Common faults of evaporator

1. Leakage of high-temperature corrosive liquid or steam

Leaks often occur in weak links such as equipment and pipeline welds, flanges, sealing fillers, expansion joints, etc.

The direct cause of leakage is often cracking caused by thermal expansion and contraction during startup and shutdown; Or it may become thinner due to pipeline corrosion, and rupture due to stress impact during startup and shutdown, resulting in the leakage of liquid or steam.

To prevent such accidents, strict equipment inspection, pressure testing, leak testing, and regular inspection of equipment corrosion should be carried out before driving.

2. Pipeline valve blockage

For solutions that are prone to crystallization during evaporation, crystallization often occurs as the material becomes thicker, causing blockages in pipelines, valves, heaters, etc., preventing the material from flowing and affecting the normal operation of evaporation.

Therefore, it is necessary to separate the salt sludge in a timely manner and wash it regularly. Once blockage occurs, it should be washed with pressurized water or remedied by vacuum suction.

3. Troubleshooting for high evaporator temperature

(1) It may be due to the expansion valve opening being too large, causing too much refrigerant to enter the evaporator and not being able to completely evaporate in the evaporator. The excess liquid occupies a portion of the heat exchange area, reducing the heat transfer area, and increasing the inlet evaporation temperature. Therefore, the expansion valve opening should be adjusted appropriately based on the cooling capacity.

(2) Another possibility is that excessive condensation temperature leads to an increase in evaporation temperature, as the compression ratio of the compressor increases, the suction coefficient decreases, and the gas specific volume increases, resulting in an increase in evaporation temperature.

4. The evaporation temperature is too low

(1) Perhaps the opening of the expansion valve is too small or the expansion valve is blocked. So there is too little refrigerant entering the evaporator, and some of the heat transfer area does not have refrigerant for heat absorption and evaporation. The gas output is insufficient for the compressor's suction requirements, resulting in a decrease in the specific volume of gas in the evaporator, a decrease in pressure, and a decrease in evaporation temperature. Therefore, the opening of the expansion valve should be adjusted appropriately according to the actual situation.

(2) Insufficient refrigerant replacement, resulting in a small amount of refrigerant entering the evaporator, causing some surface areas to be unable to perform heat exchange. The refrigerant entering the evaporator is easy to evaporate, but it cannot meet the suction requirements of the compressor, resulting in a decrease in evaporation temperature. Therefore, the amount of refrigerant should be added according to the design instructions.

(3) The temperature of the evaporator's chilled water is too low, or even frozen, mainly due to the low circulating volume of chilled water. The circulating volume of chilled water should be increased as needed, and the circulating volume of chilled water should be increased as needed, and the water pump should be checked.

5. How to repair leaks in the evaporator

For leaks in evaporator composite aluminum plate type evaporators, when repairing welding, the surrounding area of the evaporator leak should be cleaned first, and then repaired according to the following methods:

1. Melt aluminum and tin into a 2mm thick aluminum tin electrode, and then melt the aluminum solder strip with a 300 watt soldering iron. At the same time, heat and friction are carried out simultaneously at the leakage hole.

2. Remove the discarded copper layer of the circuit board, then grind the remaining epoxy resin board into powder, sieve it, and mix it with rosin powder to make solder. Place a small amount of flux around the leaking hole, and then rub the electric soldering iron and welding rod in the area with the leaking hole to firmly weld the leaking hole.

3. Mix the self setting powder and self setting water at a ratio of 10:6, wait for a few minutes, and then apply a small amount of the mixing solution to the leaking area.

4. First, take 1% dilute phosphoric acid solution and clean the surrounding area of the leak hole. After a moment, coat it with ferric chloride. After 1 minute, use a 100 watt soldering iron for repair welding. After the repair welding is completed, remove the remaining flux.

For copper tube evaporators in evaporators, leaks usually occur at the welding site. Once the leak hole is found, it should be promptly repaired.

For evaporators that can be repaired without dismantling the display cabinet evaporator, before welding, the seal on the compressor of the display cabinet evaporator should be cut open, and the display cabinet evaporator should be slightly heated to allow the vapor generated by the refrigerant in the display cabinet evaporator to be discharged from the seal. When repairing welding, a silver gun should be used for welding, and usually a small welding gun and nozzle should be used. At the same time, the flame should not be too strong, and the repair welding time should be shortened as much as possible. The action should be quick and accurate to repair leaks, to prevent excessive heating time from causing large deformation of the display cabinet evaporator.

6. What are the common faults in the three effect vacuum evaporator?

(1) Condensate backflow: If the condensate used in the condenser cannot be discharged into the water pool and is backflow into the three effect vacuum evaporator, not only will the vacuum degree decrease, but also the concentrated alkali in the three effect vacuum evaporator will be diluted, making operation impossible; More serious is the accident of vacuum pump cracking caused by uneven heating and cooling between the cylinder and piston after condensate water is poured into the vacuum pump.

The main reason for condensate injection is blockage or air leakage in the condenser and condensate discharge pipe, which is particularly prone to occur in jet condensers.

Therefore, when it is found that condensate water is flowing backwards, it is necessary to immediately stop the vehicle and check the cause. The vehicle should be driven after troubleshooting. In addition, the condenser and condensate will discharge scale from the pipes and must be regularly removed.

(2) Condensate with alkali: Condensate with alkali not only pollutes water quality and limits the application of condensers, but also wastes a large amount of caustic soda.

There are two main reasons for alkali in condensate water. Firstly, the liquid level is too high, and the alkali foam enters the secondary heating chamber with the secondary steam. This type of alkali containing secondary steam will cause alkali in the condensate water after condensation; Another reason is that the steel ribs in the heating room are cracked, causing condensation water to carry alkali.

Condensate water must be regularly checked for alkalinity with phenolphthalein reagent, and the cause should be carefully searched after alkalinity is found. For the first reason, attention should be paid to controlling the liquid level during operation, and liquid traps should be installed at the top of the evaporation chamber and in the secondary steam pipe as much as possible; For the second reason, the cracked steel pipe should be sealed or replaced.

(3) Low evaporation efficiency: There are many reasons for low evaporation efficiency, mainly due to the thick deposit in the heating chamber, which reduces the heat transfer coefficient, or due to evaporator leakage, reduced vacuum degree, abnormal fresh steam supply, or high condensation water temperature in the condenser. In short, it is necessary to conduct a physical analysis of its condition and take appropriate measures to improve the phenomenon of low evaporation efficiency.

7. Causes and handling methods of noise inside the evaporator

The cause of noise inside the evaporator is: there is air in the heating chamber; Poor drainage of condensate water; Partial heating pipe blockage; Heating pipe leakage; Evaporator components come off.

Treatment method: Open the condensate vent valve; Check the pipeline and unblock it; Cleaning; Parking treatment.