Linear Motion Design for Washdown Applications

Overview

This white paper by PBC Linear addresses the challenges and best practices in designing linear motion components for washdown environments, commonly found in food, beverage, pharmaceutical, and chemical processing industries. Washdown environments require equipment to endure cleaning with water, chemicals, or steam to kill bacteria and contaminants, demanding rigorous compliance with various regulatory standards such as FDA, USDA, 3-A Sanitary Standards, NSF International, ASTM, and European guidelines (EHEDG, IDF, ISO).

Key materials for washdown linear motion include stainless steel grades (300 series like 304 and 316 preferred for corrosion resistance and FDA compliance; 400 series like 440 used for wear resistance but prone to oxidation under washdown), anodized or coated aluminum (used carefully due to susceptibility to pitting), and electroless nickel coatings which add corrosion resistance and smoothness, often FDA compliant. Plastics and polymers used in bearing liners must be selected carefully to avoid moisture absorption, swelling, and bacterial growth, with preference for one-piece bonded, PTFE-based self-lubricating bearings that require no external lubrication and have no crevices for contamination.

Design practices emphasize minimizing crevices, joints, and assembly points where bacteria can accumulate. Utilizing standoffs to elevate rails, incorporating weep holes or drainage slots to prevent fluid pooling, and choosing smoothly contoured components reduce contamination risks and improve cleanability. Fastener placement is critical, favoring mounting from non-washdown sides or using domed nuts for easier cleaning. Shields or covers can protect non-food-compliant components when near exposed food.

PBC Linear offers specialized products for washdown, including RST round shaft self-lubricating bearings with optional 316 stainless shells, various polymer bearing liners like FrelonGOLD and FDA-compliant FrelonW, corrosion-resistant Redi-Rail aluminum guides with antimicrobial coatings, commercial rail guides made from 304 stainless steel, and V-Guide systems featuring stainless steel wheels and rails for versatile configurations.

The paper concludes that through understanding environment, standards, and material properties, engineers can select appropriate components and practices to achieve predictable service life and sanitation in demanding washdown applications. PBC Linear’s global distributor network and application engineers support customized solutions to meet these complex challenges.

For assistance, contact PBC Linear via pbclinear.com or their application engineers by phone or email as listed in the document.