Sealing device for the emergent shaft end of a rotating machine

A sealing device for preventing leakage of a hazardous gaseous fluid from a casing containing said fluid, said casing comprising a housing for a pump or the like with a rotable shaft from said pump extending through an opening in the casing, the sealing device being located in said opening around the shaft;

• said device comprising a chamber and a compartment arranged in sequence between the gaseous fluid in the casing and the atmosphere;
• the chamber comprising a sleeve circumscribing the shaft with first and second means for sealing its ends against the shaft;
• the compartment being formed by said second sealing means, an annular housing around the shaft and a floating ring contacting the periphery of said shaft;
• at least two ducts extending through the sleeve, the first duct being in fluid communication with the interior of said chamber for conducting gases away from said chamber, the second duct being for conducting a barrier gas toward said chamber and terminating at its inner end at a sealing face on said sleeve;
• the second sealing means being biased toward sealing contact with said sealing face, the second sealing means and sealing face being structured to allow the simultaneous flow of the barrier gas from the second duct into the chamber and the compartment;
• the pressure and volume of barrier gas flow into the compartment being great enough to maintain a pressure drop across the floating ring between the compartment and the atmosphre;
• and
• means for regulating a substantially constant pressure differential between the interior of the chamber and the casing.