1. ELECTRICAL ISOLATION
Heather Groll

2. ISOLATORS
Isolators electrically isolate undesirable metal structures from the pipeline that is cathodically protected. Isolators work by eliminating the metallic path from the corrosion cell.
I want to start off with a reminder of how galvanic corrosion works. Who remembers the 4 things that are needed to have corrosion?
Very Good. What is typically considered an electrolyte? What’s a typical “Metallic Path” between two piece of metal? They are either connected by ________? Or in “What” with each other?
Very good. So when we have two piece of metal in the ground in contact with one another, surrounded by all that moist soil, do we have a recipe for corrosion?
Yup!!
So we have several situations that we are going to discuss where we would want to separate two structures and where Isolators are nessesary.
But lets start out with;
What is an Isolator? You may have heard it being referred to as an “Insulator” It’s the same thing.
*Read Slide

3. CODE REQUIREMENTS
§ External corrosion control: Electrical isolation.
(a) Each buried or submerged pipeline must be electrically isolated from other underground metallic structures, unless the pipeline and the other structures are electrically interconnected and cathodically pro- tected as a single unit.
(b) One or more insulating devices must be installed where electrical isolation of a portion of a pipeline is necessary to facilitate the application of corrosion control.
Lets talk about where the requirement to isolate structures from one another comes from.
How many of you are familiar with the Code of Federal Regulations part 192? This is the DOT standard that we are required to follow in regards to pipeline safety. This specific part on this slide is in regards to “External Corrosion Control: Electrical Isolation”
*Read Slide

4. CODE REQUIREMENTS
(c) Except for unprotected copper inserted in a ferrous pipe, each pipeline must be electrically isolated from metallic casings that are a part of the underground sys- tem. However, if isolation is not achieved because it is impractical, other measures must be taken to minimize corrosion of the pipeline inside the casing.
(d) Inspection and electrical tests must be made to assure that electrical isolation is adequate.
(e) An insulating device may not be in-stalled in an area where a combustible atmosphere is anticipated unless precautions are taken to prevent arcing.

5. ISOLATORS (cont)
Isolators are used but not limited to the following uses:
Separate foreign metal structures from protected pipelines (casings and grounded structures).
Separate different types metals from each other
Separate coated lines from bare lines
Separate C/P lines from unprotected lines
Electrically isolate pipes for troubleshooting purposes
I told you that there are multiple reasons for using insulators and we are going to discuss each on of them.
Insulators are used for (but not limited to):
*read bullet points

6. DIELECTRICAL ISOLATION Primary Function (WHY?)
Method of Corrosion Control
- To stop the flow of CP current.
- To limit the amount of current needed.
- To prevent a corrosion cell.
Inserted in pipelines and structures to BLOCK the flow of electrical current.
*READ INSTEAD OF SLIDE
So why would we even use an insulator?
As we look again at the flow of current when we have the perfect recipe for corrosion, the current is flowing on the pipe. In certain situations, we want to stop that current flow.
The term Isolator is generally used to indicate electric obstruction, while Dielectric is used to indicate the energy storing capacity.
So the term Dielectric is referring to the fact that we are breaking or stopping electrical continuity between two piece of metal.
The primary function for this is for Corrosion Control
*READ SLIDE – STRAT AT BULLET POINTS

7. Failure to Provide Dielectric Isolation
Severe corrosion can take place.
New pipelines may become anodic when connected to bare or poorly coated pipelines.
Non-isolated sections of coated and bare piping would allow the potentials to fall below cathodic protection criteria.
What happens if we don’t provide adequate Isolations…..
*Read Slide
*Use images on wall as a reference

