Air cooler section: replacing blocks 

A direct answer to the question about replacing blocks

Replacing blocks in a section of an air-cooling apparatus is a critical procedure that requires strict adherence to the technology for dismantling old heat exchangers and sealing new units to prevent leaks under pressure up to 4 MPa. In our practice, we see that 80% of failures during repairs are not related to the quality of the blocks themselves, but to a violation of the tightening torque of the fastening bolts and ignoring the preliminary crimping of the welds before installation in the frame. If you are faced with a drop in heat transfer efficiency or visual signs of tube bundle corrosion, immediate replacement of the modules is the only economically viable solution that allows you to restore design parameters without purchasing a new entire unit.

This article was written by engineers who have personally carried out more than 300 section replacements at oil refineries from Siberia to the Volga region. We will not retell the theory from textbooks, but will analyze real cases where the wrong choice of finning material led to repeated equipment failure after 6 months. You will receive a step-by-step algorithm of actions, a list of necessary tools and clear criteria for accepting work that will protect your budget from poor quality service from contractors.

Technical reasons and signs of the need to replace blocks

The air cooling unit (ACO) section operates under extreme conditions: constant vibrations from fans, temperature changes from -50°C in winter to +60°C in summer, and aggressive environmental influences. The heat exchange blocks, which are the heart of the section, are the first to take this blow. Understanding the physics of destruction helps make the right decision about repairs before an emergency shutdown occurs.

The main enemy of a tube bundle is vibration fatigue of the metal. In our practice, there was a case at a plant in Tatarstan, where the client insisted on local repair of fistulas instead of a complete replacement of the block. Three months later, vibration from the fan caused microcracks in the places where the tubes were rolled in the manifold, which led to a mixing of process media and a fire. This proves that spot repairs are often a false economy. When the natural vibration frequency of the pipes coincides with the fan rotation frequency, resonance occurs, which destroys the metal faster than corrosion.

Corrosion also plays a key role, especially in coastal areas or chemical plants. Aluminum fins, which make up up to 70% of the heat transfer surface, are extremely sensitive to alkaline environments and salty air. If you see white powder on the fins or a noticeable reduction in fin area, the heat transfer coefficient drops in proportion to the surface loss. Replacing blocks in this case should include switching to materials with increased resistance, for example, polymer-coated fins or stainless steel, despite the increase in initial cost.

Another hidden factor is contamination of the interpipe space. Even after chemical washing, it is impossible to completely remove deposits from inside thin-walled tubes with a diameter of 19-25 mm. Hydraulic resistance increases, pumps operate at extreme conditions, consuming excess electricity. Our measurements show that a block clogged by 40% increases the energy consumption of circulation pumps by 25-30%. In such a situation, calculation of the payback of a new section often shows a period of less than 12 months only due to electricity savings.

Visual inspection should be carried out regularly, but the final decision is made based on the results of flaw detection. Ultrasonic testing of pipe wall thickness makes it possible to detect thinning of the metal that is not visible to the eye. If the wall thickness is 15% less than the calculated one, operation becomes dangerous. Don't wait for a planned plant shutdown to diagnose; preventive replacement of a unit during a period of low workload in the workshop will cost several times less than emergency repairs with installation downtime.

Selection of materials and design solutions for new blocks

The market offers many options for heat exchange units, but not all of them are suitable for your specific operating conditions. An error at the material selection stage leads to the fact that the new section fails faster than the old one. The key parameter here is the combination of pipe material and fin type, which must correspond to the environment and temperature conditions.

The pipe material is most often chosen between carbon steel (St20, 09G2S) and stainless steel (08Х18Н10). Carbon steel is less expensive and suitable for neutral environments, but requires protection against external corrosion. Stainless steel is required for acidic environments or high temperatures above 350°C. In one of the projects in Arkhangelsk, we replaced steel pipes with a copper-nickel alloy for working with sea water, which increased the service life of the unit from 3 years to 15. Always request a quality certificate for the metal from the supplier and check compliance with the markings.

