Advantages and Limitations: 3 Types of Mill-applied Pipeline Coatings
As mentioned in the last blog on field-applied coatings, pipelines must be coated with a protective barrier to resist corrosion from the natural elements. Coatings help to keep whatever pipelines are carrying—oil, natural gas, or water—pure and safe.
There are two main types of pipeline coatings. In the last blog, we discussed field-applied coatings that are applied on a plant location after the pipe has been manufactured. Mill-applied coatings are another pipeline coating method. This coating method is applied at the time of manufacture. Here, we will learn about some of the mill-applied coatings that can be applied to pipelines.
Multi-Layered Polyethylene
Polyethylene is one of the oldest materials used for pipeline coating, and it is classified as a thermoplastic polymer. When Polyethylene is used as a part of a multi-layered coating, it is applied as the last layer. Below that, a layer of Fusion-Bonded Epoxy and adhesive substance is applied. The adhesive substance, besides providing some degree of protection, holds the Polyethylene. The combination of High-Density Polyethylene (HDPE) and Fusion Bonded Epoxy (FBE) provides superior protection against moisture, chemicals, and other forms of damage.
Advantages
It is a very strong coating and can protect against physical impacts.
It provides excellent resistance to water and electricity.
It is resistant to corrosion and deterioration over time.
It is quite flexible, so it is resistant to breakage.
Limitations
It can only be applied at the mill and its application cannot be done on the field.
It has a relatively low resistance to heat and can get deformed.
Multi-layered Polypropylene
Like Polyethylene, Polypropylene is also a thermoplastic polymer. The chemical structure of Polypropylene makes it stronger than Polyethylene. Therefore, in pipeline coatings, Polypropylene is a more durable coating method than Polyethylene. High-Density Polypropylene (HDPP) covers some of the flaws and drawbacks of High-Density Polyethylene (HDPE). HDPP is the preferred option when a pipeline requires significant protection from the environment. When multi-layered application is performed, a layer of HDPP is put over an adhesive layer and a layer of FBE - just like Multi-Layered Polyethylene is administered.
Advantages
It has a much higher heat resistance than HDPE and doesn’t deform that quick.
Like HDPE, it provides additional protection to protruding segments of a pipe.
It provides the best protection against corrosion and penetration than any other polymer.
It has considerable electric and water resistance.
Limitations
It can only be applied at the mill. It cannot be applied in the field.
Being mill-applied, there is a fixed- cap for heat resistance.
Single and Multi-Layered Fusion-Bonded Epoxy
Fusion-Bonded Epoxy (FBE) is used widely across the world and it has several advantages that justify its popularity. It is used in a powder form and is usually applied at a mill rather than in the field. FBE gets its name from the molecular cross-linking exhibited by the resin and the way it is applied.
FBE is used both as a single-layered coating and as a multi-layered one. The multi-layered method is usually just two coats of FBE on top of each other.
Advantages
It provides superior corrosion protection for steel pipes.
It provides considerable resistance to electricity and water.
It provides resistance to abrasion.
Limitations
It is more susceptible to physical damage than other coating methods.
Water can sometimes permeate the barrier.
Polyurethane
Polyurethane is also a polymer, but the chemical composition of it is similar to that of liquid epoxy. It consists of resin and a hardener. Polyurethane is light but it provides outstanding protection against abrasion and corrosion.
Advantages
Despite its light composition, the protection it provides matches that of other polymers and protective materials.
It provides superior protection against water and electricity.
It is an easy and cost-effective process.
Limitations
The life-span of this coating is not impressive.
It is a hazardous material to work with.
Coating systems encased in a weight coat of concrete
Unsurprisingly, the use of concrete in pipeline coating is unmatched and undeniable. When we discuss Polymer Concrete, it is a coating made out of resin and concrete. If we talk about a coat of of concrete, it means that the pipelines are further enhanced by an added layer of concrete.
Advantages
The usage of concretes provides rock-hard resistance against impact and physical damage.
Total resistance against heat and electricity.
Excellent resistance against abrasion and corrosion
Limitations
Problems with transporting such pipes are commonplace.
The weight of these pipes can cause some issues if not properly addressed.
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