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Category Archive: TEMA Guidelines

Tag Archive: TEMA Guidelines

  1. Shell and tube heat exchanger standards: Part 2

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    No matter what industry you operate in, standards matter. They are the measuring stick against which companies and consumers can measure products and choose which ones best suit their needs. They are a way of demonstrating precision and care in the manufacturing of each model of a product.

    There are some industries in which meeting standards is crucial to ensuring product safety and quality. The food, beverage and dairy industries must meet guidelines set by the Food and Drug Administration to ensure products are safe for human consumption. The pharmaceutical industry must also meet these requirements so that each medicine is not only safe, but effective.

    What these industries have in common is more than consumer-facing products and FDA regulations; they also rely on shell and tube heat exchangers to help make their products as safe, effective and consistent as possible. In order for these industries to produce food, beverages and medicines that are of high quality, they must use equipment that meets specific guidelines as well.

    There are a wide range of standards a shell and tube heat exchanger can adhere to. Knowing what they mean and which ones apply to your industry and area of operation are important for successfully moving forward.

    ANSI

    The American National Standards Institute has been coordinating the voluntary standardization system in the U.S. private sector for nearly a century. Groups called standards developing organizations work together to develop and improve upon standards.

    ANSI publishes Standards Actions every week, which include calls for comments on standards proposals. In it, suggestions are made along with what machinery the standard changes would apply to. As of last year, more than 240 SDOs were accredited by ANSI, and more than 1,100 American National Standards were in place.

    3-A Sanitary Standards Inc.

    Standards for equipment design used in the dairy industry first came about in the 1920s. There were three interest groups, or associations, that worked to develop the standards: equipment fabricators, regulatory sanitarians and processors. To highlight the three associations’ collaboration, the standards became known as 3-A.

    3-A Sanitary Standards were created and are maintained to ensure that all equipment used in the food, dairy and pharmaceutical industry is kept clean so that all products coming from them are safe for consumption. According to 3-A, the ideal equipment can be mechanically cleaned through a clean-in-place or CIP system, or can be easily taken apart for thorough manual cleaning.

    API 660

    The oil and gas industry is another area in which standards are crucial. Petroleum is used in nearly every aspect of today’s world. It fuels vehicles and heats buildings, but it is also used in textiles, health and beauty essentials, cleaning products and many more applications.

    In the oil and gas industry, there are several standards companies must adhere to. Often, it is the end user or consultant who creates demand for refineries to follow these standards. The American Petroleum Institute designed standards called API Standard 660.

    A newsletter from the CoDesign Engineering Skills Academy noted that these standards were drafted based on industry experience and practical considerations. They provide specifications for the design of a shell and tube heat exchanger for use in the petroleum industry, such as how thick the tubes can be, the type of exchangers allowed in refineries and how thick the tubesheet joints can be.

    As demonstrated in the newsletter’s chart, API 660 has some similar standards as TEMA, though not always. For instance, under API 660, TEMA type P and W exchangers, which have outside packed floating heads and a floating tubesheet that is externally sealed, respectively, are not allowed to be used in a refinery. However, under TEMA’s standards, these can be used in certain situations.

    It’s important to note the differences in standards when working in an industry where meeting regulations can help define the quality of a product. Knowing your customer base and what they value is also critical, as this will help manufacturers determine which equipment and which standards are right for them.

    If you are looking for a shell and tube heat exchanger for your operations, talk to the experts at Enerquip. Their in-house engineering team will understand your needs and be able to determine which standards your equipment needs to meet.

  2. Shell and tube heat exchanger standards: Part 1

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    Shell and tube heat exchangers are important instruments in a wide variety of industries. They are used in refining oil, preparing pharmaceutical products for market, ensuring that food and dairy products are safe to eat and helping breweries create the perfect pint of beer, among other use cases.

    While these industries are widely diverse, they all encounter the same concern: which shell and tube heat exchanger to purchase for their operations. Heat exchangers have a long lifespan, especially when they are made with the highest-quality standards and materials. But, when it comes time to make a new purchase, it’s crucial that it is done right.

    Not only does the configuration matter, but so do the codes and standards the equipment meets. Industry standards help ensure all products are built in the best way possible for customers. It prevents companies from buying subpar products. The American Society of Mechanical Engineers also pointed out that costs and training time are loweredwhen everyone adheres to the same standards and methods of design.

    “Industry standards help ensure all products are built in the best way possible.”

    Ensuring your shell and tube heat exchanger is designed and built in accordance to the correct industry standards is of the utmost importance for a business. If an exchanger does not meet the right criteria, the products may not be suitable for distribution, and a new exchanger or an upgrade may need to be purchased.

