MILLWRIGHT LEVEL 3 PNEUMATICS FINAL EXAM 2024-2025, Exams of Nursing

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MILLWRIGHT LEVEL 3 PNEUMATICS

FINAL EXAM 2024-2025 WITH ACTUAL

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How does a regulator in a pneumatic system respond to a decrease of downstream air pressure? increases orfice size to increase air flow Which type of directional control valve is an on-off valve in a pneumatic system? two-way valve Where should the air intake be located? in the coolest place possible what is an air receivers purpose? to compensate for fluctuations in demand, and to dampen pulsations. what things must every air receiver have? Gauge, drain, and pressure relief valve what must the pressure relief valve be set at? must be no higher then the lowest maximum pressure rating of any part in the system. how should safety relief valves be mounted, and why? vertically, usually on top, to prevent dirt and sludge from blocking them. what are the three types of commonly used pipe systems?

the grid(dead end) system, decentralized system(unit system) and Loop system what is the preferred or recommended piping system? the loop system Describe the Grid(dead end) system of piping. its the simplest, only requires one compressor, starts with a large diameter supply line that gradually decreases. one drawback is that systems at the end of the circuit could face air starvation when upstream demand is heavy. Describe the decentralized system composed of two or more compressors each with their own grid. grids may or may not be interconnected. advantage is each compressor is close to its point of use which means there is less pressure drop and more uniform supply pressure. Describe the loop system of piping? Two or more compressors feed into the same loop allowing compressed air to flow in either direction. ensures equal air distribution throughout the plant. Flared fittings are not used where? where vibration is present. what normally open valve is installed on hoses to prevent whipping in the event of fitting or hose failure? excess flow valve what are two methods of sealing a pneumatic DCV (Directional control valves)? packed bore - o-rings are fixed in grooves in the body through which the spool slides. Packed spool - o-rings are fixed in the spool. The air pressure in a pneumatic tool will determine? torque the air flow in a pneumatic tool will determine speed what is the function of a venting type regulator? allows pressures above regulator setting to be relieved excess flow valve should be installed on air hose larger then? 1/2" how is pneumatic tubing sized?

outside diameter in a 5way/3position valve what are the 3 most common centres? pressure centre exhaust centre blocked centre what does the safety relief valve on a air reciever control? releases any excessive pressure usually set 5-10% above the systems maximum pressure. where is the drain valve located on a air reciever? must be installed on lowest point on receiver. what is the purpose of a fusible plug? will melt and release all the pressure in the receiver if the air temp becomes dangerously high. also will ensure the path in which the pressure would vent, wont endanger workers what are two types of compressed air used in industry? instrument air - must be clean dry and oil free plant air - should be clean and have low oil and moisture content. what does an excessive flow valve do? the valve is normally open, but excess flow surges push the poppet against a spring, causing flow to be cut off. What are the possible causes of why an actuator cylinder is drifting? -piston seal is leaking -operating valve is leaking -lines are leaking what is the most common deliquescent? calcium chloride what type of agent is used in a liquid dehydration process? ethylene glycol In a deliquescent dryer, is the flow normally upward or downward through the bed? upward what is dew point? the temp to which air must be lowered in order for condensation of water vapor to begin. define relative humidity

a comparison of the amount of water a sample of air holds to the maximum amount it could hold if saturated. Regenerative dryers often use a portion of the dried air for regeneration of the saturated desiccant bed. true or false true what are common desiccants? activated alumina, granular and bead type silica gel, and molecular sieves. what are the four categories of air dryers? absorption adsorption refrigeration mechanical when working on a dryer system what must you do before performing maitenance? depressurize and isolate the complete system. Define regeneration(reactivation) in gas and air dryer systems. term used for the process of removing the accumulation of moisture from the dryer bed. what percent of dry air is used to regenerate a dryer bed? 10-15% Describe the operation of an absorption dryer absorption dryers use a chemical bond between the drying agent and the gas stream being dried. Its different from a adsorption dryer in that there is no film foundation. moisture is absorbed by the absorption material and forms a solution. Describe a chemical dryer also known as a solid dehydration dryer. this type of dryer cannot be regenerated, must use deliquescents, which slowly dissolve or melt away as they combine with the moisture they are absorbing, because of this the bed must be replenished periodically because the deliquescent is consumed by the drying process. Describe liquid Dehydration an absorbing agent(ethylene glycol) is used to remove moisture, gas is brought into contact with agent being sprayed through nozzels. Describe Refrigeration dryers. least expensive method of dew point reduction, this is because there are no absorption or absorption materials that require maintenace or replacement. by cooling air in an aftercooler the air is less able to hold moisture, so water can drop out of the stream and be removed.

