uploaded by Chris Dodds - Thorne & Derrick Sales & Marketing Manager
The following information is provided courtesy of Severn Trent Water as part of their series of Lessons Learn Bulletins which highlight the potential use or adoption of products to ensure cleaner, safer and more reliable distribution of water supply – specifically this short update is focussed on duct sealing to prevent pollution of potable drinking water.
Brief Description
The Whitacre / Warwickshire team identified a shortfall in the way cable ducts are sealed following installation of new and the maintenance of existing assets.
This was identified as part of coliform investigations where there is a potential for water ingress into injection chambers, reservoirs and back wash tanks. Lack of correct duct sealing in this instance resulted in water entering a level probe chamber with the potential to pollute potable drinking water.
Several options to securely seal cable ducts have been investigated with support from Water R&D. As a result of findings Asset Creation updated the STW design manual for E&M Plant Electrical Design (DM0106-03) and issued a technical bulletin informing key departments, ensuring that the new minimum standard is adhered to.
Two duct sealing kits were used and approved by PH&S, both provided similar results.
PLEASE NOTE: These kits are not DWI Reg 31 approved and must not be used where direct contact with potable water occurs. Any proprietary seal kit used must be of the type listed in the Water Industry Mechanical & Electrical Specification 3.02 (SPC 0302-W302).
Lessons Learnt
Share at your Comm Cells with your operational and maintenance teams.
• During routine inspections check for any cable ducts which could possibly allow ingress into reservoirs or injection chambers which could lead to a water quality failure?
• Contact either of the above for any assistance for procuring and advice on installing the sealing kits.
• Track any next steps via your Comm Cell, raise WQ U/C and sign off when complete.
Examples of installed duct sealing systems
More info: Filoform Filoseal Seals | CSD RISE Seals
Thorne & Derrick supply an extensive range of underground cable duct and protection covers suitable for LV MV HV cable installations – this includes Tape Tile 11kV and Stokbord Covers 33kV used to protect underground power cables pulled and laid into trenches.
To promote the installation of cable into duct a labour-saving range of cable lubricants is available to facilitate friction-free cable pulling and reduce damage to cables. See our range of cable ducts suitable for low, medium and high voltage power and utility cables.
Key Product Categories: Duct Seals | Cable Cleats | Cable Glands | Electrical Safety | Arc Flash Protection | Cable Jointing Tools | Cable Pulling | Earthing | Feeder Pillars | Cable Joints LV | Joints & Terminations MV HVÂ
Since 1985 Thorne & Derrick based in the UK have been specialist distributors of LV, MV & HV Cable Installation, Jointing, Substation, Arc Flash Clothing & Electrical Safety Equipment – customers include UK and worldwide contractors, specifiers, traders and end-users involved in medium and high voltage cable installations, cable jointing, substation, overhead line and electrical construction.
We are specialist stockists and distributors of 11kV-33kV Cable Joints, Terminations & Connectors from manufacturers including 3M, Pfisterer, Prysmian and Nexans Euromold in a selection of cable jointing technologies including push-on, heat shrink and cold shrink joints and cold shrink terminations.
♦ 132kV Surge Arresters | 132kV Link Box Stockists
MV HV | Medium & High Voltage Power Products, Tools, Cables & Electrical Equipment
by Chris Dodds T&D - estimated reading time 3 minutes
Wildlife induced power outages are increasingly caused by the invasion of rats and rodents into medium/high voltage electricity substations via unsealed and inadequately sealed cable ducts and then gnawing electricity power cables.
Filoform FiloSeal+HD is a duct sealing system that is able to seal large heavy armoured power (multicore XLPE SWA) and high voltage cables in ducts, bore holes or cable transit frames – providing a strong support system using hexagonal tubes building a re-enterable seal with honeycomb structure.
The duct seal system is extensively approved and used by UK utilities, DNO’s and their preferred ICP (Independent Connection Provider) to protect electrical assets and cables within substations typically operating at 11kV, 33kV, 66kV and up to 132kV from rat attack.
The cable duct seal kits have been extensively tested against pressure, pulling forces, chemicals, gases and hydrocarbons for adequate sealing of LV-HV cables against the danger of flood (water ingress) or gas migration.
Recently, testing was carried out to establish the ability of the duct seal system to resist, repel or prevent rat attack through cable ducts into electricity substations and the following post provides information about the test and their conclusions.
