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Tag Archive: Heat Exchanger Maintenance

  1. Why you should consider mechanically cleaning your shell and tube heat exchanger

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    Sooner or later, your heat exchanger will foul. Over time, residue will build up on the walls of your tubes and diminish the heat transfer rate. Eventually, your heat exchanger will underperform and you’ll need to take action.

    While fouling is unavoidable, it can be addressed in a way that minimizes the impact. Heat exchanger performance must be closely watched so that dips in productivity are recognized right away. When efficiency begins to fall, the tubes need to be inspected for fouling, and cleaned in a timely manner.

    There are many ways to clean a shell and tube heat exchanger. Each has its own pros and cons, so it’s important to understand which method, or combination of methods, is best for your operation.

    Three common cleaning methods are hydroblasting, chemical cleaning and mechanical cleaning. Hydroblasting and chemical cleaning are highly effective and popular ways to clean shell and tube heat exchangers. However, they also come with disadvantages that operators can’t ignore.

    Problems with hydroblasting

    One of the most commonly turned-to methods for cleaning tubes is hydroblasting, according to Business & Industry Connection Magazine. Though this is an effective cleaning method, there are some downsides involved.

    “Mechanical cleaning can use 90 percent less water than hydroblasting.”

    Hydroblasting involves shooting jets of water into the tubes at as high a pressure as 40,000 psi. This high pressure can cause damage to the tubes, including tiny leaks that are difficult to detect. Additionally, if something should go wrong during cleaning, the water pressure can be highly dangerous to any employees nearby.

    Even though hydroblasting allows for multiple tubes to be cleaned at once, it is a time-consuming process. The exchanger often needs to be disassembled, and parts transported to an area more conducive to high-pressure cleaning than the operation floor. Additionally, getting a thorough clean can be difficult on the first pass, resulting in added time inspecting and re-cleaning parts of the exchanger.

    Finally, hydroblasting requires a large space in which the process can be conducted. Pumps and cleaning utensils, water trucks and a large team of people to operate all the equipment are all necessary to the process.

    Complications with chemical cleaners

    Some manufacturers use chemical cleaning systems to maintain their exchangers. While this method is effective, disposing of harmful chemicals properly can be an expensive endeavor, Jet News, the newsletter for the Waterjet Technology Association and Industrial & Municipal Cleaning Association, explained.

    “Chemical cleaning can pose an environmental health issue.”

    Additionally, chemical cleaning can pose an environmental health issue, wrote Hassan Al-Haj Ibrahim, a professor of petroleum refinery engineering at Al-Baath University in Syria.

    Dialing down the pressure

    Fortunately, there is a highly effective cleaning alternative to hydroblasting and chemical cleaning. Mechanical cleaning uses water at 700 psi or less, and doesn’t require the use of chemicals. Reduced water pressure allows for:

    • A smaller cleaning crew.
    • Cleaning to be done in place, without disassembling the exchanger, thereby also reducing the number of opportunities for equipment damage.
    • Reduced water use.
    • Lessened chance of injury on the jobsite.
    • Less expensive cleaning.

    Cost is usually the determining factor in deciding which cleaning method to use. While this may not always be the best judge of cleaning strategies, it definitely makes mechanical cleaning more attractive. Mechanical cleaning is less expensive than hydroblasting for several reasons.

    First, mechanical cleaning uses as much as 90 percent less water than hydroblasting. According to BIC Magazine, cleaning 21 heat exchangers produces:

    • 48,000 gallons of wastewater at 20,000 psi.
    • 5,000 gallons of water at 500 psi.

    This reduction in water is partially a result of lower water pressure, but also because mechanical cleaning systems allow the water to easily be turned off when not in use, while hydroblasting systems continue to shoot water 70 percent of the time they are being used. Lower water use will make the entire process less expensive.

    It’s not always clear which cleaning method is best for your operation. Unfortunately, there are instances when the wrong cleaning solution is chosen, resulting in a damaged heat exchanger or an incomplete cleaning job.

