3B2 E2.5 C9 Review
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Questions and Answers

What are the three main types of compressor regulation systems mentioned in the text?

  • Stop-and-Start, Constant Speed, Variable Pressure
  • Start-and-Go, Variable Pressure, Steady Flow
  • Go-and-Stop, Constant Pressure, Variable Flow
  • Start-and-Stop, Variable Speed, Constant Speed (correct)

    • When does the compressor start in a start-and-stop control system?

  • At maximum receiver pressure
  • When the pressure rises to 1000 kPa
  • When the pressure drops to zero
  • At minimum receiver pressure (correct)

    • Which type of compression system is typically used for utility air systems with generally steady load demand?

  • Start-and-Stop Control system (correct)
  • Variable Pressure Control system
  • Constant Speed Control system
  • Variable Speed Control system

    • What are two conditions that can make start-and-stop control uneconomical?

    <p>Almost continuous demand for air and large air receiver</p> Signup and view all the answers

    What is the starting torque like in a sliding vane compressor compared to full load torque?

    <p>Less than full load torque</p> Signup and view all the answers

    Which type of compressor is most suitable for a start-and-stop control system according to the text?

    <p>Small reciprocating compressor</p> Signup and view all the answers

    What happens when the receiver reaches the set pressure in the compressor system?

    <p>A small piston opens a port for air passage</p> Signup and view all the answers

    What is an advantage of the suction-unloading valve described in the text?

    <p>Quick change of compressor suction valves</p> Signup and view all the answers

    What can result from the compressor and suction piping operating under a vacuum?

    <p>Increased gasket leaks</p> Signup and view all the answers

    How is control achieved for a sliding vane compressor using start-stop control?

    <p>Low pressure in the receiver</p> Signup and view all the answers

    What is an advantage of load-unload control for a rotary compressor?

    <p>Reduced energy consumption</p> Signup and view all the answers

    In the described load-unload control for a rotary compressor, what happens when the delivery pressure exceeds the required setting?

    <p>Air is admitted to the top of the operating piston</p> Signup and view all the answers

    What is the danger associated with the method of controlling the compressor by closing the suction valves?

    <p>Compressor cylinder overheating</p> Signup and view all the answers

    What happens when the suction-unloading valve is closed according to the text?

    <p>The compressor operates at full power</p> Signup and view all the answers

    What is the operation of the valve based on in load-unload control for a rotary compressor?

    <p>High-pressure air controlled by a pilot valve</p> Signup and view all the answers

    What is the method used to control the load for rotary compressors as discussed in the text?

    <p>Modulating inlet valve</p> Signup and view all the answers

    Which control method is used to maintain a constant system pressure by varying the compressor speed?

    <p>Variable Speed Control</p> Signup and view all the answers

    Which constant speed control method holds the inlet valve in the open position to prevent air from being trapped inside the cylinder?

    <p>Inlet air unloader</p> Signup and view all the answers

    What type of control is used automatically unload the compressor during motor start-up?

    <p>Inlet air unloader</p> Signup and view all the answers

    What happens when the air receiver pressure rises to the preset cutout pressure in a pilot valve?

    <p>The piston is forced downwards</p> Signup and view all the answers

    What is the disadvantage of using an inlet air unloader?

    <p>It results in extra repair costs and longer downtime</p> Signup and view all the answers

    What happens when the demand for air decreases in a variable speed control system?

    <p>The receiver pressure increases</p> Signup and view all the answers

    Which control method is used on a compressor that runs at constant speed?

    <p>Constant speed control</p> Signup and view all the answers

    What type of compressor is most likely to go into a surge condition when the speed is reduced too much?

    <p>Dynamic compressors</p> Signup and view all the answers

    What happens when the manual unload handle on the side of the pilot valve is used for start-up of the compressor?

    <p>The compressor starts in the unloaded position</p> Signup and view all the answers

    What is the advantage of using a suction line unloading valve?

    <p>It can be used where the compressor load changes frequently</p> Signup and view all the answers

    What is the purpose of the handle labeled 'handle in start position' in the pilot valve diagram?

    <p>To start the compressor in an unloaded position</p> Signup and view all the answers

    What is the function of the pressure transmitter in a modulating system?

    <p>To send a signal to the regulating valve controller</p> Signup and view all the answers

    What is the advantage of a modulating inlet valve control system?

    <p>It is more energy efficient as power consumption is directly linked to load demand</p> Signup and view all the answers

    What is the disadvantage of inlet vane control for dynamic compressors?

    <p>The compressor can go into a surge condition if the load demand is reduced significantly</p> Signup and view all the answers

    What is the role of microprocessors in rotary air compressors?

    <p>To replace the analog controller</p> Signup and view all the answers

    What is the function of electrical transducers and sensors in microprocessor-based control systems?

    <p>To sense variables such as air pressure and flow</p> Signup and view all the answers

    What is the advantage of microprocessor-based control systems over pneumatic control systems?

    <p>They are faster and more accurate</p> Signup and view all the answers

    What is the function of mechanical trip switches in electro-pneumatic control systems?

    <p>To discontinue compressor operation when pressures or temperatures reach critical levels</p> Signup and view all the answers

    What type of control system is preferred for processes with complicated and varying demand cycles?

    <p>Microprocessor-based control</p> Signup and view all the answers

    What is the function of a suction line unloading valve?

    <p>Prevents gasket leaks in the compressor and piping</p> Signup and view all the answers

    In which scenario is there slight compression in each end of the compressor cylinder but no air is delivered?

    <p>When the suction line unloading valve is closed</p> Signup and view all the answers

    What happens when the pilot-operated inlet valve in a rotary compressor opens?

    <p>Air is admitted to the top of the piston and the suction is shut off</p> Signup and view all the answers

    What is the primary disadvantage of closing suction valves in a compressor?

