1、 Overview of Liquid Chlorine Submerged Pump

The liquid chlorine submersible pump adopts the European hydraulic model with high efficiency. It is equipped with two sets of hydraulic models at the same outlet, with a wide flow range and low NPSHR (0.5 meters). It adopts a multi-stage segmented structure, zero leakage, no dynamic seal, and magnetic drive. Safe, economical and reliable, the liquid chlorine submersible pump adopts the building block principle, with a compact structure, strong universality, easy maintenance, and complies with DIN24256/API685 standards.

2、 Structural characteristics of liquid chlorine submersible pump

1. The isolation sleeve of the liquid chlorine submersible pump is made of Hastelloy alloy, formed by a special process, with no weld seam in the axial direction, fully ensuring the sealing and chemical stability of the isolation sleeve.

2. The liquid chlorine submersible pump adopts a double-layer isolation sleeve structure with double-layer protection, which can achieve single-layer isolation sleeve leakage alarm. At this time, the liquid chlorine is still completely sealed without leakage, which is safe and reliable.

3. Special rare earth alloy is selected as the magnetic material for the liquid chlorine submersible pump, with an irreversible demagnetization temperature of 450 degrees. Fully ensure that the service life of the entire machine is greater than 15 years. 4. The sliding bearings of the liquid chlorine submersible pump are made of high-quality silicon carbide with a purity greater than 99%, which has high strength, elasticity, toughness, and wear resistance, and is completely suitable for use in liquid chlorine.

5. The axial force of the liquid chlorine submersible pump is automatically balanced, and the sliding bearing thrust plate only bears unbalanced axial force at the moment of starting and stopping, fully ensuring the service life of the sliding bearing.

6. The rolling bearings of the transmission components of the liquid chlorine submersible pump adopt SKF or NSK grease maintenance free bearings.

7. The liquid chlorine submersible pump is equipped with safety measures such as operation protectors and leakage protectors.

3、 Process flow diagram of liquid chlorine submersible pump

The shaft seal adopts double sealing, namely packing seal and air seal;

Easy to operate, can be directly started, and has no pressure requirements for the storage tank;

The sealing gas source used is dry compressed air with a dew point temperature not exceeding 40 ℃. The sealing gas pressure should be 0.05-0.1 MPa higher than the liquid chlorine pressure in the intermediate tank, and the air flow rate should be 0.5-1 m/min. The liquid level in the intermediate tank should be 600 mm higher than the pump inlet to prevent cavitation.

In addition, the shaft seal is equipped with an emergency sealing airbag made of special materials. Once the sealing gas source is interrupted, emergency sealing can be used for sealing treatment to effectively prevent chlorine gas from overflowing.

4、 Advantages and disadvantages analysis of liquid chlorine submersible pump

The advantages of liquid chlorine submersible pump are:

(1) Can achieve high flow filling, such as filling liquid chlorine tank trucks or train tank trucks, with fast filling speed, large flow rate, and high efficiency;

(2) It can achieve continuous filling and stable pressure, overcoming the frequent back pressure phenomenon caused by tank reversal in the gasification liquid chlorine boosting process, ensuring the safety of liquid chlorine filling;

(3) Effectively solved the explosion hazard caused by the enrichment of nitrogen trichloride in liquid chlorine due to gasification heating of liquid chlorine;

(4) The submersible pump is directly installed on the liquid chlorine intermediate tank or liquid chlorine storage tank, with simple process piping, making it easy to diagnose faults such as leakage and vibration;

(5) By using a submersible pump, a cooling capacity of 0.45GJ can be achieved for every 1 ton of liquid chlorine filled, and 5kg of liquid chlorine loss can be reduced.

The disadvantages of liquid chlorine submersible pumps are:

(1) The requirements for the moisture and acid content of raw chlorine gas are relatively high. So far, the submersible pump has been inspected three times, all of which were caused by high water and acid content in the liquid chlorine, resulting in iron containing chloride blocking the impeller and shaft sleeve, causing an increase in current and difficulty in starting.

(2) The requirements for sealing gas are relatively high. The liquid chlorine submersible pump requires that the sealed gas source must be dry air or nitrogen, with a dew point not exceeding -40 ℃.

(3) The impeller shaft is slender and difficult to maintain, so there should be a spacious maintenance area.

(4) The equipment is expensive and requires a high one-time investment.

5、 Key points for operation of liquid chlorine submersible pump

1. Preparation before starting the pump

1) Check the opening status of each valve, whether the pressure gauge is intact, and whether there are any leakage points;

2) Fill the oil cup with oil and fill the bearing cover with lubricating grease every Wednesday;

3) Use your hand to turn the coupling clockwise for 2-5 turns to check for flexibility;

4) Check the power supply;

5) Check if the pressure in the air tank has reached the required level, which should be lower than the original chlorine pressure, usually above 0.3 MPa.

2. Start the pump normally

1) Slightly open the balance valve of the intermediate tank and connect the hydrochloric acid system to the liquid chlorine system so that it can enter the intermediate tank;

2) Open the inlet valve of the middle tank and start the motor after the liquid level is qualified;

3) When the outlet pressure reaches 1.6MPa, slowly open the outlet valve of the submersible pump. After the outlet pressure of the submersible pump stabilizes, fully open the outlet valve;

4) Adjust the air seal pressure to prevent leakage. The first stage sealing pressure should be slightly higher than the middle groove pressure by 0.03MPa, the second stage sealing pressure should be slightly higher than the first stage sealing pressure by 0.03MPa, and the exhaust outlet pressure of the middle groove should be slightly lower than the second stage sealing pressure by 0.1MPa;

5) Control the liquid level of the intermediate tank well, and when the lower limit liquid level alarm occurs, stop the pump according to the stop pump program.

3. Normal pump shutdown

1) Slowly close the outlet valve before stopping the motor;

2) Close the bottom valve of the measuring tank;

3) Connect the balance valve of the intermediate tank to the liquefaction system using the distribution platform, and cut off the valve leading to hydrochloric acid;

4) Adjust the air seal pressure to prevent leakage, and check the air pressure every half hour.

4. Emergency pump stop

1) Quickly close the outlet valve of the pump before stopping it to prevent reverse rotation;

2) Stop the pump according to the normal shutdown procedure for the rest.

5. Key points of job operation

1) Before starting the pump, check the condition of the valves in the intermediate tank, submersible pump, and metering tank, and whether the air seal pressure meets the driving conditions;

2) Before starting the pump, manually rotate the coupling 2-5 times. If it is difficult to rotate or the coupling does not move, or if the outlet pressure is lower than IMPa during operation,

Notify maintenance personnel to conduct repairs;

3) Before starting the pump, lubricating oil should be added once, and lubricating grease should be added once a week;

4) After stopping the pump, open the intermediate tank balance valve and connect it to the liquefaction system;

5) Within three days when in standby mode, manually rotate the coupling for 2 minutes every four hours;

6) If the pump is stopped for more than three days, it must be drained first, and then the liquid chlorine in the intermediate tank must be emptied before draining;

7) When the sealing air pressure is lower than the chlorine gas pressure, notify the dispatch in a timely manner, quickly close the air pressure of the buffer tank, and open the nitrogen seal;

8) When negative pressure is applied to the middle groove, it is important to prevent the liquid from the sewage system from flowing into the submersible pump, which may cause corrosion.