About
DSEAR
DSEAR and HAC risk assessment services
DSEAR is a legal requirement obliging employers to assess workplace risks and risks of explosions with causation of dangerous substances within the workplace.
The DSEAR 2002 (Dangerous substances and explosive atmosphere regulations) place certain duties on the employer to eliminate or reduce risks from fire, explosion or other events arising from the hazardous properties of dangerous substances in connection with work.
Whether your business involves assembling garden sheds, or manufacturing paint products, as an Employer there are certain important safety actions that you need to take to comply with the Dangerous Substances and Explosive Atmospheres Regulations. (DSEAR 2002)
A DSEAR risk assessment will specifically address process hazards associated with the controlling, producing, or handling of any dangerous substances including combustible dusts and any other materials that may be explosive, and identify shortcoming in your process that could lead to a dangerous fire or explosion.
Providing a comprehensive risk assessment of the DSEAR hazards associated with you process will allow you to put measures and procedures in place so that you comply with the DSEAR regulations and protect the safety of your employees.
Employers obligations.
The HSE rules oblige employers to:
Find out what dangerous substances are in their workplace and what the risks are
- Put control measures in place to either remove those risks or, where this is not possible, control them
- Put controls in place to reduce the effects of any incidents involving dangerous substances
- Prepare plans and procedures to deal with accidents, incidents and emergencies involving dangerous substances
- Make sure employees are properly informed about and trained to control or deal with the risks from the dangerous substances
- Identify and classify areas of the workplace where explosive atmospheres may occur and avoid ignition sources (from unprotected equipment, for example) in those areas
What type of activities and industries are covered under DSEAR
Here are several examples covered under DSEAR:
- The storage and use of flammable goods in retail stores
The storage and use of chemicals in manufacturing
The storage and use of flammable gasses
Activities involving hot work – welding, soldering – that include flammable materials
Industries that handle/store dust
The wastewater treatment industry
The renewable energy industry
The petrochemical industry (onshore and offshore)
DSEAR Risk assessment Methodology
The approach used to carry out this HAC is as defined in 60079-10-1 Classification of area Explosive gas atmospheres, and 60079-10-2 Classification of area Combustible dust atmospheres.
Step 1 – Obtain data
- Materials that are or could be present – Flash point, boiling point, vapors density and LEL/UFL.
- Main plant items (p&ids/process flow diagrams).
- Facility sizing (Site GAs).
- Sizes/volumes of plant and equipment.
- Plant materials of construction.
- Relevant plant features : Vents, relief valves, access ports, control systems, heating/cooling etc.
- Ventilation systems-Open, congested, enclosed etc.
- Process parameters:
o Frequency/duration of operations
o Flow rates and mass flow
o Operational temperatures
o Operating pressures
- Operational procedures – Manual, automatic, shutdowns, maintenance etc.
Step 2-Identify sources of release
Identify where, when and how a flammable atmosphere can be present under
- Normal operation – Situation whereby the equipment is operating within its design parameters including start up and shutdown but excluding initial start up and commissioning.
- Unexpected malfunction and process upset situations – Failures such as the breakdown of equipment seals, flange gaskets, human error and control failure.
- These are not considered to be part of the scope of this HAC and will not be accounted for in this HAC
o Major accidents. eg rupture of a process vessel.
o Large scale mechanical failures of equipment or piping.
o Unanticipated conditions.
o Enhanced tight (see BS EN 1127:1) equipment and fittings.
o Releases from all welded pipework.
o Releases of flammable liquids at less that 5c below their flashpoint provided they cannot be reheated after spillage. (allow 15C for safety margin)
o Two independent BPCSs failing at the same time
o Initial commissioning of the plant.
Step 3-Determine grades of release
- Continuous grade : Continuously, or for long periods, or frequently. (More than 1,000hrs/year or 10% of the time)
- Primary grade : Occasionally during normal operation. (Between 10 and 1,000 hrs/year or 1 and 10% of the time)
- Secondary grade.
- Not in normal operation
- Only infrequently and for short periods, (Less than 10 hrs/year or 1% of the time)
Step 4-Assign Zone type (number)
Consideration will be given at this time to the type (if any of the ventilation that is present, as this can have an influence on the Zone classification given.
The effect of ventilation on the Zone classification will depend on the dilution provided by the ventilation and the ventilation availability.
- Good: Virtually continuous (usually with backup)
- Fair: Expected during normal operation. Only occasionally lost for short periods.
- Poor: Ventilation present but expected to be lost for long periods.
The resulting classification after considering the effect of ventilation, will fall into one of the categories below.
Zone 0. Place in which an explosive atmosphere consisting of a mixture with air of flammable substances in the form of gas, vapor or mist is present continuously, for long periods or repeatedly (consider more than 10% of the time or more than 1000 hours);
Zone 1. Place in which an explosive atmosphere consisting of a mixture with air of flammable substances in the form of gas, vapour or mist is likely to be present occasionally under normal operating conditions (consider less than 10% of the time / 1000 hours but more than 0.1% of the time /10 hours);
Zone 2. Place in which an explosive atmosphere consisting of a mixture with air of flammable substances in the form of gas, vapour or mist is not likely to occur in normal operation and, if it does occur, will persist for a short period (less than 0.1% of the time / 10 hours).
Step 5-Estimate the Zone extent
Estimation of the Zone extent will be done using the point source method as directed by EI15 4th edition
Step 6 - Document the assessment: which will entail
- Input data showing
- All materials/process information
- Clear identification of the sources of release
- Justification for the grades of release
- Zone types and extents for the facility
- Drawings to include
- Side views and plans
- Additional notes on heights and shapes
- Input data showing
