MBE 102Version 4 enPage1 (9)

Procedure and requirements for installation ofELECTRICAL EQUIPMENT
Heading
Special Processes and Tools / Designation
MBE 102
Version
4 en

Content

1GENERAL

1.1Scope......

2DefinitionS......

3INSTALLATION REQUIREMENTS......

3.1General......

3.2Requirements according to Nuclear Regulations......

3.3Standardisation......

3.4Tools......

3.5Inspection and calibration......

4INSTALLATION......

4.1Pulling cables out, checking maximum tensile force......

4.2Installation of Telecommunication and Computer Network Cables

4.3Removal of cable sheaths......

4.4Stripping of conductors, stripping......

4.5Stripping of coaxial cable etc......

4.6Connector crimping......

4.7Soldering......

4.8Mixing and application of potting compounds for connectors..

4.9Application of shrink tubing over crimped joints etc......

4.10Torquing of circular connectors......

4.11Torquing of screws......

4.12Expanding fasteners......

4.13Installation of permanent seals in wall or floor Entrances for cables

4.14Temporary seals......

4.15Touch up Painting......

1GENERAL

1.1Scope

MBE 102 covers processes which affect quality and which are difficult or impossible to completely verify through inspection and testing, and any deficiencies do not become apparent until after the object has been taken into service. These processes are also characterised by being repeated many times during an electrical installation project.

MBE 102 also comprises the tools used in these processes.

2DefinitionS

Crimping

A procedure whereby the terminals ferrule is crushed over the stripped cable end, forming a gas tight seal.

Sheath Removal

A task in which the cable sheaths is removed by means of a special tool or methods.

Stripping

A task in which, the conductor insulation is removed by means of a special tool of method.

3INSTALLATION REQUIREMENTS

3.1General

There are a number of processes, referenced in paragraph 1.1, which occur in conjunction with electrical installation, such as crimping, shrink tubing joints, installation of expanding fasteners in concrete etc. The results of these processes must be quality assured by using defined methods, specially trained personnel and by ensuring that materials used comply with specified requirements.

3.2Requirements according to Nuclear Regulations

Special nuclear requirements apply to safety classified components and equipment (function class 1E) such as being able to withstand DBE/DBA.

The requirements with which each specific equipment must comply are noted in the Technical Specification. Special Swedish extra requirements might apply in addition to international standards.

3.3Standardisation

The Swedish standard for testing crimped terminals on copper conductors is SEN 24 50 10. The corresponding standard for aluminium conductors is SEN 24 50 12.

3.4Tools

Tools shall be intact and clean, highly suitable for the purposes for which they are used, and approved by the supplier for the application.

3.5Inspection and calibration

Inspection and any calibration of tools shall be done before work begins and at the end of work, and at prescribed intervals during the time that work continues.

The routines for inspection and calibration are noted in the OKG/FKA quality assurance system.

Stripping tools for sheath removal on cables, or stripping of conductors shall be adapted to suit the relevant type of cable before use, so no damage is caused. See paragraph 4.3.

4INSTALLATION

The following tasks shall comply with OKG/FKA quality assurance requirements, as in item 3 above.

  1. Pulling out cables, checking maximum tensile force
  2. Installation of telecommunication and computer network cables
  3. Sheath removal
  4. Stripping of conductors
  5. Stripping of coaxial cable etc.
  6. Crimping
  7. Soldering
  8. Equipment for mixing and applying potting compound on connectors
  9. Application of shrink tubing over crimped joints etc.
  10. Torquing of circular connectors
  11. Torquing of screws
  12. Expanding fasteners
  13. Sealing of wall and floor penetrations for cables
  14. Touching up paintwork

Detailed descriptions of these tasks are found in MBE MI. The requirements in item 3 above shall be followed when new installation instructions (MI) are drafted.

4.1Pulling cables out, checking maximum tensile force

The way in which the tension tester should be connected to the cable and the strain gauge or strain failure links must be applied is described in MBE MI 1105. It is important that the cable is not subjected to a greater load than permitted. If a strain gauge is used, it shall be provided with peak value indication. The maximum tension stress shall be calculated from the table in MBE MI 3004.

4.2Installation of Telecommunication and Computer Network Cables

Requirements according to MBE801C.

4.3Removal of cable sheaths

The insulation of conductors and any screen used must not be damaged when the sheath is removed. This can normally be done in two ways, please refer to MBE MI 1106 and 1107.

