The document describes the similarities between pneumatic and electrical systems. It explains key pneumatic components like pressure regulators, non-return valves, solenoid valves, and timers and their analogous electrical components. It then provides examples of pneumatic circuits used in container spreaders and discusses common faults that can occur.

1. Pneumatics Pneumatic functions are very similar to electrical functions in many ways. Compressed air ‘flows’ in a similar way to electric current. Various hardware devices act like switches, or other electrical devices, to control the ‘flow’

2. Pressure Pressure determines the amount of force that is applied. In very simple terms, it can be considered similar to current. The higher the current, the greater the power. The higher the pressure, greater the power.

3. Flow Flow determines the speed of pneumatic systems. In very simple terms, it can be considered similar to dc voltage. The higher the voltage, the faster the dc machine will operate. The higher the flow, the faster the pneumatic operation.

4. Pneumatic Components Many simple pneumatic components can be compared to simple electrical components.

5. Pressure Regulator Reduces a high input pressure to a lower working pressure Provides a steady output, despite changes in the input pressure

6. Pressure Regulator In many ways this can be compared to a voltage regulator or zener diode.

7. Non-Return Valve (Check valve) Allows air to flow in one direction, but blocks it from flowing back in the opposite direction.

8. Non-Return Valve (Check valve) In many ways it can be compared to a diode.

9. Solenoid Valve When electrical current is applied to a coil, the valve operates and allows air to flow. Can be both Normally Closed (NC) or Normally Open (NO)

10. Solenoid Valve In many ways this can be compared to a contactor.

11. Shuttle Valve Allows air to flow to an outlet, from either of two inlets. Blocks air from flowing from one inlet to the other

12. Shuttle Valve In many ways this can be compared to a diode bridge.

13. Timer Has a delayed action, after receiving a compressed air signal Available in delayed-on or delayed-off formats

14. Timer Can be very closely compared with an electrical timer.

15. Air Preparation Usually consists of a filter, a regulator, a pressure gauge and a lubricator. The filter removes moisture and debris. The regulator and pressure gauge set a constant working pressure. The lubricator injects an oil mist to help lubricate the moving parts of the system.

16. Filter, Regulator & Lubricator

17. Pneumatic Operation Operation from the control cabinet in the crane For a simple pneumatic spreader

18. The solenoid valve energises and passes air to activate the Air Operated Valve

19. The Air Operated Valve allows air to flow from the main line to the hooks Even when the push-button is released and the solenoid valve de-energises

20. After a set delay, the timer activates and passes air to reset the Air Operated Valve The Air Operated Valve, closes, vents the line and cuts the air to the hooks

21. Pneumatic Operation Operation from the manual push-buttons on the side of the frame

22. The manual valve closes and passes air to activate the Air Operated Valve

23. The Air Operated Valve allows air to flow from the main line to the hooks Even when the push-button is released

24. After a set delay, the timer activates and passes air to reset the Air Operated Valve The Air Operated Valve, closes, vents the line and cuts the air to the hooks

25. Pneumatic Operation Meanwhile, the amount of air in the air tank is going down.

26. 8 bar 3 bar

27. 7 bar 3 bar

28. 5 bar 3 bar

29. 5 bar 3 bar The differential pressure switch detects the falling pressure in the air tank.

30. 3 bar 4 bar The contacts close, which causes the compressor to start and begin to refill the air tank .

31. 5 bar 3 bar

32. 6 bar 3 bar

33. 7 bar 3 bar When the air tank is topped up to full pressure, the differential pressure switch detects this.

34. 8 bar 3 bar The contacts open, which causes the compressor to stop.

35. 8 bar 3 bar A non-return valve between the compressor and the air tank stops air from leaking back out from the air tank.

36. Separate left and right release Some of the pneumatic circuit is duplicated. There are now two solenoid valves, one for releasing each side of the frame. The example shown is one of the more complex designs.

37. Solenoid 1 energises to release left hooks

38. The solenoid remains energised by an electrical timer

39. After a time delay, the solenoid de-energises and the air is vented.

40. To release the other side, solenoid 2 energises.

41. After a time delay, the solenoid de-energises and the air is vented.

42. The manual release passes air to the timer, which then activates the air-operated solenoid

43. When the pneumatic time delay is completed, the air signal to the air operated valve is cut.

44. The return spring inside the air operated valve, closes the valve & cuts the air to the hooks

45. “ Nagesco” Frames These frames use a slightly different operating system. All circuits operate at 110v. There are Normally Open & Normally Closed solenoid valves The release timing is via delay timers on the push-buttons.

46. Nagesco Frames Frame is marked with red & blue sides. Control box has a 3-position switch: Blue, ALL, Red There is a single release button (with delay-off timer)

47. Left & right solenoids are normally open type Main solenoid is energised and passes air through the open solenoids to the hooks

48. Main solenoid is energised and passes air through the open solenoids to the hooks

49. Push-button time delay expires and solenoid de-energises and vents line, causing hooks to lock

50. Push-button time delay expires and solenoid de-energises and vents line, causing hooks to lock

51. To release ‘blue’ side only, solenoid ‘R’ is energised which closes the flow to hooks on the ‘red’ side.

52. The main solenoid is energised and air flows to the hooks on the ‘blue’ side only.

53. So what can go wrong? As you can see, the electrical and pneumatic circuits are quite simple so what can go wrong with these spreaders? Well, not a lot really. The cause of most faults are air leaks or failed electro-mechanical timers.

54. Electrical Faults Failed compressor. Defective or wrongly adjusted pressure switch. Blown fuse or tripped circuit breaker (sometimes resulting from impact). Failed transformer Loose wiring

55. Electrical Faults Defective electro-mechanical timer unit. Wrong control box being used Defective gantry cable Water in power socket or damaged power socket. Damaged control socket or plug

56. Pneumatic Faults Defective compressor Defective or wrongly adjusted pressure regulator. Damaged pneumatic hose to hook. Defective hook (stuck or seal failure)

57. Pneumatic Faults Water in pneumatic system (drain tanks & check filter)

58. Pneumatic Faults The following is a common scenario: All hooks unlock but will not re-lock The compressor is running

59. Pneumatic Faults This is nearly always due to an air leak in the pneumatic system or because the release has been operated soon after the spreader was powered up.

60. Pneumatic Faults Check the air pressure on the main air cylinders. Is it less than 3 bar? If yes, then you probably have a large air-leak. The air is leaking out as fast as the compressor tries to fill the tanks.

61. Pneumatic Faults Some spreaders have a valve on the outlet from the tanks – close the valve and see if the air pressure in the main cylinders starts to rise. Locate the air leak and repair it. When the pressure has returned to around 5 or 6 bar, open the valve

62. Pneumatic Faults If there is no valve on the outlet of the main air cylinders- Remove power to the spreader. Repair the air leak Restore power to the spreader. Wait for the pressure in the main cylinders to rise to around 5-6 bar.

63. 2 bar 2 bar A serious air leak will cause pressure in the main cylinders to fall below 3 bar.

64. 2 bar 2 bar Below around 2 bar there is not enough pressure for the pneumatic timer to activate and reset the system

65. 2 bar 2 bar Therefore the hooks will remain open and the leak will prevent the cylinder pressure from rising, despite the operation of the compressor