Products Inert Dual Hopper Purge System
Rheo Inerting equipment Dual Hopper Purge System

Dual Hopper Purge System

The Dual Hopper Purge System electronically monitors and controls the material level and oxygen level in the feed hopper. This design is optimized for feeding injection molding machines to reduce media oxidation.

Maintaining Low Levels of Oxygen

The Rheo Dual Hopper Purge System serves as an engineering control to help maintain low oxygen concentrations within a feed hopper during the manual addition of solids. This device utilizes a safe, pneumatically-powered butterfly valve that reduces the amount of time the tank is opened to the room environment.

The pneumatic butterfly valve fills the lower hopper and is controlled using product level sensors.

Diagram showing how Dual Hopper Purge System controls the oxygen levels in the Hopper

Tank Dynamics

In order to reduce the risk of deflagration within a process tank, an inert gas must be injected in the correct quantity, location, and time of the product transfer. Understanding the tank dynamics of each application is critical to implementing the best engineering control for this process. Existing nitrogen blanketing systems frequently do not apply the gas at the correct quantities, location, or timing during the solids addition process. This results in elevated oxygen concentrations in the manway region of the tank which increases the likelihood of a deflagration near the chemical operator.

Our inerting systems provide an effective control to reduce and maintain oxygen concentrations during the solids charging process. The dual rate injection system is adjustable and can be integrated with an oxygen level sensor to provide a precise control system.

The two figures below illustrate how a properly designed inerting system can change the tank dynamics and reduce the risk of  deflagration. Figure 1 demonstrates a common tank system that allows elevated oxygen levels near the manway region during the solids addition process. All three components of the fire triangle [shown in figure 3 below] are established in this scenario. The entrained air delivers oxygen to the headspace of the tank and mixes with the dry dust and solvent vapors. Static charge can generate the energy to ignite this volatile mixture resulting in a dangerous deflagration event, injuring the chemical operator and causing significant equipment damage. Figure 2 shows a tank where the inert gas is added at the proper quantity, location, and timing of a solids addition process. A properly located O2 sensor can provide accurate O2 concentrations to confirm a safe work environment.

Rheo Dual Hopper Purge System completely disassembled.


The Rheo Dual Hopper Purge System is built from stainless steel components and can be fully disassembled.  The hopper can be fully washed down with water or light cleaning agent.


The Rheo engineering process allows this technology to be applied to virtually any application and process. Please contact your local representative for a list of custom options that can be added to the core charge hopper design.

An engineering drawing of the Rheo Dual Hopper Purge System

Single hose nitrogen connection provides power & nitrogen flow

Utility Recommendations


  • Single hose nitrogen connection provides pneumatic power to the valve as well as the nitrogen flow for the process.
  • Recommended Nitrogen Addition Rate (varies depending on application): 75 PSI [5 bar] static pressure; 300 SCFH [140 LPM] flow rate.



The control module includes a oxygen concentration readout, a nitrogen pressure gauge, and a nitrogen feed rate indicator.


Rheo Control Module with oxygen concentration readout, a nitrogen pressure gauge, and a nitrogen feed rate indicator

Rheo offers multiple surface finished for GMP compliance. See the options side by side.

Surface Finish

Rheo offers several different surface finish options to fit your application needs.

Visit our GMP Compliance page to learn more.