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The maintenance guideline of plate type heat exchanger of aluminum extrusion press

The maintenance guideline of plate type heat exchanger of aluminum extrusion press
 
Plate heat exchanger is composed of a series of corrugated stainless steel sheets. There are four corner holes for heat transfer of the two fluids: hydraulic oil and water. The stainless steel sheets are mounted in a frame which has a fixed plate and a movable plate on the side and clamped tightly by bolts. The sheets are provided with gaskets for sealing the fluid passages and guided the fluid alternately into the respective channels to form a heat exchange. Fluid flow, physical properties, pressure dropping and temperature difference are depended on the sheets quantity and size of sheets. The corrugated sheets not only enhances the degree of turbulence, but also forms a plurality of supporting points sufficient to withstand the pressure difference between the media.
 
The cleaning process of plate type heat exchanger
1) Acid pickling: to enhance the pickling temperature is good for improving the cleaning effect, if the temperature is too high, it will exacerbate the pickling solution on the heat exchanger plate corrosion, through many repeated tests, we found that appropriate  pickling temperature is 60 ℃. 
2) Pickling solution concentration: formic acid 81.0%, water 17.0% a, buffer agent 1.2%, surface active agent 0.8% concentration of preparation, cleaning effect will be more excellent.
3) Pickling method and time: pickling method should be combined by static immersion and dynamic cycle methods. First process of Pickling solution is 2 hours of static soaking, and then dynamic cycle 3-4 hours. In the pickling process should frequently take sample of test concentration, when two testing concentration difference is less than 0.2%, it can be considered that the end of the pickling reaction.
4) Passivation: After pickling, most of the dirt and oxide on the surface of plate type heat exchanger will be dissolved and felled off, the new metal will be exposed and will be easily corrosion, so after pickling, passivation treatment is necessary.
 
Specific steps for cleaning plate type heat exchanger
1) Washing: Before pickling, first at all, open the heat exchanger to wash, so there is no any mud or dirt or other impurities in the heat exchanger inside of heat exchanger, it can not only improve the effect of pickling, but also can reduce the amount of acid pickling consumption.
2) Fill the cleanout fluid to cleaning device, and then fill into the heat exchanger.
3) Acid pickling: the heat exchanger is immersed by acid solution in two hours and then  continuously dynamic calculate for 3-4 hours, during this process, take turn to clean by positive and negative at every 0.5 hour. After pickling finished, if the acid pH is greater than 2, the acid solution can be reused, otherwise, should be drained after the liquid diluted and neutralized.
4) Alkaline washing: after pickling finished, use NaOH, Na3PO4, the softened water will be prepared for according to a certain proportion, adopt dynamic cycle type to alkaline wash the heat exchanger to achieve the acid-base neutralization. So the heat exchanger sheet will not be etched.
5) Water washing: after alkaline washing completed, adopt clean soften water to swash the heat exchanger by 0.5 hour to clean out thoroughly.
6) Record: During washing, record every step time for better check the washing effect.
7) After washing completed, use the pressure device to test the heat exchanger pressure, us it after qualified.
 
The solution to avoid the dirt scaling of heat exchanger 
1) Strictly control the water quality when the machine is running, test the water quality strictly, connect to the heat exchanger after water quality is qualified.
2) New heat exchanger using, check the pipeline and clean it to avoid the dirt or impurities entering the heat exchanger.
3) Clean the dirt separator and oil filter regularly, keep the pipeline clean to avoid the heat exchanger blocking.
4) In a word, maintaining the heat exchanger regularly and when the heat exchanger, should be acid-base neutralization to avoid etching. 

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