#104 Pulp and paper valving for improved sealing, extended service life, and emissions control.  Problem: At a South Carolina paper plant, managers and maintenance personnel wanted to improve valving performance in black liquor, green liquor, and lime mud applications. Gate valves and ball valves in these applications were a problem. Particles in these fluids accumulated in gate and ball valve cavities. The gate and ball valves failed to seal properly and often "froze" and couldn't be opened or closed. The valves needed to be replaced at intervals from three to six months.  Evaluation: Plant engineers evaluated a number of alternative valves. The objectives of this reevaluation included: Improved in-line sealing . . . Extended service life . . . Better control of fugitive emissions. A number of valve brands and types were considered. Some valves had a lower initial price than the Tufline Sleeved Plug Valve. However, it was quickly determined that the improved performance expected from the Tufline valves would easily offset the initial price savings with any other valve. The expected service life of Tufline valves in this difficult application is three years - a six to twelve fold increase over previously installed valves.  Solution: There were three primary features that sold management on the Tufline Sleeved Plug Valve: The valve offered impressive in-line sealing characteristics. Adjustable, positive, 360 degree in-line sealing is provided by the large, full circumferential, chemically inert PTFE sleeve. The sealing area is much larger than that offered by ball valves or gate valves. The Tufline Sleeved Plug Valve has no cavities so there is no area for solids in the fluids to accumulate and interfere with valve operation. This feature promised greatly extended service life compared to gate and ball valves. Tufline Sleeved Plug Valves provide double stem sealing. They economically meet stringent fugitive emissions regulations without add-on packing or springs. The primary top seal is accomplished by the interaction of the plug, sleeve, and body. The secondary seal is a true, fully-redundant back-up sealing system. The valve's lightweight, compact design, and simple actuation were also factors in their selection.  Result: Tufline Sleeved Plug Valves have now been in service at this paper manufacturing facility for several years, providing greatly improved performance. Index of all performance report case histories.