Cost of Failure vs. Cost of BackupDecember 15, 2003 Backup Power for the inflator fans at the job site of a Monolithic Dome construction project is always a good idea. Murphy's Law is, "If anything can go wrong, it will." Murphy's law is with us in the dome building business just as it is in any other business. Dome Builders should ask themselves
A power failure that deflates a structure during construction is more costly than just the labor done to that point. All materials will be lost, from rebar and concrete, maybe even some equipment. The clean up to get back to a starting point takes a great deal of effort. Small DomesThe size and shape of the Monolithic Dome define the risks. We do not use backup on the smallest domes where risk is small. If an inflator fails while foaming a 20-foot dome, the risk is little. You lose some foam and the time involved for cleanup. If an inflator fails while building a 20-foot dome after foaming is complete, it should stand. After the rebar is properly placed, often the 20-footer can be shotcreted without even turning on the blower, although it is not recommended. Larger DomesWe use 100 percent backup on larger domes. When building a 60-foot dome, the risk increases significantly involving thousands of pounds of foam and worker safety. If the inflator stops and the rebar is not in place, you can be pretty sure the dome will fall, and expensive amounts of foam and time will be lost. We use a diesel generator to power one inflator and electricity to power another. Using this method allows us to switch both inflators to whichever power is working. If one source fails, both blowers can be plugged into the power source that is working. Automatic switching is great, but remember that Murphy is still with us. Note: We used to use a diesel powered inflator, but have switched to the diesel generator powering an electric inflator because of two reasons: 1) Electric inflators are easier to come by and cheaper to replace. 2) One diesel generator can power two inflators if the electricity fails. Builder risk insurance is often a very good option both for the builder and the owner. We carry it when building larger domes. All DomesRemember to always use a back draft damper on the inflator blowers. This can consist of a simple fabric flap. Thus if the blower stops you do not have an automatic air escape built in. Workers' safety firstAlways use backup where workers' safety is involved. The risk is obviously smaller while we sleep and no one is in the building - we can lose money but not people. When foam and rebar are in place, the risk is smaller. When concrete is being applied and still green the risk is much greater. Related Links:
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