    <p>Poses a danger of over heating the compressor cylinder</p> Signup and view all the answers

    What is the main advantage of load-unload control for a rotary compressor?

    <p>Reduces power absorbed by the compressor to about 20% of full load</p> Signup and view all the answers

    Why is the control strategy associated with closing suction valves considered complex?

    <p>Poses challenges in managing air compression in the cylinder</p> Signup and view all the answers

    What is the role of the adjusting nut in the suction-unloading valve?

    <p>Adjusts the operating range of the unloader</p> Signup and view all the answers

    What happens when the suction-unloading valve is closed in terms of compressor operation?

    <p>The compressor and piping operate under vacuum</p> Signup and view all the answers

    Why can start-and-stop control for a sliding vane compressor be considered energy efficient?

    <p>The driver is started at a low pressure and stopped at high pressure</p> Signup and view all the answers

    What makes load-unload control for rotary compressors suitable for steady load demands?

    <p>The piston moves downwards to shut off suction</p> Signup and view all the answers

    Which type of compressor control system is most suitable for a small reciprocating or sliding vane compressor according to the text?

    <p>Start-and-stop control</p> Signup and view all the answers

    What proportion of full-load speed must a sliding vane compressor achieve before the sliding vanes begin to function?

    <p>40%</p> Signup and view all the answers

    Which two conditions can make start-and-stop control uneconomical for a compressor?

    <p>An almost continuous demand for air and an air receiver that is too small</p> Signup and view all the answers

    Which type of compressor is most likely to go into a surge condition when the speed is reduced too much?

    <p>An axial flow compressor</p> Signup and view all the answers

    What is the main purpose of the control systems for a compressor?

    <p>To regulate the output of the compressor in accordance with the volume of air required</p> Signup and view all the answers

    Which type of control system is used on a compressor that runs at constant speed?

    <p>Start-and-stop control</p> Signup and view all the answers

    What is one of the disadvantages of using an inlet air unloader in a reciprocating compressor control system?

    <p>The unloader must be removed before the valve can be repaired, resulting in extra repair costs and longer downtime.</p> Signup and view all the answers

    What is the function of a spring-loaded piston in the pilot valve used for an inlet air unloader?

    <p>To hold the piston in the closed position.</p> Signup and view all the answers

    What is the purpose of the manual unload handle on the side of the pilot valve in an inlet air unloader?

    <p>To force the piston down and allow the receiver pressure to hold the inlet valves open during compressor start-up.</p> Signup and view all the answers

    What problem can arise when the compressor and suction piping operate under a vacuum?

    <p>The compressor can go into a surge condition.</p> Signup and view all the answers

    Which constant speed control method for reciprocating compressors uses a suction unloading valve?

    <p>Suction line unloading valve.</p> Signup and view all the answers

    What does the adjusting nut in a suction unloading valve control?

    <p>The amount of unloading required by the compressor.</p> Signup and view all the answers

    What is the primary purpose of control systems for a compressor?

    <p>To maintain a constant system pressure by varying the compressor speed.</p> Signup and view all the answers

    Which control method is used to automatically unload the compressor during motor start-up?

    <p>Inlet air unloader.</p> Signup and view all the answers

    What happens when the pilot-operated inlet valve in a rotary compressor opens?

    <p>The compressor speed is increased or reduced according to system pressure.</p> Signup and view all the answers

    What is the main advantage of using microprocessor-based control systems over pneumatic control systems?

    <p>They offer more precision and flexibility.</p> Signup and view all the answers

    What is the primary purpose of the modulating inlet valve control system?

    <p>To adjust the compressor capacity to match the load demand</p> Signup and view all the answers

    Which type of compressor control system is preferred for processes with complicated and varying demand cycles?

    <p>Microprocessor-based control</p> Signup and view all the answers

    What is the function of electrical transducers and sensors in microprocessor-based control systems?

    <p>To monitor air pressure and flow</p> Signup and view all the answers

    What is the disadvantage of inlet vane control for dynamic compressors?

    <p>It can cause the compressor to go into a surge condition</p> Signup and view all the answers

    What is the purpose of the handle labeled 'handle in start position' in the pilot valve diagram?

    <p>To start the compressor in an unloaded position</p> Signup and view all the answers

    What is the advantage of microprocessor-based control systems over pneumatic control systems?

    <p>They are faster and more accurate</p> Signup and view all the answers

    What is the function of mechanical trip switches in electro-pneumatic control systems?

    <p>To discontinue compressor operation when pressures or temperatures reach critical levels</p> Signup and view all the answers

    What is the primary advantage of modulating inlet valve control?

    <p>It provides a steady system pressure</p> Signup and view all the answers

    What is the role of microprocessors in rotary air compressors?

    <p>To replace the analog controller</p> Signup and view all the answers

    What causes surging in a compressor?

    <p>When the flow through the compressor drops to a point where the pressure being generated is not sufficient to maintain flow out of the compressor</p> Signup and view all the answers

    What happens when the pressure in the discharge line drops below the surge point?

    <p>The air will again flow through the compressor</p> Signup and view all the answers

    What is one of the methods used to prevent surging in a compressor?

    <p>Closing the discharge line blow-off valve to atmosphere</p> Signup and view all the answers

    What causes the shock wave in a compressor during surging?

    <p>The reversal of flow caused by the insufficient pressure being generated</p> Signup and view all the answers

    What type of compressors are subject to surging?

    <p>Centrifugal and axial compressors</p> Signup and view all the answers

    What happens to the direction of flow when surging occurs in a compressor?

    <p>The direction of flow reverses</p> Signup and view all the answers

    What is the primary function of the anti-surge valve in a compressor control system?

    <p>To recirculate air from the discharge to the suction</p> Signup and view all the answers

    What input signals does the surge controller receive?