In a Refrigerant circuit in a refrigeration dryer what happens to the water? because water freezes at 0C(32F) the condensed water would freeze in this dryer if the controls were set too cool the air too much. This type of dryer is capable of lowering the dew point to 2 to 3 degrees celcius. lower temps would cause it to freeze. Describe Mechanical dryers. use only mechanical, physical means to cause moisture to fall out of the air stream. these include devices that use intertia or mechanical components, such as barriers and filters. Define Liquid seperators air enters a large vessel, the reduction in velocity by the size of the dryer and the baffles inside allows contaminants such as sand,oil,acids and other liquids to slow down and drop to the bottom of the vessel where they can be removed Define a Centrifugal Separators found downstream of compressor aftercoolers the centrifugal separator uses centrifugal force to throw incoming air or gas outwards causing the heavy particles to drop to the bottom and be removed. what are Demister Pads? are a drying device that use fine wire mesh screen or pads. Pads provide a surface for the mist to adhere to until droplets become large enough to run back into the vessle. what are Coalescing filter elements? a highly effective means of oil and water removal. designed to remove fluids in the form of aerosols too small to be captured by other mechanical filtration methods. removes particles as small as .01 micron (.00001 inch) Zero degrees Kelvin is equal too -273C true or false? True Atmospheric pressure at sea level is equal to how many of each of the following. (bar, psi, kPa) 1 bar 14.7psi 101.4 kPa you calculate gauge pressure by adding or subtracting 14.7 to an absolute scale reading? subtract Define Pascals Law Pressure in a confined static fluid acts equally and in all directions at right angles to the surface. zero degrees Rankine is equal too -460F. true or false true

whats the difference between Pascals law and Bernoullis principle? pascals law deals with pressure in a non moving fluid(static), whereas Bernoulli's principle deals with a constant flow of fluid(dynamic). Boyles Law states that if temperature remains constant, the volume changes inversely to the pressure. Charles law states that if the pressure on a given volume of gas is held constant, the volume changes in direct proportion to the absolute temperature. Gay-Lussac's Law states that if the volume is constant, the pressure exerted by the gas is directly proportional to the absolute temperature. what does FRL stand for? Filter,regulator,lubricator filter to clean air and protect downstream components. (such as the regulator) regulator to maintain a set system pressure lubricator to add a mist of oil in the air stream

what would happen if a FRL was installed backwards? the oil from the lubricator would gum up the regulator and then the filter would remove any oil left in the air before it got to its point of use. air filter used to remove harmful contaminants from the air before it reaches the components.

regulator regulator is used to help reduce line pressure from the compressor.

oil mist lubricator purpose mist lubricators are fitted close to their intended point of use to feed specially selected oils to equipment.

water trap/seperator gets rid of large amounts of water and are commonly installed anywhere in a compressed air line where there is a water problem.

whats the difference between venting regulators and non-vented regulators? The difference is venting regulators also act as relief valaves for the downstream section of the circuit to prevent any possibility of an increase in pressure in this section. what are directional control valves? controls the direction of airflow by shifting poppets or spools to open or close a passage between various ports. define solenoid a wire coil around a metal plunger. coil is electrically energized, it creates a magnetic field which pulls the iron plunger into the coil. it causes the valve to move to another position and change flow path.

define check valve

allows airflow in one direction while blocking flow in reverse.

