PE Pipeline for Seawater Refrigeration System

Plastic pipelines for corrosive media with butterfly valves

We are pleased to share this reference on the design and construction of a Seawater Refrigeration System. it is with pleasure that we share the contents disclosed by our client Atolli Oy who has chosen our PVC butterfly valves for this important project.

The project involves the replacement of metallic pipeline with plastic ones, within the framework of an energy plant cooling system. The seawater flowing inside the pipeline is, as known, characterized by high corrosion properties on metals, which lead to leakage problems.

Corrosion

What is iron corrosion?

Corrosion is the deterioration of a metal produced by a natural electrochemical reaction. With its immediate surroundings. This reaction causes the metal structures or objects to convert to a more stable form, such an oxide, hydroxide or sulphides. Metals corrode when they react with another substance such as oxygen, hydrogen, an electrical current or even dirt and bacteria.

Material selection for the Seawater Refrigeration System

Sea Water is the media

The media in this project is the seawater. The water seas and oceans have an average salinity of about 35 kg/m³. The salinity measurement is made by determining its electrical conductivity, which is related to the number of salts dissolved in the water. This property has a fundamental correlation with the corrosion potential. Water itself enables fast oxidation.

Plastic against corrosion

The choice of plastic for the Seawater Refrigeration System

Most of the plants are usually made of high-quality stainless steel. However, acid or saline water limits the working life of this type of piping. Apart from this, copper, another common piping metal, degrades to saltwater a lot easier and faster than other pipes. Cast iron galvanized steel is resistant to saltwater but over time due to exposure will collapse because of corrosion.

In seawater conditions, thermoplastics are able to stand longer, offering excellent corrosion resistance, very smooth interior surfaces to prevent incrustation, and high resistance to a very wide range of chemicals. The reason why plastics are resistant to corrosion is their poor conductivity, which diminishes the electrochemical reactions between the materials and the media.

PE100

The material chosen for this project was PE100, as it offers an excellent resistance for the range of temperatures and pressure of the pipelines. Other positive factors of choice are the ease of installation and the low material costs that ended up influencing the final decision.

APPLICATION

Cooling of the thermoelectric energy plants

Thermoelectric power plants boil water to create steam, which then spins turbines to generate electricity. Once steam has passed through a turbine, it must be cooled back into the water before it can be reused to produce more electricity. Colder water cools the steam effectively and allows more efficient electricity generation.

The cooling system used in Porvoo Energia is the so-called “once-through”, which takes water from nearby sources (e.g. rivers, lakes, aquifers, sea or ocean), circulate it through pipes to absorb heat from the steam in systems called condensers, and discharge the now warmer water to the local source. Once through systems are popular because of their simplicity, low cost, and the possibility of siting power plants in places with abundant supplies of cooling water.

DESIGN

Some informations on the Seawater Refrigeration System design.

The routes were designed by Plasthouse, an expert Finnish company in industrial plastics material and applications. The pipelines were 3d-modeled, Atolli Oy takes advantages of these drawings to have:

• Fluent communication with clients
• Accurate mass list of pipes, fittings, and valves. This translates into a significant drop of costs.
• Project approval of the client, as the drawings offer a realistic representation of the final installation.
• Easier and faster installation, since routing obstacles have already been taking into account to make the drawings.

MATERIALS

In addition to PE100 fittings the project included the use of butterfly valves, very important for the regulation of fluids.

The butterfly valves were supplied by COMER S.p.A., an Italian company specialized in the production of U-PVC, ABS, PE, and PP-H fittings, and valves for use in the hydraulic, waterworks, irrigation, swimming pool, chemical plants, food, and navigation industries. Today the company is renowned at an international level for the quality of its products, the result of its experience, know-how, and strictly made in Italy working method.