    <p>Inlet air flow, suction pressure, and discharge pressure</p> Signup and view all the answers

    What happens when the discharge pressure falls below a certain value for a corresponding flow rate in an anti-surge control system?

    <p>The anti-surge valve opens to recirculate air</p> Signup and view all the answers

    What is the purpose of the two pressure inputs to the surge controller?

    <p>To ensure a certain pressure differential across the compressor</p> Signup and view all the answers

    What happens to the anti-surge valve when the compressor shuts down or is shut down for any reason?

    <p>It opens to recirculate air</p> Signup and view all the answers

    What is the purpose of the air cooler in a discharge recirculation valve (anti-surge valve) system?

    <p>To prevent the compressor from overheating</p> Signup and view all the answers

    Why does surging occur in a compressor?

    <p>The flow through the compressor is insufficient to maintain pressure.</p> Signup and view all the answers

    How may surging impact the impeller or piping in a compressor?

    <p>It may create a shock wave that can damage components.</p> Signup and view all the answers

    What is the purpose of a discharge line blow-off valve in preventing surging?

    <p>To allow air to escape to atmosphere when flow decreases.</p> Signup and view all the answers

    What characteristic of the pressure-volume curve indicates the surge point for a centrifugal compressor?

    <p>The curve's highest point.</p> Signup and view all the answers

    What condition is necessary for a blow-off valve to open in a compressor system?

    <p>Flow from the compressor drops to a certain level.</p> Signup and view all the answers

    How does surging affect the flow direction within a compressor?

    <p>It causes the flow to reverse direction.</p> Signup and view all the answers

    What happens when the surge controller receives input indicating that the pressure differential across the compressor is too high?

    <p>The compressor will shut down due to a suspected problem with the compressor.</p> Signup and view all the answers

    What occurs when the anti-surge controller begins to close the anti-surge valve after the compressor is up to speed on start-up?

    <p>The compressor will start to overheat.</p> Signup and view all the answers

    If the surge controller senses low discharge pressure at a certain flow rate, what action will be triggered in response?

    <p>The surge controller starts to open the recycle flow valve.</p> Signup and view all the answers

    What is the purpose of modern surge control technology that involves microprocessor controllers?

    <p>To stabilize the compressor for particular flow rates.</p> Signup and view all the answers

    What function does the anti-surge valve serve when the compressor is shut down for any reason?

    <p>It will recirculate air back to the suction of the compressor.</p> Signup and view all the answers

    What is the role of the discharge recirculation valve in preventing a surge condition in the compressor?

    <p>It sends flow back to the suction of the compressor to increase mass flow.</p> Signup and view all the answers

    What is the primary reason for removing water vapour from compressed air?

    <p>To prevent water hammer or damage from freezing</p> Signup and view all the answers

    What effect does oil vapour have on air-operated instruments?

    <p>It has a detrimental effect</p> Signup and view all the answers

    What is the purpose of an intercooler in an air compressor system?

    <p>To reduce air temperature and condense moisture</p> Signup and view all the answers

    What is the main purpose of intercoolers in compressors?

    <p>To reduce the power required to compress air</p> Signup and view all the answers

    Why is it important for intercoolers to have drains?

    <p>To remove condensed water and oil</p> Signup and view all the answers

    What is the role of an aftercooler in an air compressor system?

    <p>To cool the compressed air before delivery</p> Signup and view all the answers

    What is one of the additional purposes for cooling air in a compressor?

    <p>To reduce the possibility of an explosion of any air/oil vapour mixture</p> Signup and view all the answers

    What is the primary function of a discharge line blow-off valve in preventing surging?

    <p>To decrease the discharge pressure</p> Signup and view all the answers

    Why should aftercoolers have water separators installed?

    <p>To collect the moisture condensed out of the air stream</p> Signup and view all the answers

    What is the role of the discharge recirculation valve in preventing a surge condition in the compressor?

    <p>To increase the recirculation of discharge air</p> Signup and view all the answers

    What distinguishes the aftercooler in Figure 12 from the pipeline aftercooler?

    <p>Cooling mechanism</p> Signup and view all the answers

    Why are finned tubing used in air compressors?

    <p>To increase the heat transfer area</p> Signup and view all the answers

    What should be maintained slightly above the pressure dewpoint in a properly designed intercooler?

    <p>Outlet temperature</p> Signup and view all the answers

    In water-cooled intercoolers, what mechanism is employed to direct the air flow around the tubes?

    <p>Baffle plates</p> Signup and view all the answers

    Why does moisture condense out of the air stream in the intercooler?

    <p>As a result of decreased temperature</p> Signup and view all the answers

    What is the primary purpose of an intercooler in an air compressor system regarding the entrained moisture?

    <p>To condense a large portion of the entrained moisture</p> Signup and view all the answers

    What is the primary purpose of intercoolers and aftercoolers in a multistage compressor system?

    <p>To remove water vapour and oil vapour from the air</p> Signup and view all the answers

    What happens to water vapour and oil vapour when the air is cooled in an intercooler or aftercooler?

    <p>They condense and can be drained</p> Signup and view all the answers

    Why is it important to remove water vapour from the air in a compressor system?

    <p>To prevent water hammer and damage from freezing</p> Signup and view all the answers

    What is an additional benefit of cooling the air during compression?

    <p>It increases the efficiency of operation</p> Signup and view all the answers

    What is a consequence of not removing oil vapour from the air?

    <p>It can have a detrimental effect on air-operated instruments</p> Signup and view all the answers

    What is the purpose of water jacketing compressors, in addition to using intercoolers?

    <p>To aid in removing the heat of compression</p> Signup and view all the answers

    What is the primary function of the intercooler in an air compressor system?

    <p>To reduce the air temperature between compression stages</p> Signup and view all the answers

    Which component in the intercooler system is responsible for removing condensed water and oil?

