Pneumatics Flashcards
What components does a typical pneumatic system have?
Compressor, receivers, filters, pressure regulators, lubricator so, muffler, dryer, actuator, control valve, and conductors
Where should the air intake be located?
In the coolest place possible
What is the air receivers purpose?
To compensate for fluctuations in demand, and to dampen pulsations?
What is the regulatory division that enforces code, and does inspections regarding receivers?
Alberta boilers branch
What things must every receiver have?
Gauge, drain, pressure relief valve
What must the pressure relief valve be set at?
Must be set no higher than 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) Loop system
What is the preferred or recommended piping system?
The loop system
Describe the grid, or dead end system of piping
It is the simplest, only requires one compressor, usually starts with a larger diameter supply line that gradually decreases. One drawback, is that systems at the end of the line could face air starvation when upstream demand is heavy
Describe the decentralized (unit) system
it is composed of two or more compressors each with their own grid. The grids may or may not be interconnected. Its advantage of this is each compressor is close to its point of use which means there is less pressure drop and more uniform supply and pressure
Describe the loop system of piping
Two or more compressors feed into the same loop allowing compressed air to flow in either direction.
What materials are typically used for piping?
Plastic, brass, copper, aluminum, because they are all non corrosive. Black pipe is still commonly used due to its cost, but it is prone to rusting and scaling
What is a FRL unit ?
Filter, regulator, lubricator. They are installed in this order, and are often symbolized as a single valve in a drawing called a simplified air service unit
What are filters typically protecting from?
Contaminants from construction/assembly, oil and wear particles, pipe scale and rust.
How do you tell if an inline filter becomes plugged?
With gauges on either side you can see a pressure drop across the filter
Describe regulators
Different components require different pressures, and usually the supply from the compressor is too high. It is piloted downstream, with a gauge so proper pressure can be set.
What does the exhaust air contain?
It usually contains oil in the form of mists and vapours
Where is an oil lubricator located?
They are located close to the device that requires it. They are not transported all through the lines
What are some guidelines when dealing with oil in a pneumatic system
Prevent compressor oil from entering the airstream, put lubricator so close to the component they will lubricate
When does moisture fall out of compressed air?
When the dew point is reached
What do the symbols graphically portray?
Function, method of actuation, number of connection or ports, number of different switched positions, representation of flow path
Describe a lubricator symbol
Diamond shape with a small line coming from the top point
Describe a compressor symbol
Circle with a triangle pointing outward, and triangle is not coloured in
Describe a water separator symbol
Diamond shape with a horizontal line across the bottom
Describe a filter symbol
Diamond shape with dashed vertical line
Describe a simplified air service unit symbol
A box with (in order) filter dashed line, gauge symbol for regulator, small solid line from top for lubricator. This is a typical FRL unit
What is a common dcv for pneumatics?
5/3
Describe the ways in a 5/3 dcv
The out ports are similar to an A and B like hydraulics the bottom three, the middle is your pressure or supply line, and either side is exhaust
Describe an exhaust port symbol
A small triangle on the outside of s box
Describe a silencer or muffler symbol
A box with alternating lines and an exhaust symbol on far side
Describe a shuttle valve symbol
A box with check valves in two direction and a third line out
Describe the two pressure valve symbol
A box with four ports, and a I——I in the middle
Describe the quick exhaust valve symbol
Same as the shuttle valve, but with a pilot line, and exhaust symbol
What three things do valves control?
Pressure, flow, direction
What are the two types of pressure regulators?
Venting, and non venting
What does s non venting regulator symbol look like?
Like a pressure reducing valve because it’s normally open, piloted downstream
Describe the difference between venting and non venting regulators
Non- sets a pressure Venting maintains it by exhausting if pressure increases downstream
What are the three types of spools in pneumatic dcv
Packed bore, packed spoil, sliding plate
Describe a packed bore spool
The o rings are fitted inside the bore of the dcv. Difficult to repair or maintain
Describe a packed spool
The o rings are fitted directly onto the spool, much easier to repair
Describe a sliding plate spool
A plate with ports machined in it slides back and forth to open and close desired flow paths
What are the clearances in a pneumatic valve?
.002-.004mm
What is used overcome problems like destructive pounding in a high flow rate system?
They use solenoid controlled pilot operated dcv
What is another name for a two way, two position pneumatic valve?
It is used as an on off valve. A trigger of an air tool is an example
What is the purpose of a 3/2 dcv valve
It is used when air needs to be released when the valve is closed
What is always happening with a 4/2 pneumatic valve with a cylinder?
The cylinder is always either extending or retracting
5/3 are the most common pneumatic dcv. What are the three centres called?
Exhaust centre Pressure centre Blocked centre
Describe a pneumatic pressure centre
Both a and b ports are pressurized
Describe a pneumatic exhaust centre
Both a and b are exhausted, the cylinder is free to move
Describe a pneumatic blocked cylinder.
It has all lines blocked so there is no pressure or exhaust. It provides a holding or braking action
How does a shuttle valve choose which line will be supply line?
It will automatically select the higher of the two pressures
What do flow controls do?
They vary the speed of actuators. Same as hydraulics, they can meter in or out
What is the most common flow control valve
Needle valve. Ball and globe valves are used in larger systems
Which flow control has the finest control?
The needle valve because of the tapered needle and fine threads
