Gas and fire detection systems play a crucial role in reducing risks on sites world-wide. Defining the ideal location, type and quantity of gas detectors and flame detectors however has traditionally relied upon site evaluation by trained and highly experienced engineers. Gas detector placement especially presents challenges due to the complex nature of gases, and the hazard they present to personnel and facilities.
Consequences of inaction
Health and Safety Managers are increasingly required to demonstrate the rationale behind the selection of the safety systems deployed on their sites. Greater assurance is needed to confirm that the installed detectors and systems provide the intended levels of area coverage and protection. Guidance documents are published by national authorities, but they only detail general recommendations for gas detector selection and placement. They do not provide the definitive guidance that enable systems to be installed without the assessment by specialists in the discipline.
Solution and payoff
Using sophisticated computer aided design, Crowcon can provide a detailed report based on 3D site images which identifies gas and flame hazards and recommends detector quantities and location in-line with the British Standard BS 60080:2020. The review can be conducted for new sites/installations, or for established detection systems.
The review includes hazard identification and a site-specific risk assessment. The philosophy is then defined, which details the detector technologies employed, alarm set-points, performance requirements, and the environmental conditions.
Each area of the site is analyzed to calculate coverage and ensure performance requirements are correct. The Consultant will complete the performance target review and present the findings in a simple, concise report.
The report enables the client to optimise the system design and achieve the best possible balance between safety and economy. This practice improves safety and reduces operating costs by ensuring that the number of devices used is minimized while the required level of safety is maintained.
Gas Detector Coverage Assessment
A number of simplifying assumptions are used in order to make it possible to assess sites. It is assumed that all gas detectors are either ‘point’ or ‘open path’ gas detectors, and that gas is detected if the accumulation envelopes a detector or intersects the track of an open path detector.
Each area assessed is represented as a volume specified in terms of its length, width and height. The assessment results are summarised diagrammatically clearly depicting the areas of the site that are covered, and not covered by the existing or detectors. A typical gas detection coverage assessment diagram is shown below:
Flame Detector Coverage Assessment
The flame detectors are represented as two-dimensional Computer Aided Design (CAD) files depicting each detector’s field of view. The performance Targets for each area are set according to their local hazards and escalation risks. This information is stored in a ‘Grademap’ file. A custom software system then ‘overlays’ each relevant detector’s footprint onto the Grademap and constructs a graphical image of the coverage afforded by the area’s detectors. The finished graphical file provides an objective estimate of that area’s flame detection coverage physical obstruction and hazard grading, an interaction that is virtually impossible visualize without computer assistance.
In the example shown below the areas shown in green meet the flame detection coverage targets, those areas in orange and yellow meet restricted targets while those in red have poor coverage and may require revision. The tabular summary provides quantitative data on the hazard coverage.