Compressed and Instrument Air System

The compressed and instrument air system consists of three subsystems instrument air, service air, and high-pressure air. 

No design requirements associated with maintaining safety functions are placed on the compressed and instrument air system. 

As described abeady in Chap. 6, instrument air and compressed air for operating purposes are normally supplied by the ah compressor in the air separation unit A receiver in the instrument air system ensures a continuous supply during malfunctions for a period of 30 minutes. A diesel-powered auxiliary compressor is usually installed to start up the plant and ensure compressed air supply during downtimes. 

Here is another case history of a compressed air system that was modified to near disaster. Details of this incident are unavailable, but some years ago a chemical plant or refinery with multiple reciprocating air compressors and pneumatic instruments systems decided to modernize. The modernization project replaced the air supply system. Economics favored one large centrifugal air compressor, and no backup air supply was installed. 

Sample preparation is critical to the success of any spectrophotometric experiment whether using absorbance or fluorescence detection systems. Even the rapid mixing of two samples of buffer in a sensitive instrument can result in what appears to be a reaction curve. This may be caused by simple effects such as the rapid compression and decompression of an air bubble in the flow path, the nuxing of two solutions at different temperatures or the effect of the stopping process upon small dust particles present in the solution. Therefore it is essential that solutions be prepared thoroughly before use. Sometimes it is necessary to degas buffers to remove dissolved air that may otherwise come out of solution following rapid decompression of the reaction solutions. In practice, it is... 

Schematic of furnace camera system shows (1) wallbox, (2) furnace lens, (3) air-cooled CCTV housing, (4) light volume control, (5) compact CCD camera, (6) video monitor, and (7) high-efficiency compressed air filter. ("FireSight High-Temperature Remote Viewing Systems." Lenox Instrument Company brochure with photos and diagrams of system and components.)...

Heating, ventilation, refrigeration, and air conditioning systems Building instrumentation and control systems Pollution-control systems, dust-collection systems Telephone and communication systems Compressed air systems... 

Optimize compressor operation, reduce friction and air leakages in air distribution system, low pressure drop air coolers and instruments, reduction of air leaks, use of heat of compression dryers, cool compressor suction air, waste heat recovery at compressor inter-stage coolers, better control Install additional compressors in parallel. Use of heat of compression dryer Use cogeneration, ORC, KC or (hydraulic) power recovery turbines... 

Compressed air to operate ventilation-system dampers comes from two redundant, industrialsized compressors [40 standard ft /min (SCFM) at 125 Ib/in. (psi)], located in Room 222 of B6581. The two compressors operate as a primary supply and as a backup. Downstream of the normal air compressors is miscellaneous support equipment including an air receiver and filters. The air supply is then split into two separate pathways (1) general building compressed air, and (2) dry Instrument air, which is used in the HCF for ventilation system damper positioning. 

Air systems include compressed air as a plant utility and refined versions for more specialized uses. These include instrument air and breathing air. Of particular significance in a chlor-alkali plant is a supply of dry air for use in the chlorine processing section. An alternative to dry air is nitrogen, which also serves as an inert gas in the hydrogen plant and sometimes in chlorine liquefaction and tail-gas handling. For convenience, we include the discussion of nitrogen in the section on air systems. 

Energizing power systems, operational testing of plant equipment, calibration of instrumentation, testing of the control systems, and verification of the operation of all interlocks and other safety devices, without yet introducing process materials. These activities are usually described as cold commissioning . In parallel, it is usually necessary to commission the plant utilities, such as cooling water and compressed air systems, in order to enable equipment operation. 

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... 

A.1(X)6. All auxiliary systems associated with the reactor process system and the experimental facilities, such as compressed air, process sampling and equipment and floor drainage systems, shall be discussed in this section. The discussion should include the design bases, a system description, a safety evaluation, testing and inspection requirements, and instrumentation requirements. 

The design of the RCSASs should also reflect constraints imposed by the support systems and structures. Support systems include, for example, ventilation systems, compressed air systems, electric power systems and the instrumentation and control system. 

The operational test of the lube system is, as the name implies, a functional test to check as many of the features as practical under running conditions. The first and last step is a demonstration of the cleanliness of the system. This is followed by a running test of a four-hour duration. The test should simulate the field operation with the compressor in every way practical. All equipment to be furnished with the lube system should be used in the test, including the standby pump start and trip switches. All other instruments should be used to demonstrate their operation. Prior to starting the four-hour run, the system should be thoroughly inspected for leaks and the leaks corrected. If no steam is available for a steam turbine (if one is used), the four-hour run can be made on the electric pump. However, every effort should be made to use an alternate source of energy such as compressed air, to operate the steam turbine. 

Compressed air invariably contains water and usually oil from the compressor. It is also likely to pick up dirt and rust from the distribution line. For use in the laboratory, the air must be clean, particularly if it is to be used in instruments. One laboratory operator suggested the use of corrosion resistant pipes for the air distribution system in a building. This was turned down because of its high cost. The result was a heavy load of rust which began to accumulate in air filters after only a few months of operation. 

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