3M Scotch 23 Rubber Splicing Tape

Overview

3M Scotch 23, full name Scotch Rubber Splicing Tape 23, is a black, 30 mil (0.76 mm) premium grade self-fusing tape made from ethylene propylene rubber (EPR) and supplied on a removable polyethylene liner. It is one of the best known cable jointing materials in the electrical trade because a single roll can insulate a low voltage splice, pad a connector on a medium voltage joint or rebuild insulation on a cable up to 69 kV. The 3M Scotch 23 is self-certified to ASTM D4388 Type III, is rated 90°C continuous with 130°C emergency overload, and is halogen free to IEC 61249-2-21.

Seven Star LLC supplies 3M Scotch 23 to power utilities, oil and gas operators, water and desalination plants and electrical contractors across the Sultanate of Oman and the GCC. Whether the job is a motor lead repair in an Interior Oman pump station or a cable fault repair at a Sohar industrial site, we provide the 3M data sheet, discuss the jointing method with your engineers and offer engineering support from Muscat.

Working Principle

A self-fusing, or self-amalgamating, tape has no conventional adhesive. Instead, the uncured or lightly cured EPR backing of the 3M Scotch 23 bonds to itself when it is stretched and wrapped, so overlapping layers merge into a single homogeneous mass of rubber insulation. The data sheet confirms this behaviour with a fusion test at 300 percent strain. Because the layers become one solid body there is no layered interface along which moisture or electrical tracking can creep, which is exactly what high voltage splice insulation needs.

Electrically, the tape gives a minimum dielectric strength of 700 V/mil (27.6 kV/mm), and retains at least 90 percent of that value after 96 hours at 23°C and 96 percent relative humidity. Volume resistivity is at least 10¹⁴ ohm.cm at 50 percent RH and 10¹³ ohm.cm at 96 percent RH. Maximum permittivity is 4.0 and maximum dissipation factor 5 percent after water immersion at both 23 and 70°C. A nominal thermal conductivity of 0.15 W/m-K helps the splice shed heat generated in the connector.

Engineering Design of the 3M Scotch 23

The backing is a 0.76 mm EPR compound with minimum tensile strength of 1.7 MPa and minimum elongation of 700 percent, so it can be pulled hard during wrapping without breaking. It passes ozone, UV and heat resistance tests (seven days at 130°C) under ASTM D4388, which matters for outdoor joints and for terminations near hot equipment. The liner keeps the roll from fusing to itself in storage and is peeled off as the tape is applied.

For installation, 3M specifies successive half-lapped layers with the tape highly stretched throughout the whole application, so the width is reduced to a minimum of three quarters of its original value, until the required build-up is reached. As general jointing practice, the 3M Scotch 23 build-up is then covered with a vinyl jacket tape for mechanical and UV protection. Shelf life is five years from manufacture when stored between 10 and 27°C below 75 percent RH, and the tape is made in Brazil.

Key Features

The features that make 3M Scotch 23 a standard item in jointing kits are listed below.

• Primary insulation for cable splices and terminations up to 69 kV per ASTM D4388 Type III.
• Self-fusing EPR backing that bonds into a void-free, homogeneous insulation mass.
• Rated 90°C continuous with a 130°C emergency overload rating.
• Minimum dielectric strength of 27.6 kV/mm that stays above 90 percent after humid conditioning.
• High 700 percent minimum elongation for tight conforming over connectors and irregular shapes.
• Passes ozone, UV and heat resistance tests for indoor and outdoor service.
• Halogen free per IEC 61249-2-21 and compatible with common solid dielectric insulations.
• Removable polyethylene liner that keeps the roll clean and easy to unwind.

Industrial Applications

Typical uses of the 3M Scotch 23 in Oman include insulating motor lead connections on pumps and compressors, rebuilding insulation on damaged LV and MV cables, padding and filling around compression connectors before a joint is jacketed, sealing cable ends against moisture during installation, and building insulation on bus connections. Utilities and contractors working on 11 kV and 33 kV networks keep the tape in fault repair kits, while oil and gas and desalination plants use it in maintenance stores alongside vinyl jacket tape.

Seven Star LLC supplies 3M Scotch 23 with the rest of the cable termination package, including vinyl jacket tapes, glands such as the CMP T3CDS Triton cable gland and cable such as Lapp OLFLEX Classic 110. For motor starter panels we also supply switching devices like the Schneider Electric TeSys D contactor, so one enquiry can cover the whole motor circuit from Muscat.

As a general selection note, tape-built joints remain popular in the region because they need no special tooling, can be adapted on site to unusual cable sizes and conductor shapes, and allow an emergency repair to be completed with materials carried in a van. For planned medium voltage work, many engineers combine rubber tape with factory moulded or cold shrink components, and the tape is then used for padding, sealing and repair. In every case the jointing method, number of layers and test regime should follow the cable maker’s and the utility’s approved procedure.

Technical Specifications

The values below for the 3M Scotch 23 come from the 3M data sheet dated July 2021 (78-8129-9332-3 Rev C).

How to Order

To order 3M Scotch 23 for a jointing crew, a plant store or a cable project in Oman or the GCC, send Seven Star LLC your roll sizes and quantities for a formal quotation. We will share the 3M Scotch 23 data sheet, suggest the matching jacket tape and accessories, and arrange engineering support from our Muscat office.