Vacuum Lifter Selection
Following are some point worthy of consideration when reviewing the design and use of Vacuum Lifters:
• The generally accepted Standard worldwide, for the design and use of Vacuum Lifters is that covered by European Regulation EN13155. It would therefore be advisable to insist that any such device should as a minimum, be designed and certified in accordance with this Regulation. In addition, any Vacuum Lifter used in Australia should be certified, inspected and tested in accordance with Sections 5.6 and 12 of Australian Standard AS 4991 – 2004.
• To achieve absolute increased safety, the design of the Vacuum Lifter should only utilise a 24 volt power supply incorporating two batteries. In the event of a breakdown of cells within one of the batteries, the vacuum pump is able to operate with the remaining battery voltage at only 16 or 18 volts – absolutely safe! This is not possible if you only have a 12 volt supply with one battery.
• The same is valid for the alarm system. According to European Regulation, the Vacuum Lifter has to have an emergency working alarm, even in the event of the total breakdown of the energy supply. The fact is that in a breakdown of two or three cells in a 12 volt battery-system, the alarm function will not work because it has only one battery.
• Another advantage of a 24 volt system is the capacity of the batteries. For a given load, a 24 volt system needs approximately half of the amperage of a 12 volt system. This means that the time taken to discharge the battery is nearly twice the time required to discharge a 12 volt system.
• But what happens if both batteries fail at the same time, or a battery cable is broken? Even in this situation a safety device is required under European Regulation. The better machines are fitted with an additional capacitor powered emergency alarm to operate, independent of the battery system of the machine, in the event of a total breakdown of the power supply.
• Many machines have only a visual or audible indicator as a safety device. It is far better to have both visual as well as audible indicators, as it is not appropriate to depend only upon a red warning light fitted to a machine suspended from a crane in sunlight. The additional alarm horn or buzzer will be noticeable even under unfavourable construction site conditions.
• Again the better Vacuum Lifters have electronic programmable pressure switches. They show the vacuum level much more exactly than analogue vacuum gauges. This is important, especially when troubleshooting the system. The vacuum level is also capable of being adjusted, depending upon the surrounding conditions such as height above sea level. This is not possible with mechanical pressure switches and analogue vacuum gauges.
• The use of quick disconnects on all vacuum hoses is highly recommended instead of hose band clamps. Of course this is certainly more expensive but it does make it much quicker and easier to locate vacuum leakage when troubleshooting, by isolating individual circuits and components.
• All Vacuum Lifters are required by European Regulation, to incorporate “dual redundancy” or back-up in the event of primary system malfunction. On dual vacuum circuit machines this feature permits the sandwich panel or glass pane to be lifted without safety belts or other such devices. On single circuit machines “dual redundancy” is deemed to be achieved via the use of safety belts however it should be noted that they need to be removed prior to final placement, at which moment the requirement for “dual redundancy” is not fulfilled.
Despite the added safety afforded by dual circuit vacuum systems, the use of safety belts is still good practice, particularly during roof assembly applications where the panels are to be transported over personnel or where panels with damage or suspect adhesion between layers are being handled.
• In addition to dual vacuum circuitry, some Vacuum Lifters designed to suspend sandwich panels at height from a crane, incorporate two small vacuum pumps instead of one larger pump. Should one of the pumps fail, the other pump is able to maintain the same vacuum level for the safe installation of the panel.
• Taking into account the technical aspects referred to above and information generally available from vacuum lifter suppliers, it would seem appropriate to specify as a minimum, only units which are compliant with EN13155, have a 24 volt power supply and incorporate dual vacuum circuits downstream of the vacuum pump/pumps.