Corrosion is constantly attempting to degrade the performance of metal pipelines. The corrosion can be from dissimilar metals (galvanic corrosion), stray current corrosion from unintended sources of electricity, simple corrosion of similar metals (with varying anodic/cathodic sites), microbial induced corrosion and there are lesser-known types of corrosion.
Cathodic Protection Systems

To prevent simple corrosion and galvanic corrosion, owners of metal pipelines will often send an electrical field through the pipeline equalizing the electrical potential for all sites (this is commonly referred to as a cathodic protection system) that dramatically reduces the effects of corrosion. Owners will also coat the metal pipelines to reduce the cost of electricity needed to protect the pipeline.

The Role of Isolation within CP Systems

To further reduce the cost of electricity to protect the pipeline and to keep the electrical field to an effective level, isolation is often used in the form of flange isolation kits or monolithic isolation joints. Both products accomplish the same task, but flange isolation kits (FIKs) are predominately found in above ground installations while monolithic isolation joints (MIJs) are commonly found below ground. The terminology can change a bit regionally, but names like flange insulating kits, iso-kits, electrical isolation gaskets are often used to describe flange isolation kits and iso-joint, iso-block, monobloc, monoblock or insulating joint are all synonymous with monolithic isolation joints. Both FIKs and MIJs will stop the electrical flow through the pipeline and serve to keep the electricity in the areas that the pipeline owner wanted to protect. FIKs and MIJs break the metallic path in the pipeline and optimize the protection of the pipeline. Because they break the metallic path, they also stop stray current up to significant voltages. Breaking the metallic path as a function of an FIK or MIJ is very important because it will stop the electrochemical reaction between dissimilar metals. Pipelines will typically have valves, compressors, pumps, meters, pig launchers, etc. that are not made of the exact metallurgy as the pipeline itself. This difference in metallurgy brings with it differing potentials in the metals. With differing potentials and an electrolyte, the pipeline and the component are ripe to endure galvanic corrosion. By simply inserting a flange isolation kit (FIK), the metallic path between the component and the pipeline is eliminated and galvanic corrosion is then mitigated.

Microbial Induced Corrosion

When an FIK or MIJ is made to the pipe bore, this can dramatically reduce microbial induced corrosion (MIC) issues. Microbe colonies will build when there is an area to hold media such as a gap between flanges. If the FIK or MIJ is made to the pipe bore, the gap is eliminated and the potential for microbial colonies to grow is dramatically reduced.
There are adjacent benefits to using FIKs and MIJs in that by decreasing the amount of electricity needed to protect a pipeline, owners will likely see reduced issues with coating disbondment, and hydrogen induced corrosion. Both of which can be caused by higher levels of electrical flow through the pipeline.

Fire Safe Isolation Kits

There are many types of flange isolation kits and monolithic isolation joints on the market today. It is recommended that if the pipeline is carrying a flammable material that a fire safe flange isolation kit be used. If chemicals are added to the media to reduce microbial colonies from forming, to act as surfactants, to reduce iron sulfide build-up or for any other reason or if chemicals such as hydrogen sulfide are part of the media stream, it is important that the isolation kit is chemically compatible with the chemicals being used.

Role of Isolation Gasket on Emissions

Today, many companies are attempting to achieve greenhouse gas emission reduction goals. If the pipeline is part of that effort, it is recommended that glass reinforced epoxy (GRE) based isolation gaskets and phenolic isolation gaskets BE AVOIDED as these materials are permeable. It is also recommended that when an isolation product is used (either flange isolation kit or monolithic isolation joint), that a pipeline decoupler also be used to mitigate stray current or lightning effects that are beyond the capabilities of the isolation kit or joint.
A common flange isolation kit will consist of an isolating gasket, an isolating sleeve and isolating washers (preferably fully coated and encapsulated stainless steel washers).

