bp alaska gc-1 - innovation and media · bp alaska gc-1 design review project january ´03january...

BP Alaska GC-1Design Review Project January 2003

BP Alaska GC-1 Design Review Project January ´03January _03

The objective of this report is to reviewthe current design drawings for the GasDetector Installations for BP Alaska’sPrudhoe Bay GC-1 Project. The currentdesign incorporates the Spectrex OPGDdetectors.

Scope of this report includes:1. Our recommendations regarding the current gas detector

placements.

2. Any changes to the current design (placement, wiring,mounting, etc) that would need to be implemented in orderto use the Zellweger OPGD EXCEL gas detector systemsinstead of the currently specified vendor.

3. The advantages Zellweger products offer during theconstruction and installation process resulting in aLOWER COST to BP Alaska on their initial project overallcost estimate.

4. The advantages that Zellweger detectors offer during thestart-up, commissioning and troubleshooting for thisparticular site resulting in a LOWER COST to BP Alaska ontheir initial project overall cost estimate.

5. Long Term Cost of Ownership Advantages

I. Statement of requirement


After careful review of the drawings, we conclude that thespecific placement locations for the detectors are logicaland consistent with the effective use of open path gasdetection technology. The placements, as we see them,should effectively maximize detection coverage in themodule and minimize the risk of significant, undetectedcombustible gas leaks in the module. The placement of thestandard configuration OPGD detectors across the ceilingsand at the various levels of height in these modules isconsistent with our opinion on the most likely locationswhere slow leaks might build up into significant combustiblegas concentrations. The placement and utilization of theCross-Duct configuration OPGD detectors look to bothmaximize the efficacy of the technology and reduce the riskof missing an unexpected release of combustible gasesfrom outside the module that might be drawn inside themodule through the HVAC ducting. We have based ourstatements here on our knowledge of our own open pathgas detection systems’ operation and capabilities, as wellas shared input from many of our customers’ pastexperiences with this technology.

We conclude that no significant changes to the currentplacement design would be recommended for this project.

We specifically note, in reference to the placement andwiring of these systems, that we do not see any significantchanges that would need to be made in these designdrawings in order to replace the currently specifiedStandard open path gas detection kits with the Zellweger-brand Searchline EXCEL OPGD systems.

One important change, related to the Cross-Duct configurations,would be required. But the changes are certain to be anadvantage. These advantages will be discussed in detail inSections III and IV of this report.

There are a number of available features and configurationoptions, specific to the Zellweger products, which we canrecommend. These recommended options and features willimprove the ease of mounting for these detection systems,increase the ease and speed of alignment and facilitate theproblem-free start-up of the gas detection systems during initialconstruction and installation. These options and features canalso effectively reduce the difficulties that can be encounteredduring commissioning of the system and initial troubleshooting,should there be any question regarding the viability of theiroperation. These changes are certain to provide specific timeand material cost reductions that will reduce the estimatedproject costs associated with the GC-1 Gas Detection upgradeeffort. The standard features of and specific configurationoptions for the Zellweger Searchline EXCEL product line willalso benefit BP Alaska in their long-term Cost of Ownership.

II. Technical Assessment of Current Design –Detector Placement, Power Requirements, and Wiring


Powering Requirements: The power supplies used inExcel & Optima are constant power draw, switched-modetype power supplies. No change in power will be drawn withvarying supply voltage and no surge at switch-on. Thepower supplies employed in Searchline Excel ensure thatthe maximum unit powerconsumptions are never exceeded,even at power-up. This allows the cabling and power supplycalculations to be met with confidence. This should result inno unexpected modifications to the power requirementsduring the start-up process.

Each Zellweger Searchline Excel unit consumes less thanhalf of the maximum power consumed by some of the othervendors’ products. (For Example, Zellweger Analytics’Excel OPGD (Max) = 13W per complete system (bothsource and receiver, Draeger’s Pulsar (Max) = 35W).Reduces demands upon power supply and cabling.

Wiring Requirements: For the Standard OPGD gasdetections systems, no change in wiring or communicationscabling would be required. However, the duct mountedZellweger OPGD systems would only need power and RS-485 cabling / connections brought to a single position ononly one side of the duct. This will save one set of powercabling and one mounting hardware construction event oneach duct-mount installation. The specific costs of thisreduction could be reduced as much as 50% for theinstallation of the Cross Duct OPGD’s for the project.

Searchline Excel Cross Duct OPGD System

III. Advantages of the Zellweger products during theconstruction and installation phase.


Mounting Bracket Flexibility: The mounting bracketdesigned for the Searchline Excel Standard OPGD systemallows > 180 degrees horizontal and +/- 45 degrees verticalmovement of Excel unit when mounted. This accommodates alllikely pointing arrangements without requiring special supports tobe produced that "pre-align" the detector in roughly the rightdirection. The currently specified vendor’s units have mountingbrackets limited in their movement. The mounting bracket fromthe currently specified vendor is limited to - 45 deg in thehorizontal plane making it impossible to wall mount and firealong the wall.They appear to be well suited to installing units onopposite walls but will be limiting for units running along thesame wall, should BP Alaska’s locations require suchinstallations. Other vendor’s OPGD system mounting bracketsmay only allow +/- 30 degrees movement in either plane,requiring special supports to be built, when the units are to bemounted on opposite walls.