    <p>The automatic condensate drain</p> Signup and view all the answers

    What type of cooling method is typically used in pipeline aftercoolers?

    <p>Water cooling</p> Signup and view all the answers

    What is the primary purpose of an aftercooler in an air compressor system?

    <p>To cool the compressed air prior to delivery to the point of use</p> Signup and view all the answers

    Which component is responsible for changing the direction of the air stream in order to remove moisture and other particles in the aftercooler?

    <p>The water separator</p> Signup and view all the answers

    Which type of compressor control system is most suitable for a small reciprocating or sliding vane compressor, according to the text?

    <p>Load-unload control</p> Signup and view all the answers

    Which component in the intercooler system is responsible for preventing surging in the compressor?

    <p>The safety valve</p> Signup and view all the answers

    What type of compressor is most likely to go into a surge condition when the speed is reduced too much?

    <p>Dynamic compressors</p> Signup and view all the answers

    Which type of compressor control system is typically used for utility air systems with generally steady load demand?

    <p>Load-unload control</p> Signup and view all the answers

    What is the primary advantage of using microprocessor-based control systems over pneumatic control systems in air compressors?

    <p>Faster response times</p> Signup and view all the answers

    What is the main purpose of the prefilters in an instrument air system?

    <p>To remove moisture and oil vapors from the air stream</p> Signup and view all the answers

    What is the function of the coalescing filters in an instrument air system?

    <p>To gather together tiny moisture droplets from the air stream</p> Signup and view all the answers

    What is the purpose of the afterfilter in an instrument air system?

    <p>To remove particulates from the air stream</p> Signup and view all the answers

    What is the main purpose of using refrigerated dryers in an instrument air system?

    <p>To lower the dew point of the air</p> Signup and view all the answers

    What is the difference between heated and heatless desiccant dryers in an instrument air system?

    <p>Heated desiccant dryers use a heater to regenerate the moisture-laden bed</p> Signup and view all the answers

    What is the main purpose of using desiccant dryers in an instrument air system?

    <p>To lower the dew point of the air</p> Signup and view all the answers

    What mechanism is employed in a finned tube air-cooled aftercooler to direct the air flow around the tubes?

    <p>Vanes</p> Signup and view all the answers

    What effect does the compressor intake air temperature have on the air dryer dew point?

    <p>The dew point increases with increasing intake air temperature</p> Signup and view all the answers

    What is the purpose of ensuring the aftercooler discharge temperature does not get too high in an instrument air system?

    <p>To avoid overloading the air dryers with moisture</p> Signup and view all the answers

    What is the purpose of using coalescing filters in an instrument air system?

    <p>To gather together tiny moisture droplets from the air stream</p> Signup and view all the answers

    What is the primary purpose of the instrument air system?

    <p>To provide dry air for all instrumentation</p> Signup and view all the answers

    What is the function of the inlet filter in the air system?

    <p>To prevent dust and particles from entering the compressor</p> Signup and view all the answers

    What is the difference between the air in the wet receiver and the dry receiver?

    <p>The air in the dry receiver is dryer than the air in the wet receiver</p> Signup and view all the answers

    Why should the inlet air be supplied from an atmosphere away from engine or process exhaust outlets?

    <p>To prevent contaminants from entering the compressor</p> Signup and view all the answers

    What is the purpose of the aftercooler in the air system?

    <p>To cool down the air stream and remove moisture</p> Signup and view all the answers

    Why is it important to have the inlet piping at least as large as the compressor intake connection?

    <p>To prevent inlet flow restriction</p> Signup and view all the answers

    What is the primary function of the wet air receiver in an instrument air system?

    <p>To stabilize the flow through the air dryers on system load changes</p> Signup and view all the answers

    What type of air compressor is shown in Figure 14?

    <p>Rotary Screw oil-free air compressor</p> Signup and view all the answers

    What is the purpose of the prefilter and afterfilter in the air dryer package?

    <p>To ensure clean air to the instruments</p> Signup and view all the answers

    Why is an elaborate filtering system required if the air compressor is to be oil-lubricated?

    <p>To ensure oil-free air</p> Signup and view all the answers

    What is the function of the moisture separator in an instrument air system?

    <p>To remove moisture condensed in the aftercooler</p> Signup and view all the answers

    What is the primary function of the dry air receiver in an instrument air system?

    <p>To serve as a demand reservoir for the instrument air system</p> Signup and view all the answers

    What is the purpose of the control system in the packaged air compressor?

    <p>To vary the compressor load by means of a modulating inlet valve</p> Signup and view all the answers

    Why are coalescing filters used in an instrument air system?

    <p>To remove oil from the air</p> Signup and view all the answers

    What is the benefit of using a microprocessor-based control system?

    <p>It provides more precise control and monitoring capabilities</p> Signup and view all the answers

    What is the main function of the wet air receiver in the instrument air system?

    <p>To act as an additional moisture separator to reduce the amount of moisture going to the air dryers</p> Signup and view all the answers

    Which component in a packaged air compressor serves the function of remove condensed water from the compressed air?

    <p>Moisture Separator</p> Signup and view all the answers

    What is the primary function of a dry air receiver in an instrument air system?

    <p>To stabilize the system pressure as a demand reservoir</p> Signup and view all the answers

    In a compressor system, what is the purpose of using coalescing filters?

    <p>To remove oil from the air to ensure oil-free compressed air</p> Signup and view all the answers

    What effect does a dry air receiver have on the air purification system during surges in air demand?

    <p>Help avoid overloading the air purification system</p> Signup and view all the answers

    What is the function of the moisture separator in an air compressor system?

    <p>To remove condensed water from the air stream</p> Signup and view all the answers

    Which function does the wet air receiver in an instrument air system serve in preventing compressor cycling on sudden load changes?

    <p>Provide storage capacity</p> Signup and view all the answers

    What is the role of coalescing filters in an oil-lubricated air compressor?