Typical flange isolation kit:

Typical monolithic isolation joint:

Introduction

Emissions, often referred to as Greenhouse gases (GHG) have been identified as a contributing factor in climate change. Climate change is one of the worlds more pressing challenges.

*Approximately 1-3% of methane leakage is the result of leaks in equipment intentional pressure release practices, or accidental releases during normal transportation, storage, and distribution activities.

Emissions is defined as the production and discharge of something, especially gas or radiation.  In this instance we are talking about the production of unwanted gases often referred to as Greenhouse gases (GHG) that have been identified as a contributing factor in climate change. Climate change is one of the world’s more pressing challenges.  Manmade carbon gas emissions total over 29 GT(gigatons) annually.  To meet a 2° target according to the Paris Agreement, 15 GT of CO₂ must be eliminated.

Fugitive emissions (unintentional production and discharge) account for 5.2% of all Greenhouse Gas Emissions according to the World Resources Institute, 2017.  Sealing products that are extremely tight sealing are necessary to assist in the reduction of Greenhouse Gas Emissions globally.

Leakage Rates of Isolation Gaskets vs a Spiral Wound Gasket

 

Note: Testing Performed at ambient temperature/500psig He /5hrs / 7,500psi gasket stress VCS-ID™ was single design only

Another major improvement to emissions and sealing is to participate in GPT’s GFIT program, GPT Flange Isolation Training.  This program certifies participants in the proper alignment of flanges, the correct method of evaluating flange faces, tried and true torquing techniques, inspection procedures and provides “hands on” elements for both installation and isolation gasket testing.

Which Sections of Oil and Gas Processing are Under Requirements by the EPA to Adhere to Emissions Standards?

 

Have you ever installed an isolating kit in a pipeline, successfully tested for electrical isolation, but later failed isolation following a hydrotest?

An Accurate Isolation, World Pipeline Magazine, Tim Hurley.

What part does load play with emissions and sealabilty?

 Proper compression of the gasket is extremely important, but can be usurped by poor flange conditions or installation practices. We recommend using an installation procedure like this and making sure that flanges are aligned.

Is there training that can be taking to improve sealability for our products?

There are two training programs that GPT offers. One is the GFIT (GPT Flange Installation Training) program and the other is a Level I, II and III training program that teaches more about product selection, design and use.

Are there pitfalls that I can avoid regarding emissions and sealability?

The common issue that we see is the use of homogeneous GRE products in gaseous applications and then concern when they initiate some type of leak detection. It is quite common for these types of products to permeate (especially under higher pressure), so for gaseous applications, we recommend the use of a PTFE ID sealed isolation product.

Can liquid permeate through my GRE gaskets?

Surprisingly, the answer is yes. With high pressure and time, the media can permeate through the GRE. Another reason we recommend a PTFE ID seal to prevent any media contact with the GRE.

Introduction

Corrosion is a natural process where refined materials react with their environment, and revert to a more chemically-stable form. Below we discuss some of the most common topics and questions surrounding corrosion.

Table of Contents

1. Basics of Corrosion
2. The Galvanic Series
3. Cathodic Protection Design
4. Pipeline Corrosion Protection with Isolation
5. What is External and Internal Corrosion?
6. What was the Impact of Pipeline Incidents?
7. Why do we put Pipes Below Grade?  What Challenges Does it Present?
8. How does Electrical Isolation help Prevent Corrosion?
9. What Applications Require Electrical Isolation?
10. What are Common Causes for Isolation Failures?

Basics of Corrosion

Corrosion is a constant force in industries from Oil & Gas production, Maritime, to construction of highways, bridges, pipelines, & any underground systems. Corrosion is a natural process where refined materials react with their environment, and revert to a more chemically-stable form. The rate of corrosion is dependent on a number of environmental variables, but for corrosion to occur four basic elements are required (Anode, Cathode, Metallic Path, and Electrolyte).

