13-94559-5 ets-53!01!04 standard - underboringer, rørafslutning

8/18/2019 13-94559-5 ETS-53!01!04 Standard - Underboringer, Rørafslutning

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Document no. 13/94559-5 - ETS-53-01-04 v.0

132 - 400 kV AC Cable projects

Technical standard for cable components

HDD Casing termination

ETS-53-01-04 Rev. 0

T e c h n i c a l s t a

n d a r d


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Standard for HDD Casing terminations

Document no. 13/94559-5 - ETS-53-01-04 v.02 /18

REVISION VIEW

Document no.: 13/94559-5

Version Author Document status/change Reviewer Approver DateA KNK First draft USG 04-12-2013

B KNK Second draftUSG, POP, HHO,JSL

19-12-2013

C KNK Final draft SDO, HRI 19-12-2013


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Document no. 13/94559-5 - ETS-53-01-04 v.03 /18

Table of contents

1. Introduction .................................................................................................... 4

2. Standards and regulations .............................................................................. 4

3. Functional requirements.................................................................................. 5

4. Technical requirements ................................................................................... 6

5. Design requirements ....................................................................................... 7

5.1

Clean

Casing

............................................................................................................

7

5.2

Casing

edges

.........................................................................................................

10

5.3

No

air

bubbles

.......................................................................................................

12

5.3.1

HDD terminations at the same height ............................................................................... 13

5.3.1

HDD terminations with a significant height difference ..................................................... 13

5.4

Properties

of

the

sealing

method

..........................................................................

14

5.4.1

Sealing plug ........................................................................................................................ 14

5.4.2

Sealing cap ......................................................................................................................... 16

6. Documentation ............................................................................................. 18


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Document no. 13/94559-5 - ETS-53-01-04 v.04 /18

1. Introduction

This standard specifies how Energinet.dk chooses to finish the casing terminations at

Horizontal Directional Drillings (HDD), both before and after cable pulling. This standard isfocused on minimizing any risk for cable damage, there might be due to non-optimal

handling of casing termination for HDDs.

The standard is for all cable projects using Horizontal Directional Drillings (HDD).

2. Standards and regulations

There are no standards or regulations regarding the casing termination. However there are

some guidelines of how the HDD itself should be performed and some standards for the

casing.

HDD Consortium: Good practice guidelines

http://boretekinc.com/documents/front.pdf

HDD Practice Handbook

By H.J. Bayer © Vulkan-Verlag GmbH

Guidelines for Use of Mini-Horizontal Directional Drilling for Placement of High

Density Polyethylene Pipe

http://plasticpipe.org/pdf/tr-46-hdd-guidelines.pdf

The Danish NO-DIG control

http://www.nodig-kontrol.dk/default.htm

DS 475:2012 Code of Practice for trenching for underground pipes and cables

DS/EN 12201:2011 Plastics piping systems for water supply, and for drainage andsewerage under pressure – Polyethylene (PE)

Part 1: General - Part 2: Pipes - Part 3: Fittings


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3. Functional requirements

There are overall four functional requirements that must be addressed; Clean casing,

casing edges, no air bubbles and properties of sealing method.

In order to ensure clean casing, the empty casing shall be sealed before cable pulling. If

the casing is not correctly sealed, animals and soil can enter the HDD casing. If the casing

becomes scratched on the inside due to soil or animals, the contractor must perform extra

cleaning. The reason for this is that the cable insulation must not be damaged on small

rocks and unevenness in the casing, when the cable is pulled through the casing.

An important measure to take, when the cable has been pulled through the casing, is to

make sure that the cable will not be damaged due to the casing edges. The casing edges

can be sharp, and can cause damage on the cable insulation, if no precautions are taken.

Cable damage, with either material penetration or pressure damage, must be avoided.

For heat dissipation, the casing shall be filled with special Bentonite after cable pulling. For

optimal results, the Bentonite shall evenly surround the cable inside the casing. No air

bubbles are allowed inside the casing, as the surrounding thermal resistivity will increase in

case of air bubbles, resulting in hotspots. This can affect the cables loading factor, and in

worst case cause thermal damage to the cable. To ensure that there are no air bubbles

inside the casing, a ventilation pipe must be used, which allows the air to escape the casing

when filled up with Bentonite. The Bentonite shall be filled in the casing, using a filling pipe.

The Bentonite must be non-hardening, such that the cable can be flushed out of the casing,

during the next 40 years of service.

To ensure that the Bentonite stays inside the casing it must be sealed off. The casing will

be sealed off with different methods depending on the scenario.

The first scenario is when both casing terminations are on land with no significant

difference in height. The sealing method before cable pulling in this scenario will be called a

“Blanking cap” and the sealing method after cable pulling will be called a “Sealing plug”

The second scenario is when both casing terminations are on land with a significant

difference in height. The sealing method before cable pulling in this scenario will be called a

“Blanking cap” and the sealing method after cable pulling will be called a “Sealing plug” at

the “high point” termination and a “Sealing cap” at the “low point” termination.

The third scenario is when one casing termination is on land and the other is under

water. The sealing method before cable pulling in this scenario will be called a “Blanking

cap” at the land termination and a “submarine blanking cap” at the submarine termination.

