Thailand Power Plant Protect Heat Exchanger Water Box Against Galvanic Corrosion & Cavitation
A power plant in Thailand use Liquid Metal Epoxy Coating to provide robust protection against galvanic corrosion and cavitation for a heat exchanger water box, tubes and a condenser faceplate – removing the need to make an annual repair to the system.
Case Study Overview
Site Power plant
Location Thailand
Repair Type Heat exchanger corrosion protection
Products Liquid Metal Epoxy Coating
Tank Defect
The water box supplied and directed the flow of water through the heat exchanger via a series of tubes. Conditions inside the box were perfect for galvanic corrosion and cavitation.
Extreme temperatures, high pressure and unpurified water passing through the box left the metalwork, tubes and a condenser faceplate under constant attack.
A standard epoxy coating had been used for many years to protect the water box. But the rate of corrosion meant the heat exchanger had to be disassembled for repair and a new coating applied annually.
To reduce the downtime and disruption caused by the frequency of this process, the plant were now seeking a more robust, effective protective coating which did not require yearly re-application.
SylWrap Solution
Analysing conditions inside the water box helped the plant formulate a specification for their ideal protective epoxy coating.
Temperature resistance needed to be as high as 149°C with long-term performance at operational temperatures of 25–40°C. It had to be resistant to pH 8-10 and pressure up to 3 bar.
Based on these requirements, Sylmasta recommended using Liquid Metal Epoxy Coating to create a robust shell offering high corrosion resistance, a maximum service temperature of 150°C and Shore D hardness in excess of 80.
Before application, the surfaces to be coated with Liquid Metal were thoroughly cleaned to remove rust, other contaminants and any traces of the previously applied standard epoxy coatings.
Three coatings 1mm thick were applied, leaving the water box, tubes and condenser faceplate covered with a 3mm thick metallic outer layer.
Liquid Metal has a 90-minute gel and four hour re-coat time. The entire repair was completed over the course of two days, after which the heat exchanger was reassembled and put back into service.
Outcome
Six months after the repair and the manager of the engineering company responsible for maintenance at the plant contacted Sylmasta with an update.
He said: “I had a good experience with Liquid Metal. We have looked at the heat exchanger and condenser again and the coating has fully performed and protected from corrosion very well.”
Follow Up
Liquid Metal has since been used to protect 22 blowdown tanks at the same plant. It has also been approved for the repair and maintenance of different systems at other power plants across Thailand.
Products Used
Liquid Metal
Epoxy coating which cures to a hard, metallic layer protecting surfaces against corrosion
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