Cased Pipeline Crossings and VCI [Rusty Talks]

Rusty chats with Dean Lioliou, MATCOR Strategic Account Manager and AMPP Central Area Chairman

Cased Pipeline Crossings - Preventing Corrosion
Rusty: Dean, thanks for taking a few minutes to discuss the application of VCI for cased pipeline crossings. First, what is a cased crossing?

Dean: Cased pipeline crossings are a common feature in the industry. They are used primarily at road and rail crossings.

The casing (also referred to as the encasement pipe) is a larger diameter pipe that is designed to take the loading from vehicle or train traffic on the road and absorb/deflect that loading from the carrier pipeline inside the casing.

In addition to the encasement pipe and the carrier pipe there are other key elements to a case crossing. Notably, there are non-metallic spacers that position the carrier pipe inside the encasement pipe, and dielectric end seals that prevent the ingress of water and soil. Finally, there are vent pipes on each end of the casing. These provide a warning and route product to a safe location in the event of a pipeline leak inside the sealed casing.

pipeline casing vents web
Pipeline Casing Vents on each side of a road crossing in Chalfont, PA

There are tens of thousands of these cased pipeline crossings throughout the United States.

Rusty: So, what are the corrosion challenges with cased crossings? What can go wrong?

Dean: Pipeline operators have found that an inordinate amount of pipeline leaks occur at cased crossings. Therefore, operators are actively looking to eliminate these whenever possible.

It is important to evaluate existing casings periodically.
Two mechanisms can adversely affect pipeline integrity at cased crossing locations.

The first is a metallic short. This results from the carrier pipe shifting inside the encasement pipe. It causes a direct metallic contact between the carrier pipe and the encasement pipe.

Shorted casings can significantly impact the cathodic protection system protecting the pipeline. This is due to the encasement pipe drawing CP current away from the carrier pipe. Shorted casings also increase the risk of AC Interference, AC induced corrosion and shock hazards at the above ground vents.

The second casing failure mechanism is related to the integrity of the end seals over time. In many cases, these end seals develop leaks allowing water and soil into the space between the carrier pipe and the encasement pipe. This creates an electrolytic couple. The introduction of these contaminants can lead to accelerated rates of corrosion of the carrier pipe.

Rusty: What are my options if my casing is shorted or the carrier pipe exhibits signs of corrosion?

Dean: You can employ several strategies to address corrosion concerns with cased pipeline crossings:

Excavate ($$$). With this first approach, you dig up the casing and either remove it entirely or repair it. Repairing involves exposing one or both ends to repair the end seals and if necessary, readjust the spacers to clear the shorted condition. This is a construction intensive operation but, in many cases, can restore the cased crossing to an as-new condition.

Fill with Wax ($$). A second approach is to fill the annular space with a high di-electric wax. There are a variety of wax treatment options available. Typically, the wax is introduced through the vents and every effort is made to fill the entire annular space with the wax material.

The wax acts much like a coating covering the carrier pipe and prevents corrosion like a coating system. The industry has found that this is not always a complete solution, since voids in the wax fill can allow pockets of corrosion.

Fill with VCI ($). The third approach is to pump the annular space full of an aqueous gel or powder, or a slurry formulation of corrosion inhibitor material. The corrosion inhibitor is typically a combination of volatile corrosion inhibitor (VCI) and soluble corrosion inhibitor (SCI) that combine to stop corrosion. This method has received industry and regulatory approvals over the past decade and is gaining market share as operators become familiar with the technology and its advantages.

Rusty – How challenging is it to fill a pipeline casing with wax or with VCI?

Dean – Both operations are similar in many respects.

For both wax and VCI filling installations, repairing the existing casing is often the first step. You inspect the end seals and spacers, and where appropriate, remove and replace them.

The interior space between the carrier piping and the casing is flushed clean of dirt and other debris. Once the repairs are complete and the ends are sealed, you calculate the volume of product needed to completely fill the space between the carrier pipe and the casing.

Then the product is prepared according to the manufacturer’s recommendations. Pumping or filling the space is different for each of the type of fill, but both technologies require appropriate equipment and experienced installers.

Wax fills typically use a heated wax product for larger casings. Cold flowing wax can be used on some smaller casings.

For wax fill applications, the space between the carrier pipe and the casings must be completely flushed and cleared out during the repairing of the end seals.

Even with a well-prepared casing, achieving a complete wax fill is very difficult. Voids and gaps are typical.

One published study of 143 wax filled casings found that the average fill was 81%.

For VCI installation plans, the appropriate vapor corrosion inhibitor types and delivery methods are an important considerations. The VCI slurry needs to be mixed properly before being pumped into the casing using the appropriate pumping equipment.

Because VCI applications typically use an aqueous slurry with an experienced installer, VCI is easier to install than a similar wax application. The VCI component is designed to release from the aqueous solution after being pumped into the casing to fill all vapor spaces. Therefore, concerns over gaps and voids are non-existent.

Rusty – What about concerns with bacteria in the space between the carrier pipe and the casing?

Dean – This is an area where the two fill types differ significantly.

For wax filled casings the goal is to completely fill the space with wax displacing or encapsulating any bacteria. However as noted above, areas of incomplete fill or voids in the wax encapsulation can leave space for bacteria to continue to grow.

