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It seems very few Asphalt Plants have been properley assessed for Explosive risk, although it has been a requirement to have a DSEAR assessment for over 20 years.

Ensure the Comany and person conducting the DSEAR assesment can demonstrate an understanding of the regulations, standards and application as competence is a mandatory requirement.

On most sites the areas coming under the hazardous area regulation are usually minimal and will include:

Bitumen is not explosive in its own right but a source of other gases which are both explosive and toxic.
However these are generally easy to manage if correctly assessed. Please refer to the Bitumen page.

Fuel Storage

Diesel
Prior to 2015 the flashpoint cutoff was 55°C excluding Diesel (flashpoint 55-60°C) from the scope of EU ATEX directive (now replaced by the UKEX regulations). All diesel storage tanks installed after June 2015 must comply with the hazardous area standards.
However, the government guidelines are pragmatic regarding the change in status for Diesel. If the equipment was installed prior to 2015 then a risk assessment can be applied. it is not mandatory to replace with equipment certified to EN 60079.
In simple terms if the equipment was specifically designed and supplied for Diesel use prior to 2015 use the risk is minimal and it can be continued to be used with an appropriate risk assessment. Other equipment, not specifically designed for Diesel, within the zone must be suitably certified.

As Diesel is such a low risk the zone, even within the bund, can be limited, or even negligible.

Kerosene
Kerosene is a much greater risk than Diesel and a definite potential source of zones. All tanks electrical equipment must be compliant , particularly if in an enclosed space where pumps and all associated equipment must be suitably certified with Earth bonding for metal storage tanks.

LPG
Modern LPG storage systems are generally compliant and if above ground will need to be assessed in location for any other equipment in immediate vicinity.
The primary issue is likely to be pipework from the tanks and associated valves and instrumentation. On most sites the zones around the pipework will be minimal as the pipes tend to be small diameter, low pressure and leaks are low risk assuming well maintained pipework.

Natural Gas
From the Gas pipe inlet to site to the burners the pipework and associated valves and instrumentation need to be assessed. Similar to LPG, on most sites the zones around the pipework will be minimal as the pipes tend to be small diameter, low pressure and leaks are low risk assuming well maintained pipework.

Dust

The hazardous area dust standards only apply to particles less than 0.5mm diameter (flyings are a possible exception) and exclude mineral based material as it generally non-flammable nor explosive. Materials such as Recycled Asphalt (RAP) and pellet additives contains a mix of larger particles and smaller Dust <0.5mm diameter dust.

Under DSEAR, the dust should be assessed to establish if the mix can occur so as to create an explosive dust atmosphere. If the fine dust is shown to be a low proportion of the overall mix then it might not be sufficient to form an explosive mix, therefore there is no hazardous area zone.
Dust Pentagon If it is decided there is sufficient dust to present a risk then the mix should be evaluated to establish if the mix is explosive. It is not sufficient just to have flammable dust present.
Although Asphalt plants tend to be dusty places, it seems most of the dust is mineral and not flammable.

Even if the mix is not explosive it could still be a flammable risk, with the possibility of subsonic (Deflagration) as opposed to explosion (supersonic) combustion when in cloud form. This does not come under the hazardous area regulations.

This page was created in an attempt to make sense of a poorly thought out DSEAR assessment. In practice there is no MSDS or reports that generally consider Bitumen specifically as a direct explosive source for the hazardous area assessement. The risk is primarily the build up of released other gases within the silos which are vented during silo filling.
If these are identified as Carbon Monoxide and Hydrogen Sulphide then toxicity rather than explosive hazard is probably the primary concern for personel.

Working with KRA Brown Electrical Services Ltd we offer advice on DSEAR report interpretation and implementation as well as Equipment ond general compliance surveys. Refer here for a detailed list

References
The Dangerous Substances and Explosive Atmospheres Regulations 2002
Equipment and Protective Systems Intended for Use in Potentially Explosive Atmospheres Regulations 2016 (updated March 2023).

The above as amended by
The Product Safety and Metrology etc. (Amendment) Regulations (2019 and 2021)

EN 1127-1   Explosive atmospheres - Explosion prevention and protection - Part 1: Basic concepts and methodology
EN 60079-10-1 Explosive atmospheres. Classification of areas: Explosive gas atmospheres
EN 60079-20-1 Material characteristics for gas and vapour classification
Neste Oy Bitumen Safety data sheet no 10507
Shell MSDS 02459536 Bitumen (Asphalt)

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