Connecting a shell-and-tube heat exchanger: step-by-step instructions 

Connecting a shell-and-tube heat exchanger: step-by-step instructions for reliable operation

The correct connection of a shell-and-tube heat exchanger determines not only the efficiency of your process, but also the safety of the entire plant. In our practice, we have repeatedly encountered situations where saving 20 minutes at the installation stage led to loss of tightness after three months of operation and a line shutdown for two days. This manual was written by engineers who personally assembled hundreds of pieces of equipment in workshops from Novosibirsk to St. Petersburg. We will not give abstract advice to “do it carefully.” Instead, you will receive a specific algorithm of actions based on real cases, GOST standards and errors for which our clients have already paid with money.

Before starting work, make sure that you have access to the manufacturer's technical documentation. Connecting a shell-and-tube heat exchanger is a process that requires strict adherence to the sequence of operations. Any deviation from specifications, such as improperly tightening flange bolts or ignoring flow directions, may void the warranty. In this guide, we will walk you through each step, from equipment acceptance to first pressurization. If you are looking for information on how to avoid cavitation or water hammer during startup, you have come to the right place.

Stage 1: Site preparation and completeness check

The work begins long before you pick up the key. The mistake of many installation teams is that they bring equipment to the installation site without checking the condition of the foundation and compliance of the dimensions with the design solutions. Shell-and-tube devices have significant weight, especially when filled. If the supporting structure is not designed to withstand the dynamic loads of water hammer, vibration will destroy pipeline welds within the first year of operation.

You need to prepare the following set of tools and materials before starting installation:

• A set of box and open-end wrenches (including a torque wrench to control the tightening force).
• Construction level of high accuracy (error no more than 0.5 mm/m).
• Gasket material suitable for the working environment (paronite, Teflon, graphite or EPDM/NBR rubber depending on temperature and chemical aggressiveness).
• Thread lubricant (graphite or copper) to prevent bolt sticking.
• Pressure gauges calibrated for hydraulic testing.
• Load-lifting mechanisms with a safety margin of at least 20% of the weight of the device.

When accepting the equipment, carefully inspect the transport plugs on the nozzles. If they are removed or damaged, construction debris, scale, or moisture may have entered the casing or tube bundle. In one of our projects in Chelyabinsk, the customer launched the device without internal inspection, which led to clogging of 15% of the tubes after just a week of operation. The result was a drop in heat transfer coefficient by 40% and the need for unscheduled disassembly. Always request a quality certificate and EAC certificate of conformity (EAC) before starting work. The absence of markings on the main components is a red flag indicating possible counterfeit.

Check the geometry of the installation dimensions. The distance between the centers of the supports must coincide with the foundation drawing with an accuracy of ±5 mm. Misalignment will lead to additional stresses in the body of the device due to thermal expansion. If you are installing a horizontal heat exchanger, use spacers under the supports for leveling. Vertical devices require checking plumbness in two perpendicular planes. Do not neglect this step: a misalignment of even 2 degrees can disrupt the operation of the internal partitions and create zones of coolant stagnation.

Stage 2: Connection diagrams and flow directions

The most critical moment in the installation process is determining the correct direction of movement of the media. Connecting a shell-and-tube heat exchanger is impossible without a clear understanding of where the inlet is and where the outlet is for each medium. Incorrect switching leads to the device operating in countercurrent instead of forward flow (or vice versa), which reduces the efficiency of heat transfer by 20-30%. Moreover, incorrect connections can cause the pumps to cavitate or cause the permissible pressure drop across the tube sheet to exceed the permissible pressure drop.

The standard connection diagram assumes the following principles:

1. Pipe space:Typically, more aggressive, contaminated or high-pressure environments are sent here. Tubes are easier to clean mechanically or chemically than the annulus. The inlet pipe of the pipe part is often located at the bottom to ensure that the volume is completely filled with liquid and air is removed through the upper pipe or vent.
2. Interpipe space (casing):Heating steam, hot water or a less aggressive coolant is usually supplied here. When steam condenses, the entrance is made from above so that the condensate flows freely downward under the influence of gravity. If you connect steam from below, a water hammer will occur that can deform the pipes in a matter of seconds.