TalkTalk suffered a major outage caused by rodent damage to fibre optic cables in 2017.
Sealing Cables & Ducts
Filoform have carried out tests to assess the physical damage caused to the FiloSeal+HD cable sealing sealant by a group of four rats (two males and two females) which are given free access to the duct seal for a period of four weeks.
The FiloSeal+HD comprises of MD+ sealant with hexagonal tubes as the backing product which was positioned within a metal tube.
Each end of the tube was sealed with 25mm of MD+ sealant ensuring that access to the backing product could only be achieved by significant damage to the MD+ sealant.
This tube was mounted in the center of the cage and consequently, the male and female sides of the cage had access to opposite ends of the tube.
Test cage before start of study
 Immediately before rats placed in cage – side exposed to males |
 Immediately before rats placed in cage – side exposed to females |
 After one week of exposure – side exposed to males |
 After one week of exposure – side exposed to females |
 After four weeks of exposure – side exposed to males |
 After four weeks of exposure – side exposed to females |
Duct Seals | Substations
Conclusion
The results at the end of the four week study indicated that there was no apparent difference in the damage caused by the male rats in comparison to the female rats and though the damage increased over the duration of the study the MD+ duct sealant was not penetrated by the rats and the hexagonal backing tubes were not exposed or damaged.
No abnormalities, ill health or behavioural changes occurred to the rats during the study and all four rats achieved satisfactory body weight gain during the exposure period.
Several hard red pieces were observed in the large intestines of one female and in the stomach of one male and one female. There were no other abnormalities observed at the post mortem macroscopic examination at study termination on Day 29.
In conclusion as the hexagonal tubes were not damaged after 4 weeks of exposure with direct access, therefore, it is reasonable to assume that different backing products will be protected to a similar degree, when enclosed by MD+ cable duct sealant.
THORNE & DERRICK are national distributors LV, MV & HV Cable Installation, Jointing, Substation & Electrical Equipment – we service UK and global businesses involved in cable installations, cable jointing, substation, overhead line and electrical construction at LV, 11kV, 33kV and EHV.
Since 1985, T&D have established an international reputation based on SERVICE | INTEGRITY | TRUST.
Contact us for 3M Electrical, ABB, Alroc, AN Wallis, CATU Electrical, Cembre, Centriforce, CMP, CSD, Elastimold, Ellis Patents, Emtelle, Euromold, Filoform , Furse, Lucy Electric & Zodion, Nexans, Pfisterer, Polypipe, Prysmian, Roxtec, Sicame, WT Henley.
Thorne & Derrick invite you to join LinkedIn’s largest LV-HV Electrical Discussion Group : Low & High Voltage Power, Cabling, Jointing & Electricals. Discussion subjects include cable installations, cable jointing, substation, overhead line and electrical construction at LV, 11kV, 33kV and EHV. Network, engage and promote your profile, company or products with over 10,000 influencers.
Refrigerant Plant Control Wiring
Since 1985 Thorne & Derrick based in the UK have been specialist distributors of LV, MV & HV Cable Installation, Jointing, Substation, Arc Flash Clothing & Electrical Safety Equipment – customers include UK and worldwide contractors, specifiers, traders and end-users involved in medium and high voltage cable installations, cable jointing, substation, overhead line and electrical construction.
We are specialist stockists and distributors of 11kV-33kV Cable Joints, Terminations & Connectors from manufacturers including 3M, Pfisterer, Prysmian and Nexans Euromold in a selection of cable jointing technologies including push-on, heat shrink and cold shrink joints and cold shrink terminations.
MV HV | Medium & High Voltage Power Products, Tools, Cables & Electrical Equipment
Sealing Cable Ducts
Filoform FiloSeal +HD is a duct sealing system specified to protect and seal larger heavy armoured power and high voltage cables in LV, MV & HV substation ducts, bore holes or transit frames – the duct seal provides a strong support and cable sealing system using hexagonal tubes building a re-enterable honeycomb structure to resist water, gas and fire.
Re-enterable cable duct seals are easy to apply regardless of the type of cable scenario in the cable ducts as it uses a strong but flexible hexagonal tube structure to support the cable and provide a strong backing for the cable seal.
