Hydraulic Pump Fundamentals: Types, Performance, and Selection

Key Characteristics of Hydraulic Pumps

Hydraulic pumps are mechanisms responsible for producing the required hydraulic pressure and flow for a system, according to its design specifications. Key features include:

Flow

This is the volume of fluid the pump delivers per unit of time (e.g., at 1500 RPM). Pumps can be either constant flow or variable flow.

Pressure

One must know the maximum pressure the pump can support. This value is provided by the manufacturer.

Speed

You must also know the pump's operational speed to correctly calculate the drive mechanism.

Understanding Hydraulic Pump Performance

The performance and efficiency of a hydraulic pump, in its basic function of obtaining a given pressure at a certain number of revolutions per minute, is defined by three metrics:

• Volumetric Efficiency: The quotient obtained by dividing the actual volume of fluid the pump delivers by the theoretical volume it should deliver.
• Mechanical Performance: Measures the mechanical power losses that occur in the pump due to friction within its internal mechanisms.
• Overall or Total Yield: This is the product of volumetric and mechanical performance. It is called 'total' because it measures the overall efficiency of the pump.

How to Select the Right Hydraulic Pump

When selecting a pump, you must provide the supplier with the following information:

1. Indicate the exact nature of the liquid to be handled.
2. Specify the required capacity, including the minimum, normal, and maximum flow rates.
3. Provide information on the discharge pressure, including any relevant drawings and data for calculation.
4. Supply the provider with a detailed plan of the existing or desired vacuum system.

Pump Installation, Operation, and Maintenance

Installation Guidelines

1. Bases for pumps must be rigid and properly built.
2. Correctly seat the pump plate.
3. Check the alignment between the pump and its drive system.
4. Piping should not put stress on the pump housing.

Proper Operation

1. Never diminish the pump's suction to reduce flow.
2. Do not allow the pump to run dry.
3. The pump should be worked with a slight over-flow.
4. Perform frequent visual inspections.

Maintenance and Repair Tips

1. Do not completely disassemble the pump unless it is necessary for a repair.
2. Be very careful during disassembly.
3. Special care is needed when examining and overhauling the settings.
4. Thoroughly clean the water passages in the housing and repaint if necessary.

Common Types of Hydraulic Pumps

Pumps are categorized according to their working principle:

Reciprocating Piston Pumps

In these machines, the flow is discontinuous. The loading and unloading processes are performed by valves that open and close alternately.

Rotary Positive Displacement Pumps

Also known as roto-static pumps, this category includes the vane pump, lobe pump, gear pump, screw pump, and peristaltic pump.

Rotodynamic Pumps

In this type of pump, one or several impellers with blades spin to generate a pressure field and create flow.

Gear Pumps

Often called the "workhorse" of hydraulic systems, the gear pump is one of the most commonly used types. Its capacity can be large or small, and it varies in its ability to produce pressure and volume.

Vane Pumps

This design features a slotted rotor rotated by a driving shaft. Flat, rectangular blades move toward or away from the rotor slots and follow the internal shape of the pump housing.