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CABLE SOLUTIONS FOR EXTREME HIGH TEMPERATURES

By Alex Terpe, Product Manager, LAPP

 

Control cables increasingly have to withstand temperature extremes in applications such as food and beverage machines, industrial ovens, furnaces, foundries and industrial process equipment. These applications can subject the cable to continuous use temperatures as low as -50°C and as high as 180°C.

 

For these environmental conditions, customers have to think about cables with jacket materials other than PVC. You could buy very expensive speciality cables that can withstand even hotter or colder temperatures, or you could try to use a more traditional PVC control cable, whose lifecycle starts to fall dramatically in hot or cold environments.

 

A growing class of control cables occupies a middle ground between over-engineered specialty cables and commodity PVC cables. Based on silicone or cross-linked polyolefin copolymers, these cables can take over in thermal environments that would cause PVC cables to fail prematurely.

 

Here’s a closer look at these cables, and in particular, how they balance thermal performance against other desirable cable properties.

 

 

MATERIALS UPGRADE

 

Improving the thermal performance of a control cable can be a balancing act. Some of the changes to cable construction that widen the operating temperature range can compromise the cable’s electrical or mechanical properties. Silicone and cross-linked polyolefins do a good job striking that balance. Both types of materials can dramatically widen the continuous use temperature range of control cables. A typical PVC control cable, for instance, can function in a temperature range from -40 to 90°C. Compare that range to silicone-based cables, which work comfortably in a range from -50 to +180°C.

 

The conductor material is also an important factor. For higher temperatures, a coated conductor is necessary in order to protect
the bare copper effectively against corrosion. Tinned copper conductors should be used within a cable with a jacket made of silicone or cross-linked polyolefin–e.g., for 10 AWG in free air, ambient temperature of 30°C: 90°C rated conductor: 55 amperes versus 150°C rated conductor: 80 amperes (according to NEC tables 310.15).


With the most advanced cable technology, the additional thermal performance won’t affect the electrical properties of the cable at
all, and any effects on mechanical properties will be minor or even advantageous. Compared to traditional PVC cables, the silicone and
cross-linked polyolefin cables will exhibit:

    • Equivalent flexibility—though polyolefin cables are slightly
      stiffer than silicone or PVC cables
    • Improved wear resistance (for cross-linked polyolefin)
    • Improved chemical resistance
    • Equivalent flame performance
    • Halogen-free construction

 

The only downside of cables designed for temperature extremes is that they are more costly than a commodity control cable, usually
by 250% or so. However, the silicone and polyolefin cables are typically 65% less than a fluoropolymer speciality cable.

 

CABLE CONSTRUCTION: WHEN TO CONSIDER SHIELDING

 

Shielding options can provide cables with EMC protection in
the harshest industrial environments. A shield’s effectiveness is determined by its ability to maintain signal integrity in a noisy environment, such as a factory floor or other area containing a high concentration of electrical or communication equipment. Shielding, although not directly related to high heat, takes on importance when designing for thermal environments because a jacket’s material will affect the overall flexibility of the cable—a functional balancing act ÖLFLEX® HEAT products have achieved.

 

 

The ÖLFLEX® HEAT 180 MS and 125 MC cables, made from silicone and cross-linked polyolefins, respectively, integrate a tight weave of multi-strand, soft drawn tinned copper wire—an ideal shielding material for short-run cables. These braid shields provide superior structural integrity while maintaining good flexibility, and minimize low frequency interference. Both ÖLFLEX® HEAT cables provide braid coverage of 85 percent. Although generally, the higher the
braid coverage the more effective the shield, the trade-off between cost and flexibility of the cable design and braid coverage must be considered.

 

SILICONE CABLES

 

Silicone cables are suitable for applications involving high temperature, high voltage and a need for flexible wiring. They are also resistant to UV radiation, hydrolysis, oils, chemicals and plant and animal fats. For these reasons, they are commonly employed in metal processing applications, as well as in the industrial, automotive and automation industries because of their superior chemical resistance properties.


ÖLFLEX® HEAT silicone models 180 MS, 180 SiHF and 180 H05SS-F EWKF boast a temperature range of -50 to +180°C and are able to handle rapid heat increases. For these reasons, they are recommended for use in foundries, steel mills, glass factories and commercial baking equipment. These cables are also highly flexible, each featuring an unshielded minimum bend radius of 4x their diameter.