Pay attention to the markings on the device plate. Arrows should indicate the direction of flow. If markings are erased or missing, contact the manufacturer for a diagram. Never rely on assumptions like “that’s how it’s usually done.” In our practice, there was a case at an oil refinery where installers mixed up the glycol and oil inlets. Due to the difference in viscosity and required pressure, the glycol system pump failed after 48 hours and the seals were sealed. Losses amounted to more than 2 million rubles only due to incorrect interpretation of the piping scheme.

When designing the piping, take into account the need to compensate for thermal expansion. Shell and tube heat exchangers are subject to significant temperature deformations. The temperature difference between the casing and the pipes can reach 100°C or more. If pipelines are rigidly fixed without compensators (lens, bellows or U-shaped), the force will be transferred to the flange connections. This is guaranteed to lead to a leak. Leave free space around the pipes for installing expansion joints. The minimum distance from the heat exchanger flange to the first fixed support element of the pipeline must be at least 10 pipe diameters.

Stage 3: Installation of flange connections and sealing

The quality of the flange connection directly affects the tightness of the entire system. Statistics show that 60% of all leaks at industrial facilities occur in flanges due to violations of assembly technology. Connecting a shell-and-tube heat exchanger requires using the correct gaskets and maintaining the correct bolt torque. Using gaskets by eye or reusing old seals is not acceptable.

The choice of gasket material depends on the environmental parameters. Paronite gaskets are suitable for water up to 100°C. For aggressive acids, Teflon (PTFE) is required. For high temperatures and pressures, spiral wound gaskets with a metal centering ring are used. Before installation, thoroughly clean the sealing surfaces of the flanges from dirt, oil and old paint. Even a small grain of sand trapped under the gasket will create a channel for leakage under high pressure. Use lint-free wipes and degreaser.

The bolt tightening process must be carried out strictly according to the following rules:

• Use a torque wrench. Tightening "heartily" with a wrench often leads to distortion of the flange and crushing of the gasket on one side.
• Use a cross tightening pattern. First tighten all bolts to 30% of the nominal torque, then 60%, and only then 100%. This ensures even pressure distribution on the gasket.
• After the first heating and cooling of the system (thermal cycling), be sure to check the bolts. The metal of the gasket and flanges shrinks, and the tightening torque can decrease by 15-20%.

Pay special attention to the alignment of the flanges of the pipeline and the apparatus. The gap between the flanges must be the same around the entire perimeter. If you try to bolt together misaligned flanges, you create a bending moment on the heat exchanger tube. Over time, this will lead to a crack where the pipe is welded to the body. In such cases, use mounting mandrels or temporary ties for alignment before installing the bolts. Remember: the force of the bolts should only be used to compress the gasket, and not to correct errors in the installation of pipelines.

Stage 4: Hydraulic tests and air removal

Before commissioning, hydraulic testing is a mandatory step. They allow you to identify hidden installation defects, poor-quality gaskets or microcracks in the welded seams of the trim. The test pressure is usually 1.25–1.5 of the operating pressure, but should not exceed the values ​​specified in the device passport. Exceeding the test pressure is dangerous due to the destruction of the tube sheet or the casing itself.

Filling the apparatus with water should be done slowly, from bottom to top. This is critical for removing air. Air pockets in the heat exchanger create several problems: they reduce the effective heat exchange area, cause local overheating of the metal and contribute to cavitation wear. Air vents must be installed at the highest points of the housing and pipelines. Open them until a continuous stream of liquid comes out without bubbles.

The test procedure is as follows:

1. Fill one cavity (such as a pipe) with water, removing any air.
2. Smoothly increase the pressure to the operating level, wait 10 minutes to stabilize.
3. Inspect all flange connections and welds for fogging or dripping.
4. Raise the pressure to the test value. Exposure under test pressure is at least 30 minutes (according to GOST or TU).
5. Reduce pressure to operating pressure and perform final inspection.

Important note: never carry out hydraulic tests at ambient temperatures below +5°C without using special frost-resistant liquids or heating the room. Freezing of residual water in the drainage areas can rupture the housing. After successful tests, drain the water if the device is not put into operation immediately, or proceed to the start-up phase. Be sure to record the test results in the commissioning log. This document will be required to balance the equipment and pass inspections by supervisory authorities.

