This document discusses maintaining low oxygen concentrations during open manway charging operations. It introduces the nitrogen purge hopper, an engineered control that applies inert gas at the point of use to reduce and maintain low oxygen concentrations. The purge hopper controls the addition rate, reduces time the manway is open, and controls dust and vapor, helping to safely inert the atmosphere during charging. Data shown illustrates how the purge hopper maintains oxygen levels below thresholds required by safety standards. The document concludes the purge hopper is an effective technology for inerting open vessels during charging operations.

1. Maintaining Low Oxygen Concentrations
During Open Manway Charging
Robert Herrmann - Product Manager

2. Introduction
EHS Solutions LLC
Operator Centricity
Safety
Practical
Engineering
Controls
Efficacy
BREIDENSTEIN, GERMANY
PEORIA, IL USA (headquarters)
Engineered Simplicity

3. Overview
application of inerting technology
• The Practice of Manway Charging
• Using Inert Gases to Control Oxygen Concentrations
• The Importance of Maintaining Proper O2 Levels per NFPA Standard 69
• Introduction of the Nitrogen Purge Hopper
• Practical Experience with Open Manway Charging when using this
Technology

4. Charging
solids into process tanks
Container Types:
- Super Sacks
- Large Rigid Bins
- Drums
- Small Bags
Delivery Methods:
- Overhead Gravity Feed through Product Chute
- Vacuum Transfer
- Open Manway Charging

5. Process
operational and safety considerations
Operational Considerations:
- Headspace and Floor-Space
- Properties and Flow Characteristics of the Product
- Addition Rate of the Product
Safety Considerations:
- Operator Exposure to Dust and Vapor
- Operator Ergonomics
- Flammable Atmosphere and
Deflagration Risk
Photo courtesy of: PEO, Assembled Chemical Weapons Alternatives

6. Tank
1.
2.
3.
4.
5.
6.
7.
8.
overview of process tank dynamics
Nitrogen Purging Process (for pressure rated vessels)
Solvent Vapor in Headspace
Entrained Air with Product Addition (21% oxygen)
Venturi Effect of Agitator
Nitrogen Addition at Tank Dome
O2 Sensor on Tank Dome
Vent on Tank Dome
Static Discharge within Powder Cloud

7. Deflagration
the fire triangle
Static Discharge
Solvent Vapor
Product Dust

8. NFPA 69
standard on explosion prevention systems
TWO METHODS ON PREVENTION OF COMBUSTION
1. Oxidant Concentration Reduction
- Maintain levels of oxidant concentration below the
specified Limiting Oxidant Concentration (LOC)
2. Combustible Concentration Reduction
- Maintaining combustible concentrations below
Lower Flammable Limit (LFL)
Consider Proper Housekeeping Techniques
NFPA 654 – standard for prevention of fire and dust explosions

9. NFPA 69-08
application of purge gas at points of use
LOC MONITORING PRACTICES
1. Continuous Monitoring of LOC (one of the following must be met):
- Safety margin of at least 2 volume percent below the worst credible case
LOC shall be maintained
- The LOC shall be less than 5 percent in which case the equipment shall
be operated at no more than 60% of the LOC
2. Non-Continuous Monitoring of the LOC (both of the following must be met):
- The oxygen concentration shall be designed to operate at no more than
60% of the LOC or 40% of the LOC if the LOC is below 5%
- The oxygen concentration shall be checked on a regularly scheduled basis

10. Engineering
Control
Nitrogen Purge Hopper patent pending
-application of purge gas at point of use-
Reduce and Maintain Low LOC
Control of Addition Rate
Reduce Time Tank is Open
Dust & Vapor Control
Easy & Fast to Clean
Safe from Pinch Point
Fast Installation/Start-Up
Cost Effective

11. Engineered
Simplicity
Nitrogen Purge Hopper
-containment & inerting-

12. Time of Day
12:35:30
12:34:00
12:33:00
12:29:00
12:27:30
12:26:00
12:25:00
12:24:00
12:22:00
12:16:00
12:13:30
12:12:00
12:11:00
12:10:30
Tank
12:07:00
12:05:00
12:02:00
12:00:30
11:59:30
7.00
11:58:00
11:55:00
11:53:00
11:51:00
11:49:00
11:47:00
11:44:00
11:42:00
11:38:00
11:36:00
11:30:00
O2 %
Engineering
Control
Nitrogen Purge Hopper
-applied technology for effective controlOxygen % vs Time
Manway
6.50
6.00
5.50
5.00
4.50
4.00
3.50
3.00

13. Custom
equipment options & features

14. Conclusion
Maintaining Low Oxygen Concentrations During Open Manway Charging
• The Practice and Challenges of Charging Solids through an Open
Manway
• The Risks of Deflagration and Risks of Potential False Monitoring
• The Importance of Nitrogen Blanketing and Point Source Inerting in
Enclosed Vessels
• The Technology behind the EHS Nitrogen Purge Hopper
• Common Applications and Variations of the Nitrogen Purge Hopper