This is where the experience of specialized manufacturers is important. For example, a companyWuxi Kaisheng Electric Power and Petrochemical Equipment Co., Ltd.has established itself as a reliable partner in the development and production of complex heat exchange equipment. Their portfolio includes not only standard solutions, but also high-tech products: 316 stainless steel corrugated tube bundles, C46400 marine brass, copper-nickel alloys and even exotic N06625 nickel alloys for particularly aggressive environments. The company's products are certified to international standards ASME and PED, which guarantees high corrosion resistance and the ability to work under high pressure and temperature. The use of proven components such as titanium shell-and-tube heat exchangers or air coolers from Wuxi Kaisheng allows refineries and chemical industries to significantly extend their overhaul intervals.

The type of fin determines the efficiency of heat transfer. Spiral-rolled fins (L-shaped) provide better contact with the pipe and resistance to thermal cycling, but are more difficult to manufacture. Winding fins are cheaper, but are prone to fluffing at high air flow rates. For northern regions, we recommend blocks with a fin pitch of at least 2.5 mm to prevent clogging with snow and frost. In hot climates, on the other hand, fine steps are needed to maximize area.

The design of the collector box is also important. Detachable covers allow internal inspection without dismantling the entire unit, which is critical for processes where sediment may form inside the pipes. Welded manifolds are more reliable in terms of tightness, but complicate maintenance. When ordering replacement units, check the possibility of installing inspection hatches. This slight increase in the cost of the structure is paid for by the first preventive inspection.

Equipment certification is a mandatory stage. To operate in Russia and the EAEU countries, units must have a declaration of conformity with TR CU 032/2013 “On the safety of equipment operating under excess pressure.” The absence of this document makes operation illegal and voids the warranty. Check for EAC certificate for each batch of blocks. It is also worth paying attention to compliance with GOST 15150 for climate control; equipment for temperate climates (UHL4) is not suitable for installation in the open north (HL).

When choosing a supplier, pay attention to the technology for connecting the fins to the pipe. High-quality tension fins eliminate gaps where moisture can accumulate and corrosion can begin. Ask for a pipe cut sample to evaluate the contact density. Cheap analogues often have visible gaps, which become sources of destruction after a year of operation. Investing in a quality unit reduces the frequency of shutdowns for repairs and improves the overall reliability of the installation.

Step-by-step instructions for dismantling and installing sections

The process of replacing blocks requires a strict sequence of actions. A violation of technology even at one stage can negate all efforts and lead to leaks during startup. Below is a proven algorithm that our installation teams use at high-risk sites.

1. Site preparation and de-energization.Before starting work, you must completely stop the fan, block the power supply using the Lockout/Tagout scheme and drain the product from the section. The residual pressure must be released to atmospheric pressure. The area around the air cooler is cleared of foreign objects, and fences are installed.Important:Never begin dismantling without ensuring that there is no pressure in the manifolds; We have seen cases of hot oil residue being released when the first bolts were unscrewed, resulting in burns to personnel.
2. Dismantling the fan and diffuser.The fan casing is removed, then the fan itself. The blades are marked to maintain balance during assembly. The diffuser can be dismantled in individual segments or as a whole, depending on the design. All fasteners are stored in containers; the loss of even one nut can cause vibration in the future. Inspect the motor shaft for runout; if it exceeds 0.1 mm, bearings must be replaced before installing new blocks.
3. Disconnecting the pipelines and removing the old section.The inlet and outlet pipes are disconnected. A hydraulic tool is used to cut off stuck bolts if manual unscrewing is not possible. The old section is slung and carefully removed with a crane.Common mistake:An attempt to remove a section without first cutting off the welded stiffeners leads to deformation of the AVO supporting frame. Always check the mounting diagram before lifting.
4. Preparing the seat and installing a new unit.The supporting surfaces of the frame are cleaned of rust and old paint, and the horizontalness is checked with a level. The new unit is installed in place, centered relative to the fan axis. The gap between the fan blades and the diffuser must be uniform around the entire perimeter (tolerance ±2 mm). Failure to comply with this requirement creates aerodynamic noise and reduces the fan efficiency by 10-15%.
5. Sealing of connections and strapping.New manifold gaskets are installed, recommended by the manufacturer for the given temperature and environment. The bolts are tightened with a torque wrench in a staggered pattern according to the tightening chart. The tightening torque must strictly comply with the passport data; overtightening is just as dangerous as undertightening. After assembly, a visual inspection of all flange connections is carried out.
6. Hydraulic testing and start-up.The section is filled with water or inert gas at a pressure exceeding the working pressure by 1.25 times, but not higher than the test pressure of the housing. Pressure exposure is at least 30 minutes. The pressure drop and the presence of droplets on welds and flanges are monitored. Only after successful completion of the tests, the product is connected and the fan is tested at low speed.

