Instruções operacionais detalhadas para sistemas de dosagem automática

Automatic dosing systems consist of an integrated setup that includes a metering and dosing system, a chemical solution preparation system, a safety system, and a control system. These systems are characterized by their compact design, ease of maintenance, low cost, and transportability.

Important Operating Considerations for Automatic Dosing Systems

1. Metering Pump Control: The metering pump motor is controlled by a variable frequency drive. If the pump is not functioning correctly, this could indicate a fault in the drive. In such cases, activate the backup pump (normally, one is in use while the other is on standby) and follow the manual instructions to reset the fault.

2. Level Indicator Maintenance: Material may adhere to the level indicator due to moisture, affecting its performance. Regularly check and clean the dosing unit (recommended for each shift).

3. Control Cabinet Care: Prevent water from entering the electrical components in the control cabinet. Keep the cabinet door closed during operation and do not wash the cabinet with water, as this may damage electrical components.

4. Corrosion Checks: Regularly inspect mechanical parts that come into contact with chemicals, as many dosing agents are corrosive. Replace any damaged components promptly.

5. Feeder Screen Integrity: If the feeder screen inside the dosing system is damaged, replace it immediately to prevent larger particles from entering the screw feeder, which could damage the screw or the drive motor.

6. Pressure Level Indicator Maintenance: Check and clean the membrane on both pressure level indicators every month.

7. Material Flow Monitoring: Since some chemicals can be viscous, ensure the feeding pipes are unblocked, especially near the hopper exit and discharge points.

8. Hopper Functionality: Open the hopper lid while ensuring there is suction downwards. If there is no suction or a backdraft, check for blockages in the feeding lines (recommended checks every 20 hours of run time).

9. Heating Element Checks: The hopper is equipped with a heater. If the feeding pipe remains cold after some time, the heater may be damaged and should be checked or replaced.

10. Valve Operation: The inlet and outlet valves are automatic ball valves. If water continues to flow in or out after closing these valves, they may be defective and should be inspected and replaced as needed.

11. Pump Operation Guidelines: Do not run the metering pump dry or in reverse. Ensure the inlet and outlet valves are open before starting the pump and pre-fill it with the medium.

Chemical Dosing Methods

1. Chlorine Removal Agent
Calculate the dosing amount based on the original water input:
– For every 57 liters of pure water, the dosing amount (grams) should be adjusted per the incoming water flow rate. Set the dosing machine to approximately 2.5 liters per hour.
– Note: If the chlorine concentration exceeds 0.5 mg/l, double the chlorine removal dosage. Calculation: Dosage multiplier = Chlorine concentration / 0.5.

2. Flocculant Addition
For water sources (tap water) with turbidity less than 5 NTU:
– For every 57 liters of pure water, configure your dosing machine to add the specified grams of flocculant at approximately 2.5 liters per hour.
– If the source water is groundwater, surface water, or concentrated reclaimed water, double the flocculant dosage. Calculation: Dosage multiplier = Turbidity / 5.

3. Scale Inhibitor
When water hardness is between 50-100 mg/l (calcium carbonate equivalent):
– For every 57 liters of pure water, configure the dosing machine to add scale inhibitor at approximately 2.5 liters per hour.
– Note: If the hardness exceeds 100 mg/l, double the concentration of scale inhibition. Calculation: Dosage multiplier = Hardness / 100, but do not exceed 10 times.

Improving Metering Pump Repeatability

To enhance metering accuracy when the pump outlet is at atmospheric pressure, consider installing a spring in the pump discharge valve. A back pressure valve at the end of the line is also an effective method to improve repeatability.

Adjusting the Back Pressure Valve

1. Ensure the pressure does not exceed the metering pump’s working range.
2. The pressure at the discharge end of the pump must be at least 1 bar higher than the pressure at the suction end.

Choosing the Right Pulse Dampener Size

To dampen 90% of pulsation, calculate the minimum volume of the pulse dampener (in ml) by multiplying the metering pump’s delivery capacity per stroke (in ml) by 26.

Setting Safety Valve Pressure

Adjust the safety valve’s pressure setting within the rated working pressure range of the metering pump. It should not exceed the pump’s maximum working pressure. For instance, if the working pressure is 3 bar, set the safety valve to 3 bar or lower to ensure proper operation and prevent pump damage caused by overpressure.

Calculating Suction Height for Non-Water Liguid

If the fluid being transported is not water, divide the metering pump’s rated suction height by the specific gravity of the liquid being pumped.

When to Use Self-Priming Suction

Self-priming suction can be utilized in the following situations:
1. When the liquid being metered has a high volatility.
2. When the liquid has a relatively high specific gravity.
3. When a high stroke frequency is required.
4. If the metering pump operates in high-altitude environments.
5. In on-site applications requiring a large storage tank, where self-priming would be impractical.

Preventing Corrosion in Pump Heads/Seals

To avoid common issues of corrosion in pump heads during metering of acids, chlorides, fluorides, and hydrogen peroxide, choose appropriate pump head materials based on the concentration and operating temperature of the chemicals. This selection may require consultation with the manufacturer for best results.

Instructions for Using the Dosing System

1. PH Meter Installation: Install the pH meter into the designated port on the dosing unit and connect all related pipes, ensuring all threaded connections are tightly secured to prevent leaks.

2. Connecting Power Supply: Open the electrical control cabinet and connect the power supply to the metering pump motor, ensuring it meets the required specifications (three-phase, four-wire setup).

3. Shut Off Drain Valve: Ensure that the drain valve is closed before proceeding.

4. Preparing the Chemical Solution: Measure the chemical and water volumes based on the desired solution concentration. Add the chemicals into the solution tank and open the water valve to fill to the required level.

5. Solution Preparation: Pour the chemical (solid or liquid) into the solution tank and turn on the water valve. Once the liquid reaches the required level, stop the water flow. Adjust the metering system to the desired dosage and open the solution tank valve to begin dosing.

6. Dosing the Chemical: Open the dosing system valve, adjust the metering pump to the required volume, and start the pump to add the chemical to the dosing point. Continuously tweak the metering pump’s output to align with the operational requirements. If it doesn’t meet the needs, readjust the concentration of the prepared solution.

7. Residual Solution Disposal: Any leftover material in the solution tank can be removed via the drain pipe, and the liquid level can be monitored using the level indicator.

8. Low Liquid Level Alert: If the liquid falls below the designated low level, the dosing pump will automatically stop.

9. pH Monitoring: The dosing pump will automatically shut off if the pH level exceeds or falls below preset values (refer to the pH meter manual for setup).

10. Conductivity Control: If the conductivity exceeds the set limit (see conductivity meter manual for settings), open the drain valve to prevent overflow until the conductivity returns below the threshold.

11. Corrosion Monitoring: Refer to the attached instructions for the corrosion monitoring device regarding operation.

12. Metering Pump Operation: Follow specific instructions in the metering pump user manual for operation.

13. Regular Cleaning: Based on the cleanliness of the chemicals, the solution tank should be cleaned regularly to maintain hygiene and performance.

By adhering to these detailed operating instructions and precautions, users can ensure the effective operation of the automatic dosing system, maintaining optimum performance and chemical safety.