    TEMA

    One of the most widely used industry standards comes from the Tubular Exchanger Manufacturers Association. This group updates its set of standards as needed, the most recent being from 1988, according to Thermopedia.

    Under TEMA’s standards, there are three subcategories:

    • Class B, used for chemical processes
    • Class C, used in general commercial applications
    • Class R, generally used in petroleum processing, but can also be used for large-scale processing applications

    The differences between the classes are subtle but important. For instance, the nature of working with petroleum creates a need for heavier and more durable construction, while chemical processing is better done with stainless steel and lighter equipment.

    ASME

    Other common standards shell and tube heat exchangers are built to adhere to are those set by the American Society of Mechanical Engineers. The ASME VIII code refers to the pressurized parts of a shell and tube heat exchanger, according to Thermopedia. These parts are the ones inside the shell, primarily the tubes.

    Section VIII is the one most often applied to shell and tube heat exchangers, though Thermopedia explained sections II and V are also used occasionally. These refer to materials and nondestructive testing, respectively. There are a total of 11 sections in ASME’s standards.

    “Different countries have varying rules regarding standards.”

    ASME was designed to be applied to many different types of equipment, not just shell and tube heat exchangers. Many exchangers will be certified by both ASME and TEMA, as the latter was in part designed to be a supplemental level of criteria for the machines.

    PED

    As heat exchangers are an important piece of equipment for many industries, they are used all over the world. Different countries have varying rules about what standards equipment need to meet to be legal. Because of this, it’s crucial that equipment manufacturers and purchasers know where an exchanger is going, and what the rules are there. It’s also important that anyone buying or using an exchanger be fully aware of the regulations in the country the exchanger will be used.

    The Pressure Equipment Directive is one such international standard that is required in the European Union. PED covers a wide scope of equipment, from boilers to piping to pressurized storage vessels. It also applies to shell and tube heat exchangers.

    PED includes rules about:

    • Materials
    • Harmonised standards
    • Essential requirements
    • Market surveillance
    • Conformity assessment

    Each of these rules is put into place to ensure workplace safety, and that products that are processed with a particular piece of equipment are safe for the public.

    CRN

    Another international standard is the Canadian Registration Number. This is required for any boiler, pressure vessel or fitting that will be in operation in Canada. Acquiring one ensures that the equipment is certified to be used in a specific province or territory.

    The CRN is written with a multi-digit number, a decimal, and one or more numbers or letters that represent a specific territory or province. For instance, “1” indicates British Columbia, while “T” represents the Northwest Territories.

    When purchasing a shell and tube heat exchanger, getting the right certifications is crucial. Enerquip’s team of engineers will know what your industry requires and will work with you to meet your needs.

  3. How to determine which impingement protection method is best

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    A shell and tube heat exchanger is an essential part of production for many operations. These machines are built to last for years. However, some processes can be rough on the exchanger. For instance, high fluid flows can cause corrosion and vibration, which can be detrimental to the machine. Too much vibration can cause tubes to pull out and cause cross-contamination or shell or tube damage.

    The Tubular Exchanger Manufacturers Association states that, in some high-velocity situations, an impingement plate is required. This is when single-phase fluids that are non-abrasive reach a dynamic pressure, or v2, of greater than 1,500. However, with other high values, TEMA recommends devices to protect the exchanger from erosion and vibration.

    But installing these plates has some drawbacks. Process Heating pointed out that installing an impingement plate will increase the shell diameter because the plate is typically welded to the tube bundle, beneath the inlet nozzle. University of Kentucky professors R.K. Shah and D.R. Sekulic stated that when impingement methods like these are used, part of the opening will be blocked. Hydrocarbon Processing said these devices could also cause additional vibration problems of their own. This is why it is imperative that manufacturers thoroughly understand the problem at hand, the possible consequences of altering the exchanger and what the overall benefit will be.

    Testing before investing

    Of course, it can be difficult to understand the full extent of the alterations an impingement plate will make. It’s also not always easy to determine if the impingement plate is the right way to go, or if another method to reduce the risk of erosion and vibration would suit an exchanger better.

    “Computer simulations can help predict the outcome of adding an impingement plate.”

    Hydrocarbon Processing explained the use of computer simulation can help to predict how a piece of equipment will affect the exchanger’s performance. Computational Fluid Dynamics uses software that combines math and physics to predict how a fluid will flow in relation to the objects and fluids it flows past, TechTarget said.

