Processing Magazine

Pumps with safety double diaphragm exhibit excellent levels of gas tightness

September 8, 2008

KNF process pumps integrating a patented double-diaphragm system exhibit superior levels of gas tightness and leakage prevention to provide ideal solutions for safely transferring hazardous, toxic, or rare gases. Their redundant diaphragm arrangement creates an effective safeguard to contain gases without risk of escape, even in the unlikely event that the primary, or “working,” diaphragm becomes damaged. The system additionally prevents contamination from external influences. These pumps typically will be specified for emissions sampling and monitoring, analytical instrumentation, and nuclear, chemical, and process engineering applications, among others. The unique design pairs a “safety” diaphragm with an elastic “working” diaphragm held securely at their edges. An eccentric and a connecting rod move both diaphragms up and down at their center and the “working” membrane transfers the gas through automatic valves. Both diaphragms enclose a pressure- and vacuum-tight intermediate safety space that can be monitored for pressure changes and serves to prevent contamination and capture the pumped gas should the “working” diaphragm rupture. Combined with additional head machining and sealing rings, a double diaphragm system can dramatically enhance gas tightness with leak rates as low as 6 x 10-6 mbar l/s. The “safety” diaphragm is subject only to low mechanical and thermal loads to promote longer service life.