Standard Searchline Excel OPGD System bracket - exploded view

III. Continued


Standard OPGD Alignment Procedure: Instrument-assisted Alignment is used with all Zellweger standardconfiguration EXCEL kits. The telescope proceduresassociated with the currently specified OPGD systems issimilar to the course alignment telescoping procedures forthe Zellweger EXCEL OPGD systems, but the use of theHand Held Interrogator in the Zellweger system allows forfine tuning of that alignment. The hand-held unit facilitatesoptimum alignment accuracy and digitally confirms thecorrect and acceptable signal level from the source to thereceiver. The software for the hand-held will NOT allowinitialization of the system, unless the minimally acceptablesignal levels are achieved, indicating acceptable alignmentaccuracy.

Searchline Excel, Excel Duct Mount and Optima Plus canall be communicated with using a single, common SHC-1Handheld Interrogator. The currently specified OPGD unitshave no hand-held unit access. A notebook pc andsoftware is required to perform simple programming andtroubleshooting. Other vendor’s systems may have adifferent handheld for each detector type. Although othermanufacturers’ units may require a connection between thetransmitter and the receiver, Standard Searchline Excelunits can be wired using the same cabling arrangements asthe currently specified, Spectrex SafEye units.

Cross-Duct Installation: Currently specified and othermanufacturers’ cross-duct OPGD units have a separate sourceand receiver module that must be mounted on mounting plateslocated on each side of each duct. This could be very difficult toaccomplish for the construction crew, depending upon theclearance between the ducts walls and the ceiling or modulewall due to the optimal positioning of the line of sight.

III. Continued


Cross-Duct Alignment Procedure: Cross-Duct alignmentfor the currently specified detection system can becumbersome and time-consuming. The unit must bealigned during the actual construction event, potentiallyrequiring a separate, trained instrument technician to beavailable during this process. The Zellweger EXCEL Cross-Duct OPGD does not require alignment of any kind in thefield. The unit comes pre-aligned at the factory and simplyneeds to be bolted to it’s mounting bracket/plate, wired in,and connected to the power supply for on-demand start-up.The hermetically sealed Reflector Panel mounts on theopposite inside wall of the duct and does not have to beaccurately aligned. The signal does not have to be directedto the exact center of the plate due to the stable andaccurate mounting of the optical components and thefocusing of the beam within the specially designedmounting cell in the Cross-Duct kit.

III. Continued


Functional Testing of Standard Configuration OpenPath Detectors: Functional testing can be performed withtest filters for any and all standard open path gas detectionsystems in the design. However, many units are mountedat levels much higher than can be reached from floor level.For systems mounted up to 15 feet above the floor, atelescoping wand accessory is currently available fromZellweger. The test filters are mounted in the clamp of thewand and lifted into the path of the OPGD system forresponse verification.

Due to their location, open path combustible detectors thatare mounted high up in the module up to 30 meters, suchas DACG-010454-5, will be difficult to access for alignmentconfirmation, system initiation, calibration and performancevalidation, programming, diagnostics, etc. The need forgaining direct access to such detectors can be significantlyreduced by doing the following:

1. Remote System Access: BP Alaska could choose to installthe Searchline Excel receiver with its conventional junctionbox close to the unit and a cable / conduit coming down to aDX-100 M interface box mounted where it can be readilyaccessed from the floor. The DX100M interface is unique toZellweger Analytics, with an IS connection for the Hand-heldInterrogator. It was designed for non-intrusive one-manaccess to the OPGD units. All user-programmableparameters can be accessed through the hand-held device.The SHC-1 Hand-Held is a simple, 4-button, menu driveninterrogation device that is easy to operate. This is notpossible with the currently specified vendor’s systems.

2. Remote Real-Gas Calibration Verification: For use insidethe BP Alaska process modules, a Searchline Excel gassingcell accessory could be permanently installed on thereceiver and tubing can be installed flowing into this cellfrom where the DX-100 (M) is located. Calibration gas wouldbe remotely applied to the cell, and a real gas systemoperational test would be accomplished. The outlet of thecell would also be fitted with tubing and the effluent gasvented several feet away from the path of the detector.

IV. Advantage of Zellweger products during start-up,Commissioning and Troubleshooting:


Gas cell verification performed using the gas cell will beless prone to microscopic variations in thickness / changesin orientation of the filter and so will give a more accurateresult than the placing of a test filter in the OPDG beam.The use of gas as a primary standard is used in the factorycalibration of the Searchline Excel and repeating this onsite with the Sieger gas cell will give the most accurate formof functional testing of the installed device.

By installing the receiver unit as described above it will bepossible to perform functional testing, configuration anddiagnostic activities from the convenience of the floor. Theonly activities that will not be possible from the floor will bethe cleaning of windows (if necessary) and the systemalignment procedure. For the initial alignments duringconstruction, the hand-held interrogator would be usedconnected to the standard junction box with the aid of anSHC-1 Protection Device and Lead.

IV. Continued

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