The conventional cooling medium of large-scale industry is soft water and sealing gasket. The water quality adopts centralized filtration and certain chemical additives. The medium has a certain scale removal function in the circulation process. A large number of leakage of centralized circulation plate heat exchanger will cause many system interlocking problems, especially the leaked oil medium will adhere to the inner wall of system pipeline and related equipment, Due to the formation of colloidal substances after deterioration, the valve body and pump body are blocked, the remedial measures are cumbersome and the repair cost is high. It has good practical significance for the control and prevention of such accidents.

Heat transfer plate is the core component of heat exchanger, and its forming process and material characteristics have a direct impact on the sealing and heat transfer efficiency. The heat exchanger usually uses water as the cooling medium, and the plates are mostly made of stainless steel sheet. Corrugated flow tips are pressed on the plates. The space between two adjacent plates is the medium channel. When the cold and hot fluids flow on both sides of the plate, the heat exchange is carried out through the plates.

The special channel formed by the corrugation makes the fluid turbulent at very low flow rate (Reynolds coefficient R). The turbulent flow with low Reynolds coefficient has its own scale removal effect, which can destroy the thermal insulation boundary layer and reduce the thermal resistance of the liquid film on the interface. In general, the heat transfer coefficient K value of plate heat exchanger is in the range of 3 000-6 000 w / M '' ℃. At the same time, the two kinds of media flow almost in reverse flow, and the heat transfer efficiency is high. Under the same heat transfer efficiency, the plate heat exchanger only needs 1 / 2-1 / 4 of the shell and tube heat exchanger area to achieve the same heat transfer effect.

After the plate heat exchanger is used for a period of 1-2 years (according to the actual working conditions), it is necessary to carry out the necessary disassembly inspection, cleaning, pressure test, etc. The plates with problems such as deformation or perforation need to be replaced in time. In this process, the assembly of the cooling plates is arranged in strict accordance with the flow chart. The flow chart is designed according to the cooling process. The plates are connected in parallel or in series. The common methods are single flow and double flow (or multi flow combination) heat exchangers. The medium connection and outlet of the single flow heat exchanger are usually fixed on one side of the platen, and the hot medium and cold medium are respectively arranged on one side of the vertical axis of the fixed platen, The same medium is on the left side or on the right side at the same time.

The short circuit or leakage of two media caused by staggered plate arrangement. The fluid flowing in from the right always flows out from the right when the single flow plate is observed from one side of the gasket; The fluid flowing in from the left always flows out from the left. For the herringbone corrugated plate, if the fluid flows in from the left side and the herringbone pattern points upward to the A-type plate, rotate the A-type plate 180 degrees along the axis perpendicular to the plate surface to form the B-type plate, and the fluid flows in and out from the right side.

After the plate heat exchanger is disassembled and inspected, the plates need to be clamped again according to the requirements. If the plates need to be added in order to further improve the heat exchange capacity, the deformation strength of the fixed platen and the movable platen should be fully considered, and the experimental pressure of the same level should be used. The number of plates increases, and the bolt preload also needs to be increased. When the elastic deformation of the platens on both sides exceeds the allowable range, the deformation of the platens on both sides should be increased, The plane compression of the seal has radial sliding, forming dislocation. At this time, the seal fails, and the two media leak out or flow through each other, so it cannot be used normally.

For the heat exchanger which has not been put into use for a long time, it is usually necessary to relax the tension of the screw properly. The plate and gasket lose the necessary elasticity after long-term compression, and the seal is easy to fail, reducing the service life. The pressure bolts of the heat exchanger are uniformly stressed. Before installation, the plate should be clamped diagonally, and the inner distance of the two pressure plates should be measured in real time to ensure that the two pressure plates are basically parallel, and the parallelism deviation of the four corners is less than 2%. The bolts should be pre tightened according to the sequence indicated in the figure.

In order to give full play to the heat exchange efficiency, two kinds of medium circulation of plate heat exchanger adopt full countercurrent flow. In practical use, considering the problem of off-line spare parts matching of each hydraulic system, the exchanger with larger heat exchange area will be used as common parts reserve, the direction of medium interface will be different, the cold and hot medium exchange interface or the same medium in and out will be used interchangeably, Although this kind of problem will not be harmful to the seal, it will have a certain impact on the heat exchange efficiency, as shown in the figure: the temperature difference between the two kinds of media is small, the heat loss is small, and the heat exchange efficiency is high; The heat transfer efficiency is low when the temperature difference is too large.

(1) The plate heat exchanger has strict requirements on the horizontal tension of the connecting screw, especially in the hoisting of high-power heat exchanger with large weight, the special hoisting position is used, the unconventional hoisting method has certain damage to the stressed structure of the screw, and the plate of the heat exchanger is prone to dislocation. In addition, when the large plate heat exchanger is filled with cold and hot media, the weight of the media will rise greatly, and the installation of the equipment will be placed on a certain horizontal plane.

(2) At the same time, there is a heat exchange process between the exposed heat sink and the ambient air. The necessary space (more than LM) is usually reserved around the heat exchanger to form a smooth air flow environment, which is conducive to the exertion of heat exchange capacity.