What could be the possible reason for insufficient flow of Dalian acid resistant pump

As a key equipment for transporting corrosive media in industries such as chemical, metallurgical, and electroplating, the insufficient flow rate of Dalian acid resistant pumps can directly affect production efficiency and even lead to safety hazards.

1、 Entrance pipeline system issues

Inlet pipeline blockage: Solid particles or crystals in the medium may deposit at the bends and valves of the pipeline, forming local blockages. Especially when transporting corrosive liquids containing suspended solids, scaling on the pipe wall after long-term operation will reduce the flow area.

Imported filter blockage: If the Y-shaped filter or basket filter installed to protect the pump body is not cleaned regularly, the filter screen will be completely covered by impurities, which will severely limit the medium flow rate. It is recommended to check the filter pressure difference once a month.

The imported valve is not fully opened: Negligence by the operator or malfunction of the valve actuator may result in insufficient valve opening. It is necessary to check whether the valve opening indicator matches the actual situation, and for manual valves, it is necessary to confirm the number of rotations of the handwheel.

Leakage of imported pipelines: Failure of sealing at flange connections or corrosion and perforation of pipelines can cause air to be sucked in, damaging the vacuum degree of the inlet. The leakage point of the negative pressure pipe section can be detected by applying soap water method.

Low inlet liquid level: When the tank liquid level is below the required NPSHr of the pump, the effective suction height of the pump is insufficient. Ensure that the liquid level is at least 1.5 meters above the centerline of the inlet pipe.

2、 Internal issues with the pump body

Wear or corrosion of impellers: Long term erosion of acid resistant pump impellers by media can cause thinning of blades, expansion of flow channels, and reduction of head and flow rate. The clearance of the PTFE lined pump impeller increases significantly after wear.

Excessive clearance between the pump body and impeller: After the sealing ring between the pump body and impeller wears out, the liquid in the high-pressure area flows back to the low-pressure area and increases. When the gap exceeds twice the design value, the volumetric efficiency can decrease by 15-20%.

Mechanical seal leakage: When the double end mechanical seal fails, some of the medium leaks from the sealing chamber instead of being discharged through the outlet. Observing the leakage hole of the seal can determine whether the internal seal is intact.

Scaling in pump chamber: Some media (such as sulfuric acid) are prone to crystallization at specific temperatures and adhere to the inner wall of the pump casing, reducing the cross-sectional area of the flow channel. After parking, thoroughly rinse the pump chamber with clean water.

Shaft bending or bearing damage: Misalignment of the rotor system can cause friction between the impeller and the pump body, increasing operational resistance. When the vibration value exceeds 4.5mm/s, the machine should be stopped for inspection.

3、 Changes in dielectric properties

Increased viscosity of the medium: A decrease in temperature or an increase in concentration will increase the viscosity of the medium, and the flow rate in laminar flow is inversely proportional to the viscosity. For example, the viscosity of 98% sulfuric acid at 20 ℃ is 25.4mPa · s, which is much higher than that of 93% sulfuric acid.

Excessive gas content: Dissolved gases in the medium precipitate in the low-pressure zone, forming cavitation. It has been measured that when the gas content reaches 5%, the flow rate can decrease by 30%. An air purifier can be installed at the import to improve the situation.

Density variation: Inaccurate concentration monitoring leads to actual density deviation from the design value. Although the increase in density does not directly affect the volumetric flow rate, it will increase the shaft power demand.

Excessive solid content: If the contractually agreed 5% solid content actually reaches 15%, it will not only increase flow resistance but also accelerate the wear of overcurrent components.

4、 Abnormal operating conditions

Insufficient speed: The actual speed is lower than the rated value due to incorrect parameter settings of the frequency converter or belt transmission slippage. The flow rate is directly proportional to the rotational speed, and when 1500rpm is reduced to 1350rpm, the flow rate decreases by 10%.

Improper opening of outlet valve: Excessive throttling will cause the working point to shift to the left. When the valve opening is less than 50%, the system resistance curve becomes steeper and the flow rate drops sharply.

Interference between parallel pumps: If the check valve at the outlet of a single pump fails during parallel operation, it may cause medium backflow. Check the current difference when each pump operates separately.

System pressure fluctuations: Abnormal increase in downstream equipment pressure can alter the pipeline characteristic curve. Install pressure transmitters to monitor changes in pipeline pressure.

5、 Selection and design issues

Improper selection of pump type: When using high lift pumps for low resistance systems, the operating point is far away from the better efficiency zone. If IH type chemical pump is selected, only the head of FZB type self-priming pump is actually required.

Insufficient cavitation allowance: The NPSHa of the device does not take into account pipeline losses and safety margins, and should generally be 0.5-1m larger than NPSHr.

Material compatibility issues: If using a 304 stainless steel pump to transport chloride containing ion media causes pitting corrosion and increases the surface roughness of the flow channel.

6、 Solution suggestions

Establish a preventive maintenance system: dismantle and inspect the gap between the mouth ring every quarter, clean the filter every month, and record vibration and current data daily.

Installation of monitoring instruments: Install pressure gauges and flow meters at the inlet and outlet to monitor performance changes in real-time.

Optimize operating parameters: Use frequency conversion adjustment to keep the operating point in the high-efficiency zone (80-110% rated flow) at all times.

Quality control of spare parts: Select original impellers and mouth rings to ensure dimensional tolerances are within 0.05mm.

Through system analysis, it can be seen that insufficient flow rate of acid resistant pumps is often caused by the superposition of multiple factors. It is recommended to adopt the inspection principle of "from outside to inside, from simple to complex", first confirm the external pipelines and operating conditions, and then gradually dismantle and inspect the internal components of the pump body, ultimately achieving precise maintenance. Regular training on interpreting pump characteristic curves for operators can improve their ability to predict faults.