Thread Content
The areas where problems are most likely to occur during the use of shell and tube heat exchangers are the tube bundles and sealing areas. Factors such as the strength of the tube bundle, wall thickness, whether there is scaling, material, corrosion, whether the sealing points are firm, etc. are all prerequisites for the normal use of the shell and tube heat exchanger. When there is a problem with the shell and tube heat exchanger and it is not possible to determine where the problem lies, how should it be repaired? During our production process, heat exchangers must be inspected regularly and problems solved in a timely manner to ensure normal production. When inspecting shell and tube heat exchangers, the following points should be noted:: 1. Scaling on the tube wall generally occurs on both the inner and outer surfaces of the tube wall to varying degrees. Due to the different environments used (high dust in the workshop, suspended solids in water, etc.) and different media, there will be varying degrees of scaling. The presence of scaling will affect the heat exchange efficiency of the shell-and-tube heat exchanger to a certain extent, and in serious cases will cause the entire heat exchanger to be scrapped. Common types of dirt: 1) Granular dirt: The accumulation of solid particles suspended in a fluid on heat exchange surfaces. This kind of dirt also includes the sedimentation layer formed by larger solid particles on the horizontal heat exchange surface due to the action of gravity, which is the so-called deposition of sedimentation dirt and other colloidal particles. 2) Crystallized dirt: Deposits formed when inorganic salts dissolved in the fluid crystallize on the heat exchange surface, usually during supersaturation or cooling. Typical scales include calcium carbonate, calcium sulfate and silica scale layers on the cooling water side. 3) Chemical reaction dirt: Dirt produced by chemical reactions on the heat transfer surface. The heat transfer surface material does not participate in the reaction, but can serve as a catalyst for the chemical reaction. 4) Biofouling: Except for seawater cooling devices, biofouling generally refers to microbial fouling. It may produce slime, which in turn provides conditions for the propagation of biofouling. This fouling is very sensitive to temperature. Under suitable temperature conditions, biofouling can generate a considerable thickness of fouling layer. 5) Solidify dirt: Dirt formed by solidification of fluid on supercooled heat exchange surfaces. For example, when water is below freezing and freezes to form ice on a heat exchange surface. The uniformity of temperature distribution has a great influence on this kind of dirt. It is generally recommended to use chemical or mechanical cleaning technology and chemical or mechanical cleaning technology to remove scale. 2. Leakage in shell-and-tube heat exchangers We know that shell-and-tube heat exchangers are generally made of many tube bundles interspersed in the end plates. Generally, leaks mostly occur at the sealing points of the heat exchanger or on the tube bundles. Corrosion of tube bundles generally occurs on metal heat exchangers. If a fluoroplastic heat exchanger is used, corrosion of the tube bundle can be avoided to the greatest extent. During the inspection, we have to find the leakage point in order to prescribe the right remedy and repair it. Commonly used methods for inspecting heat exchangers are:: First look at the pressure gauge. If the design pressure is 0.5MPa, but the pressure read on the gauge is much less than this value, then it can be determined that there is a leak in the heat exchanger. Leak test: Leak testing is generally performed by pressurizing a section of the shell-and-tube heat exchanger into the water, and passing compressed air into the tube bundle from the other end. Observe whether there are bubbles in the water, the location of the bubbles, the size of the bubbles, and which tube has bubbles. Mark which tube, and repair and replace it after the inspection. 1) Repair of small amount of pipe leakage: If only a few tubes are leaking (the number of leaking tube bundles generally does not exceed 1/10 of the total), and if it does not affect use, the tube bundles can be blocked with plugs to prevent leakage from affecting the heat exchange effect. 2) Extensive pipe leak repairs: A large number of leaks in the tube bundle will greatly reduce the heat exchange effect and require replacement of new tube bundles. Generally, regular manufacturers will have a relatively sound after-sales mechanism and will send professional technicians to your home for repairs. 3. Pipe vibration: It is very common for shell and tube heat exchangers to vibrate during use. Slight vibration does not affect the use of the heat exchanger. When the vibration is severe, the end plate interface will become loose, causing leakage of the tube bundle. During repair, in order to reduce the looseness at the interface between the tube bundle and the end plate, low current arc welding can be used. One advantage of low current arc welding is that the welding stress is small. If the gap between the tube bundles is too large, some baffles can be added to reduce the gap between the tube bundles to reduce the vibration of the tube bundles. share: