SHF1 & SHF2 Cables – The Ultimate FAQ Guide

In the cable industry, materials are often categorized or designated with standards or codes.

These terms help manufacturers meet the necessary composition and properties of the materials going into the structure of the cable.

SHF1 and SHF2 are essentially designations of materials of cable sheathing.

SHF1 SHF2 Cables

A cable’s sheath has a protective role as it’s on the outside of the cable.

It protects both the conductor and the insulation layers from environmental and mechanical elements.

Therefore, it goes without saying that sheath is vital to the durability of any cable, of course, those that have them.

What is SHF1 Cable?

Any cable that has a sheath that meets the SHF1 designation is essentially an SHF1 cable.

SHF1 designation requires the sheath material to have the following properties:

  • Thermoplastic material
  • Halogen-free
  • Low-smoke emission

By those classifications, several materials can be SHF1.

You’ll find the classification dictated in international standards for a variety of cables.

Thermoplastic is a kind of plastic that’s moldable at high temperatures and hardens at low temperatures.

These materials have a high molecular weight.

The process of heating and shaping can be repeated, which makes thermoplastics reusable and recyclable.

Halogen-free means the material should not contain any of the halogens, which includes chlorine (Cl), bromine (Br), fluorine (F), iodine (I), and astatine (At).

This is mainly because these elements, when burnt, produce toxic gases, which may exacerbate the situation in case of a fire.

Similarly, low-smoke emission means these cables don’t produce a high amount of smoke in case of a fire.

This is a safety feature, much like halogen-free composition, which ensures that the cables don’t worsen the situation or hamper rescue efforts when there is a fire.

What is SHF2 Cable?

What is SHF2 cable? Any cable with a sheath that meets the SHF2 designation is an SHF2 cable.

SHF2 designation typically involves the following type of sheathing material:

  • Crosslinked thermostable material
  • Halogen-free
  • Low-smoke emission

Thermostable, also called thermoset, materials can be heated and shaped, but unlike thermoplastics, the process cannot be repeated. Once these are polymerized, they cannot be polymerized again. As a result, thermoset plastics are not recyclable. Thermostable materials include natural and synthetic rubbers.

Crosslinking basically makes these materials stable by tying together the molecules. Crosslinking is done after shaping the plastic, as once it’s crosslinked, it cannot be reshaped.

What is the difference between SHF1 cable and SHF2 cable ?

If you look at the classifications, there’s only really one primary difference, which is the type of material (thermoplastic for SHF1 and thermostable for SHF2).

The other two parts of the classifications are the same for both designations.

That one difference in the designation allows for even more differences both in terms of characteristics and applications.

SHF1 cables and SHF2 cables have very different properties in response to certain outer materials.

As a result, their applications are pretty different too.

Flexibility

Generally, speaking SHF1 cables are less flexible in comparison with SHF2 cables.

The individual flexibility may vary even within the same category of cables, for example, two cables with SHF1 sheathing.

However, when comparing thermoplastics with thermosets, the latter are more flexible and may offer a higher bending radius.

Oil Resistance

This is a major difference between SHF1 and SHF2 cables as SHF2 cables are far superior when it comes to oil resistance.

Mineral oils, when in contact with the sheath of a cable, can trigger chemical reactions, which ultimately damage the cable.

Oil resistance varies greatly by individual materials.

For instance, EPR, which is a thermosetting material mainly used for insulation, doesn’t offer very good oil resistance.

So it comes down to individual materials essentially, but generally, thermosets are far better.

For this reason, there isn’t an oil resistance test requirement for SHF1 sheath material.

Mechanical Stress

When it comes to mechanical stress, abrasion resistance, tear resistance, and wear resistance, SHF2 is better than SHF1.

Thermoset materials are by default sturdier than thermoplastics, which is why SHF2 cables are more durable.

SHF2 sheath has to pass a hot set test to meet the mechanical stress requirements.

SHF1 SHF2 Cables

Heat Resistance

Both SHF1 and SHF2 cables have wider thermal ranges that allow them to function properly at sub-zero and high temperatures.

The maximum operating temperature may vary by the individual material, but not by a lot.

This property is more specific to applications and the conditions that come with them.

Ozone Resistance

SHF2 cables are also tested for ozone resistance.

These cables are used in environments that may expose them to ozone degradation.

So they have to pass a test to ensure the sheath material (SHF2 designation) can offer ample protection from ozone.

On the other hand, SHF1 materials don’t have ozone degradation test requirements.

That said, they can offer decent ozone resistance but not to the standard set for SHF2.

Summary of Differences

The following chart summarizes all the differences outlined above with test results for each category.

Some tests are simply not required for each material, perhaps because of the nature of the applications.

This chart will also help you understand the difference between the two material categorization, aside from the basic differences.

SHF1SHF2
Hot oil immersion (IEC 60881-404)N/A100 ℃

Tensile strength: +/- 40 percent variation max

Elongation: +/- 40 percent variation max

Mechanical stress

(IEC 60811-508)

N/A200 ℃ for 15 minutes under a load of 20 N/mm2

Elongation: 175 percent

Permanent elongation: 25 percent max

High temperature80 ℃ for up to 4-6 hours (load as per cable diameter) Permissible deformation: 50 percentN/A
Heat shock test150 ℃ for one hourN/A
Ozone resistance (IEC 60811-403)N/A25 +/- 2 ℃ for 24 hours                Ozone concentration: Max 0.025 to 0.030 percent

 

Sheath Materials Meeting SHF1 and SHF2 Requirement

As the requirements for both SHF1 and SHF2 are strict, there are just a few materials that qualify for this designation.

Here are some examples of materials that are SHF1 or SHF2:

EPDM Rubber

EPDM is a synthetic rubber, so it has hydrocarbons in its composition.

It’s ideal for offshore cabling, as it offers resistance to many environmental threats.

This material meets the SHF2 requirements as it’s resistant to ozone, heat, and UV rays.

This material also provides water resistance, which is the de facto requirement of any offshore cable.

As for temperatures, it can operate in the range of -55 ℃ to 150 ℃.

Also, as a thermoset material, it’s pretty flexible.

As a synthetic rubber, it offers better response to mechanical stress.

It can withstand cutting and tearing pretty well, which is always a threat with marine life.

In terms of chemical resistance, EPDM provides adequate defense against acids, alkalis, water (cold and hot), and fireproof hydraulic fluids.

However, it doesn’t provide good resistance against oils, kerosene, aliphatic hydrocarbons, aromatic hydrocarbons, and gasoline.

EVA

EVA or ethylene vinyl acetate is an elastomer which is very tough and qualifies as SHF2 sheath material as per IEC standard 60092-359.

This one is also used in offshore cables.

With necessary SHF2 properties like flame retardancy and low-smoke emissions, it checks all the requirements and passes all the tests.

As you can tell from its name, it doesn’t contain any halogens either.

What makes EVA really versatile is that although it’s an elastomer, it can be combined with some thermoplastics.

But it’s SHF2 as itself without any thermoplastic additives.

As an SHF2 sheath, it offers stress resistance, UV protection, waterproofing, and toughness at low temperatures.

It’s very similar to rubber, so it replaces rubber in many cables.

Halogen-free and Flame-retardant Materials

HFFR or Halogen-free Flame-retardant thermoplastics are SHF1 as per IEC 60092-359.

PVC or polyvinyl chloride doesn’t make this distinction, although it’s the most popular thermoplastic in cables.

The reason is that it contains chlorine, which is a halogen.

HFFR materials provide the necessary low-smoke and fire retardancy properties required of SHF1 cables.

These materials don’t produce harmful gases in the event of a fire.

What are the Applications of SHF1 & SHF2 Cables?

The applications of SHF1 cables and SHF2 cables will also help explain the differences between the two.

In a way, the applications are the defining factors for their features, as the designation is based on the requirements for the particular application.

SHF1 Cable Application

SHF1 SHF2 Cables

SHF1 cables are mostly used in technical infrastructure for power supply and communication.