define shuttle valve is used to automatically select the higher of two pressure sources to supply a pneumatic signal

define flow control valves used in pneumatic circuits to vary speed of actuators in a specific part of the circuit. define quick exhaust valve normally found mounted on the end caps of the cylinders and are used to exhaust air directly to atmosphere at the cylinder rather then the air flowing through the long and restrictive lines back to the control valve. whats the purpose of a cylinder? to convert fluid power energy (compressed gas) into linear mechanical energy that can then perform work. what is a stop tube? its a metal collar that fits over the piston rod. its purpose is to keep the piston seperated from the rod gland bushing when a long stroke cylinder is used. actuator cylinder is leaking piston seal is leaking a cylinder body seal is leaking the packing on the cylinder rod is over tightened,cylinder is misaligned. the cylinder body seal is leaking the tie rods holding it together are loose the rod gland seal is leaking the seal is deteriorating

a pneumatic valve is blowing to exhaust when not actuated the inlet poppet is not sealing a pneumatic valve is blowing to exhaust when actuated the valves seals are faulty the pilot section is blowing to exhaust the poppet is not sealing. a poppet is chattering air supply pressure is too low piping should minimize _______ _______ by being large enough with as few bends as possible pressure drop a cyclone seperator can be used anywhere in the system that moisture might fall out. T or F true air recievers are used to store compressed air to take up fluctuations in demand and allow the system pressure to vary within reasonable limits. T or F true most compressed air systems run for long distances. this allows the air to cool below its dew point, which causes moisture to fall out of the airstream. T or F true flow control valves control the volume and therefore the speed of the actuator. T or F true Pilot operation refers to valves that are operated with air pressure. internally piloted means the air pressure within the valve is used to perform the shifting function. T or F true the 3/2 valve can be used if the air needs to be released when the valve is closed. A typical application is the operation of a _________ acting cylinder single A __________ acting cylinder is a common application of a 4/2 valve. double one of the first items to check in a malfunctioning system is weather there is a supply of air at sufficient flow and pressure. T or F

true what laws and theories can be applied to both pneumatics and hydraulic systems? Pascals law, Bernoullis principles, law of convservation of energy. describe absolute zero temperature. all molecular action in a gas ceases and perfect vacuum occurs. describe absolute pressure there is no pressure. zero pounds per square inch(0psia),at sea level and under normal conditions of temperature. (15.5C or 60F) what is the normal atmospheric pressure at sea level? 1 bar or 14.7 psia how is vacuum measured? vacuum is measured with a barometer, measured in mm hg or "hg. what are the properties or characteristics of compressed air? -it can be compressed or reduced in volume -air will expand to fill any container -pressure in a confined,static fluid acts the same and equally in every direction. aka Pascals law. -there must be a pressure change to control flow -air flows from high to low pressure areas. what are the ways of increasing pressure in a sealed container? -reducing volume -introducing more air to the confined space -heating the air what is a more efficient transfer of energy? laminar or turbulent flow? laminar Describe Boyle's Law at constant temperature, absolute pressure varies inversely to the volume. describe Charles law At a constant pressure, the volume of a gas varies proportionally to its absolute temperature. Describe the Ideal Gas Law because gas does not compress without a change in temperature, boyles and charles law are combined to create the ideal gas law.

how are vacuum pumps used to create fluid power? Vacuum power is a form of fluid power, a pump removes the air rather than compressing it. where is a water trap installed? wherever compressed air is cooled and may fall below dew point. common areas are after intercooler,aftercoolers and air dryers. what is an aftercooler? are heat exchangers which cool the air after if leaves the compressor and before it enters the reciever how is contamination produced in an compressed air system? -construction, assembly, maintenance debris -oil carried over from the compressor -wear particles, pipe scale, rust in lines what does a quick exhaust valve do? when a cylinder is required to return rapidly, a quick exhaust valve is installed in the retract line of the cylinder. what does a flow control valve do? restricts the flow rate in a leg of a pneumatic system. how does a shuttle valve work? is used when its necessary to have two direct control valves operating a single actuator, the valve shifts to allow either of the DCV to activate the actuator but only one at a time. 1psi pressure differential to shift. what does a muffler do air exiting a conductor usually generates a intense sound, muffler exhausts the loud noise. what prevents a hose from collapsing with flareless fittings? internal tube support.