What are the maintenance precautions for plunger pumps?

The spray system consists of a chemical tank, flow meter, liquid-level gauge, water pump, nozzles, and other components. As the heart of the spray system, the water pump is responsible for delivering and pressurizing the pesticide solution, thereby ensuring the proper operation of crop protection. In this article, we have decided to disassemble a plunger pump to explore its operating principle and, through this teardown, to explain common problems with plunger pumps and their corresponding solutions.

A plunger pump consists of three modules: the motor, the gearbox, and the pump head. How does it work? Let’s take an oil well as an example. The motor module acts as the “hand” that provides power to the pumping mechanism; the transmission module comprises the crank and connecting rod, which reciprocate to drive the suction cup up and down; and the pump head module functions like a wellbore, enabling both pumping and drainage.

Common problems with plunger pumps:

1. Low flow rate of plunger pump

The plunger pump operates smoothly, but the flow rate is low, below 4 liters per minute. This phenomenon may be caused by a blockage in the relief valve.

2. Pump Cover

The pressure safety valve is integrated into the pump cover. When the outlet pressure of the plunger pump exceeds the protection threshold, the relief valve opens, allowing the fluid at the discharge port to return to the suction inlet. This overpressure protection safeguards the water seal and sealing rings from damage.

3. Plunger pump has no flow

When no spray fluid is observed exiting the nozzle and both the solenoid valve and the nozzle appear normal, the plunger pump is operating but failing to discharge water properly. A likely cause in this situation is a stuck check valve within the plunger pump.

4. Check Valve

A plunger and two check valves form a sealed working chamber whose volume varies with the reciprocating motion of the plunger, thereby enabling the intake and discharge of liquid. The function of the check valves is to allow fluid to flow only in the direction of the inlet, while preventing backflow of the medicament at the outlet.

5. Plunger Pump Leakage

Plunger pumps exhibit excessive vibration, abnormal noise, low flow, and fluid leakage; in severe cases, they may even fail to operate. In such instances, the root cause is likely a problem with the water seal.

6. Water Seal

The water seal is a critical component of the pump’s working chamber, responsible for maintaining the pump’s seal.

7. Abnormal Noise in Plunger Pump

When a plunger pump is operating normally, abnormal vibration and noise, along with low flow, may be caused by the long-term failure to replace the lubricating oil inside the pump.

Lubricating oil ensures the smooth operation of the plunger pump. If the lubricating oil is used for too long, vibration and abnormal noise may occur during operation, resulting in insufficient flow.

8. Settlement Terms

Based on extensive case studies, these issues are predominantly caused by powder coating. Powder can inflict significant damage on components such as the check valves, relief valves, and seals of plunger pumps; therefore, the use of powder is generally not recommended.

The plunger pump serves as the pressure source for drug-liquid atomization and plays a crucial role in the atomization process. If it is damaged, operation will be interrupted. When spraying powder, clean the system promptly to prevent dried powder from clogging internal pump components. If powder has caused the aforementioned issues with the pump, we recommend taking the equipment to a service center and having qualified technicians disassemble, clean, or replace the affected parts.

Regular lubricant replacement is also crucial. It is recommended to change the lubricant every 300 operating hours, using approximately 30 ml each time. We recommend using Dajiang original lubricant (at gas stations, you can opt for the dedicated SAE 10W-30 grade) or a gear and bearing lubricant of equivalent grade available on the market.

Here’s a quick summary for you: If you want to use a plunger pump for a long time, minimize the use of powders and perform frequent maintenance.