8. Failure to Provide Dielectric Isolation (Cont.)
Current requirements would increase in order to protect the poorly coated or bare pipe not isolated from the coated piping.
Cost of cathodic protection will increase.
Corrosive environments can impact the pipeline above (Atmospheric Corrosion) and pipe below ground.
*Read First Bullet point:
When we have Cathodic Protection on a line and we are in contact with a bare pipe or poorly coated pipe, that pipe has a lot of bare area in contact with the Electrolyte. It could take a great deal of current to protect that exposed surface area. That will cause you to increase your current requirements and in turn increase the cost of your cathodic protection system. (*This is the Second Bullet Point)
*Read Last bullet point:
We’ve discussed the 4 things that are needed for Galvanic Corrosion, right? Anode, Cathode, Metallic Path, and an Electrolyte, right? So when we have a Brass fitting in contact with steel pipe, but its above ground; out of the soil, out of the electrolyte, why do we still have corrosion? If these two components are not isolated away from one another, then they are dissimilar metals in contact with on another, right? And since they are in contact with one another, there is your metallic path. So what is our electrolyte if these are above ground?
Rain, Dew, Snow, water sprinkler system, garden hose, down spout point from the roof, moisture in the air, Pipe sweating. We now have our perfect Recipe for corrosion. So we make sure to provide Isolation to separate these two metals both above and below ground.
And especially if our metals are exposed to a Corrosive environment, like corrosive soils, waste water, acid rain, stuff like that.

9. Dielectric Isolation Materials
Weld-in insulator
Compression couplings
Insulated bolted couplings
Fiber board gaskets
Insulated unions
Plastic Pipe
Insulated meter swivels
Dielectric Coatings
Isolation flanges
Some of dielectric isolation materials are:
*Read Slide
We are going through each one of these and seeing pictures and passing around samples

10. Dielectric Isolation Types
Coatings isolate the surrounding environment from the structure, this prevents the electrolyte from coming in contact with the pipeline above and below ground.
- Coatings are our number one defense against corrosion on pipelines.
*Read Slide
That is something that you will hear throughout your career in corrosion…Coatings are the #1 Defense against corrosion. If you do not have a good coating system, then you will be casing your tail with high costs and time in for repairs and more cathodic protection.

11. Dielectric Isolation Types (Cont)
- Coatings can vary on dielectric strengths, in most cases based on mil thickness and type of materials.
- Coatings keep the current on the
pipeline. Current leaving the pipeline results in corrosion
- Coatings reduce the amount of holidays on a pipeline, and lessen the amount of protective current required. This lowers the cost of materials.
*Read FIRST BULLET
*Read SECOND BULLET point
(*Refer to image of iron ions leaving- reiterate) When we have an anode on our pipe, remember, having current on our line is not where the problem is…it’s where it jumps off of our line to return to the source that is the problem…..it takes metal ions with it, hence our corrosion.
*Read THIRD BULET point
Who here knows what a HOLIDAY is??
Very Good, a break or a void in the coating. We briefly discussed before how having a poor coating system can significantly increase the amount of current that we need to protect the system…so more Cathodic protection, more maintenance, high Costs….so when we have a good coating system applied with the adequate thickness and type for that environment, we will have less breaks in the coating, less holidays, and less current will need to be applied to protect they system.

12. Dielectric Isolation – Coating Materials
Types of coatings used –
- Liquid Epoxy – field applied two part - resin and hardener, one coat thickness of mils.
- Extruded Coatings – high density polyethylene with an under coat of mastic approx. 60 mils thickness.
- Asphalt Based Mastics – cold applied with brush to desired thickness
*Read Slide

13. Dielectric Isolation – Coating Materials (Cont.)
- Fusion Bonded Epoxy – thin film coating, preheated to 400 to 500 F, with applied resin 10 to 18 mils depending on customer’s design requirements
- Cold Applied Tapes – plastic film with butyl rubber backing 15 to 35 mils.
- Cold Applied Waxes – grease type materials, blend of petroleum wax 20 to 30 mils.
*Read Slide