Common mistakes and how to avoid them

Even experienced installers make mistakes that become obvious only after start-up. Analysis of hundreds of incidents allows us to identify the most common problems when connecting shell-and-tube heat exchangers. Knowing these tricks will help you avoid downtime.

Mistake #1: Ignoring filtering.
Many people believe that it is enough to install a coarse filter (“mud filter”) at the entrance to the system. For shell-and-tube devices, especially with narrow tubes (10-16 mm in diameter), this is not enough. If scale, sand or pieces of Teflon tape get into the tube bundle, it will quickly clog. Cleaning such a heat exchanger requires complete disassembly and often ends with replacing the tubes.
Solution:Install mesh filters with a mesh size of no more than 1-2 mm directly in front of the inlet pipes of the heat exchanger. Provide a bypass line to service the filters without stopping the process.

Mistake #2: Improper drainage.
Structurally, the heat exchanger must be able to completely empty. If the drainage pipe is located above the bottom point of the cavity, water will always remain in the device. In winter, this is a guarantee of defrosting. In summer, it is a hotbed of corrosion and bacterial contamination (legionella).
Solution:When installing, ensure that the device is slightly inclined towards the drainage pipe. Use full bore ball valves on drain lines to prevent clogging.

Mistake #3: Thermal shock during startup.
A sudden supply of hot coolant into a cold apparatus causes instantaneous expansion of the metal. The temperature difference between the pipe wall and its core, as well as between the pipes and the casing, creates enormous stress. This phenomenon is called thermal shock. It can lead to pipes flaring in the tube sheet and leaks.
Solution:Start smoothly. First feed the medium at a low temperature, then gradually increase the temperature, controlling the growth rate to no more than 30-50°C per hour. Allow the metal to heat evenly.

Operation and Maintenance

Connecting a shell-and-tube heat exchanger is completed not by turning on the pump, but by organizing proper maintenance. The service life of the device directly depends on the regularity of parameter monitoring. Keep a log of temperatures and pressures at the inlet and outlet of both media. A sharp change in temperature delta (for example, a decrease in heating efficiency) is the first sign of contamination of surfaces or the appearance of bypass flows due to damage to partitions.

The maintenance schedule should include:

• Weekly visual inspection for external leaks and corrosion of supports.
• Monthly chassis vibration check. Increased vibration indicates cavitation or unstable flow.
• Scheduled chemical or mechanical cleaning according to a schedule depending on the quality of the coolants. For soft water, the interval can be 12-24 months, for hard or polluted water - 3-6 months.

Use caution when cleaning. Mechanical cleaning of pipes with brushes requires a qualified operator. Cleaning too vigorously may thin the tube walls or damage the protective coating (if any). Chemical washing requires neutralization of the reagents after the process is completed, otherwise acid residues will continue to corrode the metal even during idle time. Always use corrosion inhibitors when acid washing.

Frequently Asked Questions

Which direction of media movement is better: countercurrent or forward flow?

For the vast majority of applications, including heating and cooling, the recommended circuitcounterflow. In counterflow, the cold medium moves towards the hot one. This ensures a maximum average logarithmic temperature difference along the entire length of the apparatus, which increases the efficiency of heat transfer by 15-25% compared to direct flow. In addition, counterflow allows the cold medium to be heated to a temperature close to the inlet temperature of the hot medium, which is impossible with forward flow. Direct flow is rarely used, only in specific cases when it is necessary to limit the maximum temperature of the pipe wall or to prevent crystallization of the product at the outlet.

Can a shell and tube heat exchanger be installed vertically if it is designed horizontally?

No, this is strictly not recommended without agreement with the manufacturer. The design of the device is designed for certain loads. In a horizontal position, the weight of the tube bundle is absorbed by the supports and partitions in a certain way. When installed vertically, an axial load occurs on the tube sheets, which may exceed the design load. In addition, the circulation pattern of the coolant in the interpipe space will change: stagnant zones may form where the liquid will not wash the pipes, which will sharply reduce efficiency. If space is limited, order the unit in a vertical design from the factory, where the tube sheets will be reinforced and the baffle design will be changed.

