The 44th General Meeting of the International Intercable Association

The 44^th General Meeting of the International Intercable Association took place on November 20-21, 2012 in Heviz, Hungary.

A scientific and technical symposium including two sessions was held within the framework of the general meeting:

Session 1. “Rubber wires and cables: trends of cable production development, machinery, materials, control devices”.

Session 2. “PVC and flame retardant halogen-free compounds. The future of these materials in the cable industry”.

Session 1 included 10 reports.

As it was pointed out in the report “Achievements and problems in the manufacturing of rubber cables in Central and Eastern Europe” of VUKI a.s (Slovakia), rubber insulated cables and wires are still used in a number of areas though their production output is gradually decreasing. First of all, it is the result of the high cost of applied materials (ethylene-propylene rubber – 3.8 €/kg, Al (OH)3 – 0.9 €/kg, etc.), as well as the high value of investments required for their production. Another reason is attributed to the wider adoption of silane cross-linked polyethylene and thermoplastic elastomers in cable and wire production. Nevertheless, rubbers are used in the production of cables for submersible oil recovery electric pumps (ethylene-propylene rubber + butadiene rubber – for cables rated for the operating temperature range of –50 ÷ +135 ºС and ethylene-propylene rubber + lead – for cables rated for the operating temperature range of –50 ÷ +240 ºС). In fire resistant power cable constructions silicon rubber is used instead of mica glass tapes. In this type cables it is possible to use the combination of halogen-free compounds and silicone coatings.

The report of NexansRus Ltd. (Russia) “Modern designs of rubber cables” drew attention to the fact that rubber insulated cables in spite of their high cost retain dominant position in a number of applications. At the same time proper consideration is not always given to their advantage in respect to the service life due to the absence of the second order phase transition within the operating temperature range, i.e. stepwise temperature change in the melting zone of conventional polymers used in the cable industry. High modulus ethylene-propylene rubbers applied in low and medium voltage power cables provide higher mechanical strength and improved flexibility. Moreover, such insulation defects as treeing are not found in these cables. Rubbers are still used in cables intended for operation in mines, petroleum refinery and chemical plants and other media of high explosion hazard. Attention is drawn to the fact that not ordinary rubber but high modulus ethylene-propylene rubber is to be used in these cables. And what is very important in some cases, this rubber is more resistant to ozone exposure.

End-to-end solutions for rubber mixing workshops of cable plants and a wide range of machines for all key stages of production – from raw material processing to rubber processing up to vulcanization including the required test facilities – are offered in the report “Modern equipment for rubber processing” made by Harburg-Freudenberger (Germany). This company specializes in the development of such production solutions and projects.

HF-mixing Group also includes Farrel Corp (USA – Great Britain) and Romini (Italy), as well as some subsidiary companies, e.g. Shaw (Great Britain).

Farrel Corp produces rubber mixers with tangential rotors or self-gripping rollers. Rubber mixers with self-gripping rollers ensure better quality of mixing and are recommended for use in the cable industry. The mixing chamber capacity ranges from 90 to 190 liters.

Romini manufactures double-screw extruders. About 750 mln t of rubber is produced globally with the equipment made by НF-mixing Group.

Characteristics of continuous vulcanization cable lines are presented in the report of TROESTER GmbH & Co.KG. The lines are equipped with hot-feed and cold-feed extruders, including those with barrel degassing. For cold-feed extruders both rubber strips and granulated rubber compounds may be used. The feeding uniformity is ensured by the feed roller. The screw design in the feeding zone facilitates the capture of the processed material. The screw diameters range from 30 to 150 mm, the speed of rotation is from 20 to 60 rpm. The extrusion heads are single-, double- and three-layer. Flow separators are used for different materials. TROESTER GmbH & Co.KG developed a software for calculating the vulcanization mode. Cables of up to 120 mm diameter with conductor cross-sections up to 1000 mm² can be manufactured on the company’s continuous vulcanization lines. A line with infra-red heating is also offered.

The report of Maillefer Extrusion OY (Finland) was devoted to modern rubber insulating solutions to be implemented in cable plants. The company produces 4 types of vulcanization lines for rubber insulation:

a) for conductor cross-sections of 0.5–6.0 мм² – non-steam vulcanization of silicone rubber;

b) for conductor cross-sections of 0.75–25 мм² – horizontal continuous vulcanization lines;

c) for conductor cross-sections of 16–800 мм² – catenary continuous vulcanization lines;

d) for conductor cross-sections of ≤ 1000 мм² – Supersteam catenary continuous vulcanization lines.

The Supersteam lines are operated at lower vapor pressure (2-8 bars), so the risk of damaging particularly sensitive cables is reduced. The company provides its continuous vulcanization lines with NSS software for calculating the vulcanization mode. Altogether the company has supplied more than 400 continuous vulcanization lines and about 2000 extruders.

Nowadays rubber insulated cables are entering new fields of application: wind farms, solar energy plants, hybrid vehicles, electric vehicles, etc.

Maschinenfabrik NIEHOFF GmbH&Co.KG (Germany) in its presentation “Modern manufacturing technologies for tinned copper wires for rubber insulated cables” described the continuous galvanic tin plating technology that almost completely replaced the hot-tinning process in cable production. As is well known, the chief drawbacks of the hot-tinning method include: excess tin consumption, coating eccentricity, the need to heat tin in a bath of ≤ 1000 kg capacity up to a temperature of 330 ºС, loss of tin (5–10 %) due to oxidation (slagging) of the melt surface. The Niehoff 300 WRT galvanic wire plating line enables tinning of 1.0 – 2.6 mm diameter copper wire at a speed of up to 300 m/min with an annual output of 2000 t. The galvanic coating thickness is 5 – 15 mm, which corresponds to the tin consumption of about 12.5 kg per 1 t of wire (in the hot-tinning process the tin consumption is 21.4 kg per 1 t). The company also offers complete lines where galvanic tinning is combined with the follow-up drawing of tinned wire. The galvanic tinning lines are developed by NIEHOFF in cooperation with Steuler (Germany).

Compound Technology Services (France), a large-scale manufacturer of thermoplastic elastomeric materials (100 000 t/year), presented the report “Thermoplastic rubber – an insulating and sheathing solution for special cable”. The company specializes in the following types of thermoplastic elastomers: styrene, polyolefin, polyvinyl chloride (with nitrile rubber), polyurethane. For the cable industry polyolefin and styrene, reinforced and non-reinforced thermoplastic rubbers are recommended.

TEFA BLOCK polyolefin thermoplastic rubber is characterized by a high value of the limiting oxygen index (LOI) and low halogen content. Flame retardant cable insulation is made of styrene thermoplastic rubbers with the following characteristics: operating temperature from –40 to +125 ºС; LOI = 26 – 35; density = 1.30–1.48 g/cm³. In addition, this material allows heating up to 150 ºС during 240 hours, and the long-term operating temperature of 125 ºС is confirmed by the fact that the material properties remain actually unchanged after three years of operation.

The range of applications for these materials is rather wide: cable and wire for motor cars, robot handling systems, wind farms, solar batteries, as well as heating and sensor cables.

The report “Measuring & controlling of rubber cables” made by ZUMBACH Electronic AG (Switzerland) was devoted to the new technologies in the field of measuring and control instruments. New cable diameter gauges, insulation thickness and eccentricity measurement systems equipped with high speed laser scanners were presented. These gauges when used in the cable manufacturing process provide significant savings in material, and the pay-back period is approximately 120 days. The intelligent self-adapting controllers, like for instance SIGMA-EXPERT^® and CpK-Pilot^®, enable effective stabilization of the processing line speed and provide about 3% saving in material.

