Dosing Pump with VFD Integration

Real Story: Resolving Pulsa Feeder Pump Issues with VFD Integration for a Dosing System

Dosing systems are essential in industrial processes for precise chemical injection, such as controlling pH levels in water treatment or chemical manufacturing. This is a real-world account of how a Pulsa Feeder pump faced mechanical issues with its diamond shaft, leading to an innovative solution involving Variable Frequency Drive (VFD) integration and system optimization.

1. The Problem

1.1 System Overview

• Application: A dosing system used for pH control in a chemical processing plant.
• Equipment: Pulsa Feeder diaphragm pump.
• Control Strategy: Initially operated with manual stroke adjustment to vary the dosing rate.
• Process Parameter: pH levels monitored and maintained within a tight range.

1.2 Issue with the Diamond Shaft

• The pump’s diamond shaft, a critical component responsible for stroke actuation, began to exhibit issues:
  • Symptoms: The shaft showed excessive wear and tear, causing inconsistent dosing rates.
  • Impact: pH levels fluctuated due to uneven chemical dosing, leading to process inefficiencies and potential product quality issues.

2. Diagnosis and Challenges

2.1 Root Cause Analysis

• The diamond shaft wear was attributed to the following factors:
  • Frequent Stroke Adjustments: Manual changes to the pump’s stroke length caused mechanical stress on the shaft.
  • High Operating Pressure: The dosing system operated under high pressure, further straining the shaft.
  • Constant Operation: The pump ran continuously, even when lower dosing rates were required, accelerating wear.

2.2 Challenges in Resolving the Issue

• Simply replacing the shaft would address the symptom but not the root cause, risking recurrence.
• A more dynamic dosing control method was needed to adapt to changing pH levels without excessive mechanical adjustments.

3. The Solution

To overcome the limitations of the manual control system, the team implemented the following solution:

3.1 Open Pump Stroke to Maximum

• The pump stroke was set to its maximum limit, eliminating the need for frequent manual adjustments.
• This change reduced mechanical wear on the diamond shaft by operating the pump in a fixed configuration.

3.2 Install a Variable Frequency Drive (VFD)

• A VFD was installed to control the motor speed, dynamically adjusting the dosing rate based on process requirements.
• The VFD allowed precise control over the pump’s output without altering the stroke mechanism.

3.3 pH-Based Feedback Control

• The VFD was integrated with the system’s pH sensor and a PID controller:
  • pH readings were continuously monitored.
  • The PID controller adjusted the motor speed via the VFD to maintain the desired pH setpoint.

4. Implementation Steps

4.1 System Modifications

1. Pump Configuration:
   • The pump stroke length was locked at its maximum setting.
   • Regular maintenance was performed to ensure the shaft was in good condition for operation at full stroke.
2. VFD Installation:
   • A VFD compatible with the pump motor was selected and installed.
   • The VFD was configured for variable speed operation with input from the PID controller.

4.2 PID Controller Setup

• The PID controller was programmed with the following parameters:
  • Input: pH readings from the inline sensor.
  • Output: Signal to the VFD to adjust motor speed.
  • Setpoint: Desired pH level for the process.

4.3 Testing and Commissioning

• The system was tested under various conditions to validate its performance:
  • Simulated pH disturbances to evaluate the response time of the VFD and PID controller.
  • Adjusted PID tuning parameters to ensure stable and accurate control.

5. Results and Benefits

5.1 Improved System Performance

• The VFD-controlled dosing system provided precise chemical injection based on real-time pH readings.
• The process maintained pH levels within the desired range, enhancing product quality and reducing waste.

5.2 Reduced Wear and Tear

• Operating the pump at a fixed stroke length eliminated mechanical adjustments, significantly extending the diamond shaft’s lifespan.

5.3 Energy Efficiency

• The VFD allowed the motor to operate only at the required speed, reducing energy consumption during low-demand periods.

5.4 Simplified Maintenance

• The fixed stroke configuration reduced the frequency of pump maintenance.
• The system became easier to monitor and adjust, with fewer manual interventions required.

6. Lessons Learned

6.1 Dynamic Control Is Key

• Incorporating a VFD and feedback control system allowed the pump to dynamically respond to process demands, minimizing manual adjustments and wear.

6.2 Preventive Measures

• Regular inspections of critical components like the diamond shaft can identify potential issues before they escalate.

6.3 Optimize System Design

• Fixed mechanical settings combined with variable electronic control can improve reliability and flexibility in dosing systems.

7. Future Recommendations

8. Conclusion

By addressing the root cause of the diamond shaft issue and integrating a VFD with pH-based feedback control, the team successfully enhanced the dosing system’s performance and reliability. This innovative approach minimized mechanical wear, improved process stability, and reduced operational costs, showcasing the value of combining mechanical optimization with advanced control technologies.

For industries facing similar challenges, this solution highlights the importance of dynamic control strategies and proactive system design to overcome mechanical limitations and achieve long-term success.