14. Dielectric Isolation – Coating Materials (Cont.)
Who here has ever painted or coated smooth surface before? How did you prepare the surface before applying that coating? Why did you do that? Right, so that it has something to adhere to. Has anyone here ever painted something smooth without roughing up or cleaning the surface before? What happened? Right! It peeled right off!
In the next period, Jeff Didas will be talking to you about the different coatings and proper surface preparation, cure time, ambient temperature of application, before applying each one of them. Every different coating type has specific and detailed manufactures instructions on how to clean and prepare the surface before you apply any coating. IF YOU DO NOT FOLLOW THESE MANUFACTURERS INSTRUCTIONS ON SURFACE PREPARATION, cure time, so on and so forth, your below grade structure is going to look like this. Blisters in the coating, breaks in the coating, exposing the metal below to that electrolyte.
So again, Coatings are our number 1 defense system against corrosion. But your defense mechanism is only going to work if you install it properly.

15. Dielectric Isolation Devices
Meter Isolation & Above Ground Installations
Meter Swivels
- Installed at meter, isolates customer from pipeline
- Should be installed on outlet of meter
Read INSTEAD OF SLIDE:
This device is a meter swivel. Its installed at a gas meter and designed for Above ground use only. There is a small rubber gasket mechanism on one end of it to make sure that the metallic piping that you are connecting it to is isolated electrically from the other side.

16. Dielectric Isolation Devices
Meter Isolation & Above Ground Installations (Cont’d)
Insulated Unions
- Used on above ground metering & regulation stations to isolate piping
- Usually installed on threaded pipe
- Not recommended for below ground installation
*Read INSTEAD OF SLIDE: Another fitting is an Insulated Union. These are also for Above Ground use only. So very similar to the meter swivel, this is to be connected to two sections of pipe, one side of the pipe will be electrically continuous with the pipe and the other side has a dielectric material like a rubber gasket keeping the other side of the piping system from being in metallic contact with the other side.

17. Dielectric Isolation Devices
Plastic Pipe
- More economical to use versus weld-end fittings or flanges
- Recommended installing a minimum of 5 ft. of plastic pipe when insolating from steel pipe
- Very high dielectric properties
- No chance of failure due to shorting
If we have two sections of a metal pipe that need to isolated away from one another; Say we have a section of Bare Steel and a section of Coated steel. We can actually use a section of Plastic Pipe as an isolation method between the bare steel and the coated steel.
*Read Slide

18. Dielectric Isolation Devices
Weld-in Isolator
- Can only be installed by qualified welder (usually require NDE – x-ray and hydro test)
- Internal isolator components must be protected during welding process
Next we have Weld-In Insulators. These are purchased as one solid unit. You can see on the schematic on the slide that there is high dielectric material, usually a resin, in between the two metal halves. This piece is welded between two sections of metal pipe and there is no having mess with fittings and gaskets and other potential isolation failures. These pieces are already put together and sealed with kiss.
The only things that you have to be cautious about is that:
*Read Slide

19. Dielectric Isolation Devises
Insulated Flange Kit
- Components are non- conductive and provide isolation of pipes and fittings connected by flanges
- Flange kits consist of:
Nonconductive gasket
Isolation sleeves
Nonconductive washers
The Insulated Flange Kits are ok for both above and below ground use.
*Read Slide
There are a lot of little parts in these flange kits that can fail, but if they are installed correctly and carefully, they work pretty great. If you are unfamiliar with flanges it looks like there is continuous metallic contact going from one side to the other, but there are actually thin Millar washer rings, bolt sleeves, and gasket to make sure that continuity is broken between the two sides of the pipe.

