Food-Grade Pressure Vessel for Thermally Processing and Conveying Flour-Like Materials

General Description

Bepex International is a global leader in bulk material processing for the food, chemical, and mineral industries. Bepex designs and manufactures systems for compacting, drying, mixing and size reduction of bulk materials. For this project, KWS partnered with Bepex to supply a sanitary thermal processor for a new, highly-confidential process for one of their customers. The KWS thermal processor preheated the bulk material with steam, keeping it at an elevated temperature and conveyed it to the next step of the process. KWS is the only choice to engineer and build a solution as custom and unique as this project.

Design Parameters

Product Type: Flour-like Material (can be cohesive and sticky)
Material Density: 30 Lbs. per Cubic Foot
Capacity: 50 Cubic feet per hour
Duty: 24 Hours per Day, 7 Days per week

KWS Advantages

Bepex contacted KWS in the preliminary stages of the project looking for design assistance and budgetary costs. Bepex wanted to form a relationship with KWS because both companies manufacture high quality equipment to exacting standards. Engineers from KWS engaged with Bepex to completely understand their needs and to provide a solution. The new process would require heating and conveying several different bulk materials with various feed-rates and retention times. KWS designed the pressure vessel to operate at a very low rotational speed and with sufficient length to provide the required retention time. After several technical discussions, the KWS team developed a solution consisting of an ASME-coded jacketed thermal processor containing a polished ribbon screw.

KWS is the only screw conveyor manufacturer with certification to manufacture pressure vessels to the applicable rules of ASME Boiler and Pressure Vessel Code. The ASME certification process for the Bepex project began with a design review. The complex geometry required finite-element analysis (FEA). The design was approved and stamped by a Professional Engineer. Special ASME coded materials for the construction of the vessel were purchased, segregated and tracked. Multiple hold points were required during the manufacturing process to allow an ASME authorized inspector to survey the quality. Welds were analyzed with X-ray radiography to ensure proper penetration and thickness. The vessel was pressure tested at 1.3 times the design pressure. The end result is an ASME “U” stamped pressure vessel that was designed, manufactured and tested to the precise standards of the code. The vessel is logged and tracked by ASME so the quality and safety information of the machine is available during its entire lifecycle.

Special Features

KWS provided heat transfer through the center pipe and jacketed housing to keep the bulk materials at temperature. A tight-tolerance ribbon screw was selected to prevent the sticky bulk materials from adhering to the internal surfaces. Special paddles were added to the discharge end of the screw to prevent material accumulation and provide self-cleaning. Air purged shaft seals held internal pressure. All internal welds were continuous with no pits or crevices. All Internal surfaces were polished to a 150-grit finish to be completely food grade. The design included a provision so Bepex could remove the screw for cleaning between product changes. KWS provided an inverter-duty motor for infinite speed adjustment. The gear reducer was located in-line with the screw shaft and a low-speed coupling was incorporated to protect the gear reducer from the heat of the process and ensure long life. Food grade lubricants were used so the machine would be completely sanitary.