Roxtec Cable Seals – Sealing Cable Ducts In Substations Under Running Water Conditions (VIDEO)

Published 20 Jun 2017

Roxtec Cable Seals

Sealing Cables

  • uploaded by Chris Dodds | Thorne & Derrick Sales Marketing Manager
    Author | Gavin Cornall from Roxtec 
Gavin Cornall (Roxtec)

Gavin Cornall (Roxtec)

Roxtec are the world leading manufacturer of cable and pipe sealing transits to protect against water ingress, gas migration and fire spread.

The following article by Gavin Cornall (Global Sub-Segment Manager T&D at Roxtec UK & Ireland) discusses cable sealing applications during running water or “flood” conditions.

Firstly, running water presents a major sealing issue for the installation of mastic type seals, curing and drying is almost impossible. This can place “stress and strain” on work programme completion times, especially approaching handover phase.

Roxtec Distributor

Secondly, this applies to any solution used to seal large power cables whether in a one cable, one duct format or passing in a trefoil formation through a larger duct. Such as 11kV and 33kV power power cables feeding MV substations.

The ability of the cable seal to provide reliable operation under high water pressure is essential – the flexibility of the cable seal to be installed during running water conditions is equally crucial.

Roxtec have inspected many seals where over time the cable has caused the sealant to rip or pull out of the substation wall.

Roxtec have also seen due to the weight and orientation of the cables, its almost impossible for the installer to space the cables to get sufficient coverage of compound around the cables to maintain a seal.

Roxtec Cable Transits

Roxtec Cable Transits provide effective protection to LV HV substation cables against flood damage and water penetration be it in dry or wet conditions.

In the Whitepaper we commissioned from EA Technology on Humidity Effects In Substations, I was pleased to see the emphasis on cable retention, both in normal and fault conditions.

It highlighted what I already thought, which is that without the ability to retain, the cable seal will fail over time.

The cable seal may fail on day 1 or year 1 but ultimately it will fail over time.

Cable Sealing – Key Considerations

I would ask the following questions when evaluating cable sealing technology options from either a design, specification or installation perspective.

1) Can it be installed in “running water conditions” – if yes, look a little deeper into what that actually means.

  • Do you have to buy additional cable seals so you can install on both sides of the wall?
  • Do you have to follow a special methodology which is more onerous than the normal installation?
  • Is the installation sealed instantly or is there a drying or curing time? Is this still dependant on staying dry for an extended period?

2) Can the cable sealing solution cope with the weight and flex in operation?

  • I would always ask what is the pull out force needed to pull out the cable from the cable seal or sealant?
  • If that retention is based on unistrut or clamps on racking it won’t work as the cable will still move in operation at its point of seal.

Roxtec UG Cable Seal

Advanced Specification Sealing For MV Substation Cable Ducts

When Roxtec developed the UG range, we had a very specific set of tests in mind given our understanding of these 2 issues. We developed a cable seal that was even better than our blue rubber on constant pressure. We quickly realised it could be installed on running water just like its blue cousin, the Roxtec Multidiameter cable seal module.

But most importantly, Roxtec developed specific testing for cable retention and flex.

Roxtec UG Substation Cable Seals

We wanted to show Roxtec cable sealing solutions could maintain their seal, whilst the cables were pulled, bent and twisted, beyond the maximum bend radius of the cable.

All this whilst we cycled the temperature between +4ºC to +40ºC.

Needless to say it not only worked but it went beyond our expectations.

Our Roxtec H3 200 seal in fact had in excess of 3300nm put on it without failure, that’s over 336 kgs of pull out force!

So in conclusion, I would say if you only take one thing away from reading this article it is always consider: 1) Running Water Installation 2) Cable Retention Performance

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T&D distribute the most extensive range of LV, MV & HV Cable Jointing, Terminating, Pulling & Installation Equipment – we service UK and international clients working on underground cables, overhead lines, substations and electrical construction at LV, 11kV, 33kV and EHV transmission and distribution voltages.

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