Worldwide, there are thousands of dry bulk solid materials being handled – all with vast differences in material characteristics. Many materials also possess abrasive characteristics of varying complexities. In order to prolong the useful life and superior functionality of Vortex components, it is of utmost importance to equip slide gates, diverters, and loading spouts with application-specific features to ensure their success when handling abrasive materials.
The Physics: Conveying Abrasive Materials
Whether it be a gravity flow, dense, or dilute phase pneumatic conveying application, the physics of dry bulk material movement will have dramatic impact on the degree of wear a system is subjected to. For this reason, it is necessary to assess what system areas are more susceptible to material impact and carefully design the system to protect these areas from rapid wear.
Generally speaking, a manufacturing process will likely realize its highest degree of wear in areas where material flow pattern or air pressure are subjected to dramatic change or disruption (Figure I). This includes elbows in system ductwork, directional changes from diverting or converging, sudden halt in material flow, aspiration of displaced air, and many other variables in system design.
Depending on application parameters, several techniques can be utilized to protect a system from rapid wear and abrasion.
Valve Construction Options
For abrasive powders, pellets and granules – such as sugar, salt, chemicals, and others – 304 and 316L stainless steel options are available to provide a valve with appropriate abrasion resistance. Another way to address extreme abrasion to the Vortex Wye Line Diverter is to construct the inlet and outlet weldments from schedule 10, 20, 40 or 80 pipe, depending on the application and the material(s) handled. In some instances, this option provides customers with the dual benefit of increased abrasion resistance and better match-up with the customer’s existing system.
Straight Leg Diverting
In traditional (A-Style) diverters, rapid abrasion and wear is a concern because as materials flow through the inlet, they often make direct impact where the outlet legs meet. In flap-style diverters, this form of abrasion can cause significant damage to the blade shaft and to the outlet legs. For pneumatic conveying diverters, such as the Vortex Wye Line Diverter, this form of continuous abrasion will rapidly wear through the valve’s inlet, leaving holes in the valve body. If left unaddressed, holes in the valve body will facilitate material leakage and – in pneumatic conveying applications – air loss.
To avoid continuous abrasion to the inlet, diverters are often constructed using a straight leg (K-Style) design. The K-style diverting design is preferred because it allows a straight-through channel for material flow. This design also makes it so that the outlet legs do not meet in the direct path of travel as materials flow through the inlet.
Generally, A-style diverters (Figure II) are utilized when similar material quantities are being diverted toward each destination, and K-style diverters (Figure III) when the majority of material is being routed toward a single destination. Opinions on this concept differ, so it is advised to consult with industry professionals to determine which design is most suitable for use in your specific application.
*Note: A-style & K-style diverting options are available in both the Vortex Quantum Series & the Vortex Titan Series.
Most beneficial in pneumatic conveying applications, ceramic wrappings are used on Vortex Wye Line Diverters to protect them from continuous wear and abrasion, which is typical when materials are conveyed in dilute phase.
The purpose of ceramic backing (Figure IV) is to offer additional protection for a diverter’s inlet weldment in applications where material flow will create substantial wear to the weldment itself. Ceramic backing helps so that when materials abrade through the steel, thick layers of ceramic remain, which maintains conveying line pressure and prevents material leakage. In essence, ceramic backing allows a valve to continue operations in the midst of abrasion, rather than constantly replacing components in troublesome areas.
The need for ceramic backing is application-specific. Depending on system setup, similar handled materials can react very differently when exposed to system configurations and air pressure.
Ceramic coating is a very calculated process. To avoid turbulence or friction against material flow (which could damage material or accelerate wear to the ceramic), the layers of ceramic are smoothed in the direction of material flow.
On average, ceramic coatings will enhance steel durability for a 30-40 percent longer service life.
Similar in purpose to ceramic backing, PneuWear (Figure V) is an epoxy-based coating that is applied to a Wye Line Diverter’s inlet weldment to provide greater abrasion resistance. PneuWear is designed to protect equipment from fine particle abrasion only; the coating is less effective when handling larger material granules.
An alternative to abrasion-resistant coatings is to construct a Wye Line Diverter with a reinforced wye (Figure VI). In essence, a reinforced wye is a traditional Wye Line Diverter inlet that contains an additional piece of thick, triangular, welded steel between the weldment. A reinforced wye will prolong a diverter’s useful life before materials begin to abrade through its inlet – but yet, is often less effective than PneuWear or ceramic backing.
Valve Construction Options
In heavily abrasive applications – such as industrial sand, cement, limestone, glass, fly ash, and others – a valve’s body and material contact areas are often constructed from carbon steels and other abrasion-resistant steels. Several gauges of steel exist, so when selecting valve construction materials, it is important to assess handled material characteristics and determine which Brinell Hardness Number (BHN) of steel is most appropriate for withstanding the abrasion of certain handled materials.
Angle of Diverter Outlet Legs
In gravity flow applications, certain materials achieve optimal flow rates if they are processed through a diverter with steeper, more dramatic outlet leg angles. The flowability of materials has much to do with the material’s bulk density, and can also play into the severity of wear and abrasion.
If a diverter has more subtle outlet angles (approximately 45° from vertical), material velocity will slow, causing materials to “drag” along the bottom of the diverter as they flow through.
However, steeper angles (approximately 30° from vertical) are typically used to flow heavier, denser materials – such as aggregates. With steeper outlet angles, material is able to suspend and flow freely through the channel, which reduces the likelihood of in-line material build-up or material plugs. Additionally, when materials are suspended, the diverter makes little contact with materials and thus, is subjected to less wear and abrasion.
In essence, equipping a diverter with the outlet angles necessary to achieve optimal flow rates can reduce need for maintenance and prolong a valve’s useful life.
In flap-style and bucket-style diverters – such as the Vortex Seal Tite Diverter, Aggregate Diverter, and TLD Diverter – the valve’s inlet and outlet legs can be fitted with replaceable abrasion-resistant liners. In Vortex diverters, abrasion-resistant liners are often made from abrasion-resistant steels (Figure VII), chromium carbide, or UHMW polymer (Figure VIII). While the diverter body may be capable of handling abrasion, abrasion-resistant liners allow materials to abrade upon replaceable parts, rather than the body itself – which significantly extends the diverter’s useful life. For return-on-investment purposes, abrasion-resistant liners are of great value because they are the difference between maintaining replaceable parts or replacing a whole diverter.
“Rock Box” Blade Design
Specific to the Vortex Aggregate Diverter, a honeycomb (“rock box”) design (Figure VIIII) allows materials to accumulate in specially designed areas at the inlet, on the blade, and on the outlet legs – so that as material flows, it impacts upon itself instead of continuously abrading upon the diverter’s mechanical parts. This decreases wear and prolongs a diverter’s useful life.
All Vortex diverters feature removable wetted parts and an external access panel that allows inspection, maintenance or repairs to be made without removing the diverter from service. Even so, the honeycomb (“rock box”) design makes diverter maintenance a much less frequent process.
Vortex Loading Solutions
Spout Cone Construction
To ensure a sturdy, reliable material flow, Vortex Loading Spouts intended to handle abrasive materials can be equipped with stackable cones constructed from abrasion-resistant steels, such as Hardox® (BHN 400). In doing so, cones are less susceptible to rapid wear and abrasion, which could otherwise lead to metal contamination, loadout inefficiencies, and downtime for frequent maintenance of worn cones.
Various grades of abrasion-resistant materials are available for cone construction. However, in some applications, it may be more cost-effective to utilize cones constructed from lesser-grade abrasion-resistant materials, while planning for periodic cone replacement. Because the Vortex loading spout is of modular design, upgrading spout features is simple, should it become evident that a different cone construction material may be more desirable.
Which Technique is Most Suitable for You?
Selecting proper equipment is critical to the success of any manufacturing process. Misapplied components and deficient designs can cause unexpected maintenance costs and process inefficiencies that negatively impact a company’s overall profitability and performance.
The characteristics of dry bulk materials are endless, so there is no all-encompassing solution for every application. This is why Vortex offers a wide range of solids handling equipment to satisfy the needs of each client’s unique application – from fine powders to abrasive rock, and everything in between. With nearly 300 years of combined experience in the dry bulk material handling industry, Vortex application engineers rely on in-depth knowledge to develop the right solution for even the most demanding applications.
Read the case studies below on Vortex solutions and their enhanced reliability and life cycle in abrasive applications.
Consult with industry experts to determine which abrasion-resistant techniques will be most successful in your dry bulk material handling application.