Products Inert Manway Nitrogen Purge Hopper
Rending of Rheo' Manway Nitrogen Purge Hopper

Manway Nitrogen Purge Hopper

The patented Manway Nitrogen Purge Hopper facilitates the addition of large quantities of powders or other solids through vessel manway openings. This design can be configured to facilitate the charging of bag stock, bulk sacks, or drums.



Still from video of Rheo' Manway Nitrogen Purge Hopper in action transferring material.

Manway Nitrogen Purge Hopper

See the Manway Purge Hopper in action in this video!

Maintaining Low Levels of Oxygen

The Rheo Manway Nitrogen Purge Hopper serves as an engineering control to help maintain low oxygen concentrations within a process vessel during the manual addition of solids. This device utilizes a safe, pneumatically opened flap valve that reduces the amount of time the tank is opened to the room environment. A full perimeter annular ring injects nitrogen at dual flow rates to dilute oxygen concentrations in the manway region of the tank. This engineered system has proven to maintain oxygen levels to below 5% for the duration of a charging process.

Diagram displaying how solids are added while maintaining low oxygen concentrations using the Rheo Manway Nitrogen Purge 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.

Rending of the plate valve mechanism in the Manway Nitrogen Purge Hopper increasing operator hand/finger safety.


The plate valve mechanism is designed so that it is pneumatically opened with a simple hand or foot control. The valve mechanism has a soft spring return to eliminate finger and hand hazards that conventional valve systems may create.


A variety of options are available for the Rheo Manway Nitrogen Purge Hopper to ensure the final product meets the application needs. The following are a selection of some of the options available:

  • Product Grates/Cross Bars
  • Grounding Tabs
  • Bag Landing Table
  • Custom Manway Adapters
  • Mobile Carts
  • Removable Gravity Sealing Lids

Additional options for the Rheo Manway Nitrogen Purge Hopper

mobile Manway Nitrogen Purge Hopper demonstrating how cleanable the product is.


The Rheo Manway Nitrogen Purge Hopper 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 integrated Ventilation Sleeve has a removable cover that provides wipe-down access to all surfaces of the sleeve.

Dust and Vapor Control

By utilizing the full perimeter Ventilation Sleeve option, this fully engineered system will significantly reduce fugitive dust and vapors that often occur during the process of openly transferring solids into a tank.

Manway Nitrogen Purge Hopper with full ventilation sleeve prevent fugitive dust and vapor

These engineering drawings of the Manway Nitrogen Purge Hopper displays how customizable the Rheo product is for any application


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.

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.
  • Recommended Local Exhaust: 400 SCFM [190 L/s]; 2.5 inches WC [6.2 millibar] static pressure.

Single hose nitrogen connection

Foot or hand controls rendering for Rheo' Manway Nitrogen Purge Hopper


  • Hand control (or optional foot control) for the pneumatic valve.
  • Control activation increases nitrogen flow rate into the vessel in a nitrogen “blast”.
  • When controls are not activated, nitrogen enters the vessel at a slow flow “bleed” rate.
  • Both nitrogen “blast” and “bleed” rates are controlled independently with panel mount flow controls and can be adjusted.

Surface Finish

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

Visit our GMP Compliance page to learn more.

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