    <p>Remove oil from the compressed air</p> Signup and view all the answers

    Why does the wet air receiver help in stabilizing the flow through the air dryers in an instrument air system?

    <p>To reduce moisture going to the air dryers</p> Signup and view all the answers

    What would happen if an elaborate filtering system is not used in an oil-lubricated air compressor to ensure oil-free air?

    <p>The air would not be suitable for instrument use</p> Signup and view all the answers

    Which type of dryer does not use heat to regenerate the moisture-laden bed?

    <p>Heatless type</p> Signup and view all the answers

    Which type of filter is not used in an instrument air system?

    <p>Microfilter</p> Signup and view all the answers

    What happens if the aftercooler discharge temperature gets too high?

    <p>The air dryers become overloaded with moisture.</p> Signup and view all the answers

    What material is used in a heated desiccant dryer for the adsorption process?

    <p>Alumina</p> Signup and view all the answers

    Which pressure does not fluctuate in the instrument air system?

    <p>Air supply system pressure</p> Signup and view all the answers

    What happens if the compressor and suction piping operate under a vacuum?

    <p>Air can be trapped inside the cylinder causing a surge condition.</p> Signup and view all the answers

    What happens when the air in the compressor intake is very dry?

    <p>The dew point decreases.</p> Signup and view all the answers

    What is the primary purpose of the modulating inlet valve control system in compressors?

    <p>To maintain a constant discharge line pressure.</p> Signup and view all the answers

    Which of the following is not a type of compressor regulation system?

    <p>Hybrid compressor control system</p> Signup and view all the answers

    Which of the following does not affect the operating parameters of an instrument air system?

    <p>Compressor intake air volume.</p> Signup and view all the answers

    What is the primary purpose of the air system in a plant?

    <p>To provide dry air for instrumentation</p> Signup and view all the answers

    What happens to the air in the wet receiver?

    <p>It is drier than atmospheric air, but not as dry as instrument air</p> Signup and view all the answers

    Why is it important to install an air filter in the inlet line of the compressor?

    <p>To prevent dust and other particles from being carried into the compressor</p> Signup and view all the answers

    What is the purpose of the aftercooler in the air system?

    <p>To cool the compressed air</p> Signup and view all the answers

    What is the difference between instrument air and utility air?

    <p>Instrument air is drier than utility air</p> Signup and view all the answers

    Where should the inlet air be supplied from?

    <p>From a location away from engine or process exhaust outlets</p> Signup and view all the answers

    What could happen if the pressure dewpoint of the air begins to rise from -60°C to -40°C?

    <p>Moisture may accumulate in the instrument air lines</p> Signup and view all the answers

    Where is the moisture-sensing probe typically placed in relation to air dryers with an afterfilter?

    <p>Downstream of the afterfilter</p> Signup and view all the answers

    What happens to the desiccant in the glass bulb of an air dryer if the outlet air from the dryer is wet?

    <p>It changes color</p> Signup and view all the answers

    How does the dewpoint analyzer measure the pressure dewpoint of the compressed air?

    <p>By converting moisture content to a numeric value</p> Signup and view all the answers

    In what way does the moisture content in the air affect the moisture-sensing probe's resistance?

    <p>It creates a higher electrical resistance</p> Signup and view all the answers

    What is one of the main functions of the portable dew point monitor attached downstream of the air dryers?

    <p>To prevent moisture accumulation in the air lines</p> Signup and view all the answers

    What is the primary purpose of a desiccant in a desiccant dryer system?

    <p>Perform the drying function by adsorbing water vapor</p> Signup and view all the answers

    In a regenerative air dryer system, what is the purpose of using heated air for regeneration?

    <p>To carry away the condensed water from the desiccant</p> Signup and view all the answers

    What is the role of a restriction orifice in a regenerative air dryer system?

    <p>To create a pressure drop allowing flow through the regenerating dryer</p> Signup and view all the answers

    How are the desiccant beds in a desiccant dryer system regenerated in a heatless dryer?

    <p>By depressurizing the bed to atmospheric pressure</p> Signup and view all the answers

    What is the purpose of a pressure dewpoint in air compressor systems?

    <p>To indicate the temperature at which moisture will condense at system pressure conditions</p> Signup and view all the answers

    How does a timer system or PLC control the cycling of the two towers in a desiccant dryer system?

    <p>By controlling the regeneration valves and timing sequence</p> Signup and view all the answers

    What happens to the water vapor in the desiccant bed during the regeneration process?

    <p>It evaporates into the low vapor pressure purge air</p> Signup and view all the answers

    Why is it necessary to remove a desiccant bed before it becomes saturated in a desiccant dryer system?

    <p>To prevent moisture carryover</p> Signup and view all the answers

    What does a dewpoint temperature indicate in compressed air applications?

    <p>The temperature at which liquid water forms from moisture in the air</p> Signup and view all the answers

    Which component is responsible for carrying away the condensed water from the desiccant in a regenerative air dryer system?

    <p>Purge air</p> Signup and view all the answers

    What is the primary purpose of air dryers in an instrument air system?

    <p>To reduce the dew point of the air</p> Signup and view all the answers

    What is the function of the heater in an air dryer system?

    <p>To heat the air during regeneration</p> Signup and view all the answers

    What happens when Dryer 'A' is in adsorption mode?

    <p>The wet air flows up through the bed and the dry air leaves through the top valve</p> Signup and view all the answers

    What is the purpose of the afterfilters in an air dryer system?

    <p>To ensure no desiccant particles enter the air system</p> Signup and view all the answers

    What is the function of the switching valves in an air dryer system?

    <p>To direct flow for the appropriate cycle, adsorption or regeneration</p> Signup and view all the answers

    What happens to Dryer 'B' during regeneration?

