Editor's Note: Thanks to Peter Cox, cable expert, and a Project Manager in Belden’s Industrial IT group, for his contribution to this article.

From subsea drilling 6,000 feet below the surface to pipelines that cross many landscapes to intense refining processes, the range of conditions for oil and gas installations is very broad. As a design engineer, you may be involved with many types of projects with very different requirements. How then do you approach selecting the right cable for an oil and gas application?

But won’t any cable do? Certainly not! Cable issues account for more than 70% of signal transmission issues and they are difficult to diagnose and resolve. With downtime costing thousands of dollars per hour, availability requirements demand that the right cable is specified for each use.

The good news is that despite the broad range of oil and gas applications many of them share common cable requirements. In this article I take away the voodoo and spell out the 3 easy steps to selecting the right cable.

1. Select the Right Industrial Cable Jacket

As a resident of the Pacific Northwest I know that snowboarding is fun when I have the right layers on and walking my dog in a downpour is okay when I am in water repellent outerwear from head to toe. Having the right outerwear, or jacket, is also the key to signal reliability for oil and gas applications.

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Thus the first question to ask yourself is “How harsh is the environment for my project?” The answer to this leads to selecting the right industrial cable jacket.

The table below categorizes various types of oil and gas applications according to a harsh, harsher, harshest model and indicates the type of cable jacket suitable for each.

  Harsh Harsher Harshest
Description The environment is generally contained but is a true industrial setting The environment includes exposure to outside elements and some harsh chemicals The environment is exposed to harsh outdoor elements, very harsh chemicals or some other extreme conditions
Application Example

Natural gas compressor station:

  • Indoor, heated environment, fairly clean
  • Temperature extremes could occur
  • Unmanned so onsite maintenance or repair is expensive

Petrochemical processing facility:

  • Indoor and outdoor conditions
  • Exposure to UV radiation
  • Some exposure to oil or other harsh chemicals

Offshore natural gas and oil platform or Onshore drill rig or Onshore pump jack:

  • Temperature extremes exist
  • UV radiation exposure exists
  • Possible exposure to rain and sea water
  • May need high degree of toughness
  • May need marine certifications such as ABS or DNV
Suitable Cable Jackets
  1. PVC Thermoplastic (TP) Jackets:
    • General purpose, good for most applications
    • Economical
  2. LSZH (TP) Jackets:
    • "LSZH" means Low Smoke Zero Halogen
    • As the name implies, this type of jacket emits limited smoke and no toxic halogens when exposed to high sources of heat
  1. TPE (TP) Jackets:
    • Suitable for repeated flexing
    • Oil resistant and weld -splatter resistant, tolerates low temperature, continuous flexing and direct burial
  2. CPE (TP) Jackets:
    • Oil resistant and tolerates extra low temperature
    • "CPE" is chlorinated polyethylene
  1. XLink LSZH (TP) Jackets:
    • XLink refers to cross-linking, a process that makes the material more resistant to high temperatures
  2. FEP (TP) Jackets:
    • Extra high temperature resistant and weld-splatter resistant
  1. Armor:
    • Armor is an extra layer of external protection added to for harsh environments
    • It increases the robustness for many cable types and provides the maximum mechanical protection


2. Select the Level of Oil Resistant Cable Needed

Now that you have narrowed down the range of suitable jacket types, what level of oil proof cable do you need? Will the cable be exposed to:

  • Infrequent light splashing - Choose an “oil resistant” jacket.
  • Periodic oil exposure - Choose a jacket that is “UL Oil Resistant 1”.
  • Frequent harsh oil exposure - Choose “UL Oil Resistant 2”.

Use the following chart to narrow down and select the jacket type for your project.

  Harsh  Harsher  Harshest    
Jacket Material LSZH (TP) PVC TPE CPE (TP) XLink LSZH (TS) FEP Armor
Sunlight Resistant
  •  
  •  
  •  
  •  
  •  
  •  
  •  
Oil Resistant  
  •  
  •  
  •  
  •  
  •  
 
UL Oil Res. I   optional
  •  
  •  
  •  
  •  
optional
UL Oil Res. II   optional
  •  
  •  
  •  
  •  
optional
Weld Splatter    
  •  
   
  •  
  •  
Extra Low Temp.    
  •  
  •  
  •  
  •  
optional
Extra High Temp.          
  •  
 
Low Smoke Zero Halogen
  •  
       
  •  
 
Halogen Free
  •  
       
  •  
optional
Continuous Flex    
  •  
       
Direct Burial
  •  
  •  
  •  
 
  •  
 
  •  
Maximum Mechanical Protection            
  •  


For those of you who like to know what all of the acronyms that describe cable are, here is a summary.