    In a case study conducted by Hydrocarbon Processing, CFD simulations were compared to physical tests for the same equipment to determine whether this method would be an accurate predictor of whether impingement plates or other additions would be effective. The study found CFD was not only a reliable predictor, but it also could provide information physical testing lacked.

    Exploring other options

    Impingement plates aren’t the only method to decrease risk of vibration and erosion. According to Shah and Sekulic, annular distributors, impingement plates and impingement rods can all benefit a shell and tube heat exchanger operating at high velocity.

    An annular distributor can be installed along with an expansion joint to save on cost and space. If an exchanger’s processes easily give way to thermal expansion, this is a good solution. The installation will help to reduce erosion and vibration, but will also help decrease risk of uneven expansion that could damage the shell or the tubes.

    TEMA stated that tube-end inserts and distributor baffles can also help with issues concerning high-velocity processes.

    “Distributor baffles can help with issues concerning high velocity processes.”

    Process Heating also explained that using a longer shell will allow the inlet valve to be moved away from the tube bundle, so it is not placed directly above the tubes. Additionally, if a manufacturer has not yet built the exchanger, a U-tube design might be worth considering. If it is determined that an impingement plate is necessary, this design does not suffer from reduced shell diameter, as in a straight tube design. Additionally, if the high-velocity process may also result in damaging thermal expansion, a U-tube exchanger does not pose risk to tube pullout or shell damage. The tubes are free to expand as needed, because they are only attached to a tubesheet at the front bonnet.

    If your exchanger is running high-velocity processes and you are concerned about erosion or vibration issues, consider using one of these methods to help. The experts at Enerquip will be able to work with you to determine the best solution.

  4. Choosing an Exchanger Channel Style

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    Editor’s Note: This content was last updated 3/11/24.

    Shell and tube heat exchangers offer a myriad of configurations to suit various needs. The crucial initial step in selecting the right exchanger for your business involves choosing the optimal combination of styles. Fabricators collaborate closely with manufacturers to pinpoint the specific requirements the exchanger must fulfill.

    A pivotal decision that fabricators and manufacturers must make pertains to the type of channel, or bonnet, to employ in the shell and tube heat exchanger. This entails considering both the front channel, through which fluid enters the tubes, and the rear channel, where the fluid either exits the exchanger or undergoes another cycle.

    Each type of channel—front or rear—is denoted by a designation set by the Tubular Exchanger Manufacturers Association (TEMA).

    Varieties of Shell and Tube Heat Exchangers

    When designing a shell and tube heat exchanger, the customer and fabricator will select the front channel, the shell type, and the rear head types. Each has its own merits and drawbacks, but aligning with the specifics of the application will guide the choice. Understanding the intended use of the exchanger is crucial for determining which qualities to prioritize.

    For example, if the exchanger will handle toxic chemicals, particularly if hazardous materials will flow through both the tube side and the shell side, the N-type bonnet might be optimal. In this construction, the tubes, tube sheet, and shell are all welded together, reducing the risk of leaks. However, if welding everything together is unnecessary, there’s little advantage over other types. The N-type bonnet is challenging to clean and maintain, and replacing parts is more cumbersome compared to some alternatives.

    If ease of cleaning and maintenance are top priorities, an A- or B-type designation would be advantageous. Both facilitate easy cleaning, as accessing the tube sheet is straightforward. These are the most common channel options, suitable for most exchanger applications. When choosing between the two, considerations should include the fluid pressure in the exchanger, the importance of tube cleaning, solution cleanliness, and cost.

    The A-type is the easiest to clean because the tubes can be reached without disconnecting piping or removing the bonnet. Many manufacturers prefer A-type channels because they simplify cleaning the tube side, allowing the use of contaminated tube side fluids. However, this bonnet style has two gasketed seals, increasing the risk of leaks in high-pressure processes.

    The B-type exchanger lacks the second seal, reducing the risk of leakage, making it more suitable for high-pressure processes. However, cleaning is more challenging because the bonnet needs removal to access the tubing. Manufacturers handling clean tube side fluids but dirty shell side solutions often choose this option, which is also more economical.

    Lastly, the C-type provides access to the tubes without removing the piping, although it’s challenging to clean and maintain. It’s suitable for high-pressure applications and for handling hazardous substances on the tube side.

    There are also D-type channels, primarily used for extremely high-pressure applications. Like the C-type, repairs are difficult because the tube bundle is attached to the bonnet. However, cleaning is not problematic as the tubes can be accessed without moving the pipes. It’s the most expensive option for the front channel.

