and the siphon will not operate if the pressure falls below 1 psia anywhere in the hose. If you want to siphon the water at a rate of 1 gpm, what is the maximum height above the water level in the tank that the hose can extend and still operate ... 

Water is to be transferred at a rate of 500 gpm from a cooling lake through a 6 in. diameter sch 40 pipeline to an open tank in a plant that is 30 mi from the lake. 

A pipeline is installed to transport a red mud slurry from an open tank in an alumina plant to a disposal pond. The line is 5 in. sch 80 commercial steel, 12,000 ft long, and is designed to transport the slurry at a rate of 300 gpm. The slurry properties can be described by the Bingham plastic model, with a yield stress of 15 dyn/cm2, a limiting viscosity of 20 cP, and an SG of 1.3. You may neglect any fittings in this pipeline. 

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