A positive displacement pump which utilizes a plunger or piston to change a cavity's volume, and produce a pressure differential.
A plunger pump operates using the reciprocating motion of plungers or pistons. Depending on the design of the pump, the use of a single or multiple plungers may be used.
How a Reciprocating Pump Works
To help visualize how a reciprocating pump works, let's look at a single piston and split the process into four parts.
Action 1: The plunger or piston is pulled back. The action increases the volume of the cavity. As the cavity volume expands, fluid is drawn in through the inlet to fill the expanding cavity.
Action 2: The piston has reached it's maximum displacement. Since it is not moving into or out of the cavity, fluid is not flowing through the inlet or the outlet.
Action 3: After reaching it's maximum position, it is then pushed back into the cavity. During this process, the piston applies enough pressure to the fluid to overcome the pressure in the outlet of the pump. This pressure differential pushes the fluid from inside the cavity through the outlet of the pump.
Action 4: The piston reaches its maximum extension into the cavity. Here the volume of the cavity is at a minimum and fluid is not flowing through the inlet or the outlet. The next action repeats the process, starting again with action 1.
The process of how a reciprocating pump works can be seen here in action from start to finish:
Advantages of Reciprocating Pumps
High Pressure, Low Flow Applications: Reciprocating pumps are generally designed to pump in low flow, high head applications. One of the most extreme of these applications is water jet cutting, where only a few gallons pass through the pump per minute, but exceed pressures of 10,000 PSI.
Proven, Common Technology: Reciprocating pumps are one of the oldest, most proven pump types. Today, a wide variety of reciprocating pumps can be found in many different materials, types, and sizes. Reciprocating pumps range from less than 1 horse power to over 3,000 horse power.
Durability: Reciprocating pumps are used in some of the most abrasive and corrosive applications. Fluid ends and fluid end parts can be made in many different materials such as stainless steel, aluminum bronze, tungsten carbide, ceramic, and more. A wide selection of valve types are used in abrasive applications such as pumping cement, sand slurry, mud, etc.
Efficiency: Reciprocating pumps operate at high a higher efficiency compared to other pump designs. In most cases, at any set point, reciprocating pumps operate around 90%.
Disadvantages of Reciprocating Pumps
High Maintenance / Short Life: The main disadvantage of a reciprocating pump is the high maintenance and short life. There are many parts in the pump works, all constantly changing directions. Unless careful maintenance takes place, the lifespan of the pump is greatly reduced. While pumps such as centrifugal pumps can last 15 to 20 years with little maintenance, a reciprocating pump requires higher levels attention and rebuilding several times within the same time frame. The cost of a reciprocating pump rebuild is usually inexpensive which still makes them cost competitive compared to longer lasting, higher priced pump designs.
Pulsations: A characteristic of reciprocating pumps is the production of pressure pulsations through the pump inlet and outlets. The reciprocating motion of the pump produces these pulsations. Increasing the number of pump chambers can greatly reduce the pulsations produced, but it does not remove them completely. To negate damage to piping and surrounding systems or the pump itself, pulsation dampeners must be installed. Further system design can further decrease pulsations to nearly zero. In all cases, overall system design is important when using reciprocating pumps.
Reciprocating Pump Variations
Plunger pumps come in a variety of styles, shapes and sizes. The specific type of pump chosen for an application takes into account the pressures encountered, the flow rates needed, measurement and control systems, fluid viscosity and corrosivity, pipe material, etc. Careful attention should be given to the application before selecting a pump. Selecting the wrong pump for a job can result in damage to equipment, piping, systems, and possibly endanger personnel.
Reciprocating Pump Terms
Reciprocating pump terms are based off of how the fluid is pumped (action) and the number of plungers or pistons (arrangement). For example, a Union TX-200 is a "single acting triplex plunger pump", a Gaso 1849 is a "double acting duplex plunger pump", and a Oilwell B-558 is a "single acting quintuplex plunger pump".
Reciprocating pumps have thee types of "actions". Single, Dual, and Direct Action:
Reciprocating Pumps have a few different types of arrangements. You can learn more about each one below:
Reciprocating Pumps can use several different methods to change the volume of the cavity to produce flow. The most common are:
Piston / Swab
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