#107 Overcoming media blockage and leakage in viscous and slurry services.  Problem: One of the world's largest chemical and plastics manufacturers was having problems with media blockage in melamine slurry service. Melamine is an additive used in a number of plastics manufacturing processes. Valves which had to be opened and closed periodically, quickly became clogged and would not operate properly. Gate valves, ball valves, and standard plug valves were all tried and each lasted about a month before leaking or freezing. The restricted flow of reduced port valves was also compounding the media buildup problem.  Solution: Finally, Tufline full-port sleeved plug valves were installed. After many months, the valves were still functioning properly. In addition to the full port design, another factor that contributed to the valve's success in this application are its port-defining lips. These lips surround the ports of the Tufline sleeved plug valve. The lips improve valve performance and extend service life by breaking up and removing adhering, scaly deposits from the outer surface of the plug as it rotates. These 360 port-defining lips were developed and patented by Tufline. Tufline sleeved plug valves are also cavity-free. There is no area where viscous or slurry media can accumulate. In addition to reducing the potential for media buildup, processing systems employing full port valves with full flow capacity can often be designed more economically using smaller pumps. The full port design also permits mechanical cleaning with a pipeline pig. Tufline also offers processors three-way valves with full, round bores. Index of all performance report case histories.