Created on:2022-01-12 14:24

Troubleshooting of plunger pump

Troubleshooting of plunger pump

1. Introduction

The utility model relates to a high-pressure plunger pump of dannison hydraulic pump PV series. The power of the pump is 125KW, the pressure is 30MPa and the flow is 174 L / min. Its structure is as shown in Figure P. There are 7 small column plugs evenly distributed along the circumference in the cylinder block. Its working principle is that the cylinder block is driven to rotate through the transmission shaft, the spherical heads of the seven plungers evenly distributed in the cylinder block are installed in the spherical recess of the sliding shoe, and a riveting table is added, so that the sliding shoe and the plunger will not be separated, but can move relatively. By using the rotation of the swashplate, the rotary motion is transformed into the reciprocating motion of the plunger in the cylinder. Each plunger realizes the action of oil suction and pressure for each rotation of the swashplate. On the one hand, the plunger rotates with the cylinder body, on the other hand, it makes reciprocating motion in the cylinder body. Therefore, when the cylinder body rotates, the plunger moves back and forth relative to the cylinder body to form the change of closed volume and realize the function of oil absorption and oil discharge.

2. Fault phenomenon

The working speed of hydraulic equipment is slow and the production efficiency is low, which does not meet the production needs.

3. Fault diagnosis

Under the rated power of the pump, the output characteristics and flow characteristics between the flow and pressure of the pump and the production efficiency have the following relations: when the hydraulic cylinder has light load and low pressure, the pump works at full flow; When the load increases, the pressure increases. When the pump outputs the same pressure, the output flow of the pump is larger than the original output flow. At this time, the speed of the actuator becomes faster and the production efficiency of the machine is improved.

In the working process, the load increases continuously. If the pressure and flow of the pump become smaller at this time, the movement speed of the actuator becomes slower and the production efficiency of the equipment decreases. When the pressure and flow of the pump are small to a certain extent, the production efficiency of the equipment will decline faster, and finally the equipment can not work normally.

According to the above analysis and the phenomenon of failure, we judge that the reason for the failure is that the pressure and flow of the pump are too small.

4. Factors affecting the pressure and flow of the pump are too small

(1) Oil leakage occurs between the port plate and the port plane of the cylinder block, and between the port plate and the port plane of the pump body. On the one hand, the sealing performance between the valve plate and the valve plane of the cylinder block and between the valve plate and the valve surface of the pump body decreases. In the process of work, the oil may not be clean, which will wear the working surface of the valve plate and lead to leakage. On the other hand, due to the high-speed rotation movement between the cylinder block and the port plate, the force on the cylinder block in the working process is relatively complex. If the various forces on the cylinder block in the working process are unbalanced, the oil film formed between the cylinder block and the port plate will be damaged and generate additional torque acting on the port plate, causing wear on the working surface of the port plate, resulting in leakage.

(2) The fit clearance between plunger and plunger hole is out of tolerance. Due to the wear caused by long-time movement between the plunger and the cylinder block, the matching clearance between the plunger and the plunger hole is out of tolerance, resulting in serious leakage. At the same time, the plunger is subjected to large lateral force during the working process. The standard fit clearance between the plunger and the plug hole on the cylinder block is 0.01 ~ 0.03mm.

(3) The deflection angle of the adjusting mechanism is small. The deflection angle of the regulating mechanism is small, and the deflection angle of the regulating mechanism has a certain impact on the flow of the pump, because the flow of this form of plunger pump is realized by adjusting the deflection angle of the regulating mechanism. Due to the long-time operation of the pump, the deflection angle of the regulating mechanism may also be changed. Therefore, this factor cannot be ruled out.

5. Troubleshooting

(1) Technical status detection. According to the determination of the fault cause, we disassembled the plunger pump, carried out technical testing on the plunger, cylinder block, port plate, regulating mechanism, spring and other relevant parts, and the results of testing and identification; The technical status of spring and adjusting mechanism parts is normal; Inspection and identification results of plunger, cylinder block and port plate; The cylindrical surface of the plunger is seriously worn, the plunger hole on the cylinder block is also worn out of tolerance, and the port distribution surface of the port plate is seriously worn, with pits in some parts. This is consistent with the results of our analysis and judgment.

(2) Repair method.

1) Repair of port plate. The seriously worn parts of the valve plate shall be repaired by welding repair, cold welding with cast 308 electrode, tempering and heat preservation after welding, and grinding with a surface grinder to ensure that the perpendicularity between the working surface of the valve plate and the outer circle is less than 0.015 and the flatness is less than 0.01.

2) Repair of cylinder block.

① Repair the plug hole on the cylinder block. The 7 plug holes on the cylinder block are ground with a special inner cone sleeve grinding tool, which can ensure the requirements of geometric accuracy and surface roughness. The final size of the hole after grinding is Φ 25. The ovality is 0 002 ~ 0.005, the taper is 0 002 ~ 0.005, the surface roughness is Ra0.8, and the perpendicularity between the center of the column plug hole and the end face of the cylinder block is less than 0.01.

② Repair of cylinder block end face. After technical appraisal, the end face of the cylinder block needs to be grinded and repaired. The method is as follows:; Place it on the grinding plate with secondary precision for grinding. The flatness is less than 0.005mm, and the surface roughness Ra is 0.32.

3) Repair of worn surface of plunger cylinder. According to the wear state of the plunger surface and the results of technical inspection, it is decided to use the method of hard chromium plating for size recovery and mechanical grinding for machining. The repaired size is 25 +, the ovality is 0.002 ~ 0.005, the taper is 0.002 ~ 0.005, and the surface roughness value is Ra0.8.

After the installation and operation experiment of the repaired plunger pump, the fault phenomenon disappeared, and the experimental effect was very good. After installation and operation, it is in good condition and can operate safely and reliably for a long time. Through the analysis and diagnosis of the fault, we realize that as long as we can analyze and diagnose the cause of the fault accurately, and then select a reasonable repair method, the fault can be eliminated.

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