A bypass diaphragm pump continues to operate even when the discharge outlet is closed by internally redirecting flow. It utilizes a pressure-sensing switch and an internal bypass valve to achieve this. Here's a breakdown:
Key Components and Operation:
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Pump Heads: These contain the diaphragm, which is driven to create pumping action. Critically, they also incorporate:
- Pressure Sensing Switch: This switch monitors the pressure in the discharge line. When the pressure reaches a predetermined level (typically a set point indicating backpressure due to a closed or restricted outlet), it triggers the bypass function.
- Internal Bypass Valve: This valve allows the fluid being pumped to recirculate within the pump head instead of being forced out the discharge outlet when backpressure is too high.
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Motor: The motor provides the power to drive the diaphragm.
The Process:
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Normal Operation: Under normal conditions, the diaphragm reciprocates, creating suction to draw fluid into the pump head and then discharging it out the outlet. The internal bypass valve remains closed because the pressure in the system is below the setpoint.
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Increased Backpressure (Outlet Closed): When the discharge outlet is closed or significantly restricted, pressure builds up in the discharge line.
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Pressure Sensing Switch Activation: The pressure sensing switch detects the increased pressure and signals the internal bypass valve to open.
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Bypass Operation: The internal bypass valve opens, allowing the fluid being pumped to recirculate internally within the pump head, instead of being forced against the closed outlet. The motor continues to run, and the diaphragm continues to reciprocate, but the fluid simply goes around in a loop within the pump.
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Ready for Full Power: The pump remains primed and ready to deliver full power as soon as the system outlets are re-opened. The pressure in the discharge line drops, the pressure sensing switch deactivates, the internal bypass valve closes, and the pump resumes normal operation.
Benefits of a Bypass Diaphragm Pump:
- Prevents Damage: By bypassing the flow when the outlet is closed, the pump avoids building up excessive pressure that could damage the pump itself, the motor, or the connected system.
- Maintains Prime: The pump remains primed and ready to deliver fluid as soon as the obstruction is removed, eliminating the need for manual priming.
- Continuous Operation: The pump can continue to run without damage, even with a closed outlet, providing immediate delivery once the system is reopened. This is useful in applications where intermittent flow is expected.
- Reduced Wear and Tear: Preventing excessive pressure reduces strain on the diaphragm and other pump components, extending the pump's lifespan.
Example Applications:
- Agricultural spraying systems
- Chemical dispensing systems
- Cleaning equipment
In summary, a bypass diaphragm pump is designed to protect itself from damage caused by overpressure by internally recirculating fluid when the discharge outlet is closed or restricted. This ensures continuous operation and immediate delivery when needed.
