Date post: | 05-Jul-2015 |
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Multi Cable Transit Devices:Applications and Design Methods
Allen Gibson, Roxtec Group
Bo Millevik, Roxtec Group
Alan Bozek, EngWorks, Inc.
PCIC MIDDLE-EAST 20142
Summary
• Introduction - Background• Critical components, configurations and proper sizing of cable transits• Protection, ratings & benefits• Applications• Comparing field-based decisions to proven engineering methods• Checkpoints - Specifications for cable entries• Checkpoints – QA / QC for MCT installations• Conclusion
PCIC MIDDLE-EAST 20143
Introduction
• Multi cable transit (MCT) devices commercialized since 1950’s
• Original designs to prevent water and fire passage within submarines and marine vessels
• MCT devices accepted as standard design and safety practice through most marine and offshore oil/gas applications
− DNV, ABS, USCG, Lloyds, etc.
• Today = Transferring the knowledge from marine/offshore to land-based industrial applications
3.7.5cable transit devicean entry device, intended for one or more cables, with a seal made up of one or moreseparate elastomeric modules or parts of modules (modular internal seal), which arecompressed together when the device is assembled and mounted as intended.
NOTE Cable transit devices can also serve as Ex blanking Elements when the elastomeric modules provided allow for this function.
PCIC MIDDLE-EAST 20144
Multi Cable Transits – Simply Stated
• Best value when used for high cable density when more than one demand is present
− Fire+IP− Blast +rodent− Vapor tight + blast− Etc.
• When maintenance, expansion or future access for cables or pipes will be required
PCIC MIDDLE-EAST 20145
MCT Devices – Critical Components
• Frame (window)
• Modules (inserts)− Fixed diameter
− Adaptable layers with core− Insert blocks
• Stay plates (dividers)
• Compression (wedge or unit)
PCIC MIDDLE-EAST 20149
MCT Devices – Configurations
• Flanged
• Non-flanged
• Multiple windows – vertical
• Multiple windows – horizontal
• Combination
• Proper framing of aperture is critical
PCIC MIDDLE-EAST 201410
MCT Devices – Sizing / Packing Space
• Early engineering decisions = project savings
• Get the aperture size correct…FIRST
• Consider spare capacity for future expansions and upgrades
• Communicate aperture size requirements to civil design and building contractors…BEFORE construction begins
PCIC MIDDLE-EAST 201411
Protection: Environmental (IP)
• Most standard MCT designs should have a minimum water tight and dust tight rating equivalent to an Ingress Protection (IP) rating for electrical enclosures of IP 54 as defined by IEC 60529.
• Wall / floor applications for MCT’s should be defined by the environmental performance requirements of the structure
PCIC MIDDLE-EAST 201412
Protection: Blast
• Blast rating EX, ATEX or HazLoc approval
• Cable entries must be considered in design of blast-rated structures, just as doors and windows
• MCT devices are commonly available to provide protection against blast load to >10 psi for > 60 milliseconds.
PCIC MIDDLE-EAST 201413
Protection: Vapor-tight barrier
• Definition – “a barrier that will not allow the passage of significant quantities of gas or vapor at atmospheric pressure”
API RP 500/505
• Effective way of locating non-hazardous rated equipment adjacent hazardous areas
PCIC MIDDLE-EAST 201414
Protection: Vapor-tight barrier
An unclassified room or building may be installed adjacent to a classified area provided a vapor-tight barrier is placed between the hazardous location and the unclassified area.
•Benefits− Reduce on-site wiring costs− Allows equipment to be pre-
commissioned
PCIC MIDDLE-EAST 201415
Protection: Hazardous locations
• Cable transit devices are recognized and approved for use according to IEC 60079-0
• MCT devices used in electrical equipment within hazardous locations MUST be properly certified and labeled
3.7.5cable transit devicean entry device, intended for one or more cables, with a seal made up of one or moreseparate elastomeric modules or parts of modules (modular internal seal), which arecompressed together when the device is assembled and mounted as intended.
NOTE Cable transit devices can also serve as Ex blanking Elements when the elastomeric modules provided allow for this function.
PCIC MIDDLE-EAST 201416
Protection: Earthing, bonding & EMC
«EMC, ElectroMagnetic Compatibility »
•Cable segregation•Single Entry Panel
PCIC MIDDLE-EAST 201417
Protection: Earthing, bonding & EMC
« Metallic layers inside cables should be connected to earth »
•Electrical safety− Protective Earthing− Equipotential Bonding
•Lightning Protection
•Electro Magnetic Interference (EMI)
PCIC MIDDLE-EAST 201419
Protection: Fire Barrier
• MCT’s can provide 30 minute to 4 hour protection as a passive fire barrier
• Jet fire, A60, H60, UL1479 and more
• Some fire rated installations require installation of mineral wool insulation to comply with certifications
PCIC MIDDLE-EAST 201421
Protection: Rodents, Pests, Snakes…
“Have you experienced accidents, downtime or damage from mice, rats,
insects, snakes, etc. in your motor control, switch gear or other electrical cabinets?”
