What are the risks associated with the operation of carbon steel spiral plate heat exchangers with i
Information summary：The medium carrying solid impurities (such as sediment, metal oxide scale, welding slag, crystalline particles, fiber suspension, etc.) into the carbon steel spiral plate heat exchanger channel can bring a series of risks such as wear, blockage, corrosion, structural deformation, and heat transfer failure. According to GB/T 28712 "Spiral Plate Heat Exchanger" and relevant specifications for pressu
The medium carrying solid impurities (such as sediment, metal oxide scale, welding slag, crystalline particles, fiber suspension, etc.) into the carbon steel spiral plate heat exchanger channel can bring a series of risks such as wear, blockage, corrosion, structural deformation, and heat transfer failure. According to GB/T 28712 "Spiral Plate Heat Exchanger" and relevant specifications for pressure vessels, the following are explained:
1、 Risk of channel blockage
The spiral plate consists of two narrow and curved spiral channels with fixed gaps, making it easy for impurities to deposit and bridge.
1. Impurities gradually accumulate and reduce the flow cross-section, the medium flow rate decreases, the pressure loss continues to increase, and the system pressure difference exceeds the standard; In severe cases, local flow channels may be blocked, causing a deviation in the flow of cold and hot media, significantly reducing the effective heat transfer area and weakening the heat transfer capacity, which cannot meet the process temperature requirements.
2. Local blockage of the flow channel causes uneven distribution of the medium, resulting in dead zones. Stagnation of the medium can easily lead to local crystallization and further deposition of impurities, forming a vicious cycle.
3. The completely blocked section of the medium does not flow, and the low-temperature side freezes or the high-temperature side overheats locally, causing equipment overheating and thermal stress concentration.
2、 Erosion and abrasion damage (risk of carbon steel material protrusion)
Carbon steel has limited wear resistance, and solid particles are washed away by high-speed fluid on the plate wall, distance column, and weld area
1. The surface of the plate and the fixed distance column is continuously eroded and thinned, and the wall thickness gradually decreases, reducing the pressure bearing capacity; Long term erosion will result in localized pits.
2. The weld seam is located in a stress concentration area, and particle erosion can damage the passivation protection of the weld seam, leading to the formation of microcracks that gradually propagate and cause leakage.
3. The root of the fixed distance column is a high-risk point for erosion. In severe cases, the fixed distance column may wear and fall off, lose support, and the plate may bulge and deform under internal pressure.
3、 Corrosion risk under scale (a key risk unique to carbon steel)
Impurities deposit and adhere to the surface of the plate, forming a sediment cover layer and causing corrosion under the scale
1. The flow of the medium under the sediment stagnates, causing differences in oxygen concentration, pH value, and mainstream medium, forming a corrosive galvanic cell, and causing localized pitting corrosion of carbon steel.
When corrosive components such as chloride ions and sulfides are present in impurities, the environment under the scale will accelerate corrosion, forming corrosion holes and causing perforation of the plate and leakage of cold and hot media.
3. Sediments hinder the anti-corrosion coating/passivation effect on metal surfaces, and conventional water treatment agents cannot come into contact with the metal substrate, leading to continuous corrosion.
4、 Mechanical deformation of plates and risk of structural failure
1. Impurity blockage causes abnormal increase in pressure difference on both sides of the channel, exceeding the design pressure difference. The spiral plate bears additional lateral load, resulting in bulging and plastic deformation; Deformation further reduces the gap between channels and exacerbates blockage.
2. The fixed distance column is worn and washed off by impurities, causing the plate to lose support and the pressure bearing capacity to sharply decrease. In severe cases, the plate may tear.
5、 Risk of internal leakage and cross contamination of media
After perforation due to erosion and corrosion under scale, the cold and hot media leak into each other:
Process medium pollution and unqualified product quality;
Mixing of cold and hot media causes uncontrolled process parameters;
If one side of the medium is corrosive, it will invade the other side of the system, causing corrosion and damage to the backend pipelines and equipment.
6、 Difficulty in cleaning and risk of shutdown for maintenance
The narrow spiral channel of the spiral plate is not conducive to mechanical cleaning, and after impurities form and solidify, it is difficult to remove them solely by chemical cleaning; Multiple chemical cleaning can also cause additional corrosion to the carbon steel substrate. When the blockage is severe, the machine must be stopped and disassembled (detachable). Non detachable spiral plates often cannot be repaired and are directly scrapped, resulting in long-term production downtime and equipment replacement costs.
7、 Secondary risks associated with auxiliary pipelines and equipment
Impurities circulate with the medium and deposit and wear at the inlet and outlet, elbow, and valve positions of the heat exchanger; The large debris that falls off will enter the rear pump body, causing wear on the pump impeller and damage to auxiliary equipment such as pump jamming.
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