Spray Finishing and Touch-Ups Summer 2024
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Questions and Answers

What happens when the piston moves downward in a piston-type compressor?

  • Air is discharged through an exhaust valve
  • Air is compressed
  • Air is drawn through an intake valve (correct)
  • Air is stored in the tank
  • What is the typical tank pressure range for a single stage piston compressor?

  • 150-175 psi
  • 50-75 psi
  • 200-225 psi
  • 100-125 psi (correct)
  • What is an advantage of a two-stage piston compressor over a single stage piston compressor?

  • Less expensive
  • More air can be stored in the same size tank (correct)
  • asier maintenance
  • Quieter operation
  • What is a characteristic of rotary screw type compressors compared to piston-type compressors?

    <p>Quieter operation</p> Signup and view all the answers

    What is the purpose of the second cylinder in a two-stage piston compressor?

    <p>To compress air further</p> Signup and view all the answers

    How many cylinders are typically used in a single stage - multiple cylinders compressor?

    <p>Multiple (more than 2)</p> Signup and view all the answers

    What happens to the trapped volume of air in a rotary screw type compressor?

    <p>It decreases</p> Signup and view all the answers

    What is an advantage of rotary screw type compressors over piston-type compressors?

    <p>Quieter operation</p> Signup and view all the answers

    What is the primary function of a spray booth in spray finishing?

    <p>To provide a clean and controlled environment for spray finishing</p> Signup and view all the answers

    What is the typical unit of measurement for air pressure in a compressor?

    <p>Pounds per square inch (psi)</p> Signup and view all the answers

    What is the primary factor that determines the amount of water vapor that air can hold?

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

    What happens to the air in a storage tank when the compressor motor is turned off?

    <p>The air remains at the same pressure</p> Signup and view all the answers

    What is the primary purpose of a respirator in spray finishing?

    <p>To protect the user from inhaling airborne particles</p> Signup and view all the answers

    What is the term for the amount of water vapor in the air?

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

    What is the primary reason why air compressors and air lines are prone to collecting water?

    <p>Changes in air temperature and humidity</p> Signup and view all the answers

    What is the term for the rate at which compressed air is delivered?

    <p>Delivery rate</p> Signup and view all the answers

    What is the purpose of adding a stream of air to a liquid flow?

    <p>To break up forced liquid droplets into even finer droplets</p> Signup and view all the answers

    What are the three main ways to make liquid flow?

    <p>Gravity, Suction, and Pump</p> Signup and view all the answers

    What is a limitation of conventional spray guns with a gravity feed?

    <p>They can be top heavy when filled with finish</p> Signup and view all the answers

    What is the advantage of using a siphon feed conventional spray gun?

    <p>They are well suited for spraying thinner materials</p> Signup and view all the answers

    What is the function of the fluid needle in a conventional spray gun?

    <p>To seal the opening in the fluid tip</p> Signup and view all the answers

    What determines the shape of the spray pattern in a conventional spray gun?

    <p>The amount of air and orientation of the air cap</p> Signup and view all the answers

    Why are the air cap, fluid tip, and fluid needle typically a matched set?

    <p>They come in different sizes</p> Signup and view all the answers

    What is the disadvantage of using a conventional spray gun with a siphon feed in tight spaces?

    <p>It is cumbersome in tight spaces due to the large cup mounted below the gun</p> Signup and view all the answers

    What is the primary advantage of the Pressure Pot System?

    <p>The lightness of the gun, allowing for use in confined areas</p> Signup and view all the answers

    What is the purpose of the two regulators on most Pressure Pot System tanks?

    <p>To control the air pressure in the tank and to the gun</p> Signup and view all the answers

    What type of materials can be used with the Pressure Pot System?

    <p>Both paints and adhesives</p> Signup and view all the answers

    What is the significance of the pressure rating of the Pressure Pot System tank?

    <p>It should not be exceeded to ensure safe operation</p> Signup and view all the answers

    What is the primary difference between HVLP guns and conventional spray guns?

    <p>The size of the passageways</p> Signup and view all the answers

    How does the HVLP Turbine System generate the required airflow?

    <p>With a series of fans</p> Signup and view all the answers

    What is the characteristic of the air pressure in the HVLP Turbine System?

    <p>High volume and low pressure</p> Signup and view all the answers

    What is a limitation of the Pressure Pot System?

    <p>It is difficult to clean</p> Signup and view all the answers

    What is the primary reason for rotating the air cap 180 degrees to assess a defect?

    <p>To identify if the defect is with the air cap or fluid tip / needle</p> Signup and view all the answers

    What is the result of moving a gun in a non-parallel manner to the workpiece?

    <p>Uneven coverage</p> Signup and view all the answers

    What is the primary purpose of a vent hole in a conventional spray gun's cup lid?

    <p>To allow air to enter the cup as fluid level drops</p> Signup and view all the answers

    What is the primary benefit of using a respirator in a hazardous environment?

    <p>To protect against particulate hazards and chemical gases</p> Signup and view all the answers

    What is a characteristic of negative pressure respiratory equipment?

    <p>It relies on the wearer to pull air through the cartridge or filter</p> Signup and view all the answers

    What is the primary difference between positive pressure and negative pressure respiratory equipment?

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

    What is an advantage of powered air positive pressure respiratory equipment?

    <p>It pushes air to the hood or facepiece, reducing strain on the wearer</p> Signup and view all the answers

    What is the primary characteristic of Self Contained Breathing Apparatus (SCBA)?

    <p>It carries a source of clean air with the user in a tank</p> Signup and view all the answers

    Study Notes

    Spray Finishing and Touch-Ups

    • Overview of Spray Finishing: Equipment, materials, and techniques
    • Two parts: Theory and Practical

    Theory Topics

    • Air Compressors
      • A supply of clean, dry air is required for many shop equipment
      • Type and size of compressor depend on selected spray equipment

    Air Compressors

    • A device that uses a motor/air pump to force air into a storage tank
    • Compressed air is held in the tank until used
    • When tank pressure reaches upper pressure limit, the motor shuts off
    • When tank pressure drops, the motor turns back on

    Compressed Air/Compressor Properties

    • Pressure: Typically stated in pounds per square inch (psi)
    • Delivery Rate (Flow Rate): Typically stated in cubic feet per minute (CFM) at a specific pressure
    • Storage Volume: Typically stated in gallons or liters

    Humidity

    • Air can hold water vapor (moisture)
    • Humidity: The amount of water vapor in the air
    • Maximum amount of water vapor depends on the temperature and air pressure of the air
    • Condensation occurs when air temperature drops

    Compressors and Water

    • When air is compressed, pressure increases, and water vapor condenses
    • When air is released from the storage tank, air expands, and water temperature drops, forming condensation in air lines
    • Compressor tanks and air lines collect water depending on the relative humidity

    Types of Air Compressors

    • Piston Type
      • Creates air pressure through the action of a reciprocating piston
      • Single Stage Piston
        • Air is drawn from the atmosphere and compressed to final pressure with a single stroke
        • Tank pressure typically kept between 100 psi and 125 psi
      • Two Stage Piston
        • Two cylinders: one large and one small
        • Air compressed in two separate steps
        • Higher pressure and more air can be stored in the same size tank
        • Advantage: More air can be stored; Disadvantage: Cost
    • Rotary Screw Type
      • Utilizes two intermeshing helical rotors in a twin bore case
      • Air is compressed between one convex and one concave rotor
      • Trapped volume of air is decreased, and pressure increases
      • Quieter, higher CFM, and faster fill/recharge times

    Making Liquid Flow

    • Gravity
    • Suction
    • Pressurized Container (e.g., super soaker water gun)
    • Pump

    Spray Systems

    • Types of Spray Systems
      • Conventional Spray Guns
        • Gravity Feed
          • Material is fed from a container above the gun via gravity
          • Liquid is atomized with compressed air
          • Pros: Well-suited for spraying both thin and thicker materials, relatively quick cleanup
          • Cons: Cumbersome in tight spaces, top-heavy, must be held upright
        • Siphon (Suction) Feed
          • Material is fed from a container below the gun via vacuum or suction
          • Liquid is atomized with compressed air
          • Pros: Well-suited for spraying thinner materials, relatively quick cleanup
          • Cons: Cumbersome in tight spaces, uses more compressed air, small capacity
      • Pressure Pot System
        • Gun + separate storage container for material
        • Liquid is atomized with compressed air
        • Pros: Gun is light, can be used in more confined areas, various container sizes
        • Cons: Care should be taken not to exceed the recommended pressure rating of the tank, long change over due to amount of cleaning needed
      • HVLP Turbine System
        • ‘HVLP’ – High Volume Low Pressure
        • Pressure is less than 10 psi
        • HVLP Gun + Electric Turbine
        • Turbine generates the required airflow
        • Air travels through a series of fans, each fan stage boosts the air pressure
        • HVLP Guns: Have larger passageways, available as siphon feed or gravity feed

    Troubleshooting

    • Blockage or debris on the fluid tip/needle
      • Rotate air cap 180 degrees to assess
      • Clean vent hole to resolve pulsating/fluttering issue

    Respirators

    • Can help protect against particulate hazards and chemical gases
    • Selection of respirator type based on the type of hazard and level of exposure
    • Respiratory Equipment Types
      • Negative Pressure
        • Relies on the wearer's lungs to pull air through the cartridge or filter
        • Potential to put strain on the wearer
        • Tight-fitting, requires fit testing and seal checks before use
      • Positive Pressure
        • Equipment pushes air to the hood or facepiece
        • Powered Air (battery-powered blower) or Supplied Air (bringing in clean air from outside the contaminated area)
        • May be loose-fitting or tight-fitting, facial hair compatible
      • SCBA (Self-Contained Breathing Apparatus)
        • User carries the source of clean air with them in a tank

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    Description

    Learn about the equipment, materials, and techniques used in spray finishing, including air compressors, spray booths, and types of finishes. This quiz covers both theoretical and practical aspects of spray finishing.

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