20. Dielectric Isolation Devices
Isolation Compression Couplings
- For low to medium pressure pipelines
- For pipe up to 2” in diameter
- Non-conductive interior components
- Some devices prone to leakage
- Can fail due to soil stress or movement
- Less expensive than other alternatives
(Show real life example and mention that there is an example on the next slide)

21. Isolation Compression Coupling
Just like the weld-in insulator and the and Flange kit, this has Non-conductive interior components

22. Dielectric Isolation Devises
Isolation Bolted Couplings
- For pipelines 2” & larger in diameter
- Non-conductive interior components
- Can fail due to soil stress or movement
- Less expensive than other alternatives
Similar parameters as the Compression Coupling:
*Read Slide

23. Isolation Bolted Coupler
(Show real life example and mention that there is an example on the next slide)
Non-conductive interior components

24. Testing Isolators
Before installation check all isolators for electrical leakage. The resistance should be OL (over limit) on the meter.
Test all isolators after installation before backfilling do not use a ohm meter after the isolator has been installed.
Take pipe/soil potential reading on both sides of the isolator keeping the half cell in the same place. If the two readings are not different then the isolator may be shorted.
(Show example of OL on meter)

25. Gas Electronics Model 601 Insulation Checker
*LOOK UP MORE INFORMATION ON THIS

26. Dielectric Isolation Precautions
If the isolator is installed near high voltage AC lines or is in close proximity to electrical towers, precautions should be taken to prevent risks to personnel and damage from lightning strikes and stray AC currents.
- Methods commonly used:
Zinc ribbon
Magnesium anodes
*To provide a low resistant grounding system
*Read Slide
Stray Current was discussed in Chapter 3. When we have pipelines or below grade structures that run under over head transmission lines we have to take extra precautions to make sure that we are protecting personnel and our facilities. We also need to take extra measures to make sure that our Isolators have not failed due to stray AC currents or lightening strikes. Using the Magnesium anodes as a low resistant path for the current to drain is one way to keep damage from happening to the isolation devices and another way is to install long bands of Zinc ribbon parallel to your underground facility.

27. Dielectric Isolation Precautions
DOT subpart I, :
An insulating device may not be installed in an area where a combustible atmosphere is anticipated unless precautions are taken to prevent arcing.
- Methods commonly used:
Solid state device
Zinc grounding cell
a solid-state device allows grounding of a structure such as a pipeline, without interfering with CP current that was placed on it for corrosion
Zinc Grounding Cells are used in mitigation of voltages which may be introduced in pipelines by adjacent overhead AC power lines. Pipelines may be groundbed via zinc electrodes without attendant disruption of pipeline cathodic protection.

28. Cased Pipeline Crossing
Casings are great. They allow for additional loads to be on top of our pipe without the additional stress or compression of the load being on the pipe itself. These are typically installed under road ways and water ways. Sometimes they are old sections of larger diameter pipe that has been recycled and sometimes they are just new sections of larger diameter pipe.
So if we are inserting our metallic pipe THROUGH this metallic sleeve, what do we need to do between the two metallic sections? I’ll give you a hint,….its been the subject of this entire chapter. Good!! We need to Isolate them. So we use what’s called Casing Spacers. They are non-conductive support rings that go around the inner pipe. The pipe is then carefully inserted in the casing sleeve. Thises rings create space so that the pipe does not make contact with the walls of the casing pipe.

29. Cased Pipeline Crossings
The spacers are distributed at even intervals on the section that will be inserted into the casing.

30. Cased Pipeline Crossings
These casings are typically sealed both ends to keep mud, rocks, and water from entering into the casing. One or two casing vents are welded onto the casings for ventilation inside the casing. You may see those weird vertical pipes on either side of the road that look like canes? Those are casing vents. We will be looking at a picture of one in a few slides incase you cant image what one looks like.

31. Cased Pipeline Crossing

32. Cased Pipeline Crossings

33. Cased Pipeline Crossing
Sometimes the casings are filled with casing filler. Once the casing has been installed and backfilled, a truck with the casing filler pumps fluid into one of the two vents. When this special fluid comes flowing out the other end, then you know the casing has been completely filled with this casing filling solution. This fluid is non-conductive and the reason for filling the casing to keep other solutions such as mud and water out. You know…those conductive electrolytes.

34. Dielectric Isolation Protection
DOT Subpart I, :
All isolated metallic fittings shall be coated and cathodically protected.
Improper installation and application practices are the primary reasons for failure of isolators!
*Read Slide

35. Questions???
Thank You
Heather Groll