LAPP offers four ÖLFLEX® HEAT silicone models for the North American market:

    • 180 MS. A high temperature cable with a UV-resistant, halogen-free jacket and North American approvals. It is also available in a shielded version and overall tinned copper braid, which is recommended when electrical interference needs to be suppressed.
    • 180 SiHF. A halogen-free, high temperature cable that integrates fine stranding for improved flexibility.
    • 180 H05SS-F EWKF. A high temperature, tear-resistant control cable with <HAR> approval. It is designed for applications where high temperatures and  mechanical abuse can cause other cables to deteriorate.
    • 180 SiF A. A halogen-free and flame retardant single-core cable with North American approvals.

 

 

POLYOLEFIN CABLES

 

The second material alternative, cross-linked polyolefin, is formed from a combination of heat and high pressure—either by irradiating or chemically cross-linking the compound. These cables exhibit important electrical properties that make them ideal for medium to high voltage applications. These benefits include:

    • Increased thermal strength
    • Improved corrosion and abrasion resistance
    • Resistance to solvents, detergents and other operating fluids
    • Resistance to high temperatures

 

ÖLFLEX® HEAT cables 125 MC and 125 SC are insulated with a cross-linked polyolefin compound, making them highly flame retardant, as well as abrasion- and notch-resistant. For their thermal durability, as well as their tight bend radii, these control cables may be deployed in various lighting equipment: internal wiring of lamps, heating appliances and switchboards, for example.

 

LAPP offers two ÖLFLEX® HEAT polyolefin models:

    • 125 MC. A heat-resistant, highly flame retardant and halogen free multi-conductor cable. It is available in both shielded and non-shielded versions.
    • 125 SC. A heat-, abrasion- and notch-resistant single-core cable. It boasts excellent fire characteristics and a wide temperature range.

 

HIGH-HEAT COMPONENTS

SKINDICHT® FKM

    • Up to +200°C
    • Nickel-plated brass
    • Sealing cone: FKM
    • O-ring: FKM
    • Resistant to oils, solvents, acids, and chemicals
    • High strain relief
    • Watertight

 

SILVYN® AS

    • Up to +220°C
    • Galvanized steel
    • Highly resistant to pressure
    • Flexible design

 

SKINDICHT® CN

    • Up to +200°C
    • Chrome-nickel steel
    • Sealing cone: FPM
    • O-ring: FPM
    • Resistant to oils, solvents, acids, and chemicals
    • High corrosion and seawater resistant
    • For high mechanical stress

 

SILVYN® Steel Cable Chain

    • Heavy duty
    • Scalable to extreme size and load applications
    • Mechanical and corrosion resistant for the harshest environments

 

OTHER ADVANTAGES

 

There is typically a great deal of overlap between applications that have challenging thermal environments and those that require cables with good flame properties. With that overlap in mind, all ÖLFLEX® HEAT cables with jackets made of silicone and cross-linked polyolefin are:

  • Halogen-free. With the increased demand for safety in public areas, contractors are now being advised to install materials that are non-hazardous to members of the public in case of fire. Significantly, the mentioned ÖLFLEX® HEAT cables are halogen-free, avoiding the toxic and corrosive fumes halogenated products emit when burned. They are therefore a safe choice—both in terms of human health and the environment.

 

  • Flame retardant. The nature of the industrial environment, along with factors that include the duration of oil exposure, quantity of the liquid, surrounding ambient temperature of the oil and the cable itself, play a role in a product’s ability to withstand this type of chemical exposure, however, the greater the ability of the cable jacket to resist the possible devastating effects of oil, the longer it will perform uninterrupted. All ÖLFLEX® HEAT cables are rated to meet the varying degrees of oil resistance required for high temperature applications.

 

  • Low smoke density. When burned, ÖLFLEX® HEAT cables emit a less optically dense smoke at a lower rate—a desirable characteristic in the event of a fire, as it makes exiting the space a safer, easier experience.

For more information on ÖLFLEX® HEAT cables, explore the series for more technical specifications.