FILENAMES: VacPwr1.jpg VacPwr2.jpg DESCRIPTION: These are pictures of a railroad tank car collapsed by vacuum (for which it was not designed) . Posted by Steve Stovner . Steve provided the following description: ----------------------------------------------------------------------- Someone passed the following message to me. I have no idea who originated it. Good food for thought !! ------------------ Please share this visual with all of your employees in upcoming meetings. It is a great reminder that though many of our vessels are pressure-rated, many will not withstand significant vacuum. A vacuum can be created by simply draining a vessel without venting, or by steam cleaning and not venting --- the subsequent condensing of the steam is an extremely strong vacuum. The hotter or higher pressure of the steam, the stronger vacuum. Even the condensing of a hot hydrocarbon, with low vapor pressure can have similar results if the system is not gas/N2 blanketed or equipped with a vacuum breaker. The tank car in the linked photo is not one of ours. It is a general purpose PYGAS car that was being steam cleaned to prepare it for some maintenance work. The job was still in progress at the end of the shift, so the employee decided to block it in. Problem was there was no vacuum relief; the car cooled, the steam condensed and the car imploded." ------------------ Have a look at the accompanying photos (VacPwr1.jpg & VacPwr2.jpg).