Client Background
The client is a foodstuff manufacturer producing biofuel known to be explosible in a dust cloud. The client was able to tightly control the atmosphere of storage and use for the product.
Client Problem
Storing and using known explosible material is a risk that required expensive protective measures. The client had a Limiting Oxygen Concentration (LOC) value that would completely inert the product with nitrogen as standard practice, incurring large cost.
Client Objectives
The client wanted to know how discrete spark ignition changed with oxygen concentration, and to plot a graph of MIE value at 9, 12, 15 & 18 % oxygen.
Strategy
Sigma-HSE advised that the client identify which capacitive and inductive sparks occurred within their process to understand which MIE values would be acceptable. This way the client could take data generated and inert their system accordingly.
Sigma-HSE sourced the pre-selected mixtures of oxygen/nitrogen to replace the standard air used within the tests under normal conditions.
The theory is that the client can cross compare the located ignition sources with the graph of MIE data and decide which gas concentrations would be required to work with the material.
There would be the potential for large savings of the data generated suggested that less nitrogen could be used while still working safely within the process.
Sigma-HSE sourced the pre-selected mixtures of oxygen/nitrogen to replace the standard air used within the tests under normal conditions.
The theory is that the client can cross compare the located ignition sources with the graph of MIE data and decide which gas concentrations would be required to work with the material.
There would be the potential for large savings of the data generated suggested that less nitrogen could be used while still working safely within the process.
Insights and results
Testing Overview
Variations to the test procedure were required to sufficiently purge the altered Hartman tube apparatus, removing the atmospheric concentrations and filling with the target concentrations. Additionally, the target gas was used to suspend the sample in a dust cloud.
To ensure that these alterations were producing the target atmosphere the results at 9% and 21% were re-tested. This confirmed that 9% would completely inert the material and that 21% would readily combust.
To ensure that these alterations were producing the target atmosphere the results at 9% and 21% were re-tested. This confirmed that 9% would completely inert the material and that 21% would readily combust.
Sigma-HSE found that
Testing showed a decrease in sensitivity to ignition sources over the range of concentrations, until the material would non-explosive.
The biofuel material shows a significant step-change between 12 and 15% oxygen, with 12% oxygen being extremely insensitive to ignition.
This was able to show that at 12% oxygen the sample was unlikely to ignite based on the ignition sources present within their process. This meant saving on costs to inert sample.