Cable Acronyms Definitions
CPE Chlorinated polyethylene
PVC Polyvinyl chloride
TP Stands for "Thermoplastic" and means the material can be melted and re-solidified again, such as ice.
TS Stands for "Thermoset" and means that a material has been cured so that it cannot be melted.
TPE Thermoplastic elastomer
FEP Fluorinated ethylene propylene, also know under the brand name of Teflon
XLPE Cross Linked polyethylene. Withstands higher voltages, good for longer cable runs.

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3. Special Considerations by Industrial Cable Type

The three most common cable types used in oil and gas applications are Ethernet, VFD and Control and Instrumentation cable. Let’s take a look at the unique selection criteria for each.

Ethernet Cable

Should it be Copper or Fiber?

The key considerations for choosing copper or fiber Ethernet cable are:

  • If you have runs of 100 meters you need fiber
  • If you need data rates of more than 1GB than you need fiber
  • If you need Power over Ethernet then you need copper

Twisted or Bonded-Pair Conductors?

Bonded-pair cables provide resistance to the rigors of installation by utilizing a manufacturing technique that affixes the insulation of the cable pairs along their longitudinal axes so no gaps can develop between the conductor pairs.

Twisted pair cable construction can be susceptible to pair-gapping during installation, as well as impedance mismatches.

Belden has developed proprietary bonded-pair technology that provides:

  • Uniform conductor-to-conductor spacing, or centricity due to the absence of gaps between the conductor pairs.
  • Superior electrical performance thanks to the uniform centricity. Installation processes, such as bending, pulling and twisting, do not affect the high functioning of this cable.
     
Fig5_BondedPAirAdvantage

Twisted pair conductors have gaps which decrease performance. Belden’s patented bonded-pair technology maintains electrical performance even when cable is bent, pulled or twisted. (Click here for larger image)

VFD Cable

Many motor systems are used to pump or refine oil and gas. Often these motor systems use Variable Frequency Drives, or VFDs, to precisely control their speed, as doing so greatly reduces both costs and energy consumption. In addition, VFDs also improve process control, reduce manufacturing waste, provide a longer useful life for motors, reduce maintenance and deliver high reliably.

However, there is a downside to VFDs, and that is that they generate disruptive electrical noise in the environment around them that can create problems in the refining or pumping processes. The noise emission can be difficult to track down and eliminate, causing reduced production or downtime.

Proper cable shielding is thus essential for VFD cable, particularly when longer cable runs are required. Choosing well-designed, robust VFD cables ensures motor uptime and reliability of the VFD system and also provides protection for any sensitive instrumentation and adjacent control systems.

A challenge in purchasing VFD cables is that there are no standards for them. Thus it can be difficult to differentiate between minimum construction-grade cable sold as VFD cable and high-performing VFD cable that protects motors and ensures the maximum benefits of a VFD system.

Below is a quick guide to help you differentiate between the two.

Cable Characteristic Construction-Grade VFD Cable High-Performance VFD Cable
Shielding Copper-tape shielded building wire Braided shield construction or dual copper tapes
Insulation PVC/nylon insulation XLPE insulation
Grounding 1 full-size or smaller ground conductor Insulated grounds, shield and drains equivalent to 3 or more conductors at ground potential
Stranding Bare copper, Class B stranding, Low flex

Tinned copper conductors High strand count         High Flex

Certification Not recommended by the manufacturer of your VFDs Recommended for use by your VFD manufacturer

Instrumentation and Control Cable

In addition to selecting the right jacket type, as shown in the tables above, the important thing to determine for Instrumentation and Control cables is the type of insulation.

Here are the guidelines:

  • For Harsh environments choose PVC or PVC nylon insulation
  • For Harsher environments, choose PVC nylon, or XLPE insulation
  • For Harshest environments, choose XLPE insulation


The Right Industrial Cables Deliver High Performance and High Availability


Just like I don’t go to the mountains to snowboard without the right clothing layers and protective gear, so you don’t want cable without the right layers and protection.

If you follow the steps in this article:

  • Select the right industrial cable jacket
  • Select the level of oil resistant cable needed
  • Remember the special considerations by industrial cable type:
    • Ethernet – copper or fiber, bonded-pair technology
    • VFD – choose high performance cable characteristics
    • Instrumentation and Control – select the right insulation

You will choose a cable that provides reliable signal transmissions and high availability.

Here are some examples of the 3 types of cables for each level of environmental harshness:

Cable Type Harsh Harsher Harshest
Ethernet Heavy Upjacket (an extra jacket layer) Armored PVC or Jacketed XLink
VFD XLP, PVC XLP, CPE XLP XLink LSZH
Instrumentation and Control PVC or PVC Nylon Insulation with PVC jacket PVC Nylon or XLPE insulation with CPE jacket XLPE Insulation with XLink LSZH jacket

Good luck with your projects and I look forward to hearing whether these guidelines help.

Related Links

Ethernet Cable:


VFD Cable:


Instrumentation & Control Cable: