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Technical Article

Dust-Free Valves for Handling Spices and Other Bulk Solid Food Products


As published in Processing Magazine

Handling spices and other bulk solid food products can be complex and challenging. Among the primary concerns when handling these products are dusting to atmosphere and the viscosity of the materials being handled.

Wye Line Diverters assist a tea and coffee merchant.

Rogue dust creates potential health and safety concerns for employees and environmental consequences for nearby communities and ecosystems. Common issues faced by employees in dust-ridden environments include irritated skin to due allergic reaction, irritation of the lungs due to inhalation of materials, and slips, trips and falls due to dust accumulation on surfaces.

Dust-tight valves can help facilities mitigate potentially detrimental effects simply by the way they are designed. Dust travels through the path of least resistance. This can be a challenge when using soft polymers and packing as seals. Many dust-tight valves designed today feature hard polymer sealing surfaces because they tend to offer better wear characteristics for most applications.

The following examples show how proper valve selection can help processors achieve reliable, dust-free handling of spices and other food products.

Roller gate handling granular sugar

A sweetener producer had been using a slide gate to fill a volumetric feeder in their process, but they were having problems with the feeder overfilling. The overfilling was actually a dual problem. First, the feeder contained a very small hopper, so actuating the old slide gate to the fully open position would immediately fill the hopper. Second, the sugar flowed from the silo at a different rate during summer than during the winter. The old slide gate could not be adjusted to compensate for the seasonal flow rate differences or to slow the filling of the feeder hopper.

Vortex solved the problem by replacing the old slide gate with a roller gate with a special service inlet and a two-position, manually adjustable variable gate position assembly. The seal design of the roller gate makes it an excellent valve for handling sugar.

V-notch Roller Gates handling coffee beans.

The new valve’s variable position assembly allows for two intermediate blade position settings for metering the flow of sugar into the feeder. Operators can also shut off the flow to allow the volumetric feeder to start and stop without being under load. The intermediate blade positions are easily reset as the seasons change. The roller gate is actuated approximately 465 times every twenty hours to discharge the daily 14,000 pounds of sugar required for the application.

Handslide gate handling salt

A medical supplier required a shut-off valve on the bottom of a weigh hopper handling salt. The application required that the valve actuate smoothly, seal material and be resistant to the salt’s corrosiveness. Vortex recommended its Handslide Gate due to the valve’s self-cleaning feature, cleanliness, dust tight seal, easy actuation from either side of the gate, and the fact that the gate is available with type 316L stainless steel material contact surfaces, making it more corrosion resistant. The Handslide Gate’s narrow profile and unobstructed orifice were additional contributing factors.

The system conveys salt through a flexible screw conveyor into a weigh hopper. Once the target weight is reached, the batch is released through the manual slide gate to a second conveyor that transports the salt into a tank where it is agitated and mixed with water to create saline solution.

Wye line diverter and roller gates handling paprika

For a process handling paprika, Vortex selected a Wye Line Diverter to eliminate material cross contamination and Vortex Roller Gates to shut off and seal material at the bottom of dry blenders and mixers. Features include magnetic reed switches and stainless-steel material contact surfaces and rollers.

Roller Gates handling paprika.

The Wye Line Diverter is custom designed to eliminate cross contamination with the line being purged between batches. These valves and diverters have been in service since 2012.

Flex tube diverter and roller gate handling chili powder

A chili processor had experienced issues with valves and diverters in an old system. The diverters caused cross contamination among the product recipes, and the slide gates leaked to atmosphere. In both cases, the company had to dispose of the expensive chili powder. Chili powder leaking to atmosphere creates an airborne health hazard (eyes and skin) and a slippery floor, causing safety hazards for company employees.

When the company was considering a new blending and mixing station, much of the emphasis for the project was placed on increasing output with additional production efficiency.

The new system incorporates a Vortex Flex Tube Diverter to eliminate cross contamination and Vortex Roller Gates to shut off and seal material at the bottom of dry blenders and mixers. The company has been impressed with the performance and maintenance-friendly features of the new valves.

Wye line diverter handling dry leaf tea

A tea and coffee merchant had been using dedicated vacuum transfer systems to convey blended dry leaf tea to two packaging machines. The company asked Vortex to assist with combining these vacuum systems into one to reduce the number of vacuum pumps and the amount of pipe work while maintaining the quality, taste and structure of the tea.

Flex Tube Diverter handling chili powder.

Vortex determined that the best solution was to install two-way Wye Line Diverters. The client was able to test a set of four diverters on a trial basis for several weeks. At the end of the trial period, the diverters were performing to expectation, so an order was placed for eight more Wye Line Diverters. By using two-way Wye Line Diverters in pairing together new manufacturing and packaging lines, the client was able to eliminate three 4.3 kW electric motors, reducing power consumption as well as noise in the production area.

Pneumatically actuated roller gate handling green coffee beans

Pneumatically actuated Vortex Roller Gates proved to be the best valve solution for a client handling green coffee beans. The Roller Gates are designed with “V-notch” blades, type 304 stainless-steel material contact surfaces and Infinite Variable Positioner (IVP) assemblies.

The combination of the V-notch blade and the diamond-shaped inlet allow material to discharge centrally through the middle of the gate. As the blade moves, the opening maintains a square pattern that is easier to calculate when adjusting material flow.

The special IVP positioner includes a control panel that works in conjunction with a cylinder-mounted linear transducer, air control solenoids, and the client PLC to allow precise batching or metering of the material.

Iris valve handling salt

A salt producer required a valve capable of positive material shut-off that would not degrade the material in the gravity flow discharge of salt from bulk bags. Vortex identified its Iris Valve as the ideal solution.

Standard material of construction for Iris Valves is aluminum, but since salt corrodes aluminum, Vortex engineered a 12-inch Iris Valve constructed of type 304 stainless steel. The valve’s Quick Lock (QL) mechanism with preset stop points allows the user to meter or shut off material flow.

Iris Valves are commonly used in the gravity discharge of free-flowing dry bulk materials from bins, bulk bags, chutes, hoppers and intermediate bulk containers (IBCs). The closing action of the fabric sleeve (available in different materials to suit the material being handled) minimizes damage to delicate or friable materials.

Clear action gate handling roasted and ground coffee

A client pneumatically conveying green coffee beans, roasted coffee beans and ground coffee required reliable, self-cleaning slide gates with stainless-steel material contact surfaces and FDA-approved materials of construction. The gates needed to seal, handle differential pressure, automatically adjust to control material flow and be maintenance friendly.

Vortex provided Clear Action Gates for the client’s process. The valves’ performance has been so impressive that the client has since ordered more than 200 additional gates and other products.

Determining which valve or diverter is best for you

Each application is different, and many variables come into play when selecting the appropriate valve or diverter to handle your materials. It is important to consult with your valve supplier and be as prepared as possible with information about your application. Handling spices and other food products can be tricky, but the proper equipment can make a process much cleaner, simpler and more effective.

Austin Anderson is a content writer for Vortex Global and has written numerous case studies and technical articles. Vortex supplies slide gates, diverters, iris valves and loadout equipment designed specifically for handling dry bulk solids in gravity, vacuum, dilute- or dense-phase applications. Vortex’s in-house team of engineers enables clients to customize products for individual applications or special installations.

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