Repair and maintenance of the hottest plate heat e

2022-08-13
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Repair and maintenance of plate heat exchanger

plate heat exchanger has been widely used in beer production because of its light weight, small footprint, low investment, high heat exchange efficiency, flexible assembly, easy scaling and cleaning. However, due to the small flow cross-sectional area of the plate heat exchanger, if it is not maintained in time, it may be blocked due to scaling, affecting the safety and normal use of the equipment. Proper installation and maintenance is an important link to ensure the safety and efficiency of the heating system

1. Overhaul and disassembly of plate heat exchanger

due to the large number of plates of plate heat exchanger, and it is necessary to clean them one by one and replace all with new pads, the overall lifting away from the installation position is generally adopted during overhaul, and the overhaul is disassembled at a suitable place. Before disassembly, close the medium inlet valve, and close the high-pressure side valve first, and then close the outlet valve, so that the heat exchanger can be discharged after slowly cooling to 40 ℃, and then remove the connected pipes and lift them off as a whole

1.1 preparation before disassembly

the maintenance cycle of plate heat exchanger is generally 2 years. Before maintenance, the gaskets to be replaced shall be carefully checked, and the surface shall be smooth, the thickness shall be consistent, and there shall be no transverse cracks, bubbles, notches, aging, overlapping and docking marks. The adhesive used should also be within the validity period. For the heat exchanger body, remove the compression bolt protective sleeve, and remove rust and apply oil to all bolts; Check the sliding surface of the upper beam and wipe it clean; Check the upper roller of the movable pressing plate to make it rotate flexibly; Measure and record the stack length "a", and ensure that this size remains unchanged during reassembly

1.2 overall disassembly of heat exchanger

enter the site for construction after the parameters of system gas, pressure, temperature and so on meet the maintenance requirements. First remove the connecting pipe, and then loosen the fixing bolts in the diagonal direction. During the disassembly process, the width offset of the movable pressing plate shall not exceed 10mm, and the vertical offset shall not exceed 25mm. The movable pressing plate shall always move in a parallel state. When removing the plates, tilt the plates to one side by 15 ° ~ 20 °, and lift them up slightly to remove them. Do not remove them forcibly, so as to prevent the upper positioning groove from deformation or damage, and then code them in sequence according to the installation sequence of plates and blocks

1.3 remove the old rubber gasket and clean the plate

remove the old gasket first. One hand holds the electric hot air to heat along the bottom of the sealing groove. When the adhesive is heated and softened, the other hand pulls up the cushion and slowly peels it off. Gas spray gun can also be used for heating, but the distance from the flame to the bottom of the plate should be strictly controlled to be 10 ~ 15cm, especially for aluminum alloy plates. It is forbidden to use acetylene flame for heating under any circumstances

after the gasket is removed, the residual glue in the sealing groove can be installed on the tangential grinder with a stainless steel wire wheel with a diameter of 40 ~ 50mm and a width of 8 ~ 10mm to grind the residual glue away to ensure the smoothness of the sealing groove. The plates are generally cleaned manually and chemically, and must not be removed with sharp tools to prevent scratching the plates. When the scale on the plate is very thin and the scale layer is easily soluble in water, the plate can be placed in a special water tank and washed with a soft fiber brown brush, or washed with 1 ~ 29cg/cmz pressure water or low-pressure steam. For stainless steel plates, steel wire brushes are not allowed. The cleaning water must be free of salt, sulfur and other components, and the Cl content of the water must be less than 200ppm

1.4 inspection and repair of plate defects

when checking the heat exchanger plate, the plate should be free of cracks, scratches, deformation and other defects, the uneven deviation of plate thickness should not exceed 5%, the periphery of the plate should be smooth and flat, the shape of the sealing groove should meet the requirements of the drawing, the allowable deviation of its depth should be 0.1mm, the sealing surface should not have concave convex, wrinkle, twist, scratch and other defects that affect the sealing performance, and the allowable deviation of the corrugated depth of the plate should be 0.2mm, Its unevenness shall not be greater than 1%. For perforated plates, but some customers need general inspection, hydrogen arc welding can be used to repair and grind them flat. For plates with serious deformation, aluminum or copper models can be used for correction. If these defects cannot be handled, only the plates can be updated or reduced

1.5 requirements for plate assembly

before plate assembly, push the movable pressing plate to one end, clean the inner side and nozzle of the fixed pressing plate and movable pressing plate, and first add the nozzle rubber sleeve and rubber sleeve support ring. When installing the plates, according to the process combination, put the side without rubber pad of the first piece against the fixed pressing plate, and then hang all the plates in the order of a-b-a-b. After all the plates are hung, push the movable pressing plate together, install the 6 long bolts and tighten the bolts. During this process, keep the movable pressing plate moving in parallel. When the bolts are tightened, the deviation of the plate stack length "a" measured at the adjacent bolts shall not exceed the following standards:

when a1000mm, it shall not exceed 2mm, and the deviation of the plate stack length between bolts shall not be greater than 0.5% Ao

11. Test piece area: generally calculated as 1250mm2 6 hydrostatic test

it is qualified if there is no abnormal sound, abnormal deformation, leakage and pressure drop after slowly boosting to the design test pressure for 30min. If it is a stainless steel plate, CL in water is required for pressure test-

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