Tower Interference

The entering of a tower by hot, humid air discharged from another tower is tower interference. No thermal test code makes provision for tower interference it is necessary to determine what the wet bulb will be at that particular location in the plant. Many times the tower can be made smaller by moving it a few feet or by angling it to escape the down-wind vapor from an operating cooling tower. 

---

The use of cooling tower basins and process water pumps as fire water supply is not recommended. This water is usually treated with chemicals or may be contaminated with hydrocarbons that interfere with the use of foam extinguishing agents. At best, this supply could serve as a secondary system, should the primary supply be interrupted, using emergency connections. 

Interference is defined as an adulteration of the atmosphere entering the tower by a portion of the atmosphere leaving another nearby cooling tower. Recirculation is an adulteration of the atmosphere entering the tower by a portion of the atmosphere leaving the tower. Both are illustrated in Figure 6.8. 

These problems are typical in mechanical-draft cooling towers and virtually nonexistent in hyperbolic towers because of the height of vapor discharge. The magnitudes of interference and recirculation depend primarily on wind... 

Interference from industrial installations or multiple tower arrangements can result from poor planning of plant additions. Careful planning will provide the most effective cooling results. In general, interference can be... 

Figure 6.9 Proper tower orientation can avoid interference from multiple tower arrangements.

Also, high levels of bacteria/biomass can significantly interfere with the efficiency of the various types of tower film-fill. Typically, the film-fill and tower manufacturers propose a maximum TAB of 1 x 105 cfu/ml. This level should be reduced to 1 x 104 cfu/ml if the TSS >25 ppm or if the film-type is a particularly high-efficiency design. 

In June 1980, the venturi scrubber was removed from Train 100, allowing operation with the spray tower only. Prior to the removal of the venturi scrubber, operation with a true spray tower-only configuration was not possible without some interference from the venturi, even with its adjustable plug wide open and minimum slurry flow for flue gas cooling. 

Considerable inconvenience is sometimes encountered when setting the tower in place because it is difficult to lower the heavy vessel over the foundation bolts without bending them or damaging the threads. Figure 11-2 illustrates this difficulty. A sleeve nut is welded to the top of the bolt. It is placed so that the top of the nut lies slightly below the surface of the concrete, with a sheet metal sleeve around it. The tower may then be placed in position without interference from the bolts. Stud bolts are next inserted through the lugs on the tower, and screwed into sleeve nuts from the top. 

I-beam interference can be just as troublesome in the space above a chimney tray. In one case history contributed by D. W. Reay (334), this interference is believed to have led to severe vapor maldistribution in a refinery vacuum tower (Fig. 8.66). The maldistributed vapor profile was displayed as a carbon deposit on the siuTace of the bottom packing. The deposit formed an annular ring about 5 ft wide that extended about 1 in into the bed. In that case, liquid was known to overflow the chimneys for several months because of an incorrect location of level tappings. This overflow caused liquid entrainment. Some entrained droplets ultimately carbonized on the base of the bed. Had the vapor profile been uniform, entrainment (and therefore deposit laydown) would have been more uniform. It is believed that vapor from the side chimneys was blocked by the beams and preferentially ascended around the periphery. If liquid overflow (down the risers) had been uneven, the maldistribution could have been further aggravated. 

The athletic field was surveyed but interference from the television tower presented difficulties. The amount of fill over this pit (10-12 ft from the cut and fill maps), together with the description of the pit as deep in the 1921 Courier story, suggest that the current instruments would not be able to locate it. Finally, the explosives may have been buried in bulk, not shells. Wooden barrels have little signature for a metal detector. 

The simulation of scenario 3 is shown in Fig. 5. This scenario represents a situation when the pilot of the Hercules aircraft has erroneous expectations about the take-off clearance and initiates take-off while he should not (like in scenario 1). However, in this case the controllers in the Tower observe the conflict situation rather late, and therefore they do not have the time to interfere. As a result, both aircraft collide see atom collision(hercules, airbus) at the end of the trace. 

In this scenario the time parameters of the rule that generates the action to take off have been modified in such a way that this action is performed more quickly. This has important consequences for the opportunity of the Tower to interfere and prevent the collision. As can be seen in Fig. 5, the short duration of the take-off procedure leads to severe consequences as both aircraft perform take-off almost simultaneously on crossing runways. 

There is always a cratain amount of entrained liquor in the gas leaving the cells. This is in the form of a mist that has been known to survive beyond the gas coolers and into the drying system, and deposits can form in the chlorine piping and processing equipment. Also, the sulfuric acid used in the drying system is notorious as a source of mist that can interfere with the performance of downstream equipment. Mist eliminators installed both before the coolers and after the drying towers alleviate these problems. Section 9.1.5 covers this subject... 

A scaffold tower could interfere with the safe swinging of a load by the crane. 

For example, in San Francisco, Toronto, and Montreal, huge towers have been built to consolidate as many broadcasting facilities as possible, including VHF-TV, UHF-TV, FM, and land mobile communications services. This approach has proven very effective, not only using real estate economically, but spreading the tower costs over many users. In fact, the CN tower carries virtually all of the services in the Toronto area. These installations, of course, employ combiner networks to prevent interference among services. 

---