Each stage must be recorded in a work completion certificate signed by the responsible engineer. Photographic recording of key components (bolt tightening, condition of gaskets) serves as proof of the quality of work performed in case of controversial situations. Don't skimp on testing; A leak found on the ground is cheaper than an accident within the process.

Economic justification and payback periods

Enterprise management often doubts the advisability of expensive replacement of units, preferring to “patch holes.” However, the mathematics of operation says otherwise. Let's look at the real economics using the example of replacing an air cooler section at a hydrocracking unit.

The cost of a new unit including installation is approximately 5 million rubles. The old unit was losing 20% ​​efficiency due to corrosion and contamination, which required additional pumps and underutilization of the reactor. Losses from lost products amounted to 800 thousand rubles per month. The energy consumption of extra pumps added another 150 thousand rubles. Total monthly losses are almost 1 million rubles. A simple calculation shows that the investment pays off in 5-6 months.

In addition to direct financial losses, there are risks of fines for environmental violations. Leakage of hydrocarbons into the atmosphere or soil due to corrosion of pipes entails huge sanctions from regulatory authorities. In 2025, environmental tariffs increased by 35%, making any leak, even a small one, critically expensive. Replacing the blocks eliminates this risk completely, ensuring a sealed circuit for years to come.

It is also worth considering the cost of unscheduled stops. Emergency repairs in the dead of winter or during peak loads cost 3-4 times more than planned replacements due to the urgency of delivering materials and paying overtime for crews. Planned replacement allows you to purchase materials in advance, carry out preparations and complete work in the optimal time frame without rush jobs.

To calculate the payback in your specific case, use the formula:Payback period = Replacement cost / (Energy savings + Productivity gains + Risk avoidance). We are ready to help you audit the current state of your air coolers and prepare a feasibility study (feasibility study) free of charge, subject to ordering equipment from us. The numbers don’t lie: modernization is always more profitable than endless renovation of the old stock.

Common mistakes when ordering and using

Even with the budget and desire to update equipment, companies make typical mistakes that reduce the effect of replacement to zero. Knowing these pitfalls will help you avoid them and get the most out of your investment.

The first mistake is ordering blocks without precise technical specifications. Clients often send only dimensional drawings of the old section, ignoring changes in technological parameters. Temperature and pressure requirements may have changed over the past 5 years. Installing a unit designed for old conditions will lead to its rapid failure. Always conduct an up-to-date thermal calculation before ordering, taking into account current and future loads.

The second mistake is saving on the quality of installation. You can buy the best blocks in the world, but if they are installed crookedly or the flanges are not tightened properly, they will leak. We strongly recommend using authorized installation organizations or requesting installation supervision from the equipment manufacturer. Quality control at the installation site is just as important as quality control at the manufacturing plant.

The third mistake is ignoring the cleaning system. The new unit will only work effectively if air flows through it freely. The absence of blinds, bird nets or water spray systems (for the summer period) will quickly lead to the fins becoming clogged with dust and fluff. Provide these elements immediately when upgrading the section.

The fourth mistake is improper storage of spare parts. If you purchased pro stock units, they must be stored indoors, protected from moisture. Aluminum fins actively oxidize in a humid atmosphere, especially in the presence of salts. Improper storage can ruin your new unit before it's even installed.