    <p>A small air blower draws in atmospheric air and blows it through a heater, down through the bed, then out to atmosphere</p> Signup and view all the answers

    What is the primary function of the cartridge-type after filters in an adsorbent air dryer package?

    <p>To ensure no desiccant particles enter the air system</p> Signup and view all the answers

    What distinguishes a heated regeneration type air dryer from a heatless regenerating type?

    <p>The use of a heater to blow hot air through the bed</p> Signup and view all the answers

    What is the purpose of the three-way switching valves attached to each dryer in an adsorbent air dryer package?

    <p>To direct the flow of air for the appropriate cycle, either adsorption or regeneration</p> Signup and view all the answers

    What is the consequence of not adequately reducing the dew point of the air in a refrigerant type air dryer?

    <p>There will be water contamination of the air operated instruments and freezing problems with the air system in cold weather</p> Signup and view all the answers

    How does the regeneration cycle in a refrigerant type air dryer work?

    <p>By blowing hot air through the desiccant bed</p> Signup and view all the answers

    What is the main difference between the prefilters and afterfilters in an air dryer system?

    <p>The prefilters are used to remove solid particles and afterfilters are used to remove moisture</p> Signup and view all the answers

    What is the primary function of the restriction orifice in the air supply line of a regenerative air dryer system?

    <p>To create a pressure drop that allows flow through the regenerating dryer</p> Signup and view all the answers

    How does the system ensure that the desiccant bed is not completely saturated with water vapour?

    <p>By continuously monitoring the moisture levels using sensors</p> Signup and view all the answers

    What is the purpose of reducing the pressure to atmospheric pressure during regeneration in a heatless dryer?

    <p>To reduce the dewpoint and vapour pressure</p> Signup and view all the answers

    What component in the intercooler system is responsible for preventing surging in the compressor?

    <p>There is no such component mentioned in the text</p> Signup and view all the answers

    What happens when the system pressure is 690 kPa gauge, and the dewpoint of the air is minus 40°C at 0 kPa gauge?

    <p>The dewpoint of the air decreases</p> Signup and view all the answers

    What type of dryer uses a blower and internal electric heaters to heat the purge air?

    <p>Regenerative air dryer system</p> Signup and view all the answers

    What is the difference between Atmospheric Dewpoint and Pressure Dewpoint?

    <p>Atmospheric Dewpoint is the temperature at which moisture will condense at ambient air conditions, while Pressure Dewpoint is the air temperature which moisture will condense at system pressure conditions</p> Signup and view all the answers

    What is the main purpose of using a molecular sieve desiccant?

    <p>To achieve lower dewpoints</p> Signup and view all the answers

    What is the purpose of a dryer package in Figure 18 using a blower and internal electric heaters to heat the purge air?

    <p>To reduce the dewpoint of the air</p> Signup and view all the answers

    What is the primary difference between Atmospheric Dewpoint and Pressure Dewpoint?

    <p>The pressure conditions at which moisture will condense</p> Signup and view all the answers

    What happens to the electrical current flowing between the two electrodes in the moisture-sensing element when the air from the dryer flows through it?

    <p>It is resisted by the moisture content in the air</p> Signup and view all the answers

    Where is the moisture-sensing probe typically placed in an instrument air system with an afterfilter?

    <p>Downstream of the afterfilter</p> Signup and view all the answers

    What is the purpose of the glass bulb with desiccant in some air dryer systems?

    <p>To indicate the moisture content of the air</p> Signup and view all the answers

    What is the function of the analyzer in a dewpoint analyzer system?

    <p>To convert the electrical signal to a numeric value</p> Signup and view all the answers

    Why is it important to check the dewpoint of the compressed air regularly?

    <p>To prevent moisture from accumulating in the instrument air lines</p> Signup and view all the answers

    What is the component that converts the electrical signal to a numeric value in the dewpoint analyzer system?

    <p>Dewpoint analyzer</p> Signup and view all the answers

    What is the purpose of the air blower in the regeneration cycle of an air dryer?

    <p>To draw in atmospheric air and blow it through a heater, down through the bed, then out to atmosphere</p> Signup and view all the answers

    What is the function of the three-way switching valves in an air dryer package?

    <p>To direct the flow of air for the appropriate cycle, adsorption or regeneration</p> Signup and view all the answers

    What is the role of the after filters in an air dryer system?

    <p>To ensure that no desiccant particles enter the air system</p> Signup and view all the answers

    What is the primary purpose of prefilters in an instrument air system?

    <p>To filter out solid particles from the compressed air</p> Signup and view all the answers

    What happens when the delivery pressure exceeds the required setting in a load-unload control for a rotary compressor?

    <p>The suction valve opens to unload the compressor</p> Signup and view all the answers

    How does the compressor intake air temperature affect the air dryer dew point?

    <p>The dew point increases as the intake air temperature increases</p> Signup and view all the answers

    What is the primary purpose of an intercooler in an air compressor system?

    <p>To lower the temperature of the compressed air</p> Signup and view all the answers

    What is the purpose of monitoring the pressure dewpoint of the compressed air?

    <p>To prevent moisture accumulation in the instrument air lines</p> Signup and view all the answers

    Which material is typically used for the desiccant in a desiccant dryer system?

    <p>Silica gel or activated alumina</p> Signup and view all the answers

    Where is the moisture-sensing probe typically placed in relation to air dryers with an afterfilter?

    <p>Downstream of the air dryer and afterfilter</p> Signup and view all the answers

    What is the primary function of the moisture sensor in a desiccant dryer system?

    <p>To monitor the moisture content in the air</p> Signup and view all the answers

    How does the moisture-sensing element in the probe respond to changes in air moisture content?

    <p>By creating a resistance to the electrical current</p> Signup and view all the answers

    What is the primary purpose of a coalescing filter in an instrument air system?

