What is the mechanism of a plunger pump and what are the benefits of dispensers that utilize it?

Plunger pumps are essential equipment used in many industries. Here, we will explain in detail the overview, mechanism, types, range of applications, and maintenance of plunger pumps.

What is a plunger pump?

A plunger pump is a pump that can suck and discharge liquid by using a piston-like component called a plunger to push out a fixed amount of liquid. It is used in a wide range of industrial applications, such as chemical injection, oil transportation, and food processing.

Structure and mechanism of a plunger pump

Plunger pumps transfer liquid through the reciprocating motion of a plunger within a cylinder. When the plunger retracts, liquid is sucked (filled) into the cylinder, and when it advances, the liquid is discharged.



For example, a plunger pump used in a water treatment facility plays the role of pushing water in the cylinder at high pressure through the movement of the plunger and sending it to the sewage purification process. The high pressure generated by the piston movement enables efficient liquid transfer and purification processing.

Advantages of a plunger pump

Since plunger pumps manage discharge volume by the volume of the cylinder, their precision is excellent. Because they push out liquid at high pressure, the discharge speed is also fast. On the other hand, because of their simple mechanism, they have the advantages of being easy to maintain and highly durable.

　◎　High discharge accuracy
　◎　High discharge speed
　◎　Easy maintenance
　◎　High durability

Types of plunger pumps

1) High-pressure plunger pump

Plunger pumps with a special structure that increases pressure. In high-pressure cleaning equipment and water cutting machines, high-pressure plunger pumps are used to generate powerful water jets to remove dirt or cut hard materials such as metal.

2) Low-pressure plunger pump

In contrast to high-pressure plunger pumps designed for functions such as cleaning or cutting, those used in processes intended for liquid supply are distinguished as low-pressure plunger pumps. Low-pressure plunger pumps are suitable for cooling water supply systems and agricultural irrigation. In cooling water supply systems, plunger pumps supply large volumes of water to efficiently cool industrial processes and large machinery. In agricultural irrigation, they supply large volumes of water evenly to irrigate extensive fields.

Musashi Engineering's plunger pumps

Our company manufactures the "JUSTROPUMP," a low-pressure plunger pump designed for the constant-rate discharge and supply of liquids. We have further enhanced the constant-rate performance and high durability that are the greatest features of plunger pumps, and they are primarily used in filling processes within the food and electronic components industries.

・Precise and quantitative discharge of low-viscosity liquid materials
・High-speed discharge due to high cycle speed

How to choose a plunger pump

1) Check the liquid material and wetted materials

We offer recommendations for the material of the pump body and O-rings based on the liquid materials being used. Please feel free to consult with us if you have any concerns regarding chemical resistance or other issues.

2) Check the filling volume

We confirm the minimum and maximum discharge volumes you wish to handle with a single pump. While it is not possible to discharge a volume exceeding the pump's capacity in a single suction stroke, larger pump sizes result in coarser discharge resolution. We currently offer a lineup of 5mL and 13mL sizes, but we can also manufacture sizes up to 250mL.

3) Select the drive method

Air-driven operation is the most inexpensive and common method for driving the plunger. The plunger operates by switching the air ON and OFF in synchronization with the suction and discharge timing.

Reference) Dedicated pump controller ME-5000P

 

In the case of air-driven models, the discharge volume and speed are adjusted by opening or closing the micrometer or speed controller attached to the pump body. Therefore, if the filling volume changes frequently depending on the application or product type, a motor-driven plunger pump, which allows the volume inside the pump to be managed by a motor, is recommended. We also sell motor-driven models as custom-made products.

Disadvantages of a plunger pump

1) The applicable material viscosity range is narrow

Plunger pumps are not suitable for transferring medium- to high-viscosity liquid materials because they draw in liquid using the negative pressure generated inside the cylinder by the movement of the plunger.

2) The plunger operating speed cannot be controlled

The operating speed of the plunger affects the dispensing time. While air-driven plunger pumps allow for adjustments such as shortening or lengthening the overall dispensing time, the movement speed during the stroke from the start to the end of the plunger's travel is not constant. Therefore, even if the pump provides quantitative accuracy in the final amount of liquid dispensed, it cannot be used for applications such as drawing lines that require dispensing at a constant speed over a set period of time.

3) Filling and dispensing must always be performed as a set

In principle, plunger pumps cannot achieve accuracy unless the entire amount filled in one cycle is dispensed at once. It is not possible to stop halfway to dispense only half the amount, nor can the dispensing volume be changed mid-process.

Plunger pump type dispensers

Our MPP series dispensers apply the plunger pump mechanism to dispensers, enabling high-precision dispensing that adapts to changes in the viscosity of liquid materials while maintaining excellent durability. Furthermore, they resolve the aforementioned disadvantages of plunger pumps.

1) The applicable material viscosity range is wide

Because the liquid material is pressurized, it is possible to fill and dispense high-viscosity materials that cannot be drawn in by standard plunger pumps. This allows for the quantitative dispensing of liquid materials such as adhesives and greases.

2) The plunger operating speed can be controlled

The plunger is motor-driven and capable of dispensing at a constant speed, so it can also be used for drawing lines or dotting with adhesives. The dispensing speed can be optimally managed without changing the dispensing volume.

3) Filling volume and discharge volume can be set separately

The motor stroke amount (discharge amount) and speed can be saved for up to 400 CH, allowing the liquid material filled in a single operation to be divided and discharged as desired. This enables automatic application of multiple patterns to a single workpiece.



Our MPP series is a volumetric digital control dispenser that precisely dispenses fixed amounts of liquid materials with changing viscosities. In addition to allowing the discharge amount to be set by volume or weight, it boasts excellent durability due to its unique plunger system.

With two lineups, the MPP-5-S for precision application and the MPP-5-M for high-volume discharge, it contributes to the stabilization and improvement of application processes in a wide range of fields.

 

・Discharge volume can be set by volume or weight
・Excellent durability due to unique plunger system

 

・"Large-capacity" volumetric digital dispenser with 10 times the capacity of conventional models
・Heads can be selected to match the pump size lineup