    To learn about the best way to maintain your shell and tube heat exchanger, reach out to the experts at Enerquip.

  2. Stopping leaks in their tracks: Part 2

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    A surprise leak in a shell and tube heat exchanger is never a good thing. At best, it will cause down time, resulting in lost revenue. At worst, it could lead to cross-contamination, fouled product, damaged equipment or even a product recall.

    However, leaks are bound to happen sooner or later as a piece of equipment ages. There are ways to slow down the aging process. For example, investing in a stainless steel shell and tube heat exchanger will typically result in a much longer lifespan of the equipment than a cheaper material. But the best way to avoid leaks is to be ready for them.

    Conducting regular tests on a shell and tube heat exchanger can help you detect small leaks before they become big problems. There are many ways to check out the integrity of your tubes, including:

    1. Helium testing

    Helium gas can be very useful to hunt down a leak while a heat exchanger is offline. The gas is pumped into the shell side of the exchanger and overpressurized, according to Plant Services. The helium is forced through the vessel and seeps through any holes, welding flaws or cracks in the tubes.

    A helium mass spectrometer is attached to each tube to detect the presence of helium. According to the International Atomic Energy Agency, this method is effective due to the mass spectrometer’s high sensitivity

    2. Acoustical testing

    As anyone who has ever slowly let air out of a balloon knows, leaks tend to have a unique sound. This is the idea behind acoustical testing. A microphone is required, as an air leak in a heat exchanger usually isn’t noticed by the average ear. The pitch of the sound gives the inspector clues as to the size, shape and location of the flaw, the IAEA explained.

    Plant Services noted that this method can also be used to identify other imperfections as well, including fouling, wall loss and corrosion. Another benefit to acoustical testing is that it can be done quickly; tubes can be tested in as little as 9 seconds. Additionally, it doesn’t require a trained expert to perform these tests. However, a drawback of this method is that it isn’t as sensitive as other types of tests, such as helium testing or dye penetration. Additionally, this should be performed while the equipment is offline, as sounds from normal processing could interfere with the microphone’s ability to pick up sounds of leakage.

    3. Dye penetration

    Dyes can highlight seams, slight cracks and other imperfections that are difficult to see with the naked eye. This fact is what makes the dye penetration method so intuitively effective. When a leak is suspected, the location is painted with a low viscosity fluid with a tendency to quickly migrate along surfaces. If a leak is present, the fluid will make its way to the other side of the painted wall. This test is simple, inexpensive and sensitive to smaller leaks.

    4. Chemical reactions

    Some basic chemistry knowledge can go a long way when a simple solution to a complex problem is needed. Some gases commonly used in heat exchangers, such as ammonia, will produce a chemical reaction upon coming in contact with a particular element. In the case of ammonia, pumping hydrochloric acid into the exchanger will result in the formation of ammonium chloride gas. This is identified by white plumes resembling smoke or fog.

    When introducing new chemicals to a shell and tube heat exchanger, it’s important to be sure that they won’t react badly with any substances that are in the tubes or the exchanger itself.

    If you find that you need to replace or repair your shell and tube heat exchanger because of small leaks that could become bigger and more problematic, contact the experts at Enerquip. Our team of in-house engineers will work with you and your team to determine the best solution for your operation.

    Did you miss part 1 of stopping leaks in their tracks? Read it here

  3. Stopping leaks in their tracks: Part 1

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    Over the lifespan of a shell and tube heat exchanger, the tubes will undergo massive amounts of stress. Normal use involves rapidly flowing liquids through and around the tubes. When other factors, like the potential for maldistribution or built-up sediment, are taken into account, there are many ways a shell and tube heat exchanger can wear out.

    Investing in high-quality materials like stainless steel will certainly lengthen the life of an exchanger. However, after a while, there will come a time when parts need to be changed out or the whole exchanger needs to be replaced. While this is to be expected, it’s better to be aware of how well the equipment is holding up rather than waiting for a problem that could hold up production, create more work than necessary and ultimately eat your profits.

