Hydraulic pumps are an important component of most hydraulic systems, which convert the energy generated by pressurized fluids into usable mechanical energy. The hydraulic systems they support exist in a range of industries, among them agriculture, automotive manufacturing, defense contracting, excavation, and industrial manufacturing.
They operate under the principle of Pascal’s Law, which states the increase in pressure at one point of an enclosed liquid in equilibrium is equally transferred to all other points of said liquid.
All hydraulic pumps are composed in the same basic way. First, they have a reservoir, which is the section of the pump that houses stationary fluid. Next, they use hoses or tubes to transfer this fluid into the cylinder, which is the main body of the hydraulic system. Inside the cylinder, or cylinders, are found two valves and one or more pistons or gear systems. One valve is located at each end; they are called the intake check, or inlet, valve and the discharge check, or outlet, valve, respectively.
When pressurized fluid is pumped into the cylinder through the inlet, it picks up more force, which it carries over into the hydraulic system when it is released through the outlet. The role of the piston is to move or compress fluid. When the piston is withdrawn, the check valve is opened, creating a vacuum that pulls in hydraulic fluid from the reservoir.
When it is set back in its original position, the check valve closes and fluid pressure builds. The piston forces the valves open and closed repeatedly at variable speeds, increasing pressure in the cylinder until it builds up enough to force the fluid through the discharge valve. In this way, the pump delivers sufficient force and energy to the attached equipment or machinery to move the target load. Read More…
All hydraulic pumps can be categorized as either single action or double action. Simply put, single action pumps can propel, pull, and lift unidirectionally only, whereas double action pumps can move loads in more than one direction.
In addition, all hydraulic pumps are divided into two main groupings: piston pumps and gear pumps.
Piston pumps are those pumps detailed above; they create displacement and build pressure using pistons. Piston pumps may be further divided into radial piston pumps and axial piston pumps.
Radial pumps are mostly used to power relatively small flows and very high pressure applications. They use pistons arranged around a floating center shaft or ring, which can be moved by a control lever, causing eccentricity and the potential for both inward and outward movement.
Axial pumps, on the other hand, only allow linear motion. Despite this, they are very popular, being easier and less expensive to produce, as well as more compact in design.
Gear pumps create pressure not with pistons but with the interlocking of gear teeth; when teeth are meshed together, fluid has to travel around the outside of the gears, where pressure builds. Gear pumps are also divided into two categories: external gear pumps and internal gear pumps.
To facilitate flow, external gear pumps enlist two identical gears that rotate against each other. As liquid flows in, it is trapped by the teeth and forced around them. It sits, stuck in the cavities between the teeth and the casing, until it is so pressurized by the meshing of the gears that it is forced to the outlet port.
Internal gear pumps, on the other hand, use bi-rotational gears. To begin the pressurizing process, gear pumps first pull in liquid via a suction port between the teeth of the exterior gear, called the rotor, and the teeth of the interior gear, called the idler. From here, liquid travels between the teeth, where they are divided within them. The teeth continue to rotate and mesh, both creating locked pockets of liquid and forming a seal between the suction port and the discharge port. Liquid is discharged and power is transported once the pump head is flooded. Internal gears are quite versatile, usable with a wide variety of fluids, not only including fuel oils and solvents, but also thick liquids like chocolate, asphalt, and adhesives.
Before purchasing a pump, interested parties should ask themselves a few questions.
First, what are their operating specifications? They would be wise to make sure that their requirements are matched by the capabilities of the pump they choose. These capabilities include maximum fluid flow, minimum and maximum operating pressure, horsepower, and operating speeds.
Customers must also take stock of the space in which their pump will work. Based on this, the pump will be designed with a specific weight, rod extension capability, diameter, length, and power source.
When selecting one or more hydraulic pumps, customers also have many options from which to choose in terms of material composition. Most commonly the body of the pump–the gears, pistons, and cylinders–are made of a durable metal material, one that can hold up against the erosive and potentially corrosive properties of hydraulic fluids and the wear that comes along with continual pumping. Metals like this include, among others, steel, stainless steel, and aluminum.
To decrease the corrosive nature of certain hydraulic fluids, operators may choose to add other substances to them, such as esters, butanol, oils, glycols, water, or corrosive inhibitors. These substances differ in operating temperature, flash point, and viscosity, so they must be chosen with care.
Some manufacturers may also choose to include discharge sensors or another means of monitoring the wellbeing of their hydraulic system.
Pumps that meet operating standards are the foundation of safe and effective operations, no matter the application.