To Change a Gas Bottle

The argon and ethane supply bottles should be replaced by new (full) bottles when the bottle content drops below about 10% of its capacity. For argon, the bottle content is directly indicated by the bottle pressure: a new bottle usually contains 2000 to 3000 psig. Argon bottles should be changed whenever the bottle pressure is found to be below about 200 psig. Ethane bottles, on the other hand, contain liquified ethane. Thus the bottle pressure is just the vapor pressure of ethane at whatever the current temperature happens to be. At 70 F this is about 544 psig. The pressure guage will not tell you how much ethane is left in the bottle until it reads zero! Instead, we measure the ethane content by observing the weight of the bottle and comparing it to the weight when the bottle was full. A standard B-size cylinder contains about 32 pounds of ethane. Thus, when the bottle weight is about 30 pounds less than its full weight, the bottle should be replaced. Recent (as of April 2003) experience indicates that full bottles weigh $165\pm 1 lbs.$

Handling and connecting bottles of compressed gas require special knowledge. The high pressure gas stored in the cylinders (bottles) constitutes significant stored energy. Mishandling of a gas bottle can pose a lethal hazard! Refer to the JLab EH&S Manual[1] for safe handling practices. If you do not already know how to safely manipulate compressed gas hardware, have a knowledgeable person train you.