    “Radiotracers can be used to detect leaks while the heat exchanger is online.”

    One excellent way to keep an eye on the health of your exchanger and detect any issues that could get worse quickly is through leak detection. Leaks can be detrimental to a shell and tube heat exchanger and are never good for the company. Additionally, leaks can lead to cross-contamination, fouling or equipment damages, so it’s crucial to avoid them.

    There are several methods of leak detection available to manufacturers who want to give their equipment a checkup.

    Radiotracers

    One of the dilemmas of conducting leak detection tests is determining whether to take the exchanger offline and lose production time. If there turn out to be no leaks and the exchanger is in good shape, it could be argued that the manufacturer lost time and revenue for little gain. Luckily, there is one effective way to search for leaks without affecting the process or product, and without taking the exchanger offline.

    Radiotracers can be used to detect leaks while the heat exchanger is still in use, according to the International Atomic Energy Agency. They are comprised of several elements:

    • A radioisotope, typically inserted into whichever side of the exchanger has the highest pressure.
    • An injection detector, which monitors the flow of the radioisotope through the exchanger from the tube side inlet where it is mounted.
    • A leak detector positioned at the shell outlet that monitors the lower pressure side to see if the radioisotope ends up there.

    Usually, inserting any foreign substances into an exchanger while processes are running is frowned upon. Even slight changes could damage or alter the final product or have negative effects on the exchanger itself. However, only a miniscule amount of radioisotope is required to effectively detect leaks. The IAEA explained that, in some cases, just 10 to 17 grams is enough to detected by the leak detector.

    Conductivity and pH

    Conductivity is the measure of a substance’s ability to carry an electric current. Some fluids and objects have high conductivity, while others don’t have any at all. The various fluids in an exchanger will generally have differing levels of conductivity.

    Another way to distinguish between substances is with pH. This is the measure of how basic or acidic a fluid is, which will also differ between the materials flowing through the tubes and shell.

    “Finding leaks while they’re small is crucial to preventing production issues.”

    Both of these measurements can aid in the monitoring of where the fluids are traveling within the exchanger, according to Emerson Process. Using analyzers or sensors on the low-pressure side will help detect when a substance with a particular pH or measure of conductivity is making its way into a part of the exchanger it shouldn’t be.

    While this can be highly effective in detecting leaks and their origins, there is one shortcoming to this method: Organic substances and water often have similar levels of conductivity as well as similar pH levels. Therefore, if an exchanger is processing organic liquids and using water as the heat-transfer medium, a different leak detection method would be more beneficial.

    Finding leaks while they’re small, before they cause any major damage or problems, is crucial to keeping an exchanger in good shape and preventing production issues later on. There are many ways to monitor the health of an exchanger. What’s important is finding the method that suits your processes best.

    If you find that you need a new shell and tube heat exchanger, speak to the experts at Enerquip. Their team of in-house engineers will work closely with you and your company to determine the best exchanger design for your operation.

    Want more? Keeping read – stopping leaks in their tracks – part 2

  4. Davit Arm Assemblies

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    Heat exchanger expert, Ron, explains how to make your shell and tube heat exchangers more user friendly for your maintenance crew down the road.

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    DAVIT ARM ASSEMBLIES

  5. Chemical cleaning and hydroblasting: 2 ways to clean your heat exchanger’s tubes

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    Shell and tube heat exchangers are an integral part of many industries. Though the oil and gas industry may be vastly different from the food and beverage industry, the two have at least one thing in common: the shell and tube heat exchangers that help prepare products for sale to consumers must be in top condition.

    When injecting fluid into a shell and tube heat exchanger, that which is more likely to corrode or foul is typically placed in the tube side of the machine, according to R. Shankar Subramanian, a chemical and bioengineering professor at Clarkson University. This is because it is easier to clean or, if needed, replace the tubes than the shell. However, the fact that liquid with a high fouling risk is put into the tube side of the exchanger, makes it crucial that machine operators and owners know how to clean and maintain their tubes.

