Working Principle of PE Double Bleed Ball Valve

1. Basic Media On/Off Control

• Opening the Valve: When the operator rotates the valve stem (via the ground-mounted operating cap, typically with a wrench), the valve ball rotates accordingly. As the ball turns, its internal flow channel gradually aligns with the inlet and outlet ports of the valve body. This alignment creates an unobstructed path for the medium (e.g., gas, heating fluid) to flow through the valve, realizing the "open" state of the pipeline.
• Closing the Valve: Rotating the valve stem in the opposite direction twists the valve ball, misaligning its internal flow channel with the valve’s inlet/outlet. The solid surface of the valve ball then presses tightly against the valve seats (sealed with high-performance materials like NBR rubber). This tight contact forms a reliable seal, blocking the medium flow and achieving the "closed" state to cut off the pipeline.

2. Double Bleed (Pressure Relief) Operation

• Bleed Port Activation: The valve is equipped with two independent bleed ports (one usually near the inlet side, the other near the outlet side, or at positions to cover upstream and downstream pipeline sections). Each bleed port is paired with a small control valve (bleed valve) for easy operation.
• Pressure Relief Process: When pressure relief is needed (e.g., before disassembling the pipeline), the operator opens the relevant bleed valve(s). This action connects the bleed port to the valve’s internal cavity (or directly to the pipeline). Residual medium or pressure in the pipeline then flows out through the open bleed port, gradually reducing the internal pressure to a safe level.
• Dual Bleed Advantage: Having two bleed ports allows for targeted relief (e.g., relieving upstream pressure separately from downstream pressure) or faster overall pressure release, minimizing risks of medium leakage or equipment damage during maintenance.

Pressure relief ball valve Dn355 Images