Technical Column
【Complete understanding】The Structure and Features of the Plunger Pump/Piston Pump
There are many types of pumps, each with different applications and structures.
In this article, we will explain the definition and features of the “Plunger Pump/Piston Pump”, which is commonly used in dispensing and filling equipment among the various types of pumps.
Types of Pumps: Two Main Categories
Pumps can be broadly categorized into the following two categories.
◎Positive Displacement Pumps
These pumps work by changing the volume of liquid in a defined space through reciprocating or rotary motion, transferring energy to the liquid and moving it.
In addition to Plunger Pumps, there are various types such as piston pumps, gear pumps, and diaphragm pumps. The selection of the appropriate pump depends on the type of liquid and the application.
◎Non-Positive Displacement Pumps
These pumps use rotating blades, similar to a fan, to continuously move fluid. They are referred to as “non-positive displacement pumps” or “turbo pumps.” Examples include centrifugal pumps and axial flow pumps. These pumps are highly efficient and excel at continuously transporting large volumes of liquid.
Definition and Explanation of the Plunger Pump/Piston Pump
The plunger pump/piston pump, which falls under the category of “positive displacement pumps,” is a device that uses the volume change created by the reciprocating motion of a cylindrical piston called a “plunger” within the pump casing to carry out the suction and dispense process.
The dispense volume of a plunger pump/piston pump is determined by the plunger diameter and the plunger’s stroke length. Since the piston performs a reciprocating motion, suction and dispense occur intermittently rather than continuously.
Due to its operating principle, the plunger pump allows for precise control of the dispense volume, making it an ideal choice in applications where high accuracy is required. Compared to pressure-based dispensing systems (air-operated dispensers) that adjust dispense volume via air pressure, the plunger pump maintains stable metering even when there are changes in liquid temperature or viscosity.
Principle and Structure of the Plunger Pump/Piston Pump
Like general pumps, the plunger pump/piston pump transfers liquids by repeating the process of “suction” → “dispense.” Its principle of operation is similar to that of a syringe, where the movable part is moved back and forth in a linear line to perform the suction and dispense of liquids or gases.
Differences in structure depending on the viscosity of the liquid
Let’s take a look at the operating method based on the structure of a Hibar Pump.
CV – Suitable for low viscosity (1-5,000 CPS) materials
- ① When the plunger retreats, a negative pressure is created in the metering chamber, causing the check valve on the INLET side to open and allowing liquid to be drawn into the chamber.
- During this process, the check valve on the OUTLET side remains closed due to spring pressure.
- ② The liquid drawn in is metered to the stroke setting determined by the micrometer, and then the plunger moves forward, pushing the material in the metering chamber out.
- In this case, the check valve on the IN side closes, and the check valve on the OUTLET side opens, allowing the liquid to be dispensed from the nozzle.
Operating Image of the Check Valve System
Micrometer
RV – Suitable for high viscosity (5,000–50,000 CPS) materials
①Essentially the same as the CV type, but the suction/discharge switching mechanism uses a rotary valve. The rotary valve rotates in sync with the plunger movement via the actuator. During metering, the INLET side is connected to the metering chamber, and the liquid is drawn in.
②During dispense, the rotary valve rotates in time with the forward movement of the plunger, connecting the OUTLET side to the metering chamber, allowing the liquid to be dispensed.
*Note: The RV type is used for high-viscosity liquids, so the positions of the material IN/OUT are reversed compared to the CV type.
Operating Image of the Rotary Valve System
Rotary Valve
As you can see, the liquid is drawn into the metering chamber inside the pump in a fixed volume, and this volume is simply discharged, demonstrating the basic mechanism.
Summary of Plunger Pumps/Piston Pumps
- ・A plunger pump is not a continuous flow type pump, but an intermittent pump where the plunger (piston) repeats the suction and dispense cycles.
- ・The dispense volume is set by determining the volume of the metering chamber.
- ・The dispense speed is set by the reciprocating speed of the plunger (piston).
- ・Since the structural principle prevents fluctuations in dispensing accuracy in response to changes in viscosity, the repeatability and accuracy remain stable.
Plunger Pumps/Piston Pumps manufactured by Unicontrols
- The global standard for plunger pumps/piston pumps: “Hibar Pump.”
Features of the “Hibar Pump”
The Hibar Pump, a pioneer in plunger pumps/piston pumps (positive displacement pumps), is used for precise filling applications in over 50 countries worldwide.
In the battery manufacturing industry, it is used for electrolyte filling by battery manufacturers around the world.
In addition to the battery manufacturing industry, it is widely used in the manufacturing processes of food, cosmetics, pharmaceuticals, detergents, and other household products.
Q. How accurate is the dispensing accuracy if the accurate dispensing volume is required?
A. High-precision dispensing is possible with a measurement error of within 1%.
- ① B Series: ±0.5% (for 0.5cc dispensing using 1BC5M)
- ② H Series: ±1% or less
*Note: The accuracy may vary depending on the liquid used.
Q. What is the maximum dispensing volume?
A. We offer model that can dispense up to a maximum of 2,000cc.
- ① B Series (small capacity sizes): up to 20cc
- ② H Series (large capacity sizes): up to 2,000cc
Q. What is the viscosity range that these pumps can handle?
A. We offer two different methods depending on the viscosity of the liquid.
- ① Low viscosity (1–5,000 CPS): CV (Check Valve) Series
- ② High viscosity (5,000–50,000 CPS): RV (Rotary Valve) Series
Q. What is the drive source for the drive system?
A. You can choose from two types of drive depending on the application.
① Pneumatic-driven type
The dispense volume is set with a micrometer, and the dispense and suction speed are set by adjusting the airflow.
② Motor-driven type
The dispense volume and dispense/suction speed are set by inputting values on PC.
Comparison of Pnuematic-driven Type and Motor-driven Type
|
Drive System |
Pnuematic-driven Type |
Motor-driven Type |
|
Change in dispense volume |
△ Suitable for situations where frequent changes are not required |
◎ Easily adjustable by entering values on a PC |
|
Change in dispense speed |
△ Suitable for situations where frequent changes are not required |
◎ Easily adjustable by entering values on a PC |
|
Use in explosion-proof environments |
◎ |
△ Can be used if the motor part has air purge. |
|
Price |
◎ |
△ |
What types of liquids and applications are these pumps used for?
- ・Cooking oils and food ingredients (soups, ketchup, creams, sauces, syrups, etc.)
- ・Cosmetics (lotions, emulsions, creams, etc.)
- ・Chemicals/reagents (alcohols, inks)
- ・Electrolytes (electrolyte solutions for various batteries, gel for alkaline batteries, etc.)
- ・Toiletries (shampoo, conditioner, etc.)
- ・Liquids for mixing additives and fragrances
*The above are representative examples. We can also accommodate other liquids, so please feel free to contact us for more details.
Example of a desktop robot and Hibar pump configuration
Liquids that are not suitable due to pump structure
- ・Adhesives with rapid curing properties, such as silicone-based or cyanoacrylate-based adhesives
- ・Liquids containing hard solids or fibers
- ・Liquids with almost no flow, close to solid form
Additionally, options for solvents and anti-drip features are available. If you are interested, please click below for more information.
*These precision metering pump products are built under the technology license from HIBAR.