    Shell and tube heat exchangers come in many sizes and configurations. Some are easier to clean than others, primarily because some have tube bundles and bonnets that can be easily removed from the shell side, while others’ are connected to the body of the exchanger. Knowing what type of bonnet your exchanger has and the appropriate cleaning mechanism are critical aspects to consider when purchasing the exchanger.

    There are many different ways to clean the tubes of a heat exchanger. Each has its advantages and its disadvantages. The important thing is to know which method is right for your particular machine and operation.

    Chemical cleaning

    Chemical cleaning is a good method to use for a fixed channel box design, which is generally more difficult to clean because the tubes cannot be separated from the shell. According to Clean-Co Systems, the process for chemical cleaning can be done in several ways. Chemicals can be circulated through the tubes or cascaded. Some are foam and others liquid. Chemicals will vary depending on the type of exchanger and what it is used for. Conoco Systems explained mild acids are typically used for this type of cleaning. It is beneficial to exchangers that have high amounts of buildup, as chemicals remove more deposit than most alternative cleaning methods.

    “Chemicals remove more deposit than most alternative cleaning methods.”

    However, there are several downsides to using chemicals, Conoco Systems explained. This method is one of the most expensive ones. Also, chances are, the tubes will have to be mechanically cleaned after the chemicals have done their work to remove any residual substances that could contaminate the next product batch inserted into the tubes. It is also time-consuming and a potential environmental hazard.

    Hydroblasting

    According to Goodway, hydroblasting has been a popular way to clean tubes for many years. This method uses high-pressure water systems to blast away any debris or deposits left in the tubes. NLB Corp. explained the water can be pressurized to as much as 40,000 psi.

    Hydroblasting can be done either manually or with an automated system. The manual approach involves an operator hooking a hose up to the tubes one by one and using a foot pedal to regulate the water. This method is effective and relatively inexpensive, though human error may result in uneven cleaning. There are also safety concerns regarding the speed and force at which the water comes out of the hose.

    There are two basic types of automated systems: flexible lance and rigid lance systems. Both allow multiple tubes to be cleaned at once, which saves on the amount of time spent cleaning. U-tube heat exchangers and others with curved tubes would benefit from a flexible lance system because it is easy to maneuver the hoses around the bends. For those exchangers with straight tubes, the rigid lance systems provide greater water pressure to remove debris and buildup.

    “Flexible lance systems can maneuver around U-shaped bends.”

    According to Conoco Systems, operators who choose to use hydroblasting as a cleaning method should also be aware that the pressure of the water could weaken the tubes and create leaks that may go unnoticed. Leaks in the tube side of the exchanger could result in cross contamination between the tube side and shell side fluids. Once discovered, it might even require more time spent offline to repair or replace the tubes.

    Chemical cleaning and hydroblasting are two popular ways to maintain the cleanliness of a heat exchanger’s tube side. Deciding which method will depend on the type of exchanger you have and what it is used for. Regardless of the configuration or use of your exchanger, though, it is crucial to ensure the tubes are kept clean to prevent fouling and contamination.

  6. Tight crude oil can cause fouling in shell and tube heat exchangers

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    MicroMarket Monitor released a report stating that much of the shell and tube heat exchanger industry in North America is fuelled by the chemical and petrochemical industries. According to the report, 28.8 percent of the market share of heat exchangers in 2014 went to the chemical industry. Heat exchangers are often used for oil refining and the shell and tube variety are the most commonly used.

    The American Institute of Chemical Engineers explained only four countries are currently extracting crude oil from shale formations: Argentina, China, Canada and the U.S. Crude oil from shale formations is more difficult to retrieve and hydraulic fracturing, or fracking, is the method by which it is extracted. The U.S. is the leading producer of this type of oil, commonly called tight oil.