The sealing method after cable pulling will be called a “Sealing plug” at the land termination

and a “Sealing cap” at the submarine termination.


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4. Technical requirements

Following are the technical requirements for the casing termination:

The blanking cap must be at minimum IP54 tight.

The submarine blanking cap must be a prefabricated Polyethylene High Density

(PEHD) cap (IP68 tight).

The wire for cable pulling must be mounted on the inside of the blanking cap.

The sealing cap must be a prefabricated Polyethylene High Density (PEHD) cap

(IP68 tight), with holes for the cable and pipes.

The sealing cap and submarine blanking cap must be mounted on the casing flange

for a submarine termination.

The sealing plug must be made from Bentonite pellets.

The Bentonite pellets used for the sealing plug must be filled minimum ½ m and

maximum 1 m into the casing. The sand in the HDD pit must be able to withstand the pressure from the Bentonite

filling of the casing, to ensure that the sealing plug does not blow out.

The cable must not have contact with the casing edge when the HDD pit is closed.

The cable must be supported e.g. by sandbags in the HDD pit to ensure that the

cable does not get insulation- or pressure damage.

The cable must be protected by a cover plate which is placed approximately 20 cm

over the cable in the HDD pit.

The cable must be protected by warning net which is placed approximately 70 cm

under ground level of the HDD pit.

The ventilation pipe must not exceed more than 15 cm through the sealing plug or

sealing cap.

The end of the casing must be at least ½ m into the HDD pit from the earth wall.

The inner diameter of the casing must be 2 – 2½ times larger than the cable

diameter.


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5. Design requirementsIn this section on Design requirements, it is described how the termination of a HDD casing

must be performed.

5.1 Clean Casing

As described in the functional requirements, a blanking cap must be mounted on the empty

casing. The blanking cap must be mounted to prevent soil and animals from entering the

casing. The casing must be completely clean from soil before cable pulling. This cleaning

process will become more difficult if soil has entered the casing during casing installation.

In the case of a land termination, the standard blanking cap which is mounted on the

casings upon delivery can be used for sealing off the terminations until cable pulling. This

can easily be fitted to the end of the casing that will not get pulled through the borehole.

However it cannot alone be used on the end of the casing that will get pulled through the

borehole.

For the casing end that gets pulled through the borehole the contractor must weld a PE

plate. The contractor must remove the PE plate and attach the standard blanking cap after

casing installation. The reason for this is that the standard blanking cap is not strong

enough to withstand the pressure during the pulling which will result in soil and drilling

mud entering the casing.

Figure 1 – Standard blanking cap


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If the casing is placed in a wet environment or if there will be a long time before the cable

will be pulled in the casing, it is not allowed only to use the standard blanking cap. In this

case an alternative blanking cap can be made from fittings for PVC pipes (sewage pipes).With a flexible coupling and a PVC socket plug, a blanking cap can be made to almost all

sizes of casings

The flexible coupling is attached on the end of the casing with the clamp and the PVC

socket plug is attached to the other end of the coupling with the other clamp. This will

ensure that the casing is completely watertight.

Figure 2 – Left: Wavin flexible coupling1 , Right: Wavin PVC socket plug 400 mm2

Figure 3 – Alternative blanking cap: Coupling and PVC socket plug attached on a casing

To minimize the risk for soil entering the casing during cable pulling the casing end must be

at least ½ m into the HDD pit from the earth wall. This is illustrated on Figure 7.

1 http://www.multikoeb.dk/overgangskobling-3503/overgangskobling-f-240-265mm-t-335-360mm-euro-ig-beton-

p166391 2 https://www.bd.dk/da-dk/vand-afloeb/kloakering-og-broendgods/kloakroer-kloakfittings-og-tilbehoer/fittings-til-

glatte-kloakroer/p-192252001/wavin-pvc-prop-400-mm


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In the case of a submarine termination, the standard blanking cap cannot be used. In this

case the contractor must weld a standard flange on the casing which will be used for a

submarine blanking cap. The submarine blanking cap is bolted on the flange and can easily

be removed by a diver when the cable is to be installed.

Figure 4 - Submarine blanking cap attached to standard flange

Figure 5 - Submarine blanking cap

The contractor must attach the pulling wire on the inside of the blanking cap in all cases

and the pulling wire must be completely clean from soil before it is installed in the casing.


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5.2 Casing edges

To prevent mechanical damage of the cable, the cable must be lifted from the casing edge

both during pulling and after the HDD pit is closed. To prevent insulation- and pressure

damage, the cable is lifted from the edge by sandbags outside the casing. This must bedone, as a first step after the cables are pulled through the HDD casing. If the HDD pit is

completely dry, the contractor can use the thermal backfill for cable support.

Figure 6 shows an example of sandbags which can be used to support the cable.

