What does the arrow marked on the valve body mean?

The arrow marked on the valve body indicates the recommended pressure-bearing direction of the valve, not the direction of the fluid flow in the pipeline. For valves with bidirectional sealing capabilities, the arrow may or may not be marked. If marked, it points to the recommended pressure-bearing direction, as one of the two possible directions—either horizontal or vertical—will usually offer better performance.

The arrow direction on the valve body represents the recommended pressure-bearing direction, and is often mistakenly interpreted by engineering installation teams as the direction of the fluid flow. This can lead to improper installation, causing leakage or even pipeline accidents.

The pressure-bearing direction refers to the direction in which the valve body is designed to withstand pressure when the valve is in the closed state after installation in the pipeline.   If installed incorrectly, leakage issues may arise due to improper valve sealing.   Soft-seal ball valves, like those huge, are typically bidirectional sealing and may not mark an arrow.   However, metal hard-seal ball valves, while capable of bidirectional sealing, perform better in one direction, so they usually have an arrow indicating the recommended pressure-bearing direction.   It's advisable to consult the customer for confirmation in such cases.

For hard-seal butterfly valves with arrows marked on the body, the arrow direction may differ from the flow direction of the medium depending on the installation location. For example, if the valve is installed at the pump outlet in a pump room, the valve body arrow direction will be opposite to the flow direction. If it is installed at the pump inlet, the arrow direction will be the same as the flow direction. In main pipelines, the arrow typically follows the flow direction of the medium. The exact orientation should depend on the specific working conditions and installation position.

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