    While customized shell and tube heat exchangers are great machines to use for processing, there are some things manufacturers and operators should be aware of. According to Emerson Process Management, the refining process is highly prone to fouling. Unexpected fouling is an especially harmful problem that is becoming more common among facilities refining light tight crude oil.

    “Crude oil fouling is one of the main causes of energy inefficiency in refineries.”

    Fouling can be harmful to a refinery because it causes lost production time, increased costs and, as a result, reduced profits. Unexpected fouling means operations need to cease production for cleaning. Plus, the fouling causes excess energy consumption and decreased throughput by the crude unit fired heater. According to a report from the Department of Chemical Engineering at the Imperial College London, crude oil fouling in pre-heat trains is one of the main causes of energy inefficiency in heat exchangers. Because of the strain it causes across multiple aspects of the refinery, the cost of crude oil fouling is high. Crude oil fouling was found to cost the U.S. approximately $1.2 billion a year.

    Asphaltene precipitation leads to accelerated fouling

    Different industries may see varying causes of fouling. In processing tight crude oil, fouling is commonly due to asphaltene precipitation buildup. This is primarily due to the blending of tight oil with other crude oil types. When tight oil alone goes into an exchanger, it tends to bottleneck in the naphtha processing and crude overhead units. This is because most refineries are designed to process oil of a specific composition, the AIChE explained. Blending them will reduce the risk of limiting the efficiency of processing units in the bottom of the barrel.

    While blending these types of oil is necessary to allow the machinery to operate correctly, this practice is also the one that contributes to asphaltene precipitation causing fouling. When incompatible crude types are blended, asphaltenes are not stable in the solution, resulting in the precipitate. AIChE noted that certain ratios of incompatible oils result in less precipitate than others. For instance, a blend of 20 percent tight oil with 80 percent of another type will create fewer asphaltenes than a 30-70 mixture.

    Tight oil also contains levels of naphtha that are higher than other types of crude oil, which can also contribute to the rapid production of asphaltene precipitation.

    Prevent fouling through monitoring

    To prevent fouling, manufacturers have inspected machines periodically and taken notes manually and recorded information in spreadsheets. While this has largely been effective in the past to respond appropriately to signs of fouling, increased production of tight crude oil, which fouls more quickly than most products, manual note-taking and periodic observation is no longer a practical form of prevention.

    “Traditional forms of fouling prevention are less effective with accelerated fouling.”

    Instead, Emerson Process Management suggested manufacturers use online capabilities to constantly monitor the state of exchangers’ performance. Wireless temperature and differential pressure measuring devices are one way to constantly monitor the performance and efficiency of a heat exchanger. By monitoring the health of the exchanger, refiners are able to carefully choose when to schedule a turnaround, rather than waiting until the fouling problem is no longer avoidable, leading to an unforeseen cleaning day. By being able to choose when to clean the tubes, refiners are able to calculate which day is best, so as to minimize the financial harm a day without production will cause.

    Not only will monitoring the condition of the equipment using online devices keep refiners current about potential fouling, but it can also aid in preparing maintenance staff of what is to come when it’s time for a turnaround. It can also help indicate if additional parts need to be purchased ahead of time. Some exchangers are equipped with a bypass, so cleaning can be done without losing a day of production. However, for those that don’t have this capability, as is often the case, advance knowledge of the kind of maintenance that should occur may reduce the time the turnaround takes and mitigate some unforeseen obstacles.

  7. How to prepare to clean a shell and tube heat exchanger

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    As most manufacturers who work with shell and tube heat exchangers know, fouling can be detrimental to an operation. It is crucial that all equipment that goes into processing a product is working at its optimal capacity. To ensure this, manufacturers and operators need to take the time to inspect and clean shell and tube heat exchangers.

