What happens when you stay in a house that is not painted even on the inside?
Such a house will be vulnerable to the forces of nature. Cracks from the construction could still remain. Heat and wind might weaken the construction over time. Additionally, the living experience will not be convenient as dust and other hazards remain.
A layer of paint protects a house from damage while improving its quality.
Lining the body of valves with plastics serves a similar purpose.
When highly corrosive media such as certain acids flow through the valve, they can corrode the metal body of the valves. To prevent this, parts of the valve that come in contact with the media are lined with specific plastic materials. These might include the disc, stem, seating and internal surface of the valve.
Akin to painting, the lining material is poured into the valve. At times, discs can be coated beforehand and then inserted into the valve.
How does lining the valve benefit the user?
Better protection from corrosion
The lining of materials such as PTFE, PFA, or FRP completely protects the valve from chemical corrosion. This makes lined valves an excellent choice for demanding applications such as acids or seawater.
Improved durability and reliability
Lined valves have a longer lifespan as compared to non-lined valves. Moreover, the lined valves are safer to use and thus, more reliable for automation.
Better sealing performance
Lining the valve provides high elasticity. As a result, the sealing performance of the valve improves.
The purpose of valve lining is to avoid or limit the exposure of critical valve parts and the valve’s internal surface to corrosive media. In most cases, plastic valves are used to handle corrosive media. However, since metal valves perform better under high temperature and pressure, they are deployed with plastic lining to handle corrosive media under high pressure. All types of valves could be lined with plastics.
Lining a valve is in many ways similar to painting your house walls. For better security, the quality of paint and applying the right number of layers of paint is important. Similarly, achieving the correct thickness of valve lining is the key to the lifespan and performance of lined metal valves.
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