What is tubular sheet and how the tubular sheet work?

A tubular sheet is an essential component used in heat exchangers, boilers, coolers, and other equipment, typically made from materials like carbon steel or stainless steel. Its primary function is to secure the pipes in place and ensure a seal between the pipe system and the shell. A tubular sheet is usually a thick metal plate with many holes, and the size and distribution of these holes are matched to the diameter and number of the pipes. The pipes pass through these holes, and the tubular sheet fixes and seals the ends of the pipes, ensuring that the fluid inside the pipes does not leak or mix with the external fluid.

The tubular sheet operates mainly by physically securing and sealing the pipes and the shell. In a heat exchanger, heat is transferred between the fluid inside and outside the pipes through the pipe walls, while the tubular sheet ensures that the fluids can circulate effectively inside the pipes and prevent leakage. The tubular sheet is typically manufactured through machining and welding techniques to create the holes, and the pipes are secured to the plate through welding or other methods. In high-pressure or high-temperature applications, the design and material selection of the tubular sheet are particularly crucial to ensure the safety and stability of the system.

According to the different use environment, use different materials, generally use Q345R container plates, such as a secondary pressure vessel, no corrosive medium circulation, the use of carbon steel composite plate can be. In the case of strong acid, high pressure and high temperature, nuclear energy and other environments, stainless steel, 16 manganese, titanium alloy and other corrosion-resistant materials are needed, and the application of new synthetic materials brings new vitality to tubular sheet products.

Tubular sheets are widely used in tubular heat exchangers, boilers, pressure vessels, steam turbines, large central air conditioning and other industries. It is mainly used in chemical vessels, such as tubularheat exchangers, pressure vessels, boilers, condensers, central air conditioners, evaporators, and seawater desalination, which play the role of supporting and fixing the tubulars.

In the production of tubular heat exchanger, the welding of tubular sheet and tubular is generally manual arc welding, and there are different degrees of defects in the shape of the weld, such as depression, porosity, slag inclusion, etc., and the distribution of weld stress is uneven. When used, the tubularsheet part is generally in contact with the industrial cooling water, and the impurities, salts, gases, and microorganisms in the industrial cooling water will constitute corrosion of the tubularsheet and welds. This is what we often call galvanic corrosion. Studies have shown that industrial water, whether fresh water or seawater, will have various ions and dissolved oxygen, among which the concentration of chloride ions and oxygen changes, which play an important role in the corrosion shape of metals. In addition, the complexity of the metal structure also affects the corrosion pattern. Therefore, the corrosion of the welds between the tubular sheet and the row tubular is mainly pore corrosion and crevice corrosion. From the outside, there are many corrosion products and deposits on the surface of the tubular sheet, and there are pits of various sizes. When seawater is used as a medium, galvanic corrosion can also occur. Chemical corrosion is the corrosion of the medium, and the heat exchanger tubular sheet will be corroded by the chemical medium when it comes into contact with a variety of chemical media. In addition, there is a certain amount of bimetallic corrosion between the heat exchanger tubular sheet and the heat exchanger tubular. Some tubular sheets are also exposed to erosion by corrosive media for a long time. Especially for fixed tubularsheet heat exchangers, there is also temperature difference stress, and the connection between the tubularsheet and the heat exchanger tubular is very easy to leak, resulting in the failure of the heat exchanger. 

Medium composition and concentration: the influence of concentration is different, for example, in hydrochloric acid, the larger the concentration, the more serious the corrosion. Carbon steel and stainless steel are most corroded in sulfuric acid with a concentration of about 50%, and when the concentration increases to more than 60%, the corrosion decreases sharply;

Impurities: Harmful impurities include chloride ions, sulfur ions, cyanide ions, ammonia ions, etc., which can cause serious corrosion in some cases;

Temperature: Corrosion is a chemical reaction, and the corrosion rate increases by about 1~3 times for every 10°C increase in temperature, but there are exceptions;

pH value: generally the smaller the pH value, the greater the corrosion of the metal;

Flow velocity: In most cases, the higher the flow velocity, the greater the corrosion.

At present, polymer composite materials can be used to protect the tubular sheet for anti-corrosion, which has excellent adhesion performance and temperature resistance, chemical corrosion resistance, the material is 100% solid, no volatile substances, and can be safely used in a closed environment without shrinkage, especially the material has good isolation of bimetallic corrosion and excellent erosion resistance, excellent anti-corrosion performance, fundamentally eliminates the corrosion and leakage of the repair part, and can provide a long-term protective coating for the components.

1. Tools and equipment: sandblasting equipment, protective canvas or plastic sheet, cork, alcohol or acetone, scraper, spiral, garbage bag, hand drill, working power supply, rubber gloves, safety helmet, protective glasses, wiping cloth, brush.

2. 2. Steps

Step 1: Open the condenser end cap

Use a hair dryer and blower to dry the water on the surface and inside of the pipe, then plug the nozzle with a cork and cover the flange to ensure that the nozzle is not damaged during the sandblasting process.

Step 2: Sandblasting treatment: Cover it with canvas and other things during sandblasting to avoid staining other equipment with sand particles. Quartz sand or emery is used when sandblasting, which can produce a 4 mil surface without producing more dust, and it is necessary to play the base metal color all the time. Remove the cork after blasting.

Step 3: Solution cleaning: Use acetone to clean the impurities and oil on the metal surface.

Step 4: Coating material: first use polymer repair material metal repair material to fill the pit part on the inner wall of the condenser tubular sheet, so as to avoid the vortex of water during work, until the required plane shall prevail. Then the polymer fluid protection material is evenly applied to the entire repaired surface. Pay special attention to the joint between the panel and the pipe to achieve the purpose of sealing and plugging leaks.

Step 5: Curing: Curing according to the curing requirements of the material, and it can be put into production and operation after curing

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