MICROPACK DETECTION

Fire and Gas Detection Mapping Services

MICROPACK Detection (Americas) Inc

1227 Lakecrest CourtFort Collins, Colorado 80526Voice: 970 377 2230Fax: 970 377 2273micropackamericas.com

Company History

Micropack has been involved in the oil & gas industry for over 30 years. Through-out this time Micropack have become recognized as being experts in Fire and Gas Detection technologies.

Micropack also became involved in fire research work and the effects of site spe-cific environmental conditions on differ-ent detection technologies giving Mic-ropack a thorough understanding of the conditions encountered in Oil and Gas facilities.

As a result Micropack has developed a range of Fire and Gas Detection Map-ping Tools. These tools give an estimate of the performance of Fire and Gas De-tection coverage taking into account the target hazard types and sizes and effects on detection equipment from the local environment.

IntroductionSafety is of supreme importance throughout the oil, gas and petrochemical industries due to the hazardous nature of the products recovered and created. Fire and Gas Detection sys-tems are of paramount importance to protect our person-nel, plant, product and reputation.

Producing a fire and gas detection system layout of a hazard-ous area is imperative because this can then be assessed and optimised to ensure coverage is in line with the latest HSE requirements.

Reviews can be carried out on greenfield and brownfield fa-cilities. Micropack were pioneers of fire and gas detection mapping which has been enhanced over 30 years and re-alised on excess of 1000 projects across the globe.

Using Micropack’s bespoke Flame Detection Assessment (FDA), Gas Detection Assessment (GDA) and Heat Detection Assessment (HDA) software packages;

Micropack are able to verify F&G equipment arrangements from initial design stages through to construction and instal-lation, or existing facilities.

Micropack’s mapping technology and experience has been used in the past to evaluate older platforms that were ready for upgrade with huge benefits to all concerned;

An ageing North Sea facility had old point catalytic type gas detection that required replacement. Exchanging these cata-lytic units with newer point IR detectors was considered. Fol-lowing a Micropack fire and gas review it was advised that a new approach should be taken.

This new system recommended that 48 open path gas de-tectors could be used in place of the 438 point IR gas detec-tors that were intended to replace the catalytic devices. This solution provided far superior gas detection coverage of the facility as well as lowering the project cost and cost of own-ership through reduced maintenance costs.

At present, Micropack have to carry out all mapping projects however we are currently developing a software package for third party use.

Performance TargetsBefore a review can be carried out quantifiable performance targets must be set that can be realistically achieved with re-gards to fire and gas detection.

Flame sizes are measured in terms of distance to differing types of flames and distances with regard to the energy pro-duced by them, such as Radiant Heat Output (RHO).

Gas detection is measured according to a different set of pa-rameters in terms of concentration, volume and idealised cloud size. In both cases voting logic and response time must be clearly specified.

Assigning Grades for Flame Detection

Typical steps to applying Grades in hydrocarbon risk volumes for flame detection are:

Grade A is used for elevated hydrocarbon risks, areas which are particularly sensitive such as small hydrocarbon conden-sate pumps. Such risks will normally have well defined risk reduction measures (control actions), some of which may be active and need to be triggered by automatic fire detection. Grade A zones should extend a minimum of 1m (3.3ft) from the plant to which it applies and segregated from Grade C volumes by a further 2m (6.6ft) of Grade B.

Grade B is the “normal” level of fire detection in hydrocarbon risk areas and is used wherever another Grade is not more appropriate. Grade B equipment will include items that are not sensitive to small fires such as Oil Separation Vessels. Grade B zones should extend a minimum of 2m (6.6ft) from any plant which is protected by it, or to the area boundaries if any are within 4m (13ft) of the plant.

Grade C is used where the Grade B level of detection is exces-sive, and so a reduced performance Grade is required. Grade C equipment will include items that have little or no flam-mable inventories such as Produced Water Vessels. Grade C zones should not be within 2m (6.6ft) of Grade A volumes (i.e. there must be a Grade B area between A and C), or Hydro-carbon plant from which there is potential source of release, e.g. flanges or compression fittings (which will be Grade A or B).

Methodology

On existing facilities, setting the fire and gas performance targets will require a full list of existing detection equipment and detector location drawings.

From these, preliminary fire and gas de-tection grade maps and a survey execu-tion plan can be produced.

On new facilities Micropack can work with the client to develop a set of perfor-mance targets.

Micropack can also apply existing design and engineering practices to meet per-formance targets.

Micropack can assist in the full design process from FEED through to installa-tion and commissioning.

Methodology

Flame Detection coverage can be assessed using Mi-cropack’s proprietary software based mapping tool FDA. The input requirements for this tool are Per-formance Targets, detector layouts, elevations and details of the detector types. The detectors are rep-resented as 2 dimensional CAD files depicting each detector’s field of view.

The Performance Targets for each area are set ac-cording to their local hazards and escalation risks. This information is stored in a ‘Grade map’ file. A custom software system then ‘overlays’ each rel-evant detector’s field of view footprint inclusive of obstructions from plant congestion onto the Grade map and, using a truth table, constructs a graphical image of the coverage afforded by the area’s detec-tors.

