Cooling towers instrumentation

Acceptance Testing Test procedures to determine the water cooling capacity of towers. Instrumentation used and measurement procedures should be those recommended by the Cooling Tower Institute (CTI) in its "Acceptant Text Procedures. "... 

Cooling water (cooling towers) Chilled water Demineralised water Steam (from direct fired boilers) Compressed air (9 bar) Instrument air (9 bar) (dry) Refrigeration Nitrogen... 

Loss of utilities including electrical power, steam, cooling tower water, instrument air, and nitrogen. 

The instruments usually provided for cooling towers and circulating pumps include ... 

Float valves are required on all cooling tower systems. Their purpose is to supply makeup water to replace that lost by evaporation, blowdown, drift and system leakage. They are usually installed in the cold water basin and function to maintain a preestablished water level. A typical flowsheet showing the recommended arrangements for instrumentation and valves is given in Figure 7.4. 

The specifier must have a good understanding of instrumentation and support machinery. Any process instrumentation book will acquaint the newcomer to this area with the criteria for proper instrumentation selection. To illustrate the process involved in specifying the entire cooling tower system package, the following example has been prepared. 

The cooling tower manufacturer shall conduct the acceptance performance test and shall supply the necessary instruments to conduct the test in accordance with the requirements of the CTI Test Procedure ATP-105, latest revision. 

In 1974 the Atlantic City Electric Co. placed Unit 3 of its B L England Station into commercial operation. Condenser cooling for the unit is provided by circulating sea water in a closed-cycle, natural-draft system. The cooling tower selected for the site was a hyperbolic, counterflow unit. The thermal test instrumentation procedures and test data as well as drift measurement results are given. The paper indicates that the tower operates within design specifications for thermal performance and that it meets the environmental criteria regarding the drift. 

These are instrument system loops that are necessary to avoid a failure which could result in nonreportable environmental releases, equipment or production losses, or reduced economic life, plus all other systems and alarms that assist operations that require prooftesting. These alarms and shutdown systems include refrigeration units that have less impact or safety or environmental issues than the Class 2 units, important pump shutdown alarms, low pressure utility alarms (well water, cooling tower water, natural gas, instrument air, nitrogen), and numerous low-pressure lubrication alarms. 

Class 2 Safety Critical instruments include alarms or trips on refrigeration systems, rectifiers, cooling towers, kettles, and stills. [8]... 

Class 2 Safety Critical instruments include alarms or trips on refrigeration systems, rectifiers, cooling towers, kettles, and stills. [71 Normal Consequences—Class 3. Instrument systems that are used to alert the chemical pracess operator of a nonhazardous abnormal condition that might otherwise be undetected. The failure to react to one of these alarms may create an off-spec ificalion product such as a low-temperature alarm on certain distillation columns. These systems are not included in the prooftest program. 

Figure 2. A pipe filled with cold water makes a fanciful cooling tower. Solutions are heated at the bottom and a distilled medicinal water (an aqua vitae) is collected at the top. The depiction of alchemical instruments sometimes arose more from the imagination than from actual use. From H. Brunschwig, Das Buch zu Distillieren (Strassburg, 1532). University of Wisconsin Library.

Utilities. The utility requirements for a process are obtained from both a material and energy balance. The unit costs for each utility may be obtained from plant expense sheets, the accounting department, or a utility superintendent. These costs often increase continually, so they should be reviewed frequently. Utilities are usually steam (high-, medium-, and low-pressure) and their associated unit costs, electricity, natural gas, cooling tower water, and treated or city water. Sometimes instrument air, demineralized water, and refrigeration are considered utilities if they come from a central source and are not tied to a given process. 

Instruments are furnished to record the production flow of (1) make-up water to the cooling towers, and (2) blended and demineralized water to the storage tanks.-... 

All the instruments having to do with the operation of the plant except those directly connected with the cooling tower pumps and fans will be located in a central intrument and control house, as shown in Fig. 37. Operating headquarters for the plant will be in this building. The instruments for the cooling tower pumps and fans will be located near these units for convenience in control. 

Coolant water temperature > design instrument fault/low coolant flowrate/high coolant inlet temperature/cooling tower fault/excess condenser area. 

Process Technology 2—Systems—study of common process systems found in the chemical process industry, including related scientific principles. Includes study of pump and compressor systems, heat exchangers and cooling tower systems, boilers and furnace systems, distillation systems, reaction systems, utility system, separation systems, plastics systems, instrument systems, water treatment, and extraction systems. Computer console operation is often included in systems training. Emphasizes scale-up from laboratory (glassware) bench to pilot unit. Describe unit operation concepts solve elementary chemical mass/energy balance problems interpret analytical data and apply distillation, reaction, and fluid flow principles. 

Valves, piping, and vessels Pumps, compressors, fans, and blowers Steam turbines and motors Heat exchangers and cooling towers Boilers and furnaces Reactors and distillation columns Instrumentation Basic hand tools Lubrication, bearings, and seals Flares, mixers, and steam traps... 

Symbols and diagrams have been developed for most pieces of industrial equipment, process flows, and instrumentation. The symbols covered in this chapter include those typically used with valves, piping, tanks, pumps, compressors, steam turbines, motors, heat exchangers, cooling towers, furnaces, boilers, distillation columns, and reactors. Figure 7-6 shows many of the basic symbols for valves. 

Cooling-tower system—includes a cooUng-tower and pipe system to transfer cooled water to the unit and back to the cooling-tower water-distribution system. The cooling tower has a series of complex instrument systems to control ppm, pH, level, temperature, fan speed, and flow rate. 

A distillation process uses a complex arrangement of systems that includes a cooling-tower system, pump-and-feed system, preheat system, product storage system, compressed-air system, steam-generation system, and complex instrument control system. (See Figure 10-3.) Each of these stand-alone systems is designed to support a specific part of the distillation process. Each... 

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