When properly set up, the right scrapers will extend the life of your conveyor belts while reducing maintenance and cleaning. Conversely, scrapers that are badly adjusted or not suited to the material being moved will wear the belt faster, limit the lifespan of your belts and leave the area around the conveyor dirtier than it should be.
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Scraper systems can be as crude as a length of angle iron pressed against the belt. A better solution is an engineered mechanism that applies a constant load through a material that's matched to what the conveyor is moving. Here's some advice for getting it right.
Not all the material dropped onto the belt gets discharged. A proportion ' how much depends on the material ' stays on the surface and gets taken back on the underside. Some will drop off along the way and leave a mess. Some will instead cycle round and round, gradually building up until it falls off under its own weight. This carry-back is bad for your conveyor system. More specifically, it:
A scraper is a blade pressed against the belt surface. This knocks off material stuck to the belt. The force applied to the belt is a function of the material. Dry, granular materials stick far less so the scraper doesn't need to be pressed as firmly against the belt as if it's carrying a bituminous or tarry material.
The scraper should be applied where the belt is flat. The best place for this is at the head pulley where the drive is connected. Often this primary scraper is mounted at a 3 o'clock position relative to the pulley shaft.
A secondary scraper is used on the return side of the belt where it leaves the discharge pulley. This two-scraper arrangement effectively removes almost all material. Some conveyor operators like to have a third inner scraper to keep the underside of the belt clean.
If the scraper isn't set up to apply enough force to clean the belt you'll get material carry-back, which the scraper is intended to avoid. Conversely, apply too much force and:
To avoid these problems every scraper needs an adjustment mechanism. The simplest are adjusted manually but better systems are either spring-loaded or use a counterbalance system. These ensure a constant load is applied. The best will ride over bumps and splices without being damaged or damaging the belt.
Whatever system is used, each scraper should be inspected daily for correct adjustment and operation.
Every scraper has two main parts: a blade that presses against the belt and a mechanism that holds it in place. Both should be appropriate to the material being conveyed.
A belt used for dry, granular material that doesn't stick needs less load on the scraper and can therefore be lighter duty, perhaps with manual adjustment. A heavy sludge or tar that sticks to the belt needs the scraper to apply more force, which requires heavy-duty construction and ideally, a constant force mechanism.
A complete scraper system for a 30' belt should cost around $2,500.
The blade should be made from a material that deforms enough to avoid doing any damage but at the same time applies enough force to scrape away clingy material. It should also resist abrasion without softening excessively if it heats up. Some applications may also need water or chemical resistance.
For most applications, these characteristics are provided by a urethane blade. Scraper manufacturers produce urethane blades in durometer values of 70 to 90 Shore A. (That's about as firm as a shoe sole or the leather in a belt, but not as firm as a golf ball.)
Blade length is important. While a 6' blade will work on a 24' diameter pulley, a 12' blade will last longer and do a better job. Poor quality blades can flip or twist, which makes them ineffective. Expect to pay $220 or more for a good 6' blade and $600 for one 12' long.
A conveyor system with the wrong scrapers, or worse, no scrapers, is going to cost more to operate than one where belt cleaning has been addressed properly. There will be more wear and tear on the belt and other components, more cleaning will be needed around the structure, and it will consume more power.
As conveyor system experts, West River Conveyors is familiar with the selection and installation of scrapers and scraper blades. We carry primary and secondary scrapers and blades from several manufacturers. We can review your application, explain your options, and help determine what will work best. The result will be lower costs and longer-lasting belts.
For more advice on maintenance to reduce belt wear and tear, click below.
When selecting the proper belt conveyor for your process needs, it is critical to consider the different types of conveyor belts (and belt cleaners) available. In order for a conveyor to operate at its full potential, the correct belting and cleaning options must be selected.
While there are many types of conveyor belts, the most appropriate belt is determined by examining what belt characteristics will result in the most efficient handling solution for your material's unique characteristics at any given point in the process.
Choosing the right belting for the application at hand can mean the difference between an efficient, low-maintenance conveyor, and one that requires frequent maintenance and downtime.
This article focuses on the types of conveyor belts suited for troughed belt conveyors, shuttle conveyors, and steep incline conveyors.
In most cases, shuttle conveyors and troughed belt conveyors can run the same types of belts and belt cleaners. The most common options are discussed here.