PCIC MIDDLE-EAST 201422
Protection: Rodents, Insects & Snakes
“I've spent quite a few years fixing communications equipment contaminated by ants or dead lizards. Some years ago I had to fix some Optical Fibre equipment where mice had bitten through the fibre to either the transmitter or the receiver; as well as fouling the PCB assembly.”
Electrical Project Engineer
PCIC MIDDLE-EAST 201423
Protection: Rodents, Insects & Snakes
“I'm involved in a project where the 15 kV service-entrance gear to a facility is mouse and rat-infested. They've chewed the insulation on conductors, and generally left trails all over everything….I'd really like to see the building sealed tight.”
John Mhttp://forums.mikeholt.com/showthread.php?t=144240
PCIC MIDDLE-EAST 201424
Protection: Rodents, Insects & Snakes
“Yes. I experienced rodent entry into HV and MV switch gear in different companies I worked with. Twice lizard entered into MV switch gear, caused flash over which led to total power failure. Once a snake entered into 11KV switchgear and resulted in trip of the bus section…”
PCIC MIDDLE-EAST 201425
Protection: Rodents, Insects & Snakes
…In both cases the identified reasons were similar. Openings in switch gear providing access to cable compartment, growth of grass and weeds around the substation and non installation of rodent repeller in the substation. The total power failure was due to failure of protection system and problems with protection coordination.”Senior Electrical Engineer
PCIC MIDDLE-EAST 201426
Work Process & Design Approach
Critical Decision: Field decision or engineering decision?
OR
PCIC MIDDLE-EAST 201427
Work Process & Design Approach
Critical Decision: Field decision or engineering decision?
PCIC MIDDLE-EAST 201428
Work Process & Design Approach
Critical Decision: Field decision or engineering decision?
PCIC MIDDLE-EAST 201429
Work Process & Design Approach
Critical Decision: Field decision or engineering decision?
PCIC MIDDLE-EAST 201430
Project Award FEED
Decision for cable entry methods,
EMC requirements
& project standards
Detailed Engineering
ConstructionEPC Installation Completion
Preliminary MCT
drawings to develop
apertures / cut-out sizing.
Approved Vendor List
Engineering specification
–
Frame configuration
and acceptance
Bill of Material
finalized from final cable schedules
Materials list to relevant
sub-suppliers
Confirm frame specs
Detail design of modules
Logistical services
On-site installation training to contractors & maintenance teams
On site validation
inspections
Project documentatio
n
Work Process & Design Approach
PCIC MIDDLE-EAST 201431
EPC / Design – Required Information Input
MCT Design Software
Issue Cable Transit Schedule
NO: return to MCT manufacturer with Comments
Cable Schedule
Equipment Layouts
Building Layouts
Cable Routing
Cable Specification
Installation Specifcation
Cable type & description
Cable #, routing to/From
Location of Transit
Installation Requirements
Info Share
to Vendor
Cable data to MCT Vendor for Design
Client Input Data to Transit Designer
Transit Detail Drawings
Bill of Material
Certifications & Installation Instructions
Issue specificationCheck
andApproved
Yes
No
MCT Manufacturer – Required Actions and Output
OR
Work Process – MCT Design
PCIC MIDDLE-EAST 201432
Specification Checkpoints for Multi Cable Transits
Variables
•Blast load demands•Fire demands•Environmental (weather) or IP demands•Operating Temperature•Cable retention or pull force demands•Corrosion demands / material requirements•Preferred installation method
•Bonding, earthing, EMC demands
Interfaces
•Application - wall / floor / enclosure
•Structure Material
•Cable
PCIC MIDDLE-EAST 201433
Simple QA / QC checkpoints for MCT installations:
• Fully-tightened compression unit – most common failure point!
• Flashlight / daylight test – if you can see light through the transit, it should be re-installed or compression tightened
• Pull test – a simple pull on the cables will confirm proper installation− Slippage indicates oversized insert block for cable O.D., or− Lack of proper compression
Installation Checkpoints for Multi Cable Transits
PCIC MIDDLE-EAST 201434
Conclusions
• Project owners / end users should develop, then communicate standards for cable entries
− This will increase project safety, improve project efficiencies, and reduce design and installation risks –
− we should learn from offshore & marine markets
• MCT devices are simple, fit-for-purpose solutions that can add protection to your projects, people, equipment and operations against the hazards of blast, fire, weather (IP), rodents and vapors
• MCT devices are available for retro-fit to exsisting openings without removal / re-glanding of cables
• Manufacturers are readily available to provide MCT design support as well as onsite trainings and inspections and should be consulted early in projects to optimize efficiency and safety