In our previous blog on Non-Electrical Ignition Risk Assessments (NEIRA), we discussed the fundamental steps of a DSEAR/ATEX assessment and focused on hazardous zones, ignition sources and the different types of non-electrical and legacy equipment available in the process industry.
In this blog, we take a more ‘hands-on approach to NEIRA’ by detailing how to identify hazardous areas, how to inspect equipment, and how to assess ignition risks.
Whether dealing with fans, mixers, or conveyors, NEIRA offers a structured methodology to ensure compliance and safeguard against potential ignition sources. By understanding just a couple of key stages undertaken during a NEIRA risk assessment, you can get one step closer to effectively mitigating explosion hazards in your operations.
NEIRA Assessment Process
The NEIRA risk assessment can be used to classify, designate as safe, or self-certify equipment that is not ATEX-rated. Previously known as Mechanical Equipment Risk Assessments (MERA) the name and scope of this risk assessment was expanded to include all non-electrical equipment in 2016.
NEIRA is used for non-electrical equipment, which includes, but is not limited to:
- Fans and extraction fans
- Mixers
- Belt conveyors
- Mills
- Conveying systems
- Serving units
- Pumps
The same NEIRA methodology can also be applied to:
- Motors
- Solenoids
- Valves including pneumatic and dampener valves
Why undertake a NEIRA Assessment? ATEX/DSEAR vs NEIRA
Equipment in hazardous zones must be suitably ATEX certified. This can be accomplished by purchasing ATEX replacement equipment (certification approach) or as a cheaper alternative, the existing equipment can be re-certified by conducting a NEIRA (risk approach) assessment.
For some equipment, i.e., small solenoid valves, it may be more cost effective to replace them with ATEX rated equipment rather than doing a NEIRA. ATEX rated equipment is about 3 times more expensive than non ATEX rated equipment, but it’s recommended to comply with legislation and best practices.
Considerations:
- Scope: NEIRA can be applied to all non-electrical equipment.
- Cost vs. Compliance: ATEX rated equipment is more expensive, but you must comply with legislation and safety standards.
- Maintenance: Maintenance procedures are critical and need to be well documented and followed.
- Special Cases: For large equipment like screw conveyors or blending units NEIRA is more practical as ATEX rated alternatives are very expensive.
NEIRA Assessment Methodology
The first stage of the NEIRA assessment methodology is the systematic review of potential ignition sources. This aims to determine the likelihood of them becoming an effective ignition source (i.e., having sufficient energy to ignite an explosive atmosphere). During a NEIRA, the following steps are usually undertaken.
Step 1: Hazardous Areas and Zonal Classification
First identify your hazardous areas and classify them into zones. What non-electrical equipment are in these zones? At this point you must gather flammability data for that equipment, e.g. the Minimum Ignition Energy (MIE). If the MIE of a dust is very high (e.g. over 1,000 millijoules) you may not need to consider some ignition sources like mechanical sparking or electrostatic spark discharges.
Step 2: Equipment Inspection
The next stage is equipment inspection. This must be completed in person and not via a desktop analysis. During the inspection identify any inherent ignition sources. This can include the main contact elements such as blades and impellers. Look for signs such as rust or loose bolts which should then be noted in your risk assessment.
Step 3: Ignition Risk Assessment
Conduct the ignition risk assessment to identify any gaps in your current safety measures. This may reveal the need for new procedures, measures or safety functions. As an example, you may need to implement temperature monitoring, create a maintenance schedule or check the liquid level in lubrication systems for rotary equipment.
Assessing Ignition Consequences
As the NEIRA aims to ensure that there is not an ignition risk, assessing the consequences of a potential ignition is an important step in the risk assessment. As this can be one of the hardest aspects of the risk assessment, we have added an overly simplified version of the of the risk assessment table as per the standard below:
- Identify the Ignition Source: i.e., bearing surface temperature.
- Describe the Scenario: i.e., what happens when the bearing surface temperature rises?
- Measures in Place: i.e., lubrication, general maintenance and speed monitoring.
In the 80079-36 standard, there are multiple steps to mitigate specific ignition sources.
NEIRA Assessment Collaboration
When walking around and completing the NEIRA onsite, a team is usually required to get the biggest benefit from the risk assessment. This team should include:
Lead Facilitator: They should guide the assessment process.
Plant Area Classification Expert/s: They should know the plant area classification, the equipment, unit operations and processing details.
Equipment Manufacturer: Sometimes needed for their intimate knowledge of the equipment, including materials of construction that may not be in the user manual.
Equipment Knowledge Expert: Someone with historical knowledge of the equipment, including previous internal maintenance procedures and failures.
Historical Risk Assessment Experience
Historical experience is key when doing NEIRA assessments, especially for complex equipment like reactors that handle flammable vapours. Experience can help identify potential ignition sources like loose bolts or bearings that can smoulder. This experience can then be used to enhance the risk assessment and implement new safeguards (if required).
