Screw conveyors look simple — a shaft, some flights, a trough, and a drive. But every one of those elements is a specification decision, and getting it wrong means jamming, product damage, premature wear, or a conveyor that simply cannot move the material you feed it.
The Martin screw conveyor specification sheets we work from spell out exactly how these decisions connect. Take a rendering-grade example straight from the catalog: a 12-inch diameter screw, 11 feet 9 inches overall length, 12-inch pitch, right hand, with 3/8-inch thick sectional flights mounted on 3-1/2-inch Schedule 80 heavy pipe, continuously welded on both sides, bushed and 3-bolt drilled for 3-inch shafts. The part-number suffix RND marks it as a Rendering Grade MTO screw.
Decisions that matter
Flight thickness. Sectional flights at 3/8-inch thick are common for heavy service. Thinner flights suit light, free-flowing materials; thicker flights and hardened edges suit abrasive or heavy materials. For rendering applications, the 3/8-inch flight on Schedule 80 pipe is the standard starting point.
Pipe schedule. Schedule 80 heavy pipe is the workhorse because it resists the torsional load of a long screw. Going thinner risks flex and fatigue at the shaft.
Trough material and liner. The catalog example uses 3/16-inch thick 304 stainless steel with an angle flange, drilled with 3/8-inch bolt holes on 6-inch centers, and a 1/4-inch thick AR225 liner welded one inch above the center line. The liner is the wear surface — for abrasive materials it extends trough life substantially, and stainless resists the corrosive washdown environment.
Pitch and direction. Twelve-inch pitch on a 12-inch diameter is a 1:1 ratio, standard for general conveying. Right-hand vs. left-hand determines rotation and discharge direction — get this wrong and the conveyor pushes material backward.
Drive and component selection
The spec sheet also covers the drive train: coupling types, end shafts, hangers, and the drive shaft numbers that map to coupling diameters and shaft sizes. A complete screw conveyor quote includes the screw, trough, cover, inlet, discharge, and drive components as matched set — not a mix of incompatible pieces from different manufacturers.
When you are specifying, be precise about your material: bulk density, abrasiveness, temperature, and whether it needs food-grade or washdown-rated construction. Those four answers drive every subsequent choice, from flight thickness to whether you need 304 stainless or carbon steel.
Where to get it
RBC Industrial supplies Martin screw conveyor components — screws, troughs, hangers, shafts, and drives — with real part numbers and lead times quoted up front. The rendering-grade example above is a stock configuration; food and beverage, wastewater, and cement versions follow the same logic with different materials.
Contact RBC Industrial at (915) 845-8188 with your material details, and we will help you spec the screw conveyor that actually moves your product.