How often should flange gaskets be replaced?

The service life of gaskets is not strictly regulated in time; it depends on the number of thermal cycles and the aggressiveness of the environment. It is recommended to change paronite and rubber gaskets every time the device is opened for prevention. Spiral wound gaskets may last longer, but should only be reused if they are not visibly damaged, dented or squeezed out. In our practice, we advise changing all seals during major repairs (disassembling the bundle), since the cost of the gasket is negligible compared to the risk of downtime due to a fistula. Always have a gasket repair kit in stock.

What to do if the heat exchanger starts to vibrate?

Vibration is a dangerous symptom. Reduce the load (coolant flow) immediately. The main reasons: cavitation (insufficient pressure at the pump suction), resonance of the vortex shedding frequency with the natural frequency of the pipes or pulsation from the piston pump. Check the operation of the pumps, open the ventilation to remove air. If the vibration continues, stop the machine. Длительная вибрация приводит к усталостному разрушению труб в местах контакта с перегородками и разгерметизации развальцовки. В некоторых случаях требуется установка дополнительных демпферов или изменение режима работы насосов.

Допускается ли сварка трубопроводов непосредственно к патрубкам теплообменника?

Прямая приварка трубопровода к фланцу или патрубку теплообменника крайне нежелательна. Тепловое воздействие сварки может деформировать тонкостенный патрубок аппарата или нарушить структуру металла в зоне термического влияния. Кроме того, это делает невозможным демонтаж аппарата для обслуживания без резки труб. Правильное подключение выполняется через ответный фланец на трубопроводе, который соединяется с фланцем теплообменника болтами. Исключение составляют специальные исполнения аппаратов «под приварку», но даже в этом случае сварку должен выполнять аттестованный сварщик с соблюдением технологии, исключающей перегрев корпуса.

Conclusion and recommendations for choosing a supplier

Качественное подключение кожухотрубного теплообменника — это залог энергоэффективности вашего производства. Соблюдение описанных выше шагов позволит избежать аварийных ситуаций и продлить срок службы оборудования до 15-20 лет. Помните, что сам аппарат — это лишь часть системы. Качество монтажа, обвязки и водоподготовки играет решающую роль.

Если вы планируете закупку нового оборудования или модернизацию существующих узлов, обращайте внимание не только на цену, но и на сервисную поддержку поставщика. Надежный производитель предоставляет не только паспорт изделия, но и подробные инструкции по монтажу, чертежи общих видов и рекомендует схемы обвязки. Наличие сертификатов ЕАС и соответствие ГОСТ гарантирует, что а ппарат прошел необходимые испытания на заводе.

В этом контексте важно отметить опыт компанииWuxi Kaisheng Electric Power and Petrochemical Equipment Co., Ltd., которая специализируется на разработке и производстве высококачественного теплообменного оборудования для сложных промышленных задач. Продукция компании включает титановые кожухотрубные теплообменники, аппараты высокого давления по стандарту ASME, а также решения с трубными пучками из нержавеющей стали 316, морской латуни C46400, медно-никелевых сплавов и никелевых сплавов N06625. Такое разнообразие материалов позволяет подобрать оптимальное решение для агрессивных сред в нефтепереработке, химической промышленности и опреснении морской воды. Изделия сертифицированы по международным стандартам PED и ASME, отличаются повышенной коррозионной стойкостью и устойчивостью к экстремальным температурам и давлениям. Выбирая поставщика, подобного «Уси Кайшэн», вы получаете не просто оборудование, а индивидуальные инженерные решения, адаптированные под специфику вашего производства, что значительно упрощает последующий монтаж и эксплуатацию.

Мы рекомендуем проводить аудит существующих теплообменных узлов перед сезоном нагрузок. Часто простая замена прокладок, чистка труб и корректировка режимов работы позволяют вернуть утраченную мощность без капитальных вложений. Не ждите отказа оборудования — профилактика всегда дешевле ремонта.

Для получения консультации по подбору теплообменного оборудования, расчета тепловой схемы или заказа запасных частей свяжитесь с нашими инженерами. Мы готовы предложить решения, адаптированные под специфику вашего производства, с учетом всех требований безопасности и эффективности.

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