Pacific Western Extrusion is located in Visalia, CA, an agricultural and light industry-oriented city with a population of about 150,000. The Pacific Western pipe facility has been in operation for 20 years, and extrudes PVC pipe of diameters raging from 1/2" to 12". The facility primarily manufactures Schedule 40 white PVC pipe, but also manufactures, to a lesser extent, PVC electrical conduit.
The facility has three primary manufacturing buildings, with multiple extrusion lines in each building. A central process cooling system supplies water to the three buildings. The facility employs a chiller and cooling tower for cooling of process water. Prior to the installation of the filtration system, the only particulate control of the process water was by means of blow down and a coarse shaker screen.
Pacific Western has been experiencing solids buildup and fouling of their chiller heat exchanger tubes, as well as general plugging problems with nozzles in their extrusion troughs.
The proposed solution was to install a full stream filtration system on their central circulating water flow line. The full stream flow rate is 1,999 gal/min. Pacific Western requested filtration only of the water passing through their chiller, to protect it. As is shown on the process diagram, only a portion of the circulating water passes through the chiller. Specifically, of the 1,999 gal/min, only 793 gal/min of flow passes through the chiller. This portion is cooled and blended back with the remainder of the fluid, to bring the overall mixture temperature down to an intermediate level between that of the water temperature entering and exiting the chiller.
A 3" x 8 external source filter was installed upstream of the chiller. The filtration grade was chosen at 100 µ black discs. This filtration grade was chosen based on performance tests run at various PVC extrusion facilities, including two of Pacific Western's facilities. This installation is essentially a full stream filter for the chiller, which makes it a side stream filter for the overall circulating water system. There was a pressure of only 25.6 lbs/in2 available down stream of the filters, so an external source system was required. The external source is quality city water at a pressure of 79.6 lbs/in2.
System: 3" x 8 S. K. external source
Filtration Grade: 100 µ
Flow Rate: 793 gal/min
System Pressure: 26.1 lbs/in2
External Source Backflushing Pressure: 81.2 lbs/in2