Pneumatics Pneumatics • Pneumatic functions are very similar to Pneumatic functions are very similar to electrical functions in many ways. electrical functions in many ways. • Compressed air ‘flows’ in a similar way Compressed air ‘flows’ in a similar way to electric current. to electric current. • Various hardware devices act like Various hardware devices act like switches, or other electrical devices, switches, or other electrical devices, to control the ‘flow’ to control the ‘flow’
Transcript
PneumaticsPneumatics
• Pneumatic functions are very similar to Pneumatic functions are very similar to electrical functions in many ways.electrical functions in many ways.
• Compressed air ‘flows’ in a similar way to Compressed air ‘flows’ in a similar way to electric current.electric current.
• Various hardware devices act like switches, Various hardware devices act like switches, or other electrical devices, to control the or other electrical devices, to control the ‘flow’‘flow’
PressurePressure
• Pressure determines the amount of force that Pressure determines the amount of force that is applied.is applied.
• In very simple terms, it can be considered In very simple terms, it can be considered similar to current.similar to current.
• The higher the current, the greater the power.The higher the current, the greater the power.
• The higher the pressure, greater the power.The higher the pressure, greater the power.
FlowFlow
• Flow determines the speed of pneumatic systems.Flow determines the speed of pneumatic systems.
• In very simple terms, it can be considered similar In very simple terms, it can be considered similar to dc voltage.to dc voltage.
• The higher the voltage, the faster the dc machine The higher the voltage, the faster the dc machine will operate.will operate.
• The higher the flow, the faster the pneumatic The higher the flow, the faster the pneumatic operation.operation.
Pneumatic ComponentsPneumatic Components
• Many simple pneumatic components Many simple pneumatic components can be compared to simple electrical can be compared to simple electrical components.components.
Pressure RegulatorPressure Regulator
• Reduces a high Reduces a high input pressure to a input pressure to a lower working lower working pressurepressure
• Provides a steady Provides a steady output, despite output, despite changes in the changes in the input pressureinput pressure
Pressure RegulatorPressure Regulator
• In many ways this In many ways this can be compared can be compared to a voltage to a voltage regulator or zener regulator or zener diode.diode.
Non-Return Valve (Check Non-Return Valve (Check valve)valve)• Allows air to flow in Allows air to flow in
one direction, but one direction, but blocks it from blocks it from flowing back in the flowing back in the opposite direction.opposite direction.
Non-Return Valve (Check Non-Return Valve (Check valve)valve)• In many ways it In many ways it
can be compared can be compared to a diode.to a diode.
Solenoid ValveSolenoid Valve
• When electrical When electrical current is applied to current is applied to a coil, the valve a coil, the valve operates and allows operates and allows air to flow.air to flow.
• Can be both Can be both Normally Closed (NC) Normally Closed (NC) or Normally Open or Normally Open (NO)(NO)
Solenoid ValveSolenoid Valve
• In many ways this In many ways this can be compared can be compared to a contactor.to a contactor.
Shuttle ValveShuttle Valve
• Allows air to flow to Allows air to flow to an outlet, from an outlet, from either of two inlets.either of two inlets.
• Blocks air from Blocks air from flowing from one flowing from one inlet to the otherinlet to the other
Shuttle ValveShuttle Valve
• In many ways this In many ways this can be compared can be compared to a diode bridge.to a diode bridge.
TimerTimer
• Has a delayed Has a delayed action, after action, after receiving a receiving a compressed air compressed air signalsignal
• Available in Available in delayed-on or delayed-on or delayed-off formatsdelayed-off formats
TimerTimer
• Can be very closely Can be very closely compared with an compared with an electrical timer.electrical timer.
Air PreparationAir Preparation
• Usually consists of a filter, a regulator, a Usually consists of a filter, a regulator, a pressure gauge and a lubricator.pressure gauge and a lubricator.
• The filter removes moisture and debris.The filter removes moisture and debris.
• The regulator and pressure gauge set a constant The regulator and pressure gauge set a constant working pressure.working pressure.
• The lubricator injects an oil mist to help lubricate The lubricator injects an oil mist to help lubricate the moving parts of the system.the moving parts of the system.
• Operation from the Operation from the control cabinet in control cabinet in the cranethe crane
• For a simple For a simple pneumatic pneumatic spreaderspreader
The solenoid valve energises and passes air to activate the Air Operated Valve
The Air Operated Valve allows air to flow from the main line to the hooksEven when the push-button is released and the solenoid valve de-energises
After a set delay, the timer activates and passes air to reset the Air Operated ValveThe Air Operated Valve, closes, vents the line and cuts the air to the hooks
Pneumatic OperationPneumatic Operation
• Operation from the Operation from the manual push-manual push-buttons on the side buttons on the side of the frameof the frame
The manual valve closes and passes air to activate the Air Operated Valve
The Air Operated Valve allows air to flow from the main line to the hooksEven when the push-button is released
After a set delay, the timer activates and passes air to reset the Air Operated ValveThe Air Operated Valve, closes, vents the line and cuts the air to the hooks
Pneumatic OperationPneumatic Operation
• Meanwhile, the amount of air in the Meanwhile, the amount of air in the air tank is going down.air tank is going down.
8 bar 3 bar
7 bar 3 bar
5 bar 3 bar
5 bar 3 bar
The differential pressure switch detects the The differential pressure switch detects the falling pressure in the air tank.falling pressure in the air tank.
3 bar4 bar
The contacts close, which causes the The contacts close, which causes the compressor to start and begin to refill the air compressor to start and begin to refill the air tanktank..
