Screw Conveyor Operates at Elevated Temperature and Pressure for Conveying UHMW-PE

General Description

Ultra-high molecular weight polyethylene (UHMW-PE) is a linear polyethylene with a much higher molecular weight than standard PE. UHMW-PE offers non-sticking and self-lubricating properties, outstanding abrasion resistance, superior impact resistance, very high chemical resistance, and excellent mechanical characteristics. This versatile material is used in bulk material processing industries for bearings, wear strips, chain guides, and machinery parts.

A leading global supplier with one of the broadest portfolios of high-performance polymers and thermoplastic elastomers was implementing a new specialized process to produce UHMW-PE. The process required the storage of large quantities of UHMW-PE flakes in pressurized hoppers. UHMW-PE flakes would be transferred from storage into the process area while maintaining elevated temperature and pressure of the system.

Through collaboration with a major engineering firm, the polymer producer selected KWS to design and supply two screw conveyors to suit the unique process parameters.

Design Parameters

1. Product Type: Ultra High Molecular Weight Polyethylene (UHMW-PE)
2. Material Density: 25 to 30 Lbs. per Cubic Foot
3. Conveyor System Capacity: 600 Cubic Feet per Hour
4. Design Temperature: 250-degrees F
5. Design Pressure: 14.9-psig
6. Duty: Continuous

KWS Advantages

Engineers at KWS reviewed preliminary specifications provided by the engineering firm on behalf of the plant owner. Using provided process parameters as a starting point, KWS offered valuable engineering information and delivered a design for the screw conveyors. KWS also provided 3D parametric models of the screw conveyors to be inserted into the plant layout. This allowed plant engineers to locate possible interferences and find viable solutions well ahead of manufacturing and installation. Feedback provided by the plant engineers and maintenance personnel was valuable to confirm that the equipment would fit within the space constraints, minimize potential maintenance downtime, and exceed long-term performance expectations.

KWS Special Features

The plant layout required the use of two screw conveyors in series to span a total of 40-feet eliminating the requirement for an intermediate bearing. KWS selected 316 stainless steel materials of construction to withstand the high temperature, internal pressure, and corrosive chemical composition of the UHMW-PE flake. Both screw conveyors were designed to be identical for commonality of spare parts, reducing stock quantities and cutting overall project cost.

KWS designed the screws with flanged connections between the screw and shafts. The flanged shaft and screw connections provide a rigid assembly when compared to a typical CEMA coupling connection. KWS also provided a shaft mounted gear reducer with a torque arm bracket to allow the gear reducer to “float” on the drive shaft, eliminating any potential binding caused by the rigid flanged connections.

A KWS slider base pedestal trough end protected the end bearing from contamination and allowed for thermal expansion in this high-temperature application. Expansion and contraction are common in every high-temperature application and occur axially along the length of the screw and trough. The KWS slider base trough end is designed for thermal expansion and can account for axial expansion up to 4 inches.