Operating Procedures and Troubleshooting Methods of Dosing Device

1. Introduction of devices and systems

(1) Design scope: one PAC and one PAM dosing device.

(2) Pipeline valves: made of stainless steel.

(3) Solution tank: 1 cubic meter stainless steel medicine tank. PAC/PAM dosing device adopts two tanks and three pumps. Metering pump: hydraulic diaphragm metering pump.

(4) All the devices are installed on the steel frame for easy installation and convenient maintenance.

(5) Electrical control: equipped with an independent electrical control cabinet. On the cabinet, there are: manual transfer switch of metering pump motor, operation button, alarm light, etc.

(6) Operation mode of metering pump motor: manual button - relay - pump motor.

(7) PAC/PAM dosing device is manually operated to control motor and dosage.

Description of preparation solution:

(1) According to the required concentration, solution tank volume and pharmaceutical purity, measure the dosage and water quantity, add the medicine to the solution tank, open the water supply valve and add the required amount of water.

(2) Preparation of solution: pour a certain amount of medicament (solid or liquid) into the solution tank, open the water supply valve to inject water until the liquid level reached the specified level. Start the mixer to make the medicament in the solution tank fully and evenly mixed, so as to be used for dosing.

(3) Before dosing, open the water inlet valve to fill the solution tank, and adjust the metering device to the required dosing amount, then open the stop valve of the solution tank to start dosing.

(4) Dosing: adjust the dosing amount of the metering pump to a certain valve, start the pump, add chemicals to the dosing point, and constantly adjust the dosing amount to meet the process requirement. If not, readjust the concentration of the prepared solution.

(5) The residue in the solution tank should be discharged through the sewage pipe, and the liquid level of the solution tank should be measured by magnetic level gauge.

(6)The solution tank should be cleaned regularly.

2. Operating procedures

2.1. Preparation before startup

All PAC/PAM dosing devices are basically the same. It should be noted that the high pressure range at the phosphate dosing place should be strictly in accordance with the safety regulations.

Note: Observe that whether the rotation direction of the metering pump and the mixing motor is clockwise (rotation mark has been indicated on the motor shell).

Manual water addition: add demineralized water to the specified position of the solution tank.

Artificial dispensing: add all kinds of medicines into the tank to the specified concentration (can be measured manually).

The Y-type filter should be cleaned once every three months. After cleaning, there is air entering the low-pressure pipeline. At this time, the pump should be opened for venting (the pump should be opened manually, and the venting screw should be slightly loosened when venting, as long as there is water out). When the water flows out of the vent hole intermittently, it indicates that the pressure has entered the high pressure zone.

Adjust the liquid output of the pump:  

Small range adjustment : slightly rotate the scale on the adjustment handle by 10%～100%, and generally take 30%～90% as the value.

Large range adjustment: beside the oil filling hole, turn the small cover open, slightly adjust it with the inner hexagon, clockwise means large and counter clockwise means small.

2.2 Start

(1) Manual control: this device is a manual PAC/PAM dosing device.

Turn on the main power switch, turn on the branch power switch, turn on the control power switch, then the green light is on.

Press the button switch to the “manual” position.

When the dosing pump and other mechanical parts are normal, press the start button of the corresponding pump, at this time, the green light in off and the red light is on, then the dosing pump enters into normal operation. Otherwise, press the stop button, the green light is on, the red light is off, and the dosing pump stop running.

Similarly, the mixer motor can be started and stopped (Note: the mixer is not in the automatic range).

Pay attention to whether the indication of the pressure gauge is normal. Sometimes, because air is mixed in the low-pressure end, bubbles are gradually formed at the outlet of the pump, so that the diaphragm movement can not form pressure. At this time, the air can be drained by the vent screw and then tightened.

During the first half hour of operation, pay attention to the temperature rise of the motor, the indication of the pressure gauge and the working conditions of the components.

When the pump is in normal operation, the impact sound of cleaning should be emitted from the inlet and outlet of the pump.

(2) Automatic control: only when the manual state is normal, the automatic control can be implemented.

 ① Close the automatic dosing device switch (suggestion: turn off the manual dosing shunt switch).

② Set the switch to the “auto” position.

③ As long as the PLC has signal output, the pump motor will rotate at a certain frequency.

④ If there is any abnormal condition, should be checked according to the circuit maintenance.

3. Common faults and troubleshooting methods

3.1 No drainage at all

The reason:

(1) There are sundries in the one-way valve.

(2) The suction pipe is blocked.

(3) The suction pipe is leaked.   

Exclusion methods:

(1) Check the one-way valve.

(2) Clean and dredge the suction pipe.

(3) Compress or replace the sealing gasket.

3.2 Insufficient drainage

The reason:

(1) The suction pipe is partially blocked.

(2) There are sundries stuck in the suction or discharge valve.

(3) There is gas in the oil cavity.

(4) Insufficient or too much oil in the oil cavity.

(5) Filling valve or relief valve is leaked.

(6) The pump valve is worn and not closed tightly.

(7) Insufficient rotation speed.

Exclusion methods:

(1) Dredge the suction pipe.

(2) Clean the suction and discharge valve.

(3) Open the valve to exhaust the gas.

(4) Manually replenishing or discharging oil.

(5) Grind the valve.

(6) Repair or replace the valve.

(7) Check the motor and voltage.

3.3 Unstable discharge pressure

The reason:

(1) There are sundries stuck in the suction or discharge valve.

(2) The pipeline is not provided with back pressure valve.

Exclusion methods:

(1) Clean the suction or discharge valve.

(2) Add back pressure valve.

3.4 The measurement is not accurate enough

The reason:

(1) Leakage of diaphragm packing.

(2) The suction or discharge valve is worn.

(3) The motor speed is not stable.

(4) The adjusting handwheel has shifted.

Exclusion methods:

(1) Adjust or replace the packing.

(2) Replace the suction or discharge valve.

(3) Stabilize power frequency and voltage .

(4) Calibrate and fix the handwheel.

3.5 Impact sound in operation

The reason:

(1) The rotating parts are loose or severely worn.

(2) The suction pipe installation height is too high.

(3) Suction pipe leakage.

(4) There is air in the oil.

(5) The suction pipe diameter is too small.

(6) The discharge pressure is too high.

Exclusion methods:

(1) Tighten relevant screws or replace with new parts.

(2) Lower the installation height.

(3) Compress the suction flange or nut.

(4) Discharge the air in the oil.

(5) Increase the suction pipe diameter.

(6) Reduce the discharge pressure.