With VCI, the VCI chemistry increases the pH (9 to 9.5 is typical) inside the casing. This range makes it very difficult for bacteria to grow, while also neutralizing any acid secretions from the bacteria.

Rusty – Can Cathodic Protection help with protecting carrier pipes inside filled casings?

Dean – With wax filled casings, the wax has a high dielectric value and does not allow cathodic protection current to pass.

This prevents the carrier pipe and casing from draining cathodic protection current from the pipeline CP system, but it also provides no protection to the carrier pipe. The VCI gel that sets up is conductive and allows cathodic protection current flow. Some evidence supports the benefit of cathodic protection and VCI working in tandem to prevent corrosion.

Rusty – How can pipeline operators monitor the effectiveness of any cased crossing corrosion solution?

Dean – Most pipelines can be assessed using In Line Inspection (ILI). These pipelines can use smart tools with MFL, and other tools, to assess and monitor corrosion in the carrier pipe with a casing.

For wax filled casings, if ILI is not an option, there are no other good monitoring options. For pipelines that cannot be inspected using smart pig technology, conventional above ground pipeline testing technology is limited.

For VCI filled casings, we employ various technologies in conjunction with VCI including coupons, ER Probes and /or UT probes installed between the carrier pipe and the pipeline casing, to monitor the effectiveness of the VCI in the casing. These are installed and connected to RMUs for remote monitoring, or wired to a local junction box for direct reads during surveys.

Rusty – Any final comments Dean on Cased Pipeline Crossings?

Dean – Cased crossings are a challenge for pipeline owners.

Should you have any additional questions, please reach out to a MATCOR account representative for more information. As a full-service corrosion company, we have extensive experience and a wide range of capabilities including both wax and VCI installations for casings.


Learn about vapor corrosion inhibitors for aboveground storage tank corrosion prevention.


Have questions or need a quote for corrosion prevention materials or services? Contact us at the link below. For immediate assistance, please call +1-215-348-2974.

Contact a Corrosion Expert

Cathodic Protection Construction and Inflation

How Today’s Supply Chain Issues Affect Our Industry

For over a decade both the consumer and construction worlds have enjoyed very stable pricing with modest annual increases. 2021 is a very different picture. Suppliers are dealing with supply chain issues and price spikes. These increases far exceed the 2-3% we typically see for cathodic protection construction projects.

Cathodic Protection Construction

In today’s environment, manufacturers and service providers deal with this uncertainty by providing quotes with very limited duration. In some cases quotes are only valid for a few days. This is a far cry from the 30- to 90-day validity once common in the industry.

The challenge for everyone in the industry is the lag time between the budgeting phase of a project and the purchase of materials. For major projects, the planning, permitting and pre-construction phases of a project can take years.

It is important to note that the inflation figures we see quoted in the news are typically “consumer price index.” These inflation figures run about half of the less reported “producer price index,” which more accurately captures manufacturers’ material costs.

When you hear that the core inflation rate is 4 or 5%, you can reasonably expect that material costs are rising at 8-10%.

What can companies performing cathodic protection construction do to manage project budgets in an inflationary environment?

  • Take action quickly. Time is money. The longer you wait to purchase materials and services, the more you can expect to pay for them. Once you have approval for a cathodic protection project, order the key materials quickly.
  • Share the inflation risks fairly with your suppliers and contractors. Holding a contractor to yesterday’s prices is unrealistic and unsustainable. That contractor will be looking for ways to cut costs. And they may accomplish it by cutting quality, reducing the scope, substituting cheaper materials, or demanding change orders at every opportunity. This type of relationship does not benefit any of the parties.
  • Consider ordering materials separately from construction. This applies especially to materials you can pre-stage, have long storage life, or repurpose easily for other projects.
  • Be realistic when providing project schedules. Haven’t nailed down all the landowner or permit issues? Then don’t tell your suppliers and contractors that you expect the project to kick off next month.

What is MATCOR doing to address issues related to cathodic protection construction projects?

As a supplier of cathodic protection materials and construction services, MATCOR takes a team approach. We are eager to engage with customers and work together to minimize impacts from cathodic protection supply chain disruptions and price increases.

Stretch Your Cathodic Protection Budget

Now is a great time to think about stretching your 2021 budget and getting a jump start on 2022.

Days are growing shorter and long summer days are turning to dark winter days. This makes it difficult to spend the last of your CP budget dollars on completed construction projects this year.

Equipment and crews are generally already booked. However, MATCOR and our sister company JA Electronics can still help you spend your 2021 budget dollars productively.

We still have manufacturing capacity for this year. Purchasing cathodic protection anodes, rectifiers and other CP components now can help use up those remaining funds while also giving you a head start on 2022 projects.

Get Your Act Together

The first quarter is often a slower quarter in the construction business since companies are still planning their 2022 CP spend.

But what if you had your act together and were ready to start cathodic protection construction projects earlier in the year?

Well, we at MATCOR are eager to talk to you about special off-season pricing that we can offer for Q1 projects. Are you in a position to buy materials in Q4 and install them in Q1 of 2022? We can load share our construction capacity and provide off-peak pricing, making it very attractive indeed to have your act together.


Have questions or need a quote cathodic protection materials or construction services? Contact us at the link below. For immediate assistance, please call +1-215-348-2974.

Contact a Corrosion Expert

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