The finished graphical file is known as the ‘assess-ment’ file and provides an objective estimate of that area’s flame detection coverage. This analysis shows the typical interaction between flame detector cov-erage, physical obstructions and hazard grading, an interaction that is virtually impossible to visualize without computer assistance.

Flame DetectionCoverage Assessment

Grade Map Key

A 10kW 10kWB 10kW 50kWC 100kW 100kW

Grade A RedGrade B OrangeGrade C Green

Example: Definition of Gas Detection Grade in terms of cloud size

Grade High Gas Low Gas

S 4 Metre 14 MetrePE 5 Metre 15 MetreO 10 Metre 20 Metre

Assigning Grades for Gas Detection

The target gas cloud sizes are selected for each area based on the area’s volume, confinement and degree of congestion.

Typical gas cloud performance targets are:Confined Space (S): 4 metre (13ft) detection limitPartially Enclosed (PE): 5 metre (16ft) detection limitOpen (O): 10 metre (33ft) detection limit

Geometry of Accumulation

The methodology used in GDA (in keeping with the philos-ophy of damaging explosion overpressures) is that the gas cloud will be modelled as a nominal sphere.

This assumption (which is conservative because the ‘ideal’ spherical geometry encourages higher overpressures than the more realistic plume) permits a rapid and reasonably ac-curate assessment of detector coverage.

The gas cloud sizes considered are specified as 4m, 5m and 10m diameter clouds having volumes of 33m3 (1,165ft3), 65m3 (2,295ft3) and 523m3 (18,470ft3) respectively.

Each area assessment is represented as a regular orthogonal volume specified in terms of its length, width and height (or, using conventional Cartesian coordinates, X, Y and Z).

The assessment result is, by definition, a three dimensional structure which cannot easily be rendered on two dimen-sional paper and the results of the assessment are available both as a numerical summary and as a series of horizontal ‘slices’ through the volume. These slices are available at vari-ous intervals and, for clarity, one representative slice for each area will be reproduced in a study.

In the example overleaf, the areas shown in green meet the gas detection coverage targets for voting, orange will show alarm coverage only, while if any area was shown in red, this area would have poor coverage and may require revision.

Other types of inferential gas detector technologies includ-ing ultrasonic gas detection measures are not presently mod-elled by GDA, primarily because they effectively respond to release rates rather than gas concentrations.

Micropack can carry out ultrasonic gas leak detection map-ping surveys using alternative methods.

Gas DetectionCoverage Assessment

Cellar Deck: Grade PE - RedHiGas Diam 5.00m (16.4ft)LoGas Diam 15.00m (49.2ft)

Gas DetectionCoverage Assessment

Assigning Grades for Gas Detection

The gas detection coverage to the target gas cloud sizes can be assessed using Micro-pack’s proprietary GDA software assessment tool. The target gas cloud sizes will be pro-posed for each area based on the area’s vol-ume, confinement and degree of congestion as agreed previously.

The F&G plot plans will be used to establish their proposed location on the facility and their elevations will be required. These coor-dinates will be input into the software pack-age GDA for analysis and assessment. This package objectively assesses the coverage of the existing gas detection system against the proposed Performance Targets.

Study & Deliverables

Study Scope of Supply

If an existing facility is to be assessed an experienced sur-veyor will visit the facility to conduct the following work:

Hazardous Areas

Establish existing detection arrangements by conducting the following activities:a) Record location, elevation and maintenance accessibility of existing optical flame detectors.b) Record field of view photographs of existing optical flame detectors.c) Record field of view of proposed additional flame detec-tors.d) Record location and elevation of flammable gas detec-tors.e) Record location and elevation of proposed additional gas detectors.

Non Hazardous Areas

a) Record location & elevation of existing smoke and heat de-tectors with respect to local hazards.b) Estimate (using smoke tracer) local air movements where they are likely to influence the performance of smoke and heat detectors.

Non Hazardous Area Air Intakes

a) Record existing smoke and gas detection arrangements.b) Conduct scent tracer air transit time tests.

If the facility is at the design stage:

The Fire and Gas Detection Review shall cover all Hazardous Areas and non-Hazardous Areas as defined on the Equipment Layout drawings. This information will be used to assess the Fire and Gas detection against the site performance targets.

Review Preparation

A full set of documentation is required:• Process Flow Diagrams.• Equipment layout drawings• Fire & Gas Detection Layout drawings• Hazardous area drawings• F&G Cause & Effects• Performance Targets (if available)

Typical Deliverables

Include one draft report (for client review/comment) and one final issue that will in-clude the following;• Site Performance Targets.• Fire and Gas Detection Study including;a) Narrative covering the review process and major findings.b) Graphical Assessments of Fire and Gas de-tector coverage.c) Proposals, including sketches, detailing recommended im provements for flame, gas, smoke, and heat detection improve-ments where required.

The report will present the survey/design data together with commentary on the suit-ability of the systems with respect to hazards and site performance targets.

Flame and Gas detection coverage will be assessed using Micropack’s proprietary FDA and GDA assessment software and graphical assessments will be presented of both the present arrangements and of any proposed improvements in coverage.

MICROPACK DETECTION