The brazed heat exchanger is composed of a set of corrugated pipe plates between the front and rear baffles. The brazing heat exchanger is composed of a sealing plate, a sealing ring and a baffle. The interface types of brazed heat exchangers can be customized according to the specific requirements of the market and application fields. During vacuum brazing, a weld joint is formed at each contact point between the sheet and filler metal (brazing solder). By using this design method, heat exchangers made up of two different channels or circuits can be made. The sealing plate is used to seal the gap between the first and the last channel plates. The number of baffles depends on the type, size and pressure grade. Some are equipped with seals to seal gaps between passageways and baffles. Some sealing rings are integrated with the baffle plate and the first or the last channel plate.

The number of plates in a brazed heat exchanger can usually be as many as tens. The flow of brazed heat exchanger fluids between plates can be flexibly combined according to the specific use conditions. There are usually various combinations of single flow and multi-flow. For example, the media on both sides of the uniform single process, can also be one side of the media for a single process on the other side of the media for a double process, can also be two sides of the media for different multi-process combination. The standard combination of brazed heat exchangers is single flow on the cold and hot sides, and multi-flow heat exchangers can be customized according to customer requirements.

The brazed heat exchanger is one of the most effective ways to transmit heat between the media. The brazed heat exchanger consists of corrugated channel plates, which are combined to form complex brazed heat exchanger channels through which the distribution of cold and hot media is completed. Cold and hot media are separated on either side of the corrugated plate, as close as possible but not mixed; as they flow side by side, heat is transferred from one medium to another. Based on modular product concepts and fully customizable components, the company has always been able to find the most appropriate solution for each heat exchanger application.

(1) process requirements for brazed plate heat exchangers:

1) pickling temperature: raising pickling temperature is beneficial to improve the scale removal effect. If the temperature is too high, it will aggravate the corrosion of pickling solution to heat exchanger plate. Through repeated tests, it is found that the pickling temperature should be controlled at 60%.

2) Concentration of pickling solution: According to repeated tests, the pickling solution should be prepared according to the concentration of formic acid 81.0%, water 17.0%, buffer 1.2%, surfactant 0.8%, the cleaning effect is very good.

3) pickling method and time: acid pickling should be carried out in combination of static soaking and dynamic cycling. The pickling time was first soaked in static 2H and then circulate 3 ~ 4H dynamically. In the process of pickling, the pickling concentration should be sampled regularly. When the difference of concentration between two adjacent tests is less than 0.2%, the pickling reaction is considered to be over.

4) Passivation: After pickling, most of the scales and metal oxides on the surface of the plate heat exchanger are dissolved and peeled off, which exposes new metals and is easy to corrode. Therefore, the plate of the heat exchanger is passivated after pickling.

(two) maintenance steps of brazed plate heat exchangers:

1) Flushing: Before pickling, the heat exchanger is flushed openly so that there is no mud, dirt and other impurities in the heat exchanger, which can improve the effect of pickling and reduce the acid consumption of pickling.

2) pour the cleaning fluid into the cleaning equipment and then inject it into the heat exchanger.

3) pickling: the heat exchanger filled with acid solution is immersed in static state for 2 hours, and then the heat exchanger is continuously circulated for 3-4 hours, during which the reciprocal cleaning is carried out alternately every 0.5 hours. After pickling, if the pH value of the pickling solution is greater than 2, the pickling solution can be reused. Otherwise, the pickling solution should be diluted and neutralized and then discharged.

4) Alkali washing: After pickling, NaOH, Na3PO4 and softening water are prepared according to a certain proportion, and the heat exchanger is alkali washed by means of dynamic circulation to neutralize acid and alkali, so that the plate of heat exchanger is no longer corroded.

5) Washing: After alkali washing, rinse the heat exchanger with clean softened water for 0.5 hours repeatedly, and then rinse the residue in the heat exchanger thoroughly.

6) record: during the cleaning process, the time of each step should be strictly recorded to check the cleaning effect.

(three) preventive measures:

1) Strictly control the water quality in operation. Strict water quality tests must be carried out on the water in the system and the softened water in the softening tank before it can be injected into the pipe network.

2) When the new system is put into operation, the heat exchanger should be separated from the heating system, circulated for a period of time, and then the heat exchanger should be incorporated into the system to avoid impurities in the pipe network entering the heat exchanger.

3) In the heating system, besides the dirty and filters should be cleaned from time to time, the pipe network should be kept clean to prevent the heat exchanger from blocking.

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