    <p>To remove oil vapour</p> Signup and view all the answers

    What control system is often used for cycling between the drying and regeneration cycles in a desiccant dryer system?

    <p>PLC-based control</p> Signup and view all the answers

    What is the purpose of the small glass bulb filled with desiccant in some air dryer systems?

    <p>To indicate air moisture content</p> Signup and view all the answers

    What is the primary purpose of the modulating inlet valve control system in an air compressor system?

    <p>To regulate output air pressure</p> Signup and view all the answers

    What is the function of the analyzer in the dewpoint analyzer system?

    <p>To convert the electrical signal to a numeric value</p> Signup and view all the answers

    What is the advantage of using a portable analyzer to measure pressure dewpoint?

    <p>It can be used at multiple sampling points</p> Signup and view all the answers

    What is the function of the moisture separator in an air compressor system?

    <p>To remove moisture</p> Signup and view all the answers

    What happens to the electrical current flowing between the two electrodes in the moisture-sensing element when the air from the dryer flows through it?

    <p>Decreases</p> Signup and view all the answers

    What is the primary purpose of the control system in a packaged air compressor?

    <p>To regulate output air pressure</p> Signup and view all the answers

    What is the effect of the air intake temperature on the air dryer dew point in a compressor system?

    <p>Inversely proportional</p> Signup and view all the answers

    What happens to the desiccant bed in a heatless dryer before it enters the regeneration cycle?

    <p>Becomes completely saturated</p> Signup and view all the answers

    What is the purpose of using the term 'purge air' in the context of regenerating a desiccant bed?

    <p>Removing water vapor from the desiccant bed</p> Signup and view all the answers

    Why is the pressure in the chamber reduced to atmospheric pressure before the purge airflow is started in the regeneration cycle?

    <p>To reduce its dewpoint and vapor pressure</p> Signup and view all the answers

    How does the desorbed condensate travel in the desiccant dryer system during the regeneration cycle?

    <p>Vents to atmosphere</p> Signup and view all the answers

    In the context of the desiccant dryer system, what is the purpose of the timer system or PLC?

    <p>Controlling the regeneration cycle</p> Signup and view all the answers

    Why is it crucial to monitor the dewpoint in a desiccant dryer system?

    <p>To prevent water vapor condensation</p> Signup and view all the answers

    What triggers the regeneration valves to cycle between the drying and regeneration cycles in a desiccant dryer system?

    <p>Timer system or PLC</p> Signup and view all the answers

    How does a desiccant bed become 'saturated' in the context of a desiccant dryer system?

    <p>By adsorbing moisture to capacity</p> Signup and view all the answers

    What is the role of the molecular sieve desiccant in a desiccant dryer system?

    <p>Achieving lower dewpoints</p> Signup and view all the answers

    Why is the cycling of the two towers between the drying and regeneration cycles an essential aspect of a desiccant dryer system?

    <p>To maintain the dryness of the air</p> Signup and view all the answers

    What is the primary purpose of the pair of three-way switching valves attached to each dryer in an adsorbent air dryer package?

    <p>To direct flow for both adsorption and regeneration cycles</p> Signup and view all the answers

    What happens to the dry air in Dryer 'A' after it leaves the top valve?

    <p>It passes through a set of cartridge-type after filters</p> Signup and view all the answers

    What is the role of the heater in the regeneration cycle of Dryer 'B'?

    <p>To heat the atmospheric air that blows through the bed</p> Signup and view all the answers

    What is the purpose of the cartridge-type after filters in an adsorbent air dryer package?

    <p>To ensure no desiccant particles enter the air system</p> Signup and view all the answers

    What is the state of Dryer 'B' when atmospheric air is blown through a heater, down through the bed, then out to atmosphere?

    <p>Regeneration</p> Signup and view all the answers

    Why are there two towers in an adsorbent air dryer package?

    <p>So that one is adsorbing while the other is either regenerating or on standby</p> Signup and view all the answers

    What is the purpose of the stainless steel housing with several holes in the moisture-sensing probe?

    <p>To allow the flow of air through the housing</p> Signup and view all the answers

    What happens to the electrical current flowing between the two electrodes in the moisture-sensing element when the air from the dryer flows through?

    <p>It creates a resistance</p> Signup and view all the answers

    What is the purpose of the afterfilter in relation to the moisture-sensing probe?

    <p>To protect the probe from desiccant dust</p> Signup and view all the answers

    What happens to the desiccant in the glass bulb of an air dryer system when the air is dry?

    <p>It turns blue</p> Signup and view all the answers

    What is the function of the analyzer in a dewpoint analyzer system?

    <p>To measure the dew point of the compressed air</p> Signup and view all the answers

    What is the purpose of checking the pressure dewpoint of the air on a regular basis?

    <p>To prevent moisture accumulation in the instrument air lines</p> Signup and view all the answers

    What step must be taken to ensure the compressor cylinders are protected from damage due to overheating?

    <p>Turn on the cooling water for the compressor cylinders.</p> Signup and view all the answers

    What is the purpose of ensuring all required safety guards are put back in place before starting the compressor?

    <p>To prevent personal injury.</p> Signup and view all the answers

    Why should all leaks on flanges be tightened up before starting the compressor?

    <p>To ensure efficient compressor operation.</p> Signup and view all the answers

    What is the purpose of turning on the cooling water for the compressor cylinders?

    <p>To protect the cylinders from overheating.</p> Signup and view all the answers

    Why should the compressor be in the unloaded position before starting it?

    <p>To avoid overloading the motor.</p> Signup and view all the answers

    What should be done if leaks are found on the cooling water system?

    <p>Repair them before starting the compressor.</p> Signup and view all the answers

    Why is it important to check the crankcase/gearbox oil level?

    <p>To ensure the compressor has adequate lubrication</p> Signup and view all the answers

    What should you do if the suction and discharge pressures are abnormally low or high?

