A conveyor belt runs a hundred metres of material per minute. At the discharge drum a layer of wet ore, grain, or cement sticks to the belt surface and returns with it to the under-belt space, building up on the idlers and structure. A rubber scraper blade wears down in two months; a metal blade damages the belt cover and creates a loud screech at the contact point. Polyurethane scrapers from TIMOL solve both problems: the blade wears several times more slowly than rubber, cleans reliably, and does not harm the belt. This article explains how a polyurethane conveyor scraper works, how it compares to alternatives in numbers, and how to order a part for a specific conveyor.
How a Conveyor Scraper Works and Why the Material Matters
A primary scraper is mounted at the drive drum head, where the belt passes from the carrying run to the return run. The scraper blade presses against the drum surface of the belt with a controlled force, removing material that sticks to the rubber cover and would otherwise travel back on the return run, building up on the structure and idlers. Secondary scrapers are mounted on the return run to remove residual material the primary scraper missed.
The scraper material determines two things simultaneously: how cleanly the belt is cleaned and how long the belt itself lasts. A rubber blade is elastic and initially cleans well, but wears quickly: abrasion per DIN 53516 is 100-200 mm³, so the blade loses its working edge after a few months. A metal blade or rigid plastic blade cleans aggressively but with constant pressure on the belt cover — every hour the blade is in contact it marks and eventually cuts the rubber. A polyurethane blade finds the right balance: it is elastic enough not to damage the belt, wear-resistant enough to serve a full season.
The pressing force on the blade also depends on material elasticity. Polyurethane with a rebound elasticity of 34-61 % maintains stable contact pressure over the full worn-down range of the blade: as the working edge wears, the blade self-adjusts through the spring of the pressing mechanism and the elasticity of the material itself. Rubber loses rebound over time, and contact pressure drops.
Comparison of Scraper Materials
The choice of scraper material is best made from a direct comparison of the properties that determine performance in this application. The table compiles reference data from standard tests.
| Material | Abrasion DIN 53516, mm³ | Operating t, °C | Hardness | Rebound elasticity, % |
|---|---|---|---|---|
| Polyurethane TIMOL | 38-39 | -60…+100 | 85A-95A | 34-61 |
| SBR rubber | 100-200 | -40…+80 | 40A - 80A | 30-55 |
| NBR rubber | 80-150 | -30…+100 | 40A - 90A | 20-45 |
| UHMW-PE | 15-30 | -200…+80 | 60D - 70D | 5-10 |
| Structural steel | n/a | -40…+500 | 120-250 HB | n/a |
Polyurethane has the best balance among elastomers: lower abrasion than both SBR and NBR, comparable or higher rebound elasticity, and a wider temperature range down to -60 °C, which is important for scrapers on outdoor conveyors in cold climates. UHMW-PE has even lower abrasion (15-30 mm³) but is nearly inelastic — at 5-10 % rebound it does not self-adjust to belt irregularities and either misses material at gaps or digs in on high spots, damaging the cover. Steel cleans but damages the belt surface; it also creates vibration and noise and requires heavy pressing mechanisms. NBR rubber is better than SBR against oil-laden material but still wears 2-4 times faster than polyurethane.
Engineer’s tip: set the pressing force by the blade’s elastic deformation, not by a rigid fixed stop. A blade bent 10-15 mm from the belt surface under its own pressing mechanism weight gives stable contact over the full service life without overloading the belt. Check blade contact once per shift at the start-up of a new scraper: if you hear a high-pitched squealing, the pressing force is too high. After one week the blade settles into the belt profile and the check frequency can be reduced.
Types of Scrapers and Their Applications
Primary scrapers are installed at the drive drum and carry the main cleaning load. They are the most loaded and wear most quickly. Secondary scrapers on the return run carry the residue from the primary and provide final belt cleaning before it returns to the loading zone. In food and pharmaceutical production additional scrapers are sometimes installed at the tail drum.
Double-sided scraper segments are used for grain terminals, crushed ore, concrete, and similar materials with fine and medium fractions: the working edge operates symmetrically and the segment is turned over when one side wears down, doubling the service life before replacement. Special profiles are made for imported and non-standard conveyors: the factory reproduces the required cross-section from a drawing or worn sample.
For poultry farm litter conveyors and food-production belts, a food-grade polyurethane formulation is used that does not leave marks on the product, does not absorb moisture, and withstands washing solutions. For outdoor conveyors in cold climates — grain terminals, ports, mining operations — the operating range of -60 °C means the scraper does not harden or crack in frost, unlike rubber blades that stiffen significantly at negative temperatures. Full information on applications by industry is in the product catalogue.
Installation and Service Life of Polyurethane Scrapers
A polyurethane scraper is mounted in a standard holder or frame provided for the conveyor’s belt cleaner. The blade segment is fastened by bolts or clamping strips; when worn, it is replaced without dismantling the holder. The blade pressing force is adjusted by the spring or counterweight of the pressing mechanism to achieve reliable contact without excessive force. Correct pressing: the blade makes full contact across the belt width without chatter, contact force is checked with a pressure gauge or by the visible elastic deflection of the blade.
Service life of a polyurethane blade on a mineral conveyor is typically 4-8 months depending on material abrasivity and belt speed. For grain and agricultural material, blades last longer — up to a full season. The manufacturer recommends measuring blade edge profile depth once per month: when the blade wears to the minimum thickness specified for the holder type, it is replaced before contact with the holder body begins to damage the belt. Detailed information on scraper selection is in the reference information section, and the full range of conveyor equipment parts is in the product catalogue.
How to Order Polyurethane Scrapers
To place an order, supply the conveyor belt width, drum diameter, type of material being transported, and if available — a drawing or worn sample of the existing blade. Based on this data the factory technologist selects hardness and blade cross-section profile.
TIMOL factory produces standard and profiled scraper segments for any belt width. Both small batches for one conveyor and production quantities for a fleet of conveyors at a plant or terminal are supplied. The free-casting process allows any blade profile to be reproduced without expensive press tooling, including profiles for imported equipment.
For consultation, hardness and profile selection, and ordering, contact TIMOL factory. Engineers will select the blade for your material and conveyor and estimate service life.