- 18 November 2016
- Posted by: Stm Coatech
- Category: Educational Articles
Polyethylene is synthesized from ethylene which is a compound derived from natural gas or petroleum. It’s essentially a thermoplastic, implying that it can be molten and remolded into the desired shape making it reusable and cost-effective. Of all the different kinds of plastics produced around the world, polyethylene is the most common and significant.
Polyethylene is manufactured in three different forms namely:
Low Density Polyethylene (LDPE),
High Density Polyethylene (HDPE) and
Linear Low Density Polyethylene (LLDPE),
Each of these three plastics has different applications ranging from containers, packaging and films to buckets and bottles.
PE coating is generally used at the petrolium and gas pipelines and being increasingly used for water projects as well. PE coating provides an excellent protection due to its properties such as resistance to aging and impact. When compared with bitumen coating and epoxy coating, PE coating has three main distinctive advantages:
– Mechanical and chemical properties are far better.
– Polyethylene coating can withstand higher temperatures than bitumen coating.
– Electrical insulation is much better.
Polyethylene coating is mostly applied to steel pipes that carry flammable and/or combustible gases or liquids such as petroleum, natural gas and alike.
Polyethylene coating is also very widely used in fire extinguishing lines, tap water and waste water lines and for piling pipes used in sea water.
Polyethylene coating can either be done:
-On site, by wrapping cold applied corrosion protection PE tapes according to DIN 30672.
-At coating factory, by extruding melted polyethylene according to DIN 30670 (or EN 10288, NFA 49710 or UNI 9099)
The first method of wrapping cold applied PE tapes is a lower quality method of polyethylene coating and should only be used if there is no other solution. It should be used either to protect the welded pipes’ joints or to protect a line pipe without interrupting its service, if it is already in use.
There are standards for the degree of cleanliness of the sandblasted steel substrate. All paint specifications that include sandblasting should specify the type of blast required. The standards currently in use follow the guidelines provided by NACE (National Association of Corrosion Engineers), SSPC (Steel Structures Painting Council) or Sa (Swedish Pictorial Standards).
- 1. Layer
Initially shot blasting is performed on the pipe surface to get o proper cleanliness and roughness and then heated about to 200°C with induction coil. Following, Fusion Bondedd Epoxy (FBE) is applied on the pipe electrostatically with special spray guns. Fusion Bonded Epoxy layer is the main layer providing the corrosion resistance.2. Layer
Extruded Adhesive film layer is applied by wrapping on the rotating pipe surface and pressed by a silicon roller roller to make a good adhesion. The Adhesive layer is providing the adhesion between the fusion bonded epoxy layer and the polyethylene layer.
Polyethylene layer is the top coat and is applied like the adhesive layer. Extruded polyethylene is wrapped on the rotating pipe surface and pressed by a silicon roller. After the completion of the coating process the pipe is cooled down about to 60°C by water shower. Polyethylene layer is providing not only the mechanical protection but also good resistance to enviromental factors like heat and UV rays.
*Excellent corrosion resistance. When exposed to either acid or alkaline media, an extended lifetime in highly corrosive soils is assured
*Strong steel adhesion: 20 times more adhesive than traditional plastic tape systems
*Excellent cathodic disbondment test results
*Excellent mechanical resistance
*Free of holidays: The hot extrusion method used to perform the coating assures a continuous and a uniform thickness profile, without air bubbles and holiday-free
*High dielectric resistance
*Superior bending ability for pipe laying applications
*High impermeability: Both the high-density polyethylene has low water permeation characteristics that allow improved isolation from the surrounding sea water compared to other coating systems
*Metal surface coating facilities
* Manufacture of silo, tank and connection equipment
* Chemical plants
* Industrial applications
* Machinery manufacturing sector
* Yacht and ship manufacturing sector
* Ventilation and climate conditioning applications
* Jumping platforms in the pools
* Reinforced concrete drinking water storage tanks
* Piers and piers concrete pavement
* Food industry storage tanks and ponds
* Decorative applications
* Advertising and fair applications
1.Petek Boru, Polyethylene (PE) Coating, Date of access: 16 December 2016, http://petekboru.com.tr/en/product/127-polyethylene-coating
2.Noksel, PE Coating, Date of access: 16 December 2016, http://www.noksel.com.tr/index.php/en/spiral-welded-steel-pipes/coatings/pe-coating.html
3.Mazlum Boru, Coating & Lining, Date of access: 16 December 2016, http://www.mazlumboru.com.tr/coating-lining.html