Describe, with the aid of a sketch, the operation of a double acting, piston type positive displacement pump.
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A double-acting, piston-type positive displacement pump
A double-acting, piston-type positive displacement pump is a type of pump where the piston performs pumping action on both its forward and backward strokes. This means that fluid is discharged from the pump during both the extension and retraction of the piston within the cylinder.
1. Useful information on positive displacement pumps – Michael-Smith-Engineers.co.uk
2. CA2037591A1 – Double-acting positive displacement pump – Google Patents
Key Features:
- Two Pumping Chambers: It has two separate pumping chambers, one on each side of the piston. 1. Double Action / Dual Action. A reciprocating pump design which… | by Communications Power Zone | Medium medium.com
- Inlet and Outlet Valves: Each chamber has its own set of inlet (suction) and outlet (discharge) valves. 1. Useful information on positive displacement pumps – Michael-Smith-Engineers.co.uk www.michael-smith-engineers.co.uk
- Continuous Flow: Compared to single-acting pumps, double-acting pumps produce a more continuous flow of fluid, although some pulsation may still be present.
- Higher Flow Rate: For a given pump size and speed, a double-acting pump generally delivers a higher flow rate than a single-acting pump because fluid is displaced during both strokes.
Operational Principle:
- Forward Stroke (Extension):
- The piston moves forward, increasing the volume in one chamber (Chamber A) and decreasing the volume in the other (Chamber B).
- The inlet valve in Chamber A opens, allowing fluid to enter.
- The outlet valve in Chamber B opens, discharging fluid.
- Backward Stroke (Retraction):
- The piston moves backward, reversing the volume changes in the chambers.
- The inlet valve in Chamber B opens, allowing fluid to enter.
- The outlet valve in Chamber A opens, discharging fluid.
Advantages:
- Higher Flow Rate: Delivers more fluid per unit time compared to a single-acting pump of the same size and speed.
- Smoother Flow: The flow is more continuous with reduced pulsations compared to single-acting pumps.
- Compact Design: Can achieve higher flow rates in a smaller package compared to a single-acting pump.
Disadvantages:
- More Complex Design: The presence of two sets of valves and additional sealing requirements makes the design more complex than a single-acting pump.
- Higher Maintenance: The increased number of moving parts and seals may require more frequent maintenance.
Applications:
Double-acting piston pumps are used in a wide range of applications where higher flow rates and smoother flow are desired, including:
- Hydraulic Systems: Providing high-pressure fluid power for machinery and equipment.
- Oil and Gas Industry: Transporting crude oil, refined products, and other fluids.
- Chemical Processing: Handling various chemicals, including corrosive and abrasive fluids.
- Water Supply and Treatment: Pumping water for various purposes.
- Marine Applications: Used in various onboard systems like bilge pumps, fire pumps, and hydraulic systems.
In summary, a double-acting, piston-type positive displacement pump is a valuable tool for applications requiring high flow rates, smoother flow, and the ability to handle various fluids, including viscous and abrasive ones. While slightly more complex and requiring more maintenance than single-acting pumps, their advantages in terms of flow capacity and smoother operation make them a popular choice in many industrial and marine settings.
Operation
Core Mechanism:
- Cylinder and Piston: The pump comprises a cylinder within which a piston reciprocates (moves back and forth) due to an external drive mechanism (often a crankshaft connected to a motor). 1. Double Acting Reciprocating Pump – Virtual Labs fmc-nitk.vlabs.ac.in
- Two Chambers: The piston divides the cylinder into two separate chambers, each having its own inlet (suction) and outlet (discharge) valves. 1. How does a piston pump work? – Hawk Pumps www.hawkpumps.com
- Valves: These valves are check valves, allowing flow in only one direction. They ensure fluid enters the chamber during the suction stroke and exits during the discharge stroke. 1. Double Acting Reciprocating Pump – Virtual Labs fmc-nitk.vlabs.ac.in2. PISTON DIAPHRAGM PUMP – deka-adhinusa.co.id deka-adhinusa.co.id
Operational Cycle:
The pump operates in a continuous cycle, with each stroke of the piston contributing to fluid displacement.
- Suction Stroke (Chamber A):
- The piston moves backwards within the cylinder, creating a vacuum in Chamber A. 1. Piston pumps: how do they work? | EMILTEC www.emiltec.com
- The inlet valve in Chamber A opens due to the pressure difference, allowing fluid to flow into the chamber. 1. Piston pumps: how do they work? | EMILTEC www.emiltec.com
- Simultaneously, the outlet valve in Chamber B closes, preventing backflow from the discharge line.
- In Chamber B, the piston’s backward motion compresses the fluid, forcing it out through the open outlet valve.
- Discharge Stroke (Chamber A):
- The piston moves forward, reducing the volume in Chamber A and increasing pressure.
- The inlet valve in Chamber A closes, preventing backflow.
- The outlet valve in Chamber A opens, allowing the pressurized fluid to be discharged into the delivery line.
- Meanwhile, in Chamber B, the piston’s forward motion creates a vacuum, and its inlet valve opens to draw in fluid while its outlet valve remains closed.
Key Points:
- Double Action: Fluid is discharged during both the forward and backward strokes of the piston, leading to a more continuous flow compared to single-acting pumps. 1. Positive Displacement Pumps (Part One): Reciprocating Pumps | Pumps & Systems www.pumpsandsystems.com
- Valve Timing: The precise timing of the inlet and outlet valves is critical to ensure efficient operation and prevent backflow.
- Pulsation: Despite being double-acting, some degree of pulsation in the flow is still inherent to this pump type, although it’s less pronounced than in single-acting pumps. Pulsation dampers may be used to further smooth the flow if needed.
- Drive Mechanism: The reciprocating motion of the piston is typically driven by a crankshaft connected to an electric motor or an internal combustion engine.
Advantages:
- High Flow Rate: Delivers a higher flow rate than a single-acting pump of similar size and speed.
- Smoother Flow: Produces a more continuous flow with reduced pulsations compared to single-acting pumps.
- Self-Priming: Can handle air and create a vacuum, making it capable of self-priming. 1. Positive Displacement Pumps – Common Types, How They Work – DAE Pumps www.daepumps.com
- Handles Viscous Fluids: Can effectively pump thick or viscous fluids.
Disadvantages:
- More Complex Design: The presence of two sets of valves and the need for sealing on both sides of the piston makes the design more complex.
- Higher Maintenance: The increased number of moving parts and seals can lead to higher maintenance requirements.
In essence: A double-acting piston pump uses the reciprocating motion of a piston within a cylinder to displace fluid on both its forward and backward strokes. This design results in a higher flow rate and smoother flow compared to single-acting pumps, making it suitable for various applications demanding these characteristics.