TPC 309 Flashcards
In a pneumatic system, force must be present at all times for the system to function. What is this force?
Compressed Air
What is the formula for work?
Work = Force x Piston Travel
What does Charles law state?
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 absolute temperature of the gas.
If the original force is applied to the large piston instead of to the small piston, the force exerted on the small piston?
Decreases, but it’s amount of travel increases.
If the kinetic energy increases and the total energy remains the same, the potential energy of the air moving in a reduced flow passage is reduced. If the potential energy is reduced…
The pressure of the air is also reduced.
Positive-displacement compressors that are capable of compressing air to relatively high pressures are commonly used in pneumatic power systems. What is one kind of these devices?
Reciprocating Piston
What opens the valves on a reciprocating compressor?
The negative pressure allows the air at atmospheric pressure to open the valves.
What do cooling components allow for in compressors?
The need for less power because the cooling between stages reduces the volume of air that is compressed in the second stage.
What are the two functions of compressor lubricating oil?
Reduce friction and improve the transfer of heat in the compressor.
What does unloading allow for in large compressors?
It does not compress air and is easier to start.
Single stage vane compressors are capable of developing up to what psi discharge pressure?
50 PSI
What speeds do screw compressors operate at?
Between 3,000 and 12,000 RPM
Impeller compressor also knows as blowers are designed to?
Move high volume and low pressure air.
What compressors require more horsepower per cfm?
Centrifugal Compressors.
When trying to control the centrifugal compressor output what is the most effective way?
Speed variation, however many compressors lose efficiency when the speed is reduced too much.
What can change the amount of water content in pressurized air?
Humidity and Temperature.
What cooling is economical for what type of compressors?
Medium-Sized single stage compressors operating more than 8 hours a day and for larger compressors or any that operate more than 10 hours a day.
What do air receivers allow for?
The capability to balance off available compressor capacity against much larger peak air-flow demands that occur.
Centrifugal separators also known as internal separators work in what way?
The inertia of a heavy moving particle to aid in the separation, the heavier a particle is and the faster it is moving, the more it tends to travel in a straight line, therefore when it is forced into a circular path it has a natural tendency to move outward.
If it stops 100% of a given particle size, this size is referred to as?
Absolute Rating
Wetted air filters have a slightly higher initial cost than dry filers but…
They can be cleaned many times.
Fire lubricators are especially effective in what systems?
Complicated piping systems and intermittent equipment operation.
To avoid turbulence in inner walls for an air piping system what should you do?
The inner walls should be smooth and piping should not change direction more than necessary, also the number of fittings should be kept to a minimum.
The slope when installing air lines should be what?
1 inch for every 10 feet as well as in a downward direction in the direction of air flow.
What pipe thread is used for pneumatic piping?
NPT (National Pipe Thread)
What can the number of primary system connecting ports be?
Two, Three, Four, and Five.
What Valve is a two way valve and is excellent for high pressure service?
A Needle Valve.
What are the benefits of a spool valve?
It is easy to operate even with high pressures because the internal forces balance each other.
What are 4 way valves used for?
To simplify pneumatic circuits.
What is a five way valve?
It is a special four way valve with five external connections.
The poppet is held against the valve seat how?
By the force of the adjustable poppet spring.
What is cracking pressure?
The pressure at which the valve initially opens, is determined by the adjustment of the spring.
A diaphragm relief valve responding to increasing air pressure opens much faster than what?
A poppet valve.
When does a regulator valve close?
When the discharge pressure increases.
A diaphragm valve will control difference in psi how?
By modulating continuously to maintain desired pressure.
It is difficult to adjust a separate pressure-relief valve to operate at pressures just above regulator pressure settings, what is used?
A built in relief valve is desirable for this application.
Thrust is greater when the piston is moved to the left than when it is moved to the right most standard pneumatic cylinders are?
Double Acting.
What is a spring return cylinder?
A modified single acting cylinder is equip with an internal spring.
Many single and double acting cylinders are equip with an exhaust flow control metering valve, what does this do?
The valve restricts the amount of exhaust air that can pass from the cylinder through the valve and governs the speed at which the cylinder can retract.
Pivoted cylinder mountings are classed as being?
Trunnion or Clevis and have no rigid support.
What is used to check if a control valve is capable of handling the air of a cylinder?
The capacity coefficient.
What is stalling torque?
The force necessary to stop the motor once it’s running.
The maximum power output is obtained how?
At the medium speed and medium torque output.
How does an axial piston motor work?
Compressed air entering the inlet ports acts on the piston against a wobble/cam plate attached to the offset shaft causing the cam plate to rotate this motion transferring through gears to the output shaft.