5 bar 3 bar
6 bar 3 bar
7 bar 3 bar
When the air tank is topped up to full When the air tank is topped up to full pressure, the differential pressure switch pressure, the differential pressure switch detects this.detects this.
8 bar 3 bar
The contacts open, which causes the The contacts open, which causes the compressor to stop.compressor to stop.
8 bar 3 bar
A non-return valve between the compressor A non-return valve between the compressor and the air tank stops air from leaking back and the air tank stops air from leaking back out from the air tank.out from the air tank.
Separate left and right Separate left and right releaserelease• Some of the pneumatic circuit is Some of the pneumatic circuit is
duplicated.duplicated.
• There are now two solenoid valves, one There are now two solenoid valves, one for releasing each side of the frame.for releasing each side of the frame.
• The example shown is one of the more The example shown is one of the more complex designs.complex designs.
Solenoid 1 energises to release left hooks
The solenoid remains energised by an electrical timer
After a time delay, the solenoid de-energises and the air is vented.
To release the other side, solenoid 2 energises.
After a time delay, the solenoid de-energises and the air is vented.
The manual release passes air to the timer, which then activates the air-operated solenoid
When the pneumatic time delay is completed, the air signal to the air operated valve is cut.
The return spring inside the air operated valve, closes the valve & cuts the air to the hooks
““Nagesco” FramesNagesco” Frames
• These frames use a These frames use a slightly different slightly different operating system.operating system.
• All circuits operate at All circuits operate at 110v.110v.
• There are Normally There are Normally Open & Normally Closed Open & Normally Closed solenoid valvessolenoid valves
• The release timing is via The release timing is via delay timers on the delay timers on the push-buttons.push-buttons.
Nagesco FramesNagesco Frames
• Frame is marked Frame is marked with red & blue with red & blue sides.sides.
• Control box has a 3-Control box has a 3-position switch:position switch:Blue, ALL, RedBlue, ALL, Red
• There is a single There is a single release button (with release button (with delay-off timer)delay-off timer)
Left & right solenoids are normally open typeMain solenoid is energised and passes air through the open solenoids to the
hooks
Main solenoid is energised and passes air through the open solenoids to the
hooks
Push-button time delay expires and solenoid de-energises and vents line, causing hooks to lock
Push-button time delay expires and solenoid de-energises and vents line, causing hooks to lock
To release ‘blue’ side only, solenoid ‘R’ is energised which closes the flow to hooks on the ‘red’ side.
The main solenoid is energised and air flows to the hooks on the ‘blue’ side only.
So what can go wrong?So what can go wrong?
• As you can see, the electrical and As you can see, the electrical and pneumatic circuits are quite simple so pneumatic circuits are quite simple so what can go wrong with these spreaders?what can go wrong with these spreaders?
• Well, not a lot really.Well, not a lot really.
• The cause of most faults are air leaks or The cause of most faults are air leaks or failed electro-mechanical timers.failed electro-mechanical timers.
• Defective or wrongly adjusted Defective or wrongly adjusted pressure regulator.pressure regulator.
• Damaged pneumatic hose to hook.Damaged pneumatic hose to hook.
• Defective hook (stuck or seal failure)Defective hook (stuck or seal failure)
Pneumatic FaultsPneumatic Faults• Water in pneumatic system (drain Water in pneumatic system (drain
tanks & check filter)tanks & check filter)
Pneumatic FaultsPneumatic Faults
The following is a common scenario:The following is a common scenario:
• All hooks unlock but will not re-lockAll hooks unlock but will not re-lock
• The compressor is runningThe compressor is running
Pneumatic FaultsPneumatic Faults
This is nearly always due to an air This is nearly always due to an air leak in the pneumatic system or leak in the pneumatic system or because the release has been because the release has been operated soon after the spreader was operated soon after the spreader was powered up.powered up.
Pneumatic FaultsPneumatic Faults• Check the air pressure on the main air Check the air pressure on the main air
cylinders.cylinders.
• Is it less than 3 bar?Is it less than 3 bar?
• If yes, then you probably have a large If yes, then you probably have a large air-leak. The air is leaking out as fast air-leak. The air is leaking out as fast as the compressor tries to fill the as the compressor tries to fill the tanks.tanks.
Pneumatic FaultsPneumatic Faults• Some spreaders have a Some spreaders have a
valve on the outlet valve on the outlet from the tanks – close from the tanks – close the valve and see if the the valve and see if the air pressure in the main air pressure in the main cylinders starts to rise.cylinders starts to rise.
• Locate the air leak and Locate the air leak and repair it.repair it.
• When the pressure has When the pressure has returned to around 5 or returned to around 5 or 6 bar, open the valve6 bar, open the valve
Pneumatic FaultsPneumatic Faults• If there is no valve on the outlet of the main If there is no valve on the outlet of the main
air cylinders-air cylinders-
• Remove power to the spreader.Remove power to the spreader.
• Repair the air leakRepair the air leak
• Restore power to the spreader.Restore power to the spreader.
• Wait for the pressure in the main cylinders to Wait for the pressure in the main cylinders to rise to around 5-6 bar.rise to around 5-6 bar.
2 bar2 bar
A serious air leak will cause pressure in the main A serious air leak will cause pressure in the main cylinders to fall below 3 bar.cylinders to fall below 3 bar.
2 bar2 bar
Below around 2 bar there is not enough pressure for Below around 2 bar there is not enough pressure for the pneumatic timer to activate and reset the the pneumatic timer to activate and reset the systemsystem
2 bar2 bar
Therefore the hooks will remain open and the leak Therefore the hooks will remain open and the leak will prevent the cylinder pressure from rising, will prevent the cylinder pressure from rising, despite the operation of the compressordespite the operation of the compressor