In the fight against corrosion, integrity engineers focus on removing the presence of one or more of these basic elements. The first defense against corrosion is a coating system which helps to protect the asset from the surrounding electrolyte. Coatings are typically used as a barrier coating, protecting the substrate from contact with the Electrolyte. In addition to serving as a barrier, some coatings also use inhibitive, or sacrificial pigments, causing passivation, or a sacrificial anode to form at any Coating Holidays or defects.

Integrity engineers must also utilize cathodic protection (impressed or passive) to protect assets, as coatings can be damaged, which can amplify corrosion locally at the defect (Coating Holiday, cracking, etc.). Cathodic protection systems combat corrosion by converting all of the anodic (active) sites on the metal surface of an asset to cathodic (passive) sites by supplying electrical current (or free electrons) from an alternate source to equalize the potential on the surface of the metal structure (left).

The Galvanic Series

Materials are listed from most Noble (passive), to most electronegative (active) in the Galvanic series. In reference to the below graphic, Magnesium is the most active. When two metals are coupled, the more active will share electrons with the more noble material causing an oxidation reaction (rust) at the electronegative material, and a reduction reaction at the more electropositive (noble) material.

Cathodic Protection Design

CP does not eliminate corrosion, but actually transfers corrosion current from the protected structure (asset) to the cathodic protection anode. This is the case in Galvanic (Sacrificial) anode systems, and impressed current system.

A sacrificial anode system is easily installed, requires no external electricity, and minimal right-of-way cost. The limitations of sacrificial anodes are current output, require anodes to be replaced once an anode has been spent / consumed, and a higher cost per unit ampere than impressed current. Based on the above characteristics, galvanic systems are used in specific applications (offshore, within vessels, or in an area with many other metallic structures). Galvanic anodes are commonly used in combination with impressed current systems at problem/ repair areas, shorted casings, cathodic interference / stray current discharge points, areas influenced by electrical shielding, and locations with significant coating damage.

Impressed current systems are comprised of an external power source and anodes. The power source (rectifier) forces current to flow from the anode to the structure to through the electrolyte.

Pipeline Corrosion Protection with Isolation

Pipe and the metallic pipeline components are supplied coated (Valves, Fittings, etc.). Following welding, and inspection field applied epoxies are used to cover exposed weld bevels.

What is Pipeline Isolation?

In metallic pipelines, corrosion is the constant attempt by nature to reduce pipelines to their original oxide state. It is an electrochemical reaction that has four parts: anode, cathode, metallic path and electrolyte. Flange isolation and joint isolation are a means of preventing electrochemical reactions from occurring between two dissimilar metals by breaking the metallic path, or preventing the current in a cathodic protection (CP) from traveling beyond the area intended to be protected by the CP system. ;

In addition, Cathodic protection (CP) systems are used to supply extra electrons causing the asset to be a passive location or a cathode. In order to control what is protected by these electrons, isolation is used as the ‘bookends’ of a CP system. Isolation will allow you to protect specific assets, and eliminate any dissimilar metals connection. An example would be a pipeline coming into a compressor station, the role of the CP system is to protect the pipeline, but not the compressor station. Isolation would be used on either side of the compressor station to avoid the large metallic compressor station draining the CP current.

What is External Corrosion?

External corrosion occurs due to environmental conditions on the exterior surface of the steel pipe that can cause an electrochemical interaction between the exterior of the pipeline and the soil, air, or water surrounding it. Galvanic and atmospheric corrosion are common types of external corrosion.

What is Internal Corrosion?

Internal corrosion occurs due to a chemical attack on the interior surface of a steel pipe from the products transported in the pipe. This can be from either the commodity transported, or from other materials carried along with the commodity, such as water, hydrogen sulfide, and carbon dioxide.

Is Natural Gas Corrosive?

Natural Gas can mean gas containing methane, Ethane, H2S, water, and COS, and other components. Natural Gas will be corrosive because of the H2S and water. Commercial Natural Gas is treated, and it is no longer corrosive.

