Pneumatic Systems Flashcards
What must always be considered before working on pneumatic systems?
Trapped air in the system even though gauge reads 0
Breathing oils mist from pneumatic systems can result in?
Respiratory problems
Basic pneumatic systems include:
Compressors
Receivers
Filters
Regulators
Lubricators
Mufflers
Dryers
Actuators
Control valves
Conductors
Air intake for the compressor system should be located where?
Coolest part of the building. Cooler air is more dense which makes compressors more efficient
Air receivers compensate for fluctuations in demand and can also _________ with reciprocating compressors.
Dampen pulsations
Safety relief valves must be mounted _________ on receiver tanks?
Vertically
What should the pressure relief valve be set to?
No higher than the lowest maximum pressure rating of any part of the the system
What problems does moisture cause in the system:
Air supply’s can freeze
- rust receivers and piping forming sludge and rust
- some processes such as painting can be harmed by water
- harmful effects to proper lubrication.
Because pressure are under 200 psi moisture is often present in the lines. It is common to use non corrosive materials such as:
Plastic
Brass
Copper
Aluminum
What problem increases expenses and reduces performance of tools?
Air leaks
FRL stands for ?
Filter - cleans air
Regulator - sets system pressure
Lubricator - adds a mist of oil to components
Contaminants left in a air system may be from?
Contaminate left from assembly or maintenance
Oil and west particles from the system
Pipe scale and rust from the system piping
What is the purpose of the regulator
Most parts of the system require less pressure than what comes from the compressor.
You can regulate pressure to different actuators in you system
Lubricators?
Supply clean oil, cool and seal different components
Does compressor oil carry over aid the pneumatic system?
No it tends to accumulate in the piping causing addition problems of gumming up the system
What is one test to determine if the valve s are getting the right amount of oil?
Hold a piece of paper near the exhaust port on the valve. Pale indication of oil should be present. If oil is dripping off the page it is getting to much oil
Where do you find water traps?
Anywhere in a system where water can be a problem.
Whenever see point is reached moisture falls out of the air
Symbols are meant to graphically portray the characteristics of pneumatic parts which are:
-function
- method of actuation and return
- number of connections and parts
- number of different switched positions
- simplified representation of the flow path
Symbols are not meant to show?
- size or dimension of part
- physical relationship between parts
- orientation of ports
- manufacturer or method of construction
- unions or connections other than junctions
Shut off positions symbol
Symbol inlet outlet ports
Mechanically operated symbols
Pneumatic control symbols
What is the main difference between pneumatic and hydraulic valves?
Hydraulic valves operate on much higher pressure
Pneumatic systems often only operate at 100 psi
What is the difference between a vented and non vented regulator?
Vented regulator can also act as a relief valve for the downstream section
When should full flow relief valves be used?
Whenever large flows of air must be released
Hydraulic valves use used lapped spool design to seal. Because that system needs constant lubrication pneumatic valves use packed bore, packed spool, or sliding plate design
Both packed bore and packed spool use ________ to seal the space between the spool and bore?
O rings
Sliding plate
Can provide many millions of trouble free cycles even in less ideal conditions
A typical pneumatic DCV configuration is ?
Four-way/three-position (4/3), spring centred, solenoid actuated valve
What is a solenoid?
A wire coil around a metal plunger when the coil is electrically energized it builds a magnetic field which pulls the iron plunger into the coil
What restrictions are commonly overlooked?
Quick disconnects
Hoses with ID’s that are to small
Sharp bends
Kinks in hoses
Pilot operated valves are operated with _______ and can be internally piloted or _________.
Air
Externally piloted
Externally piloted valve requires air source to the _______ port. This pressure can be from a low pressure source if _______ shifting is adequate but if quick reaction time ________ is used in conjunction with a quick exhaust.
Slow
High pressure
Internally piloted valves need ________ and _________ pressure to operate properly.
Minimum
Maximum
Directing control valves are used for?
Control flow path
Speed
Sequence events
Check valves
Allow air flow in one direction
What is the 2/2 valve used for?
Usually on off it’s only function is to allow air to flow through. A trigger on a air tool
3/2 two valves are used when?
Air needs to be released when the valve is closed. Typical operation would be a single acting cylinder.
Schematics for DCVS are usually drawn showing the ________ Position. The way they would come out of the manufacture packaging.
De-activated
What is happening in this drawing?
3/2 valve being used to send a pilot signal another 3/2 actuating valve.can be remotely activated.
What is a common use for a 4/2 valve?
4 ports: one pressure 2 actuator and 1 exhaust
Reversible motion of a cylinder or motor
4/2 valves are always extending or retracting. If there is no movement needed what type of valve would you use?
4/3
4/3 valve with a closed centre allows for what?
Piston rod to be stopped in any position but because air is compressible it’s not an accurate way of controlling location
5/2
Same as 4/2 but two exhaust ports
Which special 5/3 valve is like the 4/3 closed centre valve?
5/3 blocked centre
Allows load to be held in position
What does a 5/3 pressure centre do?
Extends two single acting cylinders at once in the centre position. And when shifted to either side controls the cylinders on their own.
5/3 exhaust centre
In the centre position both cylinder ports are open to exhaust. Rod can be moved in either direction by hand.
What does a shuttle valve do?
Automatically selects the higher of two pressure sources to supply a pneumatic signal
What is the purpose of a flow control?
To vary the speed of the actuators in a specific part of the circuit
Needle valve is the most popular style of flow control. What other styles are there?
Ball and globe flow controls are used in larger systems.
Needle gives the finest control
Usually built in _______ valves are included in the flow control. What is the purpose?
Check valve
To offer little resistance to flow in the opposite direction
What factors affect the accurate control of flow?
Uniformity of the applied load
Friction forces (piston seals, rod seals)
Acceleration forces (rate speed is gained)
Where is a quick exhaust located and purpose?
Used with 3 or 4 ways valves to increase exhaust flow(speed of cylinder)
Normally mounted on the end caps of the cylinder
What are excess flow valves
Minimize hose whipping the a line breaks
What motors are used in impact guns, grinders and drills?
Vane motors
High speed grinders and dentist drills use what motor
Turbine
Gear motors are used when high torque is needed. Up to how much HP
60
When trouble shooting pneumatic systems it is important to use a systematic approach?
Either start at the actuator and work you way to the compressor or vice versa
Common causes making a cylinder inoperable would be
Corrosion
Dried out lubricant
Gumming
Deterioration of rubber parts
Bad piston seals
Sluggish or slow moving control valve can be caused by:
Lack of lubrication
Swollen seals
Deteriorating packing
Binding caused by excessive pressure
Actuator cylinder is drifting
- piston seal is leaking
- operating valve is leaking
- connecting lines are leaking
Cylinder is sticking or binding
The packing on the cylinder rod was overtightened
- cylinder is misaligned
- seals are defective
- pilot pressure is low
Cylinder body is leaking
Tie rods are loose
- pressure at the cylinder is excessive
- cylinder body seal is pinched or extruded
- tie rods are loose
Rod gland seal is leaking
Seal is deteriorating
Pneumatic valve is blowing to exhaust when not actuated
The inlet poppet is not seating
Pneumatic valve is blowing exhaust when actuated
Valve seals are faulty
- the valve-to-base gasket is faulty
- spool is damaged
Pilot section is blowing to exhaust
Pilot cover is loose
Poppet is not sealing
Poppet is chattering
Air supply pressure is to low
Pilot pressure or signal pressure is to low