  • A “notch” is made in a ring around the cable, using a cutting tool at the point where the sheath is to be removed, and along the cable from this point to the end. The sheath is then split away from the cable. The tool should be set so that the depth of cutting does not exceed the thickness of the sheath and risk damaging the conductor insulation or shield.
  • A cutting tool is used, in which the knife is hook-shaped, and the end is provided with a “sledge” which is inserted beneath the sheath and then cuts up along the cable to the desired length.

Special instructions may apply to individual cables.

4.4Stripping of conductors, stripping

When conductors are striped, the insulation shall be removed, leaving bare metal, for connection to screw terminals, crimping etc. The individual wires in the conductor must not be damaged. The insulation shall terminate with a distinct edge. The length of stripping shall be adjusted to suit the object to be connected. The tool shall be adapted to suit the conductor and the type and thickness of insulator. Stripping tests shall be made to check that the requirements are met. Checks shall be made whilst work is in progress to ensure that quality is maintained, please refer to MBE MI 1109.

4.5Stripping of coaxial cable etc

When coaxial cables etc are stripped, special tools with built-in knife cassettes shall be used, adjusted to suit the type of cable and the pattern of stripping, please refer to MBE MI 1108.

4.6Connector crimping

Crimping is a method of electrical connection, in which a terminal is crushed around a conductor in such a way that the joint is given suitable electrical and mechanical properties.

The properties of a crimped joint depend on the reduction of area of the conductor and the terminal together, which are achieved by the press tool.

The press tool together with the conductor and terminal shall be chosen so that they give the reduction in area, which provides the best possible properties. The curve in Figure 1 describes the correlation between the reduction of area and the mechanical and electrical properties.

Figure 1“Correlation between reduction of area, mechanical and electrical properties.”(100% is the total metallic area before pressing.)

Stripping of conductors shall be done in connection with crimping. This is particularly important for aluminium conductors.

Sample crimping shall be done in accordance with SEN 24 50 10 or 24 50 12 for each new combination of crimped components, conductors and tools, such as conductor area expressed in AWG and crimped components in mm², parallel joints with different areas and differing number of wires in the conductor. The combination of press tools, crimped components, types of conductors and result of crimping shall be documented.

Avoid crimping solid conductors

ASEA TB 2084.007-1 applies to crimping of Combiflex sleeves.

Crimped components with “press burrs” must not be used. Poor crimping must never be improved by renewed crimping. Cut the terminal off and install a new one!

Crimped components must only be crimped once, unless special instructions specify otherwise

Moulding or other work on conductors, such as twisting tighter than normal pitch, tinning or soldering must only be done in accordance with special instructions.

4.7Soldering

Soldering should be avoided. If soldering has to be done anyway, it should be done in accordance with the commonly accepted standard as in TBE 105. The standard to be used shall be chosen by the responsible designer.

4.8Mixing and application of potting compounds for connectors

Some connectors and encapsulations need to be filled with potting compound to comply with the requirements for environmental endurance for safety classified equipment. This means that the potting compounds in combination with the cables and connectors/ encapsulations have been tested and qualified for their applications. It is necessary to follow the manufacturer’s instructions for treatment and preparation of the potting compounds and any pre-treatment with cleaner and primer etc on the surfaces to which they are to be applied, in order to achieve the desired properties. Potting compounds are basically applied in accordance with the following steps:

  1. Establishment of a workplace for potting
  • Clean and sufficiently large area, well lit and with ventilation complying with National Board of Occupational Safety and Health requirements. No activities must be in progress in the area of work.
  • Clean vessels and stirrers for mixing the various components of the potting compound and any primer etc.
  • Facilities for measuring temperature, humidity and time to permit hardening or drying to take place in the correct manner. An oven may be necessary to raise the temperature or controlled conditions. The temperature of the oven shall be registered during the entire process.
  • Facilities for measuring the hardness of the potting compound may be needed for some grades.
  • Space for storing products in use and finished products
  1. Check that the conductors are correctly connected in the connector or encapsulations.
  2. Cleaning and pre-treatment of cable/conductors and connectors/housings.
  3. Mixing and pre-treatment of potting compounds.
  4. Application of potting compounds.
  5. Hardening/drying
  6. Inspection, testing.
  7. Documentation of completed work and batch of potting compound etc.

