multi cable transit devices: applications & design methods, pcic middle east feb. 2014

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


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.


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


MCT Devices – Critical Components

• Frame (window)

• Modules (inserts)− Fixed diameter

− Adaptable layers with core− Insert blocks

• Stay plates (dividers)

• Compression (wedge or unit)


Applications – Walls & Floors


Applications – Terminal / Junction Boxes


Applications – Pre Terminated Connectors


MCT Devices – Configurations

• Flanged

• Non-flanged

• Multiple windows – vertical

• Multiple windows – horizontal

• Combination

• Proper framing of aperture is critical


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


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


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.


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


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


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.


Protection: Earthing, bonding & EMC

«EMC, ElectroMagnetic Compatibility »

•Cable segregation•Single Entry Panel



« Metallic layers inside cables should be connected to earth »

•Electrical safety− Protective Earthing− Equipotential Bonding

•Lightning Protection

•Electro Magnetic Interference (EMI)


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


Protection: Fire Barrier


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?”


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



“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



“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…”



…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


Work Process & Design Approach

Critical Decision: Field decision or engineering decision?

OR


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



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


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


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


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