Atmospheric tanks elevated

All d/p cells can be provided with zero, span, elevation, and depression adjustments, either mechanical or electronic. Table 3.114 shows some typical d/p cell ranges and the available elevation and suppression setting adjustments for each. Whenever the d/p is at an elevation other than the connecting nozzle on an atmospheric tank, the zero of the d/p cell needs to be elevated or depressed. It is important to realize that two zero-reference points exist. One is the level in the tank that is considered to be zero (lower-range value) when the tank is almost empty. The other zero-reference point is the point at which the d/p cell experiences a zero differential pressure (zero value of the... 

Example 1 Application of the total mechanical-energy balance to noncom-pressible-flow systems. Water at 61°F is pumped from a large reservoir into the top of an overhead tank using standard 2-in.-diameter steel pipe (ID = 2.067 in.). The reservoir and the overhead tank are open to the atmosphere, and the difference in vertical elevation between the water surface in the reservoir and the discharge point at the top of the overhead tank is 70 ft. The length of the pipeline... 

Applications. PBCMO is used especially as material resistant in corrosive atmospheres at moderately elevated temperatures. Useful applications are found as adhesives, coatings, sheeting, lining pipes, tanks, etc. It must also be noted that BCMO and other oxetanes are also used to prepare polyglycols which are used in polyurethanes, polyesters, and polyamide-type elastomers. 

Dissolution of air at high pressure in part of the stream, with its snbsequent release in fine bubble form on reduction of the pressure to atmospheric level—This method is widely used in DAF process. In this process, a clean water stream is partly saturated with air at an elevated pressnre at 4-6 atm gange. The high-pressnre stream is mixed with the influent at the flotation tank inlet. The tiny bubbles are formed and released from the excess air originating from the pressure reduction of the stream. 

Use Eq. (4.32). Take station a at the surface of the liquid in the tank and station b at the discharge end of the 2-in, pipe. Take the datum plane for elevations through the station a. Since the pressure at both stations is atmospheric, p — p. The velocity at station a is negligible because of the large diameter of the tank in comparison with that of the pipe. For turbulent flows the kinetic-energy factor a can be taken as 1.0 with negligible error. Equation (4.32) becomes... 

Example 2.14. Figure 2.14 shows a tank of gas connected to a manometer. The manometer is a U-shaped glass tube open to the atmosphere at one end and containing water. From the elevations shown, calculate the gauge pressure in the vessel. ... 

The cold water feed can be provided by direct coimec-tion to the mains (in which case all components must be able to withstand mains pressure) or from a feeder tank (which is in an elevated position and filled from the mains through a float valve similar to the water closet-cistern float valve). For mains pressure systems most utilities or water supply authorities require the installation of a nonreturn valve. Whereas low pressure (feeder tank) systems are open to the atmosphere through a vent pipe, mains pressure systems must be protected against overpressure (due to thermal expansion of water as heated) by a pressure relief valve, as well as against collapse (implosion), which could be caused by a suction effect (vacuum formation) in case of an aceidental water discharge, by an air intake (or breather) valve. 

Waste Disposal Stack, The stack for waste disposal will serve mainly to dilute the H2O2 mixture from the flash tank condenser to below the explosive limit and to discharge it, along with any other gaseous wastes from the process, to the atmosphere at a safely high elevation. In its base an induced draft fan will be located which should handle about 1400 cfin of air. Quite possibly this stack can be eliminated by use of others in other imits of the project if these are located nearby. 

A preferred system, which the process industries increasingly tend to use, provides a free fall or an air gap to achieve isolation. Figure 12.13 is the familiar break tank. As drawn, the water supply line does not enter the break tank. It should end at least two line diameters above the flood level of the receiver. The supply line can extend into the tank if a positive overflow is provided and the proper gap is maintained between supply and overflow. Good practice then also includes a break in the overflow pipe. The disadvantage of a break tank, especially the open type, is the loss of line head when the water is held under atmospheric pressure. This can be restored by elevating the break tank or by pumping the water from the break tank for distribution. 

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