    However, this is easier said than done. Cleaning a shell and tube heat exchanger is no easy task, especially for those with hard-to-access tubes. In addition to how difficult the process is, taking a day or two to inspect and clean your machines will result in lost production and therefore, lost revenue. It’s important to think about which day is best to minimize the losses incurred by scheduled maintenance. It is also crucial to plan it ahead of time, not only to account for the downtime, but also to plan out the turnaround schedule to ensure everything goes smoothly.

    “Taking a day to clean your machines will result in lost production.”

    Knowing when to clean

    In sanitary industries, like food, dairy and pharmaceutical, there are often well established protocols established for the timing of heat exchanger cleaning. These cleanings are most commonly accomplished through the use of an automated CIP (clean-in-place) system that will clean and sanitize the tubing without having to disconnect the piping or exchanger parts. These cleanings are often done daily, weekly of between batches of product.

    According to Conoco Systems and Conoco Consulting Corp., companies in more industrial settings can determine whether a maintenance day where machines would be offline is worthwhile by considering the hourly cost of the losses over time and the cost of fouling. Determining the right time for the loss to be at a minimum will tell manufacturers what the best cleaning intervals are.

    Chemical Processing explained that over the past half-century, companies have changed the way they view scheduled maintenance days. In the past, these cleanings took place one or more times a year. The years have brought equipment that is more reliable and requires fewer cleaning days. Today, the norm is closer to cleaning once every four to 10 years. Of course, this depends on the exchanger type and what it is being used for. Some materials that pass through an exchanger are less prone to fouling than others. For this reason, it is important that operators and manufacturers know the signs of fouling and the nature of the chemicals and products they work with.

    There are many advantages to going several years without a cleaning. The fact that cleanings are less necessary indicates the resiliency and efficiency of the exchanger. It also means there are fewer days during which the company loses profit due to ceased production. However, there are some downsides to this as well. Chemical Processing points out that since the last turnaround day may have happened as long as a decade ago, fewer operators and maintenance experts will be familiar with the process of cleaning and inspecting the machines. Because of this, it is important that all people involved in the cleaning day be properly educated and prepared for it.

    Getting prepared

    Chemical Processing advised people getting ready for a turnaround day to make a checklist of everything that needs to be completed on that day. This will help someone who is inexperienced or out of practice keep track of all necessary tasks. This list should include recording how the machine is operating just before you shut it down, whether all the measuring tools available make sense or if others would be best, layout dimensions for the machine and all its parts, and whether there is any damage or other factors that could cause harm to the product or machine later on. It is also important to have any replaceable spare parts on hand, like gaskets, O-rings and hardware, so that any damaged or compressed parts can be replaced before the unit is re-connected and brought back on line. Because exchanger parts can be very heavy, it is also important to have a safe lifting plan with adequate clearance to remove bonnets, piping and other parts in order to gain access to the tube bundle.

    How to clean

    If the company will allow photography of the equipment, it’s a good idea to take pictures of everything mentioned in the notes taken throughout the day. This will help explain any damage encountered and provide reference for the notes the person performing the turnaround takes.

    Conoco Systems explained there are many ways to clean a shell and tube heat exchanger, though most require being offline. The most widely chosen method is mechanical cleaning. This involves determining what kind of deposits you will be removing from the tubes. Deposits range from small amounts of silt to substances that are more difficult to remove, depending on the materials that are used in the exchanger. Once this is determined, decide which cleaning method is appropriate. Some common examples include brushes, used for lighter debris; calcite cleaners, used to remove stubborn calcite deposits which couldn’t be removed with acid; and metal tube cleaners, used for harder deposits.

    Hydroblasting has also been commonly used, though precautions to reduce risk of injury or tube damage must be taken if managers choose to go with this option. Good Way explained this method involves water pressurized to 10,000 to 25,000 pounds per square inch, which is then blasted through the tubes to remove deposits.

    Chemical cleaning is another preferred method, though it is a more expensive option, Conoco Systems explained. Chemicals that are mildly acidic will take off debris faster and more efficiently than a mechanical process. However, the tubes will still need to be cleaned of the chemicals used to prevent contamination or environmental hazards.