What is PHMSA?

PHMSA is a portion of the DOT. PHMSA is the Pipeline and Hazardous Materials Safety Administration. Est. 1970.

How Many Pipeline Failures are the Result of Corrosion?

Data shows that from 1998-2017 approximately 18% of pipeline incidents on average were caused by corrosion, learn more here.

What was the Impact of Pipeline Incidents?

Why do we Put Pipes Below Grade?  What Challenges Does it Present?

While there are above ground pipelines, most notably the Trans-Alaska Pipeline System (TAPS). The significant majority of pipelines are buried. Pipelines are often located below grade due to permitting requirements in order to minimize the impact to the surrounding communities by concealing it from view. Pipelines will come above ground for pump stations, valves, and other equipment requiring access.

Locating pipelines below grade introduces the pipeline into constant contact with an Electrolyte, one of the four elements needed for a corrosion cell. The first line of defense is a Barrier Coating, which creates a barrier between the Electrolyte and the metallic structure.
How Does Electrical Isolation Help Prevent Corrosion?

Electrical Isolation in a pipeline system is achieved by installing Flange Isolation Kits (FIKs), or Monolithic Isolation Joints (MIJs) in line to separate equipment or pipeline segments. FIKs & MIJs utilize materials with resistance to electrical current in order to block the transfer of electrons, effectively eliminating the metallic path, one of the four elements needed for a corrosion cell.

What Applications Require Electrical Isolation?

Electrical Isolation is used to break up pipeline segments to optimize current output from rectifiers in Impressed current cathodic protection systems. It is advantageous to break up long pipeline runs with isolation to improve efficiency, and minimize the impact of maintenance or repair on the pipeline.

Electrical Isolation is also used to prevent interference or damage to electronics, which may be found in valves, sensors, compressor stations, and other equipment.
Electrical Isolation should also be used in the presence of any dissimilar metal connection to prevent a galvanic coupling.

What are Common Causes for Isolation Failures?

Failure of electrical isolation gasket, joint, or union can be caused by environmental factors, mechanical forces exerted on the pipeline system, or improper installation. The likelihood of failure due to environmental factors can be controlled by the materials used.

A variety of materials are used to provide electrical isolation within a pipeline systems. The different materials have different characteristics which impact their efficacy (Electrical Resistance, Water absorption, Dielectric Strength, Permeability, Temperature range, Chemical Resistance, Compressive strength).

Electrical resistance is a measure of how well a material resists electrical current.

Isolation materials which have a high water absorption will be impacted by humidity, rainwater, and snowmelt. The moisture within the isolation material will cause a significant reduction in the electrical resistance. In conditions with temperatures fluctuating from above to below freezing also have the potential for cracking of the isolation material.

Introduction

A seal assists in connecting systems or mechanisms together by preventing leakage, containing pressure or excluding contamination.

A flange Isolation(insulation) gasket used in conjunction with an isolation kit (washers & sleeves), does all these things, but also provides electrical isolation, reducing or mitigating the build up of corrosion.

Table of Contents

1. What is Pipeline Sealing?

2. Why do Pipeline Sealings Fail?

3. Changing Oil and Pipeline Gas Conditions

4. GRE Isolation Gasket Pitfalls

Why do Pipeline Seals Fail?

Over 80% of leakage or isolation issues are from poor installation.

Installation

The most common pitfalls for a good seal is installation.  Over 80% of leakage or isolation issues are from poor installation although we see this potentially changing in the future due to the fact that oil and gas companies are becoming more concerned about greenhouse gas emissions.  As levels are put in place as maximum leakage levels, gaskets that were once deemed acceptable from a sealing level would potentially be labelled as “leakers” requiring a selection of a new type of isolation gasket. This could be entirely independent of the method of installation.