The presentation made by SIKORA AG (Germany) – “The story of the perfect rubber cable” – focused on the characteristics of control, test and measuring devices installed in the CV lines for on-line monitoring of the cable parameters. With the newly developed CV-INTUBE 6000 SIKORA presents a device perfectly suited for product diameter measurement directly in the telescopic tube of both steam and nitrogen vulcanization lines. The device can be adapted to every control system via serial or analog interfaces. If another diameter gauge is installed before the crosshead the average insulation thickness value may be calculated using the difference method.

The X-RAY 8000 NXT system measures cable diameter, eccentricity and coating thickness. It is installed directly into the moving part of the telescopic tube and allows measuring of up to three coating layers. To control the rubber cable quality the X-RAY 6000 system may be integrated into the CV lines for outer sheathing. This system provides continuous measurement of wall thickness, eccentricity, diameter and ovality. The X-RAY 6000 system is usually installed between the two cooling sections to control the parameters of the cable outer sheath. A diameter gauge is installed additionally at the end of the production line to register the material shrinkage. The X-RAY 6000 PRO system is used to measure up to three coating layers, for single-layer coatings the X-RAY 6000 BASIC is suited.

Davis-Standard (USA) in its report presented rubber processing equipment and outlined the key features of the rubber insulating lines. Extrusion system offerings include lines for manufacturing rubber insulated cables rated at voltages up to 10 kV with cross-sections up to 500 mm².

Vulcanizing tubes are manufactured in-house. Extrusion groups are comprised of 1-4 extruders with single-, double- and three-layer extrusion heads. Extruders and crossheads are water cooled; material loading systems for bands \ granulate or universal are used. According to Davis-Standard the best results may be obtained with the use of special feed rollers. In principle it is advisable to give up rubber band feeding in favor of granulated rubber feeding. Main advantages of the rubber pellet feeding system are described.

Quick steam generators are recommended to produce water steam. 60 % of the vulcanizing tube is filled with steam and 40 % with water (water provides primary cooling and functions as an end water seal). Silicon rubber coatings are applied by vulcanization in air using infra-red heating ovens.

PVC and halogen-free flame retardant compounds were the subject of wide discussions within the framework of Session 2. The future of these materials was also discussed.

The report of JSC VNIIKP “The comparative evaluation of PVC and HF compounds used in flame retardant power cables in Russia” was devoted to the main stages of development of flame retardant and fire resistant cable production in Russia starting from 1984 and the key factors of cable fire performance. The method of cone calorimetry used to measure and evaluate the parameters of fire retardancy of polymeric materials has not been standardized in the CIS yet, however it ensures the most objective measurement results. With the cone calorimetry method it is possible to obtain time dependences of heat release rate, total heat release, CO/CO₂ production rate, mass loss rate during burning, smoke emission rate per unit area of the specimen. A mathematical model is offered for a polymer sample pyrolysis during cone calorimeter test. The results of simulation correlate well with the test data. The basic technical requirements for the polymer compounds used in flame retardant cable constructions are specified.

VUKI a.s. (Slovakia) presented a report under the title “The influence of new materials on the European Union standards and the European Union standards influence on new materials”. Abbreviations of cable material labelling that are in use within the limits of the European Union (EU) are given. Consideration is also given to the EU methods of testing flame retardant cables which help to set up the requirements for new materials. One of the most stringent requirements placed upon fire-resistant cables is the maintenance of functional capabilities under fire conditions at a temperature of 1036 ºС during 90 minutes – for cables laid in trays.

A review of test methods for cables of improved fire safety in compliance with the requirements of EU and UL (USA) standards is presented in the report of Alpha Gary Ltd. (Great Britain). It is stated that about 50% of all cables produced in the USA are of flame retardant design. Criteria for choosing materials for particular fire-safe cable types are given. It is noted that PVC compounds are still generally used in the USA to manufacture cables of low fire hazard. The halogen-free compound market in the USA is limited to 5%.

