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OCR for page 505
Me contract. The requirements are usually statM at such a high level Hat when Recompounded
to detailed requirements and implementation approach Be contract is left open to significant
inteIpretabon. For a design/build contract to achieve jurisdictional objectives, requires adequate
definition of fimcdonal requirements, interfaces, standards, modularity, reliability,
maintainability, compatible technology, diversity, and other factors deemed important to the
jurisdiction. For example, a high-level specification may require closed circuit television
(CCTV) technology be used. Adding standards assures open architecture, but definition of
technology to be used (such as digital signal processing) may protect the installation from
obsolescence, since Me industry is in a major transition from analog to digital cameras. Network
compatibility for video distribution to multiple surveillance users may be a further requirement.
similarly, main tang video quality through distribution may be important to the jurisdiction,
supporting the use of Electronic Industnal Association ~A) 250C (medium hours) as a contract
requirement. Without defining sensitivity, a low-cost camera with low sensitivity may be
selected by a contractor as opposed to a higher quality camera win higher sensitivity, supporting
viewing at dusk prior to street light activation. Thus, without adequate attention to Be
requirements and design specifications, a design/bu~ld contact can result In major project
conflicts. Table A5.2~2 details a design/build contract from three points of view.
A.5.3 Life Cycle Cost Analyses and Evaluation of a Technology
The tree cost of a technology is not just the cost of procurement. It includes all costs associated
wad the acquisition, installation, testing, maintenance and operations of Be equipment over its
expected life cycle. Some of the cost elements to be considered in a life cycle cost analysis
Include those sued in Table A.5.3-~. (The reader should also refer to B.S. Blanchard's
book, Design ar~Manage to Life Cycle Cost; M/A Press; Portland, Oregon; ISBN 0-930206-
00-2.)
Technology should be evaluated on Be bases of:
· Performance,
· Life cycle cost,
· Open standards compatibility, and
L::\NCHR~Pha~' NCHRP 3-51 · Phase 2 Fmal Report
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OCR for page 508
· Risks of supportability.
Reliability and maintainability directly impact life cycle cost. Reliability is expressed in many
ways including mean time between failures IF, mean time between critical failures
~3CF), mean time between maintenance activations ~MA) and mean time between
corrective actions ~BCA). The difference in MTBF and M=CF lies within fault tolerance
of equipment design. A failure which results in nonperformance of a system function is
considerM a cntical failure. Win fault tolerance, a failure can occur but He system continues to
perform. This is not a cntical failure, but a failure which needs maintenance attention on a
scheduled rawer than crisis basis.
BMA and MTBCA are essentialRy the same. MTBMA is a term coined by life cycle cost
analysts while MBTBCA is a term related to reliability. Bow relate to Be probable time period
between deployments of maintenance personnel to fig a failure.
Fault tolerance allows for conservation in maintenance activity cost. The reason is Rat failures
in equipment can occur and maintenance can be planned. Thus a maintenance technician can be
deployed to fix sever failures rather Man a single failure. While actual corrective action time is
not reduced, travel time can be significantly reduced. In InteNigent Transportation Systems
travel time to a field site can be significant compared wig actual corrective action time at the site
of the failure. The benefits of fault tolerance must be considers on a system level basis to
determine Be probably number of failures Cat could be combined into one maintenance field trip
and Be resulting savings achieved compared wig one top per failure.
simplistic terms at Printed Circuit Board (PCB) level, Be cost of a failure can be determined
by utilizing MTBF and mean time to repair (MTIB) of equipment and understanding Be
associated cost of repair. While Be equipment manufacturer should be able to provide an
MOOR for this equipment, what must be added is:
· Mean Travel Time (MTT), and
· Mean Access of Closure Time ~ACT) of equipment.
~:`NCHRP\Phasc~p ~NCHRP3-51 ~ Phase2Fm~Report
A5-10
OCR for page 509
MA is based on field deployment locations and MACT is based on equipment cabinet location,
and ease of access. Access to a splice closure mounted on the top of a communications pole may
require a bucket Buck. The more difficult He accessibility, He greater MACr. M1TR includes
all activities of maintenance personnel:
Determining He location of the failure;
Idendfying the failed module;
Searching log~shcs files for spare modules;
Obtaining replaceable modulefs) to accomplish the repair;
Travel to the failure site;
Setting up at the site for maintenance activity;
Accessing He cabinets containing He suspected failed module;
Accomplishing any on-site diagnosis to verify isolation and identification of the failed
module;
I Replacing He failed module;
Verifying He failure has been repaired;
Cleaning up He repair site and packing test equipment;
· Logging repair activity; and
Retuming to the maintenance shop.
.
All of He above time is allocated to repair time of a failure at the system/subsystem level (i
PCB replacement), thus, there are two M1TRs Hat are important:
· Correcting He failure at Be system or subsystem level, which involves changing an
electronic module (PCB); and
.
1 ~
_.,
Troubleshooting, isolating He component(s) fault(s), replacing failed component(s) on He
electronic module (printed circuit board), and verifying that He module properly operates.
This currently involves printed circuit board test equipment and system/subsystem level test
sets (possibly hot mockup).
Typically MITR at the system and subsystem level are 20-30 minutes (not including travel and
access time) and 30-60 minutes at the punted circuit board (PCB) level.
~;~NCHRP~Phasc:~pr NCHRP 3-51 · Phase 2 final Report
A5-11
OCR for page 510
Usually jurisdictions perform system/subsystem maintenance. Circuit card level maintenance is
typically accomplished through depot maintenance supplied by We manufacturer or a Bird party
depot, trained and certified by Be manufacturers. While some jurisdictions do maintain circuit
cards (especially for NEMA 170, and 179 controversy He trend is to use depot maintenance.
