Pneumatics Flashcards
In a pneumatic system what must be present at all times for the system to function
Force
When you add gauge pressure to atmospheric pressure you get
Absolute pressure
Force x distance in feet or inches equals
Foot pounds or inch pounds
A physical law dealing with heat is Charles law, it says if the volume of a confined quantity of gas remains the same,
The change in the pressure of the gas varies directly with a change in the absolute temperature of the gas
A principal of leverage states that for every force increase there is a corresponding movement what
Decrease
As temperatures increase the molecules bump into each other more frequently while they are moving, which gives them a greater resistance to flow this is called
Dynamic viscosity
Positive displacement compressors do what
Confine the air and compress it by decreasing the volume of the space
Dynamic compressors do what
Accelerate the air with rapidly turning rotor blades
Less power is needed to compress air because what is used between stages
Inter cooler, cooling between stages reduces the volume of air that is compressed
What does lube oil do
Reduce friction and improve heat transfer
What is unloading a compressor
Relieving all internal pressure, so it starts easier
Single stage vane compressors can develop up to how much psi
50 psi
Wet type rotary screw compressors do not use
Timing gears
The impeller compressor is designed for what
High volume rather than high pressure
Two disadvantages of centrifugal compressors are that they
Require more horsepower and that they operate at very high speeds
Four control methods of a centrifugal compressor is what
Speed variation, suction throttling, discharge throttling, and recirculation, the most efficient tho is speed variation
The recommended method of cleaning dry filters are
To use recommended solvent to clean
The amount of moisture or water vapor that exists in free air depends on the temp and weather conditions. The amount of moisture in the air at anytime compared to the amount of water vapor the air could hold if it were completely saturated is referred to as
Relative humidity
Water cooled compressors are used with
Large compressors or medium sized compressors that run for more than eight hours a day
After coolers are built strong because why
They operate at high pressures
Most systems or aftercoolers have what to remove moister
Mechanical separators
Deliquescent is what
Desiccant used to absorb moisture
Air receivers do what
There most important purpose is their ability to store compressed air
What is used as a pre filter to pick up large dirt particles
Inertial separators
Absolute rating in reference to a filter is
It’s ability to stop 100% dirt particles
Closely packed fine metallic wire is used in what type of filter
Depth filter
Wetted filters cost more than dry filters but
They can be cleaned and reused many times
Fine lubricators mist oil and are used for
Long distances complicated piping and systems with intermittent equipment operation
Lubricators should be mounted blank the pressure regulator
After
Turbulent flow creates
Heat
How to avoid turbulence
Inner walls of air line should be smooth and with the least amount of bends possible
Pressure loss in a pipe is affected by
Airflow volume, pipe diameter, and the air pressure
Airflow at lower pressures is affected blank by friction
More
Npt threads seal how
Flank to flank (side to side) contact with the air of pipe dope
Compressor discharge and distribution lines should slope 1 inch for every
10 feet, the slope should be downward in the direction of air flow
Control valves are identified how
Number of connecting ports, type of control element, method of operation, number of control positions
A needle valve is made is excellent at
High pressure service but has high pressure losses
A plunger controls the entire air flow through a valve in what kind of valve
Direct acting normally closed two way solenoid valve
Spoil valves are great, why
Easy to operate even at high pressures, they can be made to shift to more than one position
Three way valves may be used how
Diverter or selector valves, holding valves, and directional valves. The only difference is how they are hooked up
Four way valves are used to
Simplify pneumatic circuits
A five way valve is
A special four way valve with an extra exhaust port
A pressure control valve is done how
Unloading, holding back or blocking open the valve ports
Relief valves are located where
Between the pressure reg and the individual piece of equipment, it protects from full outlet line pressure if the regulator fails
Cracking pressure is adjusted how
By adjusting the spring
Diaphragm valves respond much faster than poppet valves because
The compressed air works on a much larger pressure sensitive area (a diaphragm)
Pressure relief valves do what
Only job is to protect the system and its components from damage
Pressure regulators sometimes have what built in
A relief valve
Pneumatic cylinders do not require what
Air lines to return air to the receiver
Which side of the piston has less pressure on it
The rod side
A single acting cylinder is equipped with
An internal spring
An exhaust flow control metering valve prevents the cylinder from experience what
Shock
Pivoted cylinder mountings are classed as being
Trunnions or clevis and have no rigid support
Capacity coefficient is what
A control valves ability to handle the air of a cylinder
The valve port size should be what than the cylinder port size
No smaller, equal
Pneumatic motors need a starting or break a way force called
Torque
Positive displacement motors are usually the
Fixed displacement type
Maximum power output is obtained at what speed
Medium speed and medium torque output
The horsepower output of pneumatic motors is the product of the shaft…
Speed and torque
Starting torque is what
Is the turning force the motor exerts from a dead stop typically 75% of the stalling torque, this means it’s really hard to stall the motor
The thrust of the piston causes the wobble (cam) plate to
Rotate, this motion is transferred through gears to the output shaft
The force applied to the hydraulic fluid is spread over a smaller area so it creates what
Greater pressure ( pressure multiplier )
