Wheat Flour Milling Machine Roller Mill And Plansifter Performance Data

Wheat Flour Milling Machine Roller Mill and Plansifter Performance Data

The wheat flour milling machine has evolved through continuous engineering improvements over the past century. Today these machines produce over 500 million metric tons of wheat flour annually worldwide. Understanding the core components and their performance metrics helps mill owners optimize production. Tehold International presents technical data on roller mills and plansifters, the two most critical elements of any wheat flour milling machine.

A modern wheat flour milling machine operates on the gradual reduction principle. The grain passes through four to six break passages and eight to twelve reduction passages. Each passage consists of a roller mill pair followed by a plansifter. The roller mill cracks the grain or reduces semolina, while the plansifter separates particles by size. This systematic approach achieves consistent flour particle size distribution with 85 to 90 percent of particles falling between 40 and 200 microns for white flour.

Roller mill specifications directly impact flour quality. Roller diameter typically measures 250 millimeters for break passages and 200 millimeters for reduction passages. Roller length ranges from 500 to 1500 millimeters depending on machine capacity. The roll surface features flutes cut at specific angles. Break rolls use 3 to 5 flutes per centimeter with a spiral angle of 10 to 14 degrees. Reduction rolls have 8 to 12 flutes per centimeter with spiral angles of 3 to 5 degrees. These flutes create shear forces that separate bran from endosperm without excessive bran fragmentation.

Roll speed differential is a key setting. The fast roll rotates at 450 to 550 revolutions per minute while the slow roll rotates 250 to 350 revolutions per minute. This speed differential ratio of 1.5 to 2.0 to 1 creates the grinding action. For hard wheat, a differential of 1.8 to 2.0 to 1 works best. For soft wheat, 1.5 to 1.6 to 1 produces less flour damage. Roll gap settings range from 0.2 to 2.0 millimeters. Break passages use wider gaps of 1.0 to 2.0 millimeters to crack whole grains. Reduction passages use narrower gaps of 0.2 to 0.6 millimeters to reduce semolina to flour.

Temperature control matters during milling. Each roller mill pass raises wheat temperature by 2 to 3 degrees Celsius. A full milling system with 12 passes can increase product temperature by 25 to 35 degrees Celsius. To prevent starch damage and protein denaturation, modern wheat flour milling machines incorporate temperature sensors that trigger feed rate reduction if product exceeds 45 degrees Celsius. Some designs include water cooled rollers for temperature sensitive applications.

The plansifter is the second critical component. This machine contains up to 30 sieve trays stacked vertically. Each tray measures 650 by 650 millimeters or 850 by 850 millimeters. Sieve mesh sizes range from 40 mesh for coarse semolina to 130 mesh for fine flour. The entire stack rotates eccentrically at 250 to 300 revolutions per minute with a throw of 35 to 45 millimeters. This motion moves material across the sieve surface at 0.3 to 0.5 meters per second.

Sieve performance is measured by throughput per square meter. A well designed plansifter processes 180 to 220 kilograms per square meter of sieve area per hour. For a 12 tray plansifter with 0.42 square meters per tray total sieve area of 5.04 square meters, this gives a capacity of 900 to 1100 kilograms per hour per machine. Sieve blinding or blockage reduces this by 15 to 30 percent. Automatic sieve cleaners using rubber balls or rotating brushes restore capacity by knocking particles loose every 30 to 60 seconds.

Purifiers are an optional but valuable component in a wheat flour milling machine for semolina production. These machines use air aspiration and sieve motion to separate bran particles from purified semolina. Airflow of 18 to 22 meters per second lifts lighter bran particles while denser semolina passes through the sieve. Purifier capacity ranges from 300 to 500 kilograms per hour per square meter of sieve area. This improves final flour ash content by 0.05 to 0.10 percent on a dry basis.

Flour quality parameters from a wheat flour milling machine must meet regulatory standards. Ash content for white flour typically measures 0.45 to 0.55 percent on a 14 percent moisture basis. Protein content varies by wheat source but finished flour from a well calibrated machine shows less than 0.3 percent variation from target. Wet gluten content ranges from 24 to 32 percent for bread flour and 18 to 22 percent for cake flour. Falling number, which indicates enzyme activity, should measure 250 to 350 seconds for most applications.

Extraction rate optimization is an economic consideration. A wheat flour milling machine set to maximize white flour extraction at 78 percent produces flour with 0.60 percent ash and reduced baking quality. A more conservative extraction of 72 to 74 percent yields flour with 0.45 to 0.50 percent ash and superior baking performance. The trade off between yield and quality means most commercial mills target 73 to 75 percent extraction for standard white flour.

Energy efficiency improvements have been substantial. Older wheat flour milling machines consumed 75 to 90 kilowatt hours per metric ton of flour produced. Modern designs with high efficiency motors and optimized pneumatic conveying reduce this to 45 to 55 kilowatt hours per metric ton. Variable frequency drives on roller mill feed rolls reduce no load energy use by 30 to 40 percent during reduced production periods.

Pneumatic conveying systems move material between machines. Air velocity of 18 to 22 meters per second transports flour and semolina through 50 to 100 millimeter diameter pipes. Air to product ratio of 2.5 to 3.5 to 1 by weight achieves reliable conveying with minimal product degradation. Each conveying fan consumes 5 to 15 kilowatts depending on system length and vertical lift. Total pneumatic system power represents 25 to 30 percent of the entire wheat flour milling machine energy consumption.

Control systems provide real time data. Modern machines include flow meters on each feed line accurate to plus or minus 2 percent. Temperature sensors at each roller mill and plansifter outlet. Vibration sensors on main bearings detect misalignment before failure. These sensors feed data to a central programmable logic controller that adjusts parameters automatically. The controller logs production data including total throughput, average extraction rate, and energy per metric ton. Operators can access this data remotely through secure web interfaces.

Maintenance costs for a wheat flour milling machine average 3 to 5 percent of initial purchase price annually. Roller refluting costs 800 to 1200 USD per roller pair. Sieve cloth replacement for a full plansifter costs 400 to 600 USD. Bearing replacement for all roller mills averages 2000 to 3000 USD every 8000 operating hours. Labor for a full maintenance shutdown of a 10 metric ton per hour mill requires 4 to 6 technicians working 40 to 60 hours.

Tehold International supplies complete wheat flour milling machines including roller mills, plansifters, purifiers, and pneumatic conveying systems. Each component is tested at the factory for vibration, temperature rise, and throughput before shipping. Installation supervision and operator training are included with systems above 5 metric tons per hour capacity.