Where depot maintenance is used, cost of the circuit card maintenance is determined by:
· Junsdiction cost of completing repair request forms, packaging, and mailing Be PCB to Be
depot;
· Depot repair charges; and
· Jurisdictional cost of receiving the repaid PCB, logging it in, and returning it to spares
inventory.
After a finite number of repairs, at Be component level, He PCB probably will require
replacement. Board damage typically is directly related to the number of integrated circuits that
are difficult to remove and replace. Thus, spares replacement cost must be included in life cycle
cost based on the MTBF of a specific type PCB (i.e., part number), He number of specific PC13s
in He system and He number of spares ong~naDy ordered. If a specific PCB fails every 2,000
hours of operation, and there are two in the system, plus one spare, then within a 10,000 hour
operating period, 10 failures can occur. The probability is that a new spare avid be required on or
before five repairs; therefore, within 15,000 hours, replacement of the spare PCB most likely
will be moored.
Where PCBs are repaired by He junsdiction, cost of repair is based on MUIR at the component
replacement level plus cost of materials (replacement components). There is an additional cost
associated with returning the repaired PCB to spares inventory, updating inventory records and
updating PCB repair history log. Similarly, there is a cost associated wad maintaining
component spares inventory. Similarly He cost of test equipment is increased where component
level repair is supported. PCB card testers are necessary and in many cases a 'Dot mockup" of
the subsystem is necessary to verify repair. Where radio frequency communications equipment
repair is accomplished, a special test environment (such as a screen room) to prevent external RF
interference furring alignment of sensitive receiver components, may be necessary. Similarly,
c:\NCHRP`Phase~rpt N~3-51 ~ P~2F~n
A5-12
OCR for page 511
component level repair generally Squires electrostatic discharge (ESD) protection, especially
where CMOS integrated circuits are used.
ESD understanding and training is important for PCB replacement and repair of components on
PCBs. Component repair requires special grounding provisions at He maintenance workbench.
In general, it is too costly to consider acquisition of test equipment to diagnose and test to the
component level for advanced communications equipment PCBs. Similarly, cost of
mainlining skilled technicians for troubleshooting to the component level of a PCI3 and for
Maintaining a component replacement inventory is prohibitive compared to depot level repair.
Where a quality manufacturer is used, generally more reliable board-level repair is obtained by
contact depot maintenance compared wig "do it yourself' junsdictional maintenance. The
reasons are Mat Me manufacturer has:
· Much more sophisticated test equipment for failed component isolation and repaid PCB
operation validlation;
Formal quality test procedures; and
Formal certification of cost of test equipment supporting component level troubleshooting
and repair.
Other factors that contribute to Me Semi for depot maintenance include:
· Cost of component replacement equipment;
· Cost of component inventory;
· Cost of Gaining maintenance personnel for component level troubleshooting and
replacement;
Cost associated with PCB repair damage and replacement; and
t:`NCHRP ~NCHRP3-51 · Phase2FmalRepore A5-13
OCR for page 512
Cost of ESD practication at component level replacement.
Depot maintenance cost to the jumsdiction includes:
· Cost of retulIiing a failed board to the depot;
Cost of receiving He repaired board and returning it to inventory;
Repai} technicians for soldering alla component replacement;
Special tools needed for surface mount component replacement;
Environmental test capability to verify electromechanical connections;
Formal ESD procedures and equipment;
Large inventory of components and, where component part number has changed, an
acceptable replacement part number cross reference must be maintained.
By using depot level maintenance for PCB repair to the component level, the following
jurisdictional costs are eliminated:
Actual depot repair coil changed by the contractor; and
Cost of resolving any unacceptable repair quality problems wig the supplier of depot
maintenance services.
As can be seen, calculations of life cycle cost can be very complex depending on the level to
which Be analysis is taken. In general, during a procurement phase for advanced technology,
cost consideration cannot include all Be details. Thus, it is prudent to consider primarily Be
highly visible and important cost elements including:
· Acquisition cost;
b;WCHR~as~Jpt NCHRP 3-51 ~ Phase 2 final Report AS-14
OCR for page 513
· Cost of operating power over like expectancy;
· InstaBation and test cost;
.
Cost of recommended spares based on fonnal ~BF and numbers and types of PCBs;
System level repairs cost, based on MTBF, MI - , and average cost for maintenance labor;
Depot PCB repair, either flat cost per year or average repair cost and MTBF;
· Cost of test equipment and brining; and
· Cost of data
What is generally found In advanced comrnun~cabons technology is Hat power use is
competitive, as are installation, test, and training costs. Generally, operations manpower is
insignificant. For the same type of technology, Be test equipment required to support
maintenance at Be PCB level is usually equivalent. Thus, Be significant variation is in failure
rates and cost of depot service. Since equipment u ill generally be located in similar locations,
travel time for repair cost only becomes significant in the additional maintenance trips necessary
to service a lower MTBF product. Depot maintenance cost can have significant variation based
on Be manufacturer's use of separate contract maintenance facilities, its production test
facilities, or Bird party maintenance. Similarly, PCB board-level maintenance cost may be
Impacted by shipping cost to depot facilities. Thus a local depot repair facility can save bow
shipping and insurance cost
Cost of data may have significant variations wad some companies charging for manuals
separately, some providing manuals as part of a training program, and some providing manuals
as part of equipment cost. Manuals are required to support instalIabon, test, and corrective
maintenance. Most manuals are copynghted by companies, therefore a sufficient number of
copies must be ordered or permission to copy obtained from the manufacturer so that manuals
ate available for both system support and training.
L:~NCHR~Pba ~NCHRP 3-51 · Phase 2 Fmal Report
A5-15
Representative terms from entire chapter:
test equipment
