The Process industry manufactures many types of unique compounds and substances and uses a range of processing equipment for manufacturing these end products. The storage, processing, handling and packaging of materials create potentially hazardous conditions in the workplace with a risk of fire and explosion due to a flammable atmosphere that can be created by dust.
In order to mitigate the risk of fire and explosion, the industry is required under different global and local legislation and in some cases with the compliance requirement to undertake an adequate risk assessment and identify hazardous areas. To be able to understand the risk and perform the risk assessments adequately, it is imperative to know the physical properties of the material being processed.
As per our experience, the MSDS may not always provide all the data needed. In some cases relying on the internet data or published data alone could result in hazardous under-engineering or expensive over-engineering of the levels of protection within the site. Typical equipment used in the Process industries are:
- Pneumatic Conveyors
- Dryers
- Granulators
- Sachet Filling
- Rip & Tip Operations
- Centrifuges
- Grinders and mills
- Dust Collectors
- Mixers / Blenders
- Hoppers and Silos
- FIBC Handling (charging & discharging)
With respect to the various unit operations of the process industry, Sigma-HSE ISO 17025 testing laboratory in combination with experienced consultants has made the process safety testing easy by breaking it down into 3 main Basis of Safety approaches:
- Avoidance of Ignition Sources
This approach looks at the testing of materials to determine how sensitive they are to specific ignition sources such as electrostatic discharges, mechanical sparks and hot surfaces.
This Basis of Safety is often used when charging vessels from sacks, IBCs or FIBCs, pneumatic conveying, milling and many other operations.
Many materials, that can create a flammable atmosphere, are found to be insensitive to ignition and therefore it is easy, practical and cost effective to ensure an ignition source capable of initiating a reaction is not present.
Minimum Ignition Energy (MIE) (with & without inductance), Standard: BS EN 13821
The Minimum Ignition Energy test is conducted to determine the lowest spark energy that will ignite a powder when dispersed in air, as a dust cloud.
Minimum Ignition Temperature (MIT), Standard: BS EN 50281–2–1
The Minimum Ignition Temperature test is conducted to determine the lowest temperature at which a hot surface will ignite a powder when dispersed in air, as a dust cloud.
Layer Ignition Temperature (LIT), Standard: BS EN 50281–2–1
The Layer Ignition Temperature test is conducted to determine the lowest temperature at which a hot surface will ignite a powder when settled as a dust layer.
Powder Volume Resistivity
The test is performed at two controlled relative humidity conditions, a higher humidity of 50% and lower humidity of 15%, in order to see the changes in resistivity as humidity falls.
Charge Relaxation Time
The Charge Relaxation Time compliments the Powder Volume Resistivity measurement as it indicates how long material can retain its electrostatic charge.
- Explosion Protection and Prevention
Explosion Protection and Prevention accepts that ignition is possible, as potential ignition sources cannot be controlled and then, for Explosion Prevention, either ensure that airborne levels of material are kept to a level below the lower explosive limit (a flammable atmosphere is not present) or reduces the oxygen concentration, using inert gas blanketing to a level where combustion will not occur. For Explosion Protection the test data determines whether containment, venting or suppression systems can be applied safely.
Minimum Explosive Concentration (MEC), Standard: BS EN 14034 part 3
The Minimum Explosive Concentration test is conducted to determine the minimum quantity of powder dispersed in air, as a dust cloud that will form an explosive atmosphere. Thus, keeping below this concentration can prevent an explosive atmosphere formation.
Explosion Severity (Pmax & Kst) (20L), Standards: BS EN 14034 parts 1 & 2
The explosion severity test is conducted to determine maximum pressure (Pmax), Maximum rate of pressure rise (dP/dt)max and Kst of an ignited powder, dispersed in the air, as a dust cloud.
Limiting Oxygen Concentration (LOC) Standard: BS EN 14034 part 4
The Limiting Oxygen Concentration test is conducted to determine the minimum quantity of oxygen, within an atmosphere, that will enable a powder dispersed in air, as a dust cloud to ignite. Thus, keeping below this determined oxygen level will prevent an explosion from occurring. The test is performed using nitrogen as the inert gas, but conversion factors can be applied if other inert gases are to be used.
- Thermal Decomposition
If materials are to be used at elevated temperature as would be experienced in drying operations, then it needs to be determined whether they can undergo an exothermic, self-heating reaction close to the dryer operating temperature. For most manufacturing operations, solvent evaporation is the main application for a need to increase the temperature and as these operations are performed at low temperature circa. 60°C thermal stability is not an issue. However, in the manufacture of many products and intermediates higher temperatures may be encountered and therefore data on self-heating is required.
Air Over Layer Test
A thin layer of powder, nominally depth of 15mm is exposed to heated air, flowing around it. The temperature is measured and recorded in the surrounding airflow and 3 measurements in the sample.
Bulk Powder Test
As the name suggests the testing is used to define safe processing conditions where the bulk powder is present with limited air availability. Typical applications are for the base of large spray dryers, fluid bed dryers where the flow-through air has stopped, storage of big bags, etc.
Aerated Cell Test
The test uses the above Bulk Powder test cell but a lid is attached with a sintered glass base. Pre-heated air is then pushed through the sample mimicking a condition where there is a bulk of powder with a large amount of air availability such as a fluid bed dryer or rotating dryer
Benefits of Sigma-HSE Services
The service offered by our experienced team at Sigma-HSE is much more than a standalone test result.
- Over 50 years of combined testing and consultancy experience to ensure that our accurate and methodically generated test data is applied to your process safety applications correctly to protect your staff, your site and your brand reputation.
- Free technical advice to ensure the correct test package is selected for your needs.
- Complimentary after-sales support, to ensure you are happy with the data and understand the implications for your project.
The ISO 17025-certified Sigma-HSE testing laboratory has new, state-of-the-art equipment and is operated by senior laboratory staff with decades of testing knowledge. Internationally recognized standards are followed such as those adopted by the EU (BS & EN standards) and also ASTM standards as adopted within the USA.
Our quality systems ensure that all results are accurate with traceable test data. However, data alone is only one part of a process safety plan and must be used with both caution and expertise for it to be effective. Interpretation and implementation is where Sigma-HSE Consultants can also bring a wealth of expertise from many years of experience providing process safety solutions to national and multi-national companies.
