Nine Anti-Corrosion Measures of Valves (4)
Adopting electrochemical protection
There are two kinds of lectrochemical protection, anode protection and cathodic protection.
If zinc is used to protect iron and it is corroded, zinc is called the sacrificial metal. In the production practice, the anode protection is used less than the cathodic protection because cathodic protection is a simple and economical method to protect the large and important valves. The method of adding zinc into the asbestos packing to protect the valve stem also belongs to the cathodic protection.
Controlling the corrosive environment
The so-called environment can be understood in the broad sense and the narrow sense. In the broad sense, the environment refers to the surrounding around the installation place of the valve and the medium flowing in the valve. In the narrow sense, environment refers to the conditions around the installation place of the valve.
Most of the environments can not be controlled, and the production process can not be changed. Only based on the premise of not causing damage to the valve products or processes can methods of controlling the environments be adopted, for example, the deoxidation of boiler water. From this point of view, the addition of corrosion inhibitors, the electrochemical protection, etc. also belong to the methods of controlling the corrosive environments.
The atmosphere is full of dust, water vapor, smoke, etc., and toxic gases and powder generated by the chimneys and equipment in the production will have different degrees of corrosion on the valve.
Operators should be in accordance with the regulations of the operating procedures, regularly cleaning, purging and refueling the valve, which are effective measures to control environmental corrosion. The valve stem can be fitted with a protective cover; the surface of the valve can be sprayed with the paint; these are methods of preventing the corrosive substances from corroding the valve.
The rising of the temperature and air pollution will accelerate the corrosion on equipment and valves especially in the closed environment. Measures like using the open and ventilated plant and decreasing the temperature can help to slow down the environmental corrosion.
Improving the processing technology and the structure of the valve
The corrosion protection of the valve is supposed to be considered at the very beginning of the design process. There is no doubt that the reasonable structure design as well as the correct process of the valve will have good effects on slowing down the corrosion on the valve.
Source: China Valves Manufacturer – Yaang Pipe Industry (www.ugsteelmill.com)