Case Studies » Pretoria Energy
A visit was made to the Pretoria Energy Biogas site at Chittering in September 2014 to consider compliance with the Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR). The visit also included a review of the ongoing fire safety arrangements on-site in line with the Regulatory Reform (Fire Safety) Order 2005.
The Chittering process utilises anaerobic digestion (AD) technology to convert organic matter into Biomethane for injection into the national gas network – with some gas converted to electricity for use on-site. Commissioning of AD plant and ancillary equipment was at an advanced stage at the time of survey, and many process stages were fully operational.
The AD process involves routine formation of potentially-hazardous Methane and other gases; it incorporates biogas purification arrangements and has provision for processing spent digestate material. Any flammable gas accumulation may add to the residual DSEAR hazard.
The solution provided
The site footprint extends to over 10000m2; the largely rural site is located directly off the main highway with AD operations focussed around newly-built digestion tanks, gas transfer systems & associated plant rooms etc.
Documentary evidence was provided pertaining to existing material inventory, site procedures and maintenance - plus an overview of safety systems at the time of survey. Additional information was provided by management to allow a detailed assessment to be completed on the arrangements in place.
Recognised standards and guidance were used in determining the appropriate status and extent of DSEAR hazardous zones for site operations. Significant findings from the survey were set out in the DSEAR report, along with recommendations to mitigate fire and explosion hazards or support best practice on-site.
Hazardous area classification applies to those areas where a flammable atmosphere may persist either briefly or for longer periods of time as outlined in the regulations – specifically within confines of equipment or around flammable handling or storage locations.
Methane properties require strict procedures and maintenance of key equipment to minimise life safety risk. Adequate statutory checks are a critical requirement for pressure systems installed on-site, while gas isolation and relieve vents / valves also need routine testing.
Plant separation distances were also highlighted at time of survey as there may be some potential for impact from radiant heat transfer between site infrastructure.
The significance of earthing and continuity checks was also emphasised verbally to client - and in the report.
All of these issued were considered and a detailed DSEAR report, hazardous zoning plan and series of recommendations was issued to management to ensure sufficient control of DSEAR risks is maintained.