The duct seal system provides waterproof and gastight sealing of LV-HV and 11kV-33kV power cables into ducts. The FiloSeal+HD is suitable for any cable configuration (single, trefoil cables or multiple cables) contained within one duct and also allows for easy re-entry of the duct seal to add or remove cables or pipes as required.
Filoform Filoseal+HD is covered by a Test Report documenting successful pass status at Nedlab Laboratory for the following – this is based upon using Filoform’s hexagonal support system and sealing cable using their MD+ sealant.
FiloSeal+HD Cable Duct Seals – Honeycomb Structure
Steve Groocock is the Duct Seal Product Manager at Filoform. Below he explains about attending a data centre site where he provided installer training prior to the installation of Filoseal +HD Re-enterable Duct Seal System.
“A skill is something that is learned over a period of time but sometimes it is best to pass along experience to a new user of any equipment, this includes cable duct seals. Recently, I attended site for a company who were working on the LV cabling associated with a new build data centre into an existing building structure.
The LV cable, ducting and electrical distribution system utilised existing switch rooms where possible but in order to add capacity to these areas, new penetration holes for the cabling needed to be added. These holes were core drilled directly through the existing structure. Once the cables had been pulled, there remained clear passages for the ingress of moisture, gas, dust and rodents into cable ducts.
Taking the strips of adjoined hex tubes, insert them around and between the cables to be sealed ensuring the spacing required is maintained – the strips can be inserted as a flat line or rolled to form a tight group of 5. If space is not available, the strip of hex tubes may be torn down to individual hex tubes.
Start at the bottom of the cable duct with the large blue tubes and build up to completion. Should there be heavy cables in the ducts, such as 11kV/33kV high voltage power cables, the hex tubes can be nested i.e. one small tube placed inside the other larger tube. The small light blue hex tubes are used to fill and seal the remaining small gaps in the cable duct. The installer should ensure the tubes are packed tightly to prevent cable movement.
Filoseal+HD duct sealing kits have been tested to provide watertight, gastight and/or fire resistant cable seals and were thus specified to fill in the voids in the concrete core drilled holes at the data centre.
Training took two hours and in this time it was up to me to pass on as much experience as possible at a steady pace so the new installer could take it understand and adopt the knowledge. The installer had previously not seen a duct sealing system like this so I took time to familiarise them with the component parts and how a finished cable duct seal installation should look like by way of a sample in a clear duct replica. I also showed the excellent Filoform HD installation video which can be viewed below.
The hands on training starts with myself and the trainee cleaning and abrading the cables and cable duct for the first 20-25mm inside the hole in the wall – cleaning cloth is provided with the duct seal kit. Preparation is key to the whole system – the most important point I stressed to achieve a hexagonal backing piece between each and every cable to create a reliable water and gastight cable duct seal.
The hexagonal tubes are placed around the cables to be sealed filling up all the gaps using the large and small hexagonal backers to ensure the cable support system is compact and tight resembling a honeycomb structure.
This is explained in the Video and instructions supplied with the duct seal kit but until seen it is not necessarily clear as to why. The space is there to ensure the duct sealant component, called Filoseal MD+, can reach all the areas of the void or cable duct needed to be sealed. This site was particularly challenging as the low voltage cables were held down close and clamped to the work face by cable cleats. However, I moved to the other side of the wall and moved the cables in a pit until my trainee could get the hexagonal pieces between each and every cable and between the cables and the core drilled hole edge.
Here the cables are pictured clamped to the cable channel using trefoil cable cleats as the cables depart the duct which was sealed using Fioloseal type duct sealing mastics.
This is the end of stage one. Once we both looked and examined the backing ensuring there were gaps around the cables to be sealed as specified, we moved on to the addition of the sealing mastic. The cable sealing mastic can be applied using a standard mastic gun, however we recommend investment in a quality installation gun. Once the sealant mastic is loaded in the gun I demonstrated on the lower half of this cable install how to ensure a cable seal by running a good bead around the hole edge on every cable. Once we had gone through several tubes of mastic we brought out the finishing sponge to wipe down and tidy the mastic finish – the duct sealant can take from 4 to 20 days to fully cure depending on local ambient temperatures and air humidity levels. Typically in the UK curing takes 8-20 days and backfilling of the installation should be avoided until at least 10 days after installation.