    Choosing the right bonnet is a critical decision in planning the fabrication of a shell and tube heat exchanger. While many exchangers perform well with an A-type or B-type channel box, there are instances where an N-type, C-type, or D-type may be preferable. Manufacturers should carefully discuss the options with their fabricator and understand the expected uses of their machine before making a final decision.

    Machined vs. Fabricated Channels

    Depending on the application, you’ll also need to decide if a machined channel or a fabricated channel is a better option.

    Machined designs involve creating parts from solid stainless steel plate or forging through milling and drilling, ensuring cleanability and easy draining. On the other hand, fabricated designs are built from raw materials, offering larger volume for product hold-up and removable covers for tube cleaning, making them ideal for more viscous product applications. Depending on the specific requirements of your application, one may be more suitable than the other.

    Enerquip provides various designs for both machined and fabricated channels, each offering unique benefits. Here, we compare the two.

    Enerquip Simplifies the Decision-Making Process

    If you’re in the market for a shell and tube heat exchanger but uncertain about the best style for your application, consult the experts at Enerquip. With experience in designing and fabricating shell and tube heat exchangers since 1985, we’ve likely worked with your exact process conditions. Contact us today or request a quote.

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  5. Designing a shell and tube heat exchanger

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    Shell and tube heat exchangers are in integral part of many operations. The product flowing through the exchanger, such as dairy, food or pharmaceuticals, will eventually be in the hands of customers who rely on consistent quality for their health and well-being. For this reason, it is crucial the exchanger is the best one for the job.

    Manufacturers need to choose the right style of shell and tube heat exchanger. Different processes and industries have different requirements for their equipment. Because of this, customizing a shell and tube heat exchanger takes expertise on the part of both the supplier and the buyer of the equipment. There is a lot that goes into fabricating a heat exchanger and taking all pertinent items into consideration is essential during the design phase.

    The shell

    Perhaps the most recognizable part of the shell and tube heat exchanger is the shell itself. According to Chemical Engineering Progress, the design of the shell is among the most complicated parts of the exchanger to design. There are many different options for the shell design, including one-pass shells, two-pass shells, double split flows, divided flows and cross flows. These are all classified as different standards with the Tubular Exchanger Manufacturers Association. There are also several streams within the shell that need to be taken into consideration when designing it.

    “The materials should be resistant to corrosion.”

    There are many different materials that shells can be made from. The materials should be resistant to corrosion and sturdy enough to encase the tubes and the high-pressure processes that will occur within. Carbon steel is a common material used for shells, as is stainless steel. Stainless steel is highly resistant to many forms of corrosion, making it a preferred material for many manufacturers.

    It’s important to understand what liquid will be flowing through the shell side. Knowing the liquid that will be used will help to determine the material, as the metal chosen should not react with the fluid used. Generally, condensing fluids are used on the shell side, according to Chemical Processing. Viscous fluids can be used either on the tube side or the shell side. However, many exchangers use viscous liquids on the shell side experience vibrations, which puts the equipment at risk of damage and maldistribution.

    Tubes and tubesheets

    Chemical Engineering Progress explained there are three types of tubesheet designs. A fixed tubesheet has tubes that run from one end of the shell to the other and is welded to the shell. A U-tube heat exchanger only requires one tube sheet because the tubes leaving the tube sheet are bent at the end of the exchanger and returned to the same sheet. The third type is the floating head. This requires two tubesheets; one, which is fixed to the shell, and a second, which is located at the other end but is not fixed, allowing for tube expansion.

    There are many factors to consider when choosing between these three. One of them is cost. The fixed tubesheet is the least expensive because the design is the simplest. The U-tube tubesheet itself may be less expensive because only one is needed, though the tubes are generally more expensive because they require more work to bend properly. Finally, the floating head tubesheet is the costliest.

    “It is crucial that the tubes and tubesheets be cleaned and maintained.”

    However, while cost plays an important part in the decision-making process, it cannot be the only factor. It is crucial that the tubes and tubesheets be cleaned and maintained to prevent breaks, leaks and fouling. The fixed tubesheet’s tubes can be taken out for cleaning, but the tube bundle cannot be removed from the shell, making cleaning difficult. On the other hand, the U-tube and floating head designs allow for the bundle to be removed, so cleaning is easier.

    As the Wolverine Tube Heat Transfer Data Book explains, it is important to note that replacing the tubes after corrosion or vibration damage occurs is relatively easy. This is not only a concern for the design of the tubes and tubesheets; manufacturers must also ensure the exchanger is positioned in an area large enough to perform maintenance on the machine. This can only be guaranteed when the size and shape are considered before fabrication.