Pipelines can be translated as the modern mode of transport for essentials like water, oil, gas and many other things, within the country or even across countries. These pipelines pass through a variety of environmental conditions, both above ground as well as underground. These changes in atmosphere include changes in soil (marshy, salty and dry), composition of soil, changes in temperature, humidity, UV exposure and many other factors that may affect the performance of the pipeline.
The distribution of pipelines is a large and complex network that cannot be amended or changed frequently. These metal pipelines are generally used to carry crude oil, gases, water, chemicals, steam, and other petroleum products. Due to the constant need of these essential materials, it is not possible to approach the pipeline once it is installed. Therefore, it becomes very important to use highly durable materials while manufacturing these pipelines.
Risks To Pipeline Due To Corrosion
Just the way corrosion takes place on any metal surface, the same electrochemical reaction, also plays a big role in pipelines. In order to avoid corrosion, many household pipes have already shifted to PVC pipes, but due to the size of the pipes required for carrying essentials such as oil, water and gas, the same is not possible. For this reason, these large pipes need to be manufactured using metal and hence are subject to corrosion over a period of time.
Corrosion can not only lead to a loss in efficiency in transporting these essentials but more importantly, there is a huge risk of leakage. For this reason, in newer generations of pipes, the inside and outside coating of a pipe play an extremely crucial role.
Types Of Pipeline Coatings
Since steel or metal pipelines are prone to corrosion, they require extra attention in the form of high-quality coatings that can help to increase the service life of the pipeline. Based on the environmental condition, location, durability, and a variety of other climatic factors, a customized solution can be developed.
The coating for pipelines can be of two types: internal that is applied on the internal of the pipelines and comes in contact with the substance that is being transported, and external, which provides protection against all external factors that were listed above.
1. External Coating
The choice of coatings for external surfaces is driven by the area that is exposed. That requires answering questions such as: whether the pipeline is open to the sky or buried under the soil? Is it covered with insulating materials like glass wool or cement cladding? What are the various temperatures the pipeline will be exposed to over the year? What is the life of the pipelines the customer is looking for? The external coating without cladding is covered while coating with cladding or insulation falls under another class of coating viz. CUI – Corrosion Under Insulation Coatings.
Some basic criteria to keep in mind while developing these coatings are corrosion resistance, abrasion resistance, and high tensile strength yet relatively strong to withstand UV rays and other chemicals in the soil. Abrasion resistance is one of the important criteria which drives coating selection, as coated pipes are pushed through the soil in case of buried pipelines, while over-the-ground pipes are continuously exposed to factors like rain, sunlight, pollution, and mechanical abuses. Depending upon exposure condition, below coatings are prescribed:
a. 3LPE – 3 Layer Polyethylene
LPE is a complex process of external coating. This process includes three different layers of coating, hence it is named 3 LPE.
- First layer is application of fusion bonded epoxy powder (FBE) over a superheated pipe
- Second layer is application of hot melt copolymeric or grafted adhesive
- Third layer is application of readymade polyethylene sheet over the adhesive
This process is complex and it is a factory applied process. The performance parameters of 3LPE should conform to specifications like ISO 21809, CSA Z 245.
b. Liquid Coating
1 – High Solids Epoxy Coating
Liquid epoxy pipeline coating are amongst the most widely applied coatings for pipelines. Due to epoxy’s high cross linking density, epoxy paints are highly durable and provide excellent chemical resistance.
2- Coal Tar Epoxy Coating
Coal tar epoxy is used for external and internal of pipeline coating. This coating system is cost efficient and offers excellent corrosion resistance, but due to slow drying property and more importantly its carcinogenic nature, governments are discouraging the use of this coating.
3- High Solids Polyurethane Coatings
More popularly known as elastomeric polyurethane coatings, liquid polyurethane coatings offer a highly flexible yet hard coating for pipelines. These products are fast drying and can build up a film of almost 1mm and are very easy to apply. Due to these advantageous properties, these coatings have gained popularity in the market against the time-consuming and expensive process of cement grouting operation for concrete pipes.
AWWA C222 is a widely used specification for Elastomeric coating of pipelines.
2. Internal Coating
The choice of coating for internal of pipeline is driven by the material which will be flowing through it. Generally water, oil or gas flows through the pipes and there are various systems prescribed in different standards and specifications, accordingly.
Epoxies are known for their corrosion resistance, excellent mechanical performances, hence it is the most preferred system for internal of pipeline.
The coating applied to the internal surface of the water carrying pipeline should be solvent free and free from any contaminants which are harmful to human life at large. The coating have to pass through different national and international specifications, like CFTRI, IS 158, US FDA, WRAS, BS 6920, AWWA C210, NSF 61, etc., where products are tested for various properties like change in quality of water, leaching of chemicals, bacterial growth, change in taste and smell, and reduction in oxygen demands. Once product conforms to above mentioned standards then the product can be used for application in potable water carrying pipeline.
Gas is another major material which flows through the pipe, generally gas contains sulphur compound so there is high probability for corrosion. Secondly, gas flows under pressure and to maintain continuous flow, pressure needs to be maintained. To ensure that, a coating with no or very low resistance to the flow of gas is required. These coatings must meet the performance requirement as per API RP 5L2, ISO 15741.
Importance Of Pipeline Coatings
Pipelines are widely used across the world. As per current data, pipeline networks are spread across 124 countries measuring up to 80 lakh kilometres. US, Canada & Russia alone contributes to approximately 70% of this network, transporting oil, gas and sewage. In India, the network is relatively small, approximately 50,000 kilometres, mainly for water and gas. Due to the sensitivity of the materials these pipelines carry, the maintenance of this network is very important as any disruption due to corrosion or leakage can impact the nearby community and possibly even the economy of the country.
How To Select Pipeline Coating Companies?
Before applying pipeline coating to industrial pipes, it is extremely important to focus on the quality and durability of the coating. Being one of the top paint manufacturers in the industry, Grand Polycoats is a trusted brand that have a wide range of product offerings for varied sectors. From railways to manufacturing companies, electrical industry and water or gas processing companies, all depend on the pipeline network to process their entire work.
Grand Polycoats is the best choice to cater all pipeline coating needs for your business. You can expect a wide range of products like Polyurethane Elastomeric Coatings, Glass Coating, Weldable Coatings, and Plastic Pipeline Coatings.
We hope this blog was helpful in getting to know Pipeline Coating and its importance. If you have any questions or need assistance in choosing the right system, please reach out to us at firstname.lastname@example.org.