I answered a call at work from a construction contractor wondering how much static pressure one of our company's fans that he had was designed to generate. The fan was a direct drive fan with a double shaft motor and a prop mounted at each end. He explained that they were installing a storage tank, and they would lift the lid in place with a fan like this. I tracked down the information, then asked one of our senior engineers about the process. He told me that, yes, they construct the lid on forms inside the tank, install a seal around the edge of the lid, then turn on a fan which would build up pressure on the bottom of the lid and raise it into place. Then, they would drive in pins to hold it in place. I had never heard of that before, so I went and found a video. Pretty cool:
I would think that would be one of the more stressful parts of the job. You've got a lot of money riding on that cushion of air.