When backfilling ensure adequate packing is below the sealed cables in the duct before adding materials above the cables. In a vertical cable duct, group together strips or rolled groups of tubes and squeeze them into the a duct as one single unit.
Then proceed to maintain the required cable spacing by adding either large or small tubes (groups of or singly).
Duct Sealing – Preparation Is Key
The mastic should be patted in and around every cable ensuring each and every part of the cable duct seal was treated the same way – this patting motion encourages the cable sealant mastic to adhere to the hexagonal backing. Final checks led me to further pat parts between cables using the sponge edge.”
| Filoform Ref | Cable Duct Seal Description | Max Cable Duct Diameter (mm) | Order Unit |
|---|---|---|---|
| 280010 | FiloSeal+HD – 75mm > 110mm | Ø 110 max. | per piece |
| 280020 | FiloSeal+HD – 125mm > 160mm | Ø 160 max. | per piece |
| 280030 | FiloSeal+HD – 180mm | Ø 180 max. | per piece |
| 280040 | FiloSeal+HD – 200mm | Ø 200 max. | per piece |
| 280050 | FiloSeal+HD – 225mm | Ø 225 max. | per piece |
| 280060 | FiloSeal+HD – 250mm | Ø 250 max. | per piece |
Duct seals suitable for LV-HV power cables in single, trefoil or multiple configurations, including 11kV Triplex and 33kV high voltages
Provides advanced and assured sealing against water and gas for cable ducts, bore holes and openings
Re-enterable sealing system future-proofed for retrofit of new cables or re-routing of existing through cable ducting
Cable duct seals provide protection of substations and basements against flood, fire and gas ingress dangers
Filoseal+HD duct seal system using MD+ has been heavily tested against pressure, pulling forces, chemicals, gases and hydrocarbons for use with low, medium and high voltage cables. Below we can summarise the results from Nedlab Laboratory Test Reports.
| Duct Seal Test Description | Measurement | Result | Pass or Fail |
| Pressure | 2.0 Bar | 1.0 Bar long term, 2 Bar short term | PASSED |
| Pulling Force | 100Kg | 100Kg – 1000 Newtons | PASSED |
| Bend Test | 10xd at 45 Degrees | 10xd at 45 Degrees, with 1 Bar pressure | PASSED |
| Chlorine Gas | 100% for 7 Days | Slight change on colour and texture | PASSED |
| Methane Gas | 100% for 7 Days | Slight change on colour and texture | PASSED |
| Diesel | 100% for 2 Years | Hardly any change | PASSED |
| Petrol / Benzene | 100% for 2 Years | Hardly any change | PASSED |
| Ethanol | 100% for 42 Days | Hardly any change | PASSED |
| AD Blue | 100% for 21 Days | No change | PASSED |
| ASTM Oil | 100% for 2 Years | Hardly any change | PASSED |
| Hydrogen Sulphide (H2S) | 200ppm for 5 Days | Hardly any change | PASSED |
Final Pressure Test – after completion of the bending and pull strength test the cable duct seals are tested at a pressure of 2.0 Bars.
Note the Test Results documented above have been done in accordance with Filoform installation instructions, however values achieved in field installations can vary if the instructions are not followed and results may vary depending on cable and duct tolerances such as cable duct size, material and cable density volume.
Further reading:
THORNE & DERRICK are national distributors LV, MV & HV Cable Installation, Jointing, Substation & Electrical Equipment – we service UK and global businesses involved in cable installations, duct sealing, cable jointing, substation, overhead line and electrical construction at LV, 11kV, 33kV and EHV.
Since 1985, T&D have established an international reputation based on SERVICE | INTEGRITY | TRUST.
Contact us for 3M Electrical, ABB, Alroc, AN Wallis, CATU Electrical, Cembre, Centriforce, CMP, CSD, Elastimold, Ellis Patents, Emtelle, Euromold, Filoform , Furse, Lucy Electric & Zodion, Nexans, Pfisterer, Polypipe, Prysmian, Roxtec, Sicame, WT Henley.Invitation: Thorne & Derrick invite you to join LinkedIn’s largest LV-HV Electrical Discussion Group : Low & High Voltage Power, Cabling, Jointing & Electricals. Discussion subjects include cable installations, cable jointing, substation, overhead line and electrical construction at LV, 11kV, 33kV and EHV. Network, engage and promote your profile, company or products with over 10,000 influencers.
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