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For conveyors handling material coming off of hot processes, heat-resistant belts offer an excellent option, resisting degradation associated with heat. Typical conveyor belting is rated for 200°F steady operating temperature. Heat-resistant belt ratings are 400°F, but are available for temperatures as high as 750°F.
When working with moderately oily materials such as waste products or some fertilizers, an oil-resistant belt provides protection from swelling or ply separation due to oil exposure. This type of belting is also referred to as MORS.
Raised profile belting can be used for inclined conveyors carrying material at limited angles exceeding 20°. This type of belting features low-profile cleats to assist in preventing material fallback while conveying on an angle. Despite this raised profile, this type of belting is still flexible enough to be used on conveyors with small-radius pulleys.
Other belt types can be sourced for chemical resistance, flame retardance, and solar resistance.
Some materials, particularly those that are wet or sticky, have a tendency to adhere to the belt surface, causing carryback, build-up, and ultimately preventing the conveyor from operating correctly. These problems contribute to increased wear and mechanical failures, as well as higher maintenance costs and downtime.
As such, belt cleaners are an essential tool in prolonging conveyor belt life and protecting pulleys, keeping belt conveyors in optimal condition and ensuring efficient operation for years to come.
Several options and designs exist for keeping conveyor belts clean. Commonly used implements include:
A conveyor belt cleaner, also referred to as a belt scraper, is a spring-loaded blade or plate that scrapes the conveyor belt in order to clear any fugitive material sticking to the belt. The scraper blade may be made up of plastic or metal and is usually mounted at the tangent point of the discharge pulley, removing material before it is carried past the discharge point.
A dual conveyor belt cleaner setup is an ideal option for materials with a higher moisture content, or that require more aggressive belt cleaning.
This setup prevents material from traveling to idlers and other components through the use of a primary and secondary belt cleaner; by positioning a primary belt cleaner at the head pulley, the cleaner is able to remove the bulk of material. A secondary cleaner, positioned lower than the primary cleaner, sitting just behind the head pulley, removes any remaining material for a more thorough clean.
The return side belt plow, also commonly called a V-plow, is another belt cleaning option. This v-shaped 'plow' is positioned just before the tail pulley on the return (non-carrying) side of the belt in order to prevent any large particles from getting lodged between the belt and pulley, which could otherwise cause rips and tears.
In addition to external belt cleaners, self-cleaning tail pulleys are also useful in preventing material from getting pinched between the pulley and the belt, avoiding buildup and excess wear.
Various self-cleaning tail pulley designs are available on the market, including wing pulleys, chevron pulleys, spirals, and more.
While many manufacturers use only a self-cleaning tail pulley when fugitive material is a concern, FEECO recommends employing both the self-cleaning tail pulley and the v-plow for optimal protection of the tail pulley and belt.
Because of their design differences, steep incline conveyors cannot proficiently use any of the same components (belts or cleaners) as troughed or shuttle conveyors unless the angle is under approximately 20 degrees.
Pocket belt conveyors instead utilize special belting known as corrugated sidewall belting.
This style of conveyor belt contains material with corrugated sidewalls. Sidewalls are flexible enough to contain material and work with a variety of pulley sizes. The belting is available with a range of cover compounds for various types of handling, including standard, oil-resistant and heat-resistant.
Corrugated sidewall conveyors also employ cleats along the belt in order to contain material during vertical handling, creating pockets for material to rest in (it is for this reason that the steep incline conveyor is also frequently referred to as a pocket belt conveyor). Cleats can range in height from 1' ' 6', and can be either integrated or detachable.
Steep incline conveyors are limited in their cleaning ability, due to the special type of belting they use. For this reason, dry, less-adhesive materials perform better with this style of belt conveyor.
When some type of cleaning is necessary, producers employing a steep incline conveyor can enlist the help of a belt thumper.
A belt thumper is mounted to the underside of the belt on the return side of the conveyor. This mechanism creates a high-speed rotating action that causes the belt to vibrate, loosening and removing any material that may be stuck, before it reaches the feed location.
At FEECO, we know it's critical to have a solid understanding of the process and the material before selecting the proper type of conveyor belt for each conveyor style in every unique setting. This allows us to confirm that all of our equipment will have the right configuration to meet or exceed the customer's requirements. Our long history in bulk solids handling, in combination with our concept testing facility, ensures that we can find an innovative solution for your bulk material handling requirements. For more expertise on belt conveyors and other bulk material handling equipment, contact us today.
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