Most likely it has to do with installation.  Over 80% of failures are attributed to installation issues.  The most common installation issue is not creating a large enough gap for the gasket to EASILY be inserted between the flanges.  Flanges should be aligned prior to the insertion of the gasket. The second most common cause of failure is improper application of torque.  Make sure to use the manufacturer’s recommended torque, to install in three even increments of 33%, 66% and 100% of the recommended torque. Also, be sure to use a “star” pattern when torquing.  A few other quick checks would be to make sure you are not using a lubricant that contains metallic particles, make sure that your washers are not “reversed” the metal washer must be the washer contacting the nut and make sure the nut “flat” is toward the washer, not the nut side that has raised printing.

Changing Oil and Gas Pipeline Conditions

Pipeline conditions have been changing over the last 50 years.  More and more aggressive chemicals are finding their way into the media stream (hydrogen sulfide, steam, carbon dioxide, carbon monoxide, etc.).  Temperatures have risen, pressures have risen and we are seeing a trend towards larger diameter pipelines which can be much more difficult to properly install and seal.

As a world leader in the manufacture of isolation products coupled with a significant engineering team, GPT has discovered that the changes in our pipelines are affecting traditionally used isolation gaskets.  The combination of higher temperatures and higher pressures can cause blowouts of GRE based materials that do not have a glass transition temperature high enough for the operating temperature. Chemical combinations of sour gas can chemically attack GRE.  What can compound this issue is the propensity for GRE to all media to permeate into the body of the gasket. This can cause a loss of volume, mass and density of the GRE. This in turn, can reduce bolt load causing greater leakage and potential for blowout.

Changes in the workforce have not helped pipelines to become better sealing either.  The 5 year average for pipeline incidents according to PHMSA data shows that there have been an average of 666 incidents for the 5 year period from 2014 through 2018, however the 5 year average from 1999-2003 was only 474 incidents.  Some likely reasons are that millenials are changing jobs at a much greater rate than baby boomers. LinkedIn has studied 500 million users over a 20 year period and has found that a millennial will change jobs an average of four times their first 10 years out of school.  This means that the likelihood of a pipefitter being a long term, highly trained individual is diminished. Since more than 80% of gasket failures occur due to poor installation, a lesser trained workforce will not benefit the situation.

GRE Isolation Gasket Pitfalls

Unfortunately, Glass Reinforced Epoxy (GRE) the material that most isolation gaskets are constructed of, has significant permeation (see photo to the right).  This is a GRE gasket (G10 in this case) with 300psi Nitrogen gas. Snoop™ leak detector has been applied and it is evident that the nitrogen gas is easily passing through the gasket.  Carbon monoxide and carbon dioxide would perform similarly as would ethane and methane.

Oddly enough, isolation gasket manufacturers for years knew that the gases permeated through the GRE, but attempted to develop ways to use the media to drive through the body of the gasket and push the seal against the flange creating a seal (often called a “self energizing seal” and sometimes called a “leak to seal” design).

Fortunately, GPT has developed a patented method for sealing the media before it ever gets to the GRE.  The product is called VCS-ID and has a PTFE inside diameter (ID) seal (see image).

The PTFE ID seal is machined to lock into the GRE and the 316SS metal core so that it is unable to come.

When I put “Snoop” on my gasket in a flange, bubbles appear very quickly and easily.  Can I put more load on the gasket and stop the leak?

Probably not if you are using a glass reinforced epoxy (GRE) gasket.  It is much more difficult to compress a GRE gasket as compared to a fiber or PTFE gasket.  GRE unfortunately is prone to “permeation” and what you will often be seeing is permeation through the gasket rather than leakage past the seal.  The solution to this is VCS-ID or Evolution which has a PTFE seal that stops the media before it gets to the GRE.

What is the best sealing isolation gasket?

From our lab testing, the Evolution gasket is the best available isolation gasket for an extremely tight seal.  Typical sealability values are in the range of 1x10-9 Pa.m3/s/mm helium in ambient temperature testing. Most other isolation gaskets are in the 1x10-4 range.