4.9Application of shrink tubing over crimped joints etc

The purpose of the shrink tubing is to insulate the joint, to make the mechanical and electrical properties similar or better than the insulation of the conductor. It is a requirement that the shrink tubing should seal securely against the conductor, so that no current paths are formed between the conductor and the shrink tubing where moisture, free water etc can cause a conductive path and lead to stray currents. In other words, there is a special process, which is intended to generate this seal with the desired properties in a secure manner.

Shrink tubing is shown in MBE MI 1104, which is applied on top of straight joints, but should be possible in principle to use on other similar applications where desired.

The type/grade and dimensions of shrink tubing to be used is normally specified in MBE 400.

If the tubing is to function correctly, the object to be surrounded must have dimensions which suit the area of application of the shrink tubing, i.e. the largest and smallest diameters after shrinking. If the conductor for an object with considerably smaller diameter, or if the shrink tubing is too large, so-called shimming will have to be used. Please refer to MBE MI 4018.

Shrink tubing must be heated to the specified temperature. Please refer to MBE MI 1103.

4.10Torquing of circular connectors

The sections of the connector must be torqued, unless otherwise specified, to give secure function and durability. Please refer to MBE MI 1102.

4.11Torquing of screws

Screws must be torqued with a calibrated torque wrench. Once a screw has been torqued until the torque wrench triggers, the screw or nut shall be marked. Recommended tightening torques for electrical connections are found in MBE MI 1101

4.12Expanding fasteners

Expanding fasteners are used for fixing components in concrete walls and joists when cast-in fixings are not found. Expanding fasteners may be used for seismic installation.

If it isn’t possible that few full fit-up will produced washersareput in with surface conditioning ¹. Expanders will be assembled with the tightening torque that is stated of the producer or design engineerinstructions.

Assembly of the attachment will take place according to the producer's installation instruction. Before paste-up is rinsed the drilling hole from drilling flours and the drilling hole control is measured.

Fasteners shall be installed in accordance with the manufacturer’s recommendations.Beforemounting is rinsed the drilling hole from drilling flours and the drilling hole measured.

Product/types of expander exists described in MI 5302 and MI 5303

¹ According to TBY

4.13Installation of permanent seals in wall or floor Entrances for cables

The seals are intended as fire barriers and, in some cases, to be gas and pressure tight when used between the dry well and the wet well of the reactor containment. Seals are therefore of great importance for a safe reactor shutdown.

Cable pulling through fire cell boundaries must be carefully planned to avoid putting the integrity of the fire cells out of order.

All holes/apertures made in the building drawingsby the structural engineer in charge. These documents are to be used as control documentation at the erection works acceptance procedure.

Installation of the seals shall be performed in accordance with the manufacturer’s directions and with a particularconsideration to the statements listed below.

When compressionseals with packing elements, such pieces asmodule seals are used, it is particularly important to plan the works by making a RG plan, to select the appropriate packing elements, in order to obtain an accurate seal to the cable and the frame. When pressure-proof versions are used, it is important that cables, packing elements and frames are lubricated to facilitate the settling of the components and in accordance therewith, to achieve a better seal. The seals should be allowed to settle for 24 hours before pressure tests are made.

It is important that packing elements, cables and frames are carefully cleaned before the seals are installed.

When cabling is performed through existing wall entrances, all packing elements concerned must be replaced.

As times goes by the packing elements are ageing and their elasticity will decrease which leads to a deterioration of the sealing capability. When cabling is performed through wall entrances with ageing elements, all packing elements concerned must be replaced.

Sealing material for fire protection, such as Fire Seal, must be handled by specially trained personnel. The sealant emits silicones, which could damage electrical equipment, such as machines with commutators, switches, relays etc. When the sealant is used in the vicinity of such equipment, an exhausting air device or some other approved method must be used to prevent harmful dispersion. It is also important to keep the working area clean to prevent the substance to spread.

Product/types of fireseals exist described in MI 5206, MI5207, MI5208, MI5209, MI5210 (3) and (4).

4.14Temporary seals

While works are ongoing, temporary seals shall be used for a limited time.

Aperturesperforating fire cells shall be sealed immediately after the aperture is made with exception of the time needed for the cabling through the aperture.

The time for changing the temporary seals to permanent ones shall be scheduled by other instructions or plans.

Fire stop bricks and fire stop cushions are to be used as temporary seals please refer to MI 5211.

4.15Touch up Painting

Touch up painting may only be performed as directed in TBY (Technicalrequirementforsurface conditioning) which is a document, common to the Swedish Nuclear Plants.

2006-02-23(mbe102en)