Copyright Goodheart-Willcox Co., Inc. 392 Fluid Power Dresser-Rand. Describes a centrifugal compressor designed for a process application in the oil, gas, or chemical industries. FS-Elliott Co., LLC. Describes a line of centrifugal compressors. Illustrated with a general description of the operation of a two-stage unit including intercoolers. Hydraulics & Pneumatics Magazine. Review two articles: Air Compressors–Part 1 and Air Compressors– Part 2. These articles cover the styles of compressors available in the pneumatic field, emphasis on rotary compressors. Also includes information on power and efficiency, lubricated or lubrication-free compressors, cooling methods, and capacity control. Ingersoll Rand Company. Provides information on reciprocating air compressors manufactured by the company. The brochure linked on the page refers to single- and two-stage air compressors. Jenny Products, Inc. Guide to selecting an air compressor for a small business operation or home shop. Covers factors such as the need for staging, type of prime mover, and specific questions that should be answered before purchasing a compressor. Saylor-Beall Manufacturing Company. Manufacturer that produces reciprocating and screw compressor units. Information contained includes product brochures and service manuals with illustrated, informative materials covering general questions and answers. SENCO Brands, Inc. Product manual for a single- stage, reciprocating compressor. Applications for these compressors range from the home shop to industrial situations. Chapter Review Answer the following questions using information in this chapter. 1. A compressed air unit classified as a portable unit gives a(n) _____ air supply. A. industrial B. prime mover C. receiver D. central 2. True or False? Double-acting reciprocating compressors have compression chambers at each end of the pistons. 3. True or False? The crankshaft is the only moving part in a centrifugal compressor. 4. True or False? Displacement of a compressor is the volume of air displaced per revolution of the unit. Summary • Compressed-air units produce pressurized air for the pneumatic system. • A compressed-air unit consists of a prime mover, a compressor, and components that condition and store the pressurized air used by the system workstations. • Compressed-air units can be portable or permanently mounted to provide air to fixed workstations from a central supply. • The basic operation of any compressor design used in a pneumatic system includes three phases: air intake, air compression, and air discharge. • Compressors are classified by displacement (positive-displacement or nonpositive-displacement designs) and fundamental pumping motion (rotary or reciprocating designs). • Positive-displacement compressor designs mechanically reduce a compression chamber in size to compress air. Nonpositive-displacement compressors use impellers or vanes rotating at high speed to increase air velocity and pressure. • Reciprocating-piston compressors use a cylinder and a reciprocating piston to compress air. Rotary designs use continuously rotating vanes, screws, or lobed impellers to move and compress the air. • Compressor-capacity control systems are used to match the volume of compressed air produced by the compressor to the volume of compressed air consumed by the working pneumatic system. The closer the compressor air output matches system consumption, the more cost effective the system operation. • Compressor-capacity control systems include bypass, start-stop, inlet valve unloading, speed, and inlet size controls. • Determining the required output of a compressor can be accomplished by identifying the actuators used, the volume of compressed air needed for the operation of each item, and the percentage of time each functions during system operation. Internet Resources The following are some useful resources available on the Internet. Enter a company or organization name into a search engine to access its website. Explore the various areas of the sites to discover useful fluid power resources. Atlas Copco. Enter “screw compressors” in the product search box to review product information on the various rotary screw compressors manufactured by the company. Includes stationary and portable units. Copyright Goodheart-Willcox Co., Inc. Chapter 15 Source of Pneumatic Power 393 Apply and Analyze 1. Which type of compressor would you choose for each of the situations listed below? Why? Identify specific aspects of compressor design or operation that allow the compressor to meet the stated needs. A. A steady, continuous supply of air. B. Low volumes of high-pressure air. C. Very large volumes of oil-free pressurized air. D. Minimal vibration of the compressor. E. Large volumes of air, but space for installation is limited. 2. For each of the following compressor types, where does energy loss occur during operation? A. Reciprocating-piston compressor. B. Rotary sliding-vane compressor. C. Centrifugal compressor. 3. You are assisting a company that is installing new compressors and updating their pneumatic system. The company is interested in minimizing not only initial investment costs, but also costs of operation. A. What specific advice would you give them in their choice of compressors? B. What information would you need to determine the best method(s) of compressor-capacity control for improving the efficiency of the system during operation? Explain your answer. Research and Development 1. Lubrication is critical for the performance and service life of many air compressors. Investigate the different methods of lubrication used for the main types of positive-displacement compressor. Prepare a chart that illustrates the benefits and drawbacks of each lubrication method. 2. Using air compressor manufacturers’ product listings found online, find and compare two compressors which could be used for similar applications, but which have different basic designs, such as rotary and reciprocating. Develop a fact sheet to be used to help a potential customer choose between the two compressors. 3. Investigate the historical development of air compressors. Produce a time line that shows design changes as well as the use of new materials or machining methods to improve performance. 4. Research an application that uses dynamic compressors to pressurize air. Write a report that describes the application, discusses the design and capacity of the compressor, and explains why this type of compressor is used. 5. True or False? Single-acting compressors use cylinders, pistons, connecting rods, and crankshafts similar to the type found in internal combustion engines. 6. An automatic compressor capacity control method is commonly used with a smaller compressor using _____ as the prime mover. A. steam power B. electric motors C. pneumatics D. gasoline engines 7. True or False? The housing around the centrifugal compressor forms a volute collector that directs the airflow through the compressor. 8. Lobe-type compressors typically only develop air pressures ranging from 10 to _____ psi. A. 20 B. 35 C. 60 D. 100 9. Typically, today’s nonpositive-displacement compressors compress air using _____. A. impellers B. cylinders C. chambers D. pistons 10. True or False? An impeller turning at relatively low speed moves air through a centrifugal air compressor. 11. In the lobe-type compressor, there is no reduction of air volume in the compressor as the impellers turn. The air is simply swept from the inlet port to the _____ port. 12. Using a number of compressor units to increase pressure in small increments is called ______. A. start-stop B. capacity control C. bypass D. staging 13. Compressor-air output and system-air demand are matched by using some type of _____ control system. 14. A common method of compressor-capacity control used with reciprocating compressors is inlet valve _____. 15. True or False? When selecting a pneumatic system compressor, only one or two factors need to be considered. Internet Resources help you fi nd websites that extend learning beyond the scope of this text. Summary provides an additional review tool for you and reinforces key learning objectives. Apply and Analyze activities develop higher-order thinking skills, extend your learning, and help you analyze and apply knowledge. Chapter Review questions allow you to demonstrate knowledge, identifi cation, and comprehension of chapter material. Research and Development activities provide additional opportunities for you to explore and deepen your understanding of key concepts from each chapter.