Condor Compounds (Germany) presented the report “Halogen-free compounds which provide high fire safety are the future of the cable industry”

Flame retardant compounds are supplied with due account for the requirements of IEC, BS and CENELEC. Cables intended for use in nuclear power plants (NPP) are the main area of application for these compounds. Compounds with improved fire resistance are manufactured using two methods – radiation and silane cross-linking. The operating temperatures for different types of these compounds range from 90 ºС to 155 ºС, limiting oxygen index is from 26 to 50, density is from 1.46 to 1.52. The compounds manufactured by Condor Compounds can be used as part of a cable product during 3000 hours at a temperature of 155 ºС. In addition to nuclear power plant cables other fields of application for these compounds include automotive wires, shipboard and railway cables.

The report of VIPA s.r.l. (Italy) under the title “Fire safe cables for a global concern over public health & safety” deals with one of the global problems – survival of people and protection of their health. The EU requirements for fire-safe cables and fire test methods are described. It is well known that the use of flame retardant cables reduces the risk of loss of life or health hazard in offices, residential and public buildings. However not only fire-resistant cables should be used to ensure fire safety. Cable constructions with flame retardant materials (PVC compounds, halogen-free compositions, etc.) comprise an alternative solution. The same materials may be used in cable constructions with different fire performance characteristics.

The presentation of Momentive Performance Materials GmbH (Germany) “Silquest Silanes for halogen-free flame retardant compounds” was devoted to the effect that silanes used for cross-linking have on the characteristics of compounds with improved fire resistance.

Momentive Performance Materials is a specialty chemicals company focused on silicon chemistry with annual sales of over EUR 5 billion. The company offers a series of Silquest® silanes for cross-linking halogen-free compounds, as well as silanes to be added in silicon rubber compounds applied in flame retardant cable designs.

Prominvest Plastic Ltd. (Ukraine) in its report “Tendencies of improved fire safety requirements for wire and cable polymeric compounds” analyzes the criteria of fire danger assessment for cables used both in the EU and in the CIS, first of all in the RF. Toughening of fire safety requirements for cable products resulted in more stringent requirements for the applied halogen-free compounds developed by the Ukrainian company. It is noted that the high value of limiting oxygen index (LOI) in itself cannot guarantee that the flame retardancy requirements for cables laid in bunches are met. Attention is drawn to the need of testing cable materials with the use of a cone calorimeter standardized in ISO, ASTM, BS and some other documents.

Borealis AG (Austria) made a report under the title “New developments in reduced fire hazard jacketing compounds for energy cables”. The presentation informs about the new Construction Products Regulation (CPR) that has been adopted by the European Commission.

All manufacturers of cable products and some materials have until July 1, 2013 to ensure that their products meet the CE requirements of the new Regulation. The aim of the new Regulation is to remove technical barriers in the EU and to simplify the material turnover in the European market. The CPR gives the European cable fire classification based on the heat release value (А, В2, С, D, E, F classes). The most commonly used class C defines rigid fire requirements for cables laid in bunches. Borealis compounds primarily correspond to fire safety class E.

The principles of inflammation and flame propagation are discussed in the report “New trends in HFFR cable formulations” of Kablelovna Kabex a.s. (Czechia). Burning of Kablelovna material leads to charring of the cable surface. This material is based on organic and nitrogen phosphates. Other phosphates may also be used but it will result in higher cost of the material. Reactive glass particles are used as filler to ensure reduced smoke emission and lower toxicity of gases.

OAO Saranskkabel (Russia) was expelled from the Intercable Association for its failure to pay the membership fees.

STP Cables (Azerbaijan), one of the major European plants, joined the Intercable Association.

The next regular general meeting of the International Intercable Association will take place on May 20-24, 2013 in Baku (Azerbaijan).

Scientific and technical seminar “Telecommunication cables – expected future development” will be held within the framework of the general meeting.