    <p>Shut down the compressor and have the problem rectified</p> Signup and view all the answers

    Why is it necessary to check around the compressor for leaks?

    <p>To prevent damage to the compressor and surrounding equipment</p> Signup and view all the answers

    What can happen if the cylinder lubricator is not working?

    <p>The compressor will experience excessive wear of the cylinder walls and pistons</p> Signup and view all the answers

    Why is it necessary to ensure the crankcase/gearbox oil levels are at the required levels?

    <p>To ensure the compressor has adequate lubrication</p> Signup and view all the answers

    What should you do if you notice unusual noises around the compressor?

    <p>Find the cause of the noise and have it corrected</p> Signup and view all the answers

    What is the consequence of starting the motor when the breaker is being closed?

    <p>Triggering excessive wear of the cylinder walls and pistons</p> Signup and view all the answers

    What should be done if the cylinder lubricator is not working?

    <p>Add additional lube oil</p> Signup and view all the answers

    Why is it important to check the cylinder lubricator before starting the compressor?

    <p>To mitigate excessive wear on the compressor cylinders</p> Signup and view all the answers

    What could happen if the compressor is loaded too quickly?

    <p>Lack of lubrication for the compressor cylinders</p> Signup and view all the answers

    Why is it necessary to check for leaks around the compressor?

    <p>To tighten them up</p> Signup and view all the answers

    What is the primary reason for slowly loading the compressor?

    <p>To prevent damage to the compressor cylinders</p> Signup and view all the answers

    Which action is crucial to prevent overheating damage to the compressor cylinders before starting the unit?

    <p>Turn on the cooling water for the compressor cylinders</p> Signup and view all the answers

    What is the purpose of ensuring the compressor is in the unloaded position before starting?

    <p>To avoid overloading the motor and potentially damaging it</p> Signup and view all the answers

    What safety measure should be taken to prevent personal injury when starting the compressor?

    <p>Ensure that no one is working on the compressor</p> Signup and view all the answers

    Why should leaks on flanges be listened for after opening the suction and discharge valves?

    <p>To ensure that all leaks are tightened up before starting the compressor</p> Signup and view all the answers

    What is the primary function of the cooling water system in the compressor?

    <p>To protect the compressor cylinders from damage due to overheating</p> Signup and view all the answers

    What step should be taken to ensure the compressor motor is not overloaded when starting?

    <p>Ensure that the compressor is in the unloaded position</p> Signup and view all the answers

    What is the first step when starting up the lube oil system?

    <p>Listen for any unusual noises in the system</p> Signup and view all the answers

    What is the immediate course of action if leaks are observed in the lube oil system during start-up?

    <p>Shut down the system and have the leak repaired</p> Signup and view all the answers

    What is the next step after confirming no leaks and observing proper lube oil pressure in the system?

    <p>Load the compressor slowly or ensure the microprocessor brings the compressor on line properly</p> Signup and view all the answers

    What action must be taken if unusual noises are observed in the system?

    <p>Immediately shut down the compressor</p> Signup and view all the answers

    When should you load the compressor after beginning the start-up procedure?

    <p>After confirming no leaks and proper lube oil pressure</p> Signup and view all the answers

    Before starting a dynamic compressor/blower, what must be ensured?

    <p>That all maintenance personnel have completed their work on the unit</p> Signup and view all the answers

    Why is it important to ensure that all manual block valves in the suction or discharge lines are open?

    <p>To ensure the system will not shut down due to low suction pressure or high discharge pressure</p> Signup and view all the answers

    What should be done to the surge valves before starting the compressor?

    <p>They should be wide open</p> Signup and view all the answers

    What is the purpose of doing an inspection to ensure all flanges are tight?

    <p>To prevent damage to the system or compressor</p> Signup and view all the answers

    Why is it important to ensure the lube oil reservoir has an adequate level?

    <p>To ensure the compressor lube oil system is ready for service</p> Signup and view all the answers

    What should be closed before starting the compressor?

    <p>The motor breaker</p> Signup and view all the answers

    What must be ensured before starting a dynamic compressor or blower, according to the text?

    <p>Surge valves are closed and suction flow control valve is open.</p> Signup and view all the answers

    Why is it critical to ensure the surge valves are open and the suction flow control valve is closed before starting the compressor?

    <p>To prevent damage to the system due to high suction pressure.</p> Signup and view all the answers

    What should be the status of the motor breaker before attempting to start the compressor?

    <p>Open and not closed by an electrician.</p> Signup and view all the answers

    Why is it necessary to ensure that manual block valves in the suction or discharge lines are open?

    <p>To avoid system shutdown due to low suction pressure or high discharge pressure.</p> Signup and view all the answers

    Why is it crucial to inspect that all flanges are tight and tools have been removed from the compressor unit before starting?

    <p>To prevent personal injury.</p> Signup and view all the answers

    What step ensures that the compressor lube oil system is ready for service, according to the text?

    <p>Verify that the lube oil reservoir has an adequate level of oil.</p> Signup and view all the answers

    What should be checked and corrected, if found, before loading the compressor during its start-up procedure?

    <p>Insufficient flow of lube oil to all the bearings</p> Signup and view all the answers

    During start-up, what immediate action should be taken if leaks are observed in the lube oil system?

    <p>Shut down the system and repair the leak</p> Signup and view all the answers

    Which component in the intercooler system is responsible for preventing surging in the compressor?

    <p>The anti-surge valve</p> Signup and view all the answers

    How does a desiccant bed become 'saturated' in the context of a desiccant dryer system?

    <p>When the desiccant material adsorbs water vapour from the air stream</p> Signup and view all the answers

    What should be done if the cylinder lubricator is not working during the start-up procedure?

    <p>Shut down the compressor and repair the lubricator</p> Signup and view all the answers

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