Figure 6 - Sandbags3

3 http://www.allstakesupply.com.au/Sand-Bags


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Figure 7 and Figure 8 show how the HDD pit shall be closed. At the bottom layer of the pit,

the thermal backfill must be stiff compressed. The sand must support the sandbags, for

proper support of the cables. Water must therefore be kept from wahsing the supportingsand and sandbags away. Only when needed, gravel can be used underneath the sand, for

ensuring proper support. This will make sure that the water can get away from the HDD

pit. 30 cm of normal thermal backfill, as used in the cable trench, shall be placed on top of

the cables, under the reestablished surrounding soil.

Figure 7 – Example of HDD pit cross section with sandbags.


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To protect the cable there must be a cover plate and warning net, as used in the cable

trench. The cover plate is put in the thermal backfill approximately 20 cm over the cable

and the warning net is put in the soil, approximately 70 cm beneath ground level.

5.3 No air bubbles

At the casing termination, the ventilation pipe must be pulled through the sealing plug in

order for air to escape. However it must not exceed more than 15 cm through the sealing

plug. This is illustrated in Figure 9.

Figure 9 – Ventilation pipe at the casing termination

Figure 8 – Example of cable trench cross section with cables.


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5.3.1 HDD terminations at the same height

When the two HDD terminations are installed at approximately the same height, two

ventilation pipes must be used; one in each end of the casing. This allows the air to escapethrough both terminations when the Bentonite is filled in, from the centre of the HDD. This

is shown in Figure 10.

5.3.1 HDD terminations with a significant height difference

HDD terminations with a significant height difference could for instance be the case for a

submarine cable landfall or a drilling from the top of a hill to the bottom. In this case there

shall be used a minimum of one ventilation pipe, which is placed at the higher point of the

casing and it is important that the filling pipe is pulled all the way to the lower point of the

casing.

When the Bentonite is filled from the “low point” termination of the HDD, it will fill the

casing from the bottom to the top. Therefore, the air will be pressed up towards theventilation pipe, where it can escape the casing. This is shown in Figure 11.

Figure 10 – HDD terminations at the same height

Figure 11 – HDD terminations with a significant height difference


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In the case of a large difference in height between the two termination points, the pressure

on the lower termination can get very high. In the case where the pressure is so high that

the sealing plug will get blown out of the casing, a sealing cap must be used. This sealing

cap is described in chapter 5.4.2.

5.4 Properties of the sealing method

Leaking of Bentonite is under no circumstances allowed, and must be avoided at all time.

5.4.1 Sealing plug

Before the Bentonite is filled into the casing, it must be sealed off to remove any possibility

for a Bentonite leak.

In the case of a land termination the casing is sealed off with Bentonite pellets. These

Bentonite pellets must be a product similar to DantoPlug or Cebogel QSE. These are 100%

natural sealing materials with a high swelling capacity and swelling pressure which makes it

suitable for sealing off the casings. These products will begin the swelling process after

approximately ½ hours and will swell up to 800% after 24 hours. This means that they are

fairly easy for the contractor to control and make a good and solid sealing plug.

Figure 12 - Example of Bentonite pellets to be used for sealing plug.4

4 http://en.eijkelkamp.com/products/water/hydrological-research/groundwater-monitoring-pipes/bentonite-

pellets.htm


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The sealing plug must be placed in the casing after placing cable and pipes correctly. The

sealing plug must consist of Bentonite pellets and shall be installed with a thickness of ½ m

– 1 m into the casing. To reduce the use of Bentonite pellets the contractor must use a

backstop made of old towels or cloths. When the Bentonite pellets harden they will fixatethe cable and pipes. Figure 13 shows how the Bentonite sealing plug covers the cable and

pipes. Only after the Bentonite pellets are hardened and in place, can the Bentonite be

filled in to the casing.

Figure 13 – Cross section of sealing plug


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5.4.2 Sealing cap

In the case of a submarine termination or a land termination with large height difference, it

is not possible to use a Bentonite sealing plug to seal off the casing. In this case a special

sealing cap must be used. This sealing cap must be made of Polyethylene High Density(PEHD) and have a hole for the cable, and perhaps a communication- and/or ventilation

pipe. The specific type and thickness of the PEHD sealing cap can vary from different

projects, depending on the pressure from the filling of Bentonite.

The cap shall be bolted to the casing flanges with the cable and pipe pulled through the

holes. To ensure that the cap is watertight, rubber insulation must be used surrounding the

cable and pipes.

Figure 14 – Left: PEHD sheets5 , Right: Rubber insulation sheet 6

5 http://www.blockenstock.com/15x-75x113mm-pehd-500-

blanc/product_info.php/products_id/3083?osCsid=439eed32d8a6c6d629ed63b657469efd

6 http://www.indiamart.com/ecotherminsulation/rubber-insulation.html#closed-cell-nitrile-rubber-insulation


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Figure 15 shows an example of how the sealing cap shall be made. This example is for a

sealing cap made by Energinet.dk

Figure 15 – Sealing cap


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6. Documentation

The documentation for the casing termination must include:

Type of blanking cap used. The procedure for constructing the sealing plug.

The procedure for constructing the sealing cap, including drawings.

The Bentonite filling procedure.

The ventilation pipe layout.

Drawings and photos of the casing termination.

A Description of the HDD pit layout, including drawings.

A plan for preventing Bentonite Blow outs.

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