In one case, Sigma-HSE recommended more frequent pressure testing of an agitator on a reactor, before each batch to ensure the bearings are not damaged or deformed. This was based on both historical knowledge and an individual’s prior knowledge and experience with that piece of equipment.
Having a knowledgeable team especially someone with knowledge of the equipment’s history and maintenance makes the risk assessment process more accurate and effective than just with a standalone viewing.
Equipment and Plant Data
When conducting a NEIRA, the gathering of comprehensive information about your equipment and plant is key to the overall success of the assessment. While site layouts, operational procedures and product inventories generate the foundation for your information gathering exercise, you should aim to gather more detailed information about your operations. Examples of this information can include:
Speed of Moving Parts: This information is particularly relevant for assessing mechanical sparking risks, as rotational speeds below 1m/s typically eliminate mechanical sparking as an ignition source.
Material Construction: Identify non-sparking materials, such as certain bronzes.
Bearing Types and Seals: Information on electrostatic properties and/or grounding systems, as insulating seals, for example, can lead to issues with static electricity.
Grounding: A common recommendation in NEIRA is to ensure proper earthing of all equipment, particularly after maintenance or disassembly.
Operating Environments: Equipment running in short batches may allow for cooling periods, which can later be used as a potential safeguard.
Drawings: Important for understanding the clearances between rotary equipment and outer casings or walls, as well as any mitigation systems in place, such as water-cooled jackets in reactors that provide internal cooling.
Procedural Information
To compliment the data gathered on your equipment, you will need to utilise the records you have of your operating and maintenance procedures.
Many maintenance tasks like the emptying of dust collectors are often done by external contractors, so make sure you have records of their activities.
Record-Keeping (we have found that this is often overlooked so make sure you keep it organized and accessible). Make sure your records have:
- General integrity checks.
- Bearing checks.
- Bearing replacements.
Manufacturer Instructions and equipment manuals with instructions should be kept up to date. For example, legacy equipment manuals may have bearing greasing intervals like every 100 hours. The guidelines for proper maintenance must be followed and documented.
Normal Operation, Expected Malfunction or Rare Malfunction
As the NEIRA assessment can be used for dealing with a wide variety of legacy equipment, there may be a range of ignition sources and scenarios that you may encounter. This may include:
- Bearing failures.
- Belt slips.
- Loss of lubrication or wrong lubrication medium.
Note: Static electricity should also be considered. Belts that are not anti-static can produce small sparks, especially in vapor atmosphere. As a result, the NEIRA assessment should check if the belts are anti-static in that vapor zone.
NEIRA Safeguards
As the NEIRA assessment focuses on identifying and mitigating potential ignition sources, the overall aim and objectives are to address non-electrical sources of ignition. Below are just a few examples of the most common safeguards and measures included in the risk assessment:
Hot Surfaces
Common hot surface safeguards include:
- Temperature monitoring systems with alarms and auto cut-offs.
- Air purge of bearings (hanger bearings).
- Seal flush systems.
- Periodic thermal imaging.
- Operator walkthroughs.
Note: Thermal imaging, especially for motors, can indicate impending failure which if not addressed can lead to ignition.
Mechanical Sparking
There are a variety of safeguards against mechanical sparking:
- Vibration monitoring.
- Other indirect sensors like blockage sensors in screw conveyors which can also detect hot surfaces or mechanical sparking.
- Component replacement within rated life especially bearings.
Note: Bearings should be replaced before they fail as failure can happen suddenly. NEIRA reports usually recommend a replacement schedule.
Static Electricity
Static electricity is an ignition source, especially for dust. Make sure everything is grounded and has electrostatic continuity to earth. Propagating brush discharges can occur if an insulating belt with two conductive materials has a small layer of paint that breaks and creates a discharge.
Documentation
Documentation, as for any process safety risk assessment, is key to the continuity of workplace safety. In your documentation, you must include hazardous zones, flammability data, completed templates (risk assessment tables) and an action list with designated responsibilities.
These should be the recommendations that have come out of the assessment. Again, this should be treated like any other process risk assessment.
Furthermore, a review is required whenever changes are made. If new materials with higher temperature requirements are introduced, then your maximum temperature may decrease. In this case, additional or updated safeguards are required and a NEIRA review is needed.
Ensure Workplace Safety
Ensuring that your workplace remains safe from the hazards posed by non-electrical ignition sources and legacy equipment can be a challenge for a variety of businesses in the process industry, especially for those that come up against ever increasing budgetary constraints.
At Sigma-HSE, we take the time to understand your business and processing needs. We are experts in the use and implementation of process risk assessments and standards such as BS EN 80079-36.
Our utilisation of the NEIRA methodology can aid you and your business in the management of non-electrical ignition sources. We can also aid you in the identification of flammable atmospheres, potential ignition sources, and the establishment of a suitable basis of safety as necessary in the DSEAR/ATEX legislation.