SHF1 cable applications also depend on locations.

You may find these cables at:

  • Office buildings
  • Hotels
  • Schools/Colleges
  • Hospitals
  • Subway system
  • Shipboard

SHF2 Cable Application

SHF1 SHF2 Cables

SHF2 cables are primarily used on vessels and offshore structures.

This is because the characteristics of these cables are suited for the tough environments underwater and on vessels.

The sheath protects the insulation and conductor from water, pressure, chemicals, etc.

SHF2 sheath is present in both shipboard and marine cables.

These cables may be used for power supply, communication, and instrumentation.

These main structures in SHF2 marine applications include:

  • Offshore Drilling rigs
  • Submarines
  • Cruise ships
  • Navy vessels

What are the Benefits of SHF1 & SHF2 Cables?

SHF1 and SHF2 offer many different benefits, some of which are exclusive to certain applications.

Let’s discuss their benefits, although some benefits are exclusive to SHF2 only as it’s tougher than SHF1.

  • Flame-retardant: This is the most fundamental characteristic of SHF1 and SHF2 materials that they are flame-retardant. These materials are essentially self-extinguishing. In other words, they don’t propagate fire or cause one. However, that’s different from fire-resistant, which actively stops the fire from melting the insulation.
  • Low-smoke and Halogen-free: This is an extension of their fire retardancy, as both SHF1 and SHF2 cables are low-smoke and halogen-free. Even if the fire from the source is sustained, and the cables are on fire, they won’t release a lot of smoke. More importantly, these cables won’t burn to produce harmful gases from halogens that can wreak havoc in the human/animal respiratory system.
  • Flexibility: SHF1 and SHF2 cables offer adequate flexibility, SHF2 more than SHF1. So for applications that don’t have fixed installations, SHF2 is a better choice compared with SHF1.
  • Weather-resistance (SHF2): SHF2 offers incredible weather resistance. It protects the integrity of the conductor from virtually all natural elements. From water to UV rays, it will ensure nothing damages the cable. It also provides more than adequate protection from mechanical stress and age-related wear and tear.
  • Recyclable (SHF1): SHF1, being a thermoplastic, is recyclable, which makes them economical and environmentally friendly to some extent. On the other hand, SHF2 cables cannot be recycled or reused for other purposes.

What are the Standards?

Both SHF1 and SHF2 sheath materials are essentially standardized.

The standards that dictate the properties of these materials and the applications of the cables they go in are included in the most frequently used IEC standards.

The IEC 60092-360 is the standard for shipboard cables that specifies the standards for SHF2 sheathing material.

Previously, this standard was numbered IEC 60092-359.

Also, SHF1 cables are fire-retardant to IEC 60332-1-2, whereas SHF2 is fire retardant to IEC 60332-3-24.

Another important specification to note is NEK 606.

NEK 606 is a technical specification from the Norwegian Electrotechnical Committee that helps identify SHF1 and SHF2 cables.

It shouldn’t be mistaken for a standard.

SHF1 SHF2 Cables

Earlier, the distinction between the two sheaths was not well-defined.

However, the updated NEK 606 specification has clarified the difference.

In fact, they have identified a new subclass of SHF2 cables, the SHF2 MUD.

The MUD specification is related to mud resistance, which is a step up from just oil resistance.

It’s related to offshore drilling and all the substances that are part of the mud.

For oil, the specification offers two levels of resistance: minimum required and enhanced.

Conclusion

SHF1 and SHF2 cables essentially tell you the sheathing of the cables, as SHF1 and SHF2 are designations/classifications for sheathing material.

These are primarily used in offshore and marine applications for both power and communication.

In fact, these are designated specifically to distinguish them from other cables and sheath materials used on the ground.

The standardization/designation just helps take out the guesswork and ensure that companies using these cables choose the right materials.

The materials that are sturdy for commercial use on land are not enough for marine use.

SHF1 and SHF2 deal with those special requirements.

These both are similar in some ways but different in a lot of other ways.

The very nature of the materials is quite different, which, in turn, results in different features.

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