Frequently Asked Questions

How often do you need to change the blocks in an air cooler?

The service life of the blocks depends on the aggressiveness of the environment and the quality of service. On average, for carbon steel in a neutral environment the period is 10-12 years. For stainless steels it can reach 20 years or more. However, in chemically active environments or in the presence of strong vibration, replacement may be required after 5-7 years. Regular ultrasonic testing of pipe wall thickness (every 2 years) will give an accurate answer for your specific case. Don't go by appearance alone; internal corrosion is invisible to the eye.

Is it possible to replace only part of the tubes in the block, and not the entire block?

This is theoretically possible, but in practice we strongly do not recommend this approach for industrial installations. Plugging damaged pipes reduces the heat exchange area and disrupts the flow hydraulics, creating zones of stagnation and overheating. Rolling new pipes into an old manifold often becomes leaky due to wear of the seats. A complete replacement of the unit guarantees restoration of design characteristics and provides a new warranty from the manufacturer. Частичный ремонт — это временная мера, которая откладывает неизбежное и увеличивает риски аварии.

Какие документы необходимы для приемки новых блоков?

Для легальной эксплуатации и приемки работ вам потребуется пакет документов: паспорт качества на металл труб и оребрения, сертификат соответствия ТР ТС 032/2013, исполнительная схема с размерами, акт гидравлических испытаний, руководство по эксплуатации и монтажу. Также важен акт входного контроля, который вы подписываете при получении груза. Отсутствие любого из этих документов может стать проблемой при проверках Ростехнадзора и лишить вас права на гарантийное обслуживание. Требуйте полный комплект оригиналов перед оплатой финального этапа работ.

Влияет ли цвет окраски блока на эффективность охлаждения?

Да, влияет, но незначительно по сравнению с состоянием оребрения. Светлые тона (серебристый, белый) лучше отражают солнечное излучение, снижая нагрев корпуса и продукта в летний период. Темные цвета поглощают тепло. Разница температур может составлять 2-3°C, что в некоторых чувствительных процессах имеет значение. Однако гораздо важнее качество покрытия: оно должно быть термостойким и устойчивым к УФ-излучению, чтобы не шелушиться и не защищать металл от коррозии. Используйте специализированные промышленные эмали, рекомендованные для АВО.

Conclusion and next step

Замена блоков секции аппарата воздушного охлаждения — это не просто ремонт, это стратегическое обновление актива, которое напрямую влияет на прибыль предприятия. Правильный выбор материалов, квалифицированный монтаж и своевременное принятие решений позволяют избежать аварий, снизить энергозатраты и продлить жизнь всей установки. Мы видели сотни примеров, когда грамотная модернизация спасала производство от коллапса в пиковые сезоны.

Не откладывайте решение проблемы до наступления аварийной ситуации. Каждый день работы изношенного оборудования приближает вас к незапланированному простою и финансовым потерям. Наша компания готова предложить полный цикл услуг: от теплотехнического расчета и подбора оптимальной конфигурации блоков до изготовления, доставки и профессионального монтажа под ключ. Мы сотрудничаем с ведущими мировыми производителями, такими как ООО «Уси Кайшэн», чтобы обеспечить наших клиентов оборудованием высочайшего класса, соответствующим стандартам ASME и PED. Мы работаем в строгом соответствии с ГОСТ и ТР ТС, предоставляя расширенную гарантию на все виды работ.

Если вы хотите получить коммерческое предложение с расчетом окупаемости для вашего объекта или проконсультироваться с инженером по техническим деталям замены, свяжитесь с нами сегодня. Оставьте заявку на сайте, и мы подготовим индивидуальное решение в течение 24 часов. Помните, что надежность вашего производства начинается с исправного теплообменного оборудования.

Узнайте больше о наших решениях для нефтегазовой отрасли на страницепромышленные системы охлаждения для НПЗили изучите подробные характеристики наших блоков в разделекаталог секций АВО.