Project: Construction of three Ø 2000 mm solid PE 100-RC storage tanks
Product: PE 100-RC sheets and fittings
Manufacturer: Oy Fluorotech Ltd (Finland)
Year of installation: 2019
Material: PE 100-RC
Medium: NaOH (Caustic soda)
Temperature: Ambient
Conceptualization and installation by Oy Fluorotech Ltd (Finland) of three solid storage containers and the welding of the piping system using AGRU E-fittings within a water purification plant for caustic soda.
The purpose of the project was to replace a metal container by three PE 100-RC containers storing caustic soda (NaOH). In this application the caustic soda is used as a pH control agent in a wastewater treatment application. Additionally, because of the chemical resistance of PE 100-RC the concentration of the solution could be increased from an initial 20 % to 50 %. This led to a reduction in operating costs of the treatment process.
Sodium Hydroxide (NaOH), also known as caustic soda, is a common inorganic compound typically used as a strong chemical base. It is known to be very corrosive for metals. Caustic soda is used during water purification to regulate the pH value of water supplies.
Due to the chemical resistance and good mechanical properties of PE 100-RC, it can store and transport caustic soda solutions. The use of PE 100-RC storage containers and pipelines is one of the most cost effective variants that is able to offer a potential 10+ year of service life at ambient temperature.
All the tanks needed to be installed interior to avoid the freezing point of a 50% solution of NaOH.
Thanks to plastic, the concentratio
of the sodium hydroxide solution
could be significantly increased.
Low temperatures, starting at +15 °C, can cause the crystallization of caustic soda. The container’s design and dimensioning strictly followed the DVS (German Welding Association) standards to fulfil the mechanical and chemical requirements.
The main goal was to optimize the connection between the storage containers and the actual process, where the caustic soda was used. Therefore, the tanks were placed next to the road, so they could be easily loaded from a truck and are, at the same time, close to the water cleaning system.
The pipeline design (see Figure 3) and installation had to ensure four basic functions:
The main welding method used for the installation was electrofusion, which ensures an accurate and error-free welding quality. This method uses special, injection moulded AGRU E-fittings (see Figure 4) with a built-in conductible heating element to weld the joints together.
