Across a multitude of industries, heat exchangers play a critical role, especially when it comes to thermal efficiency. Among the various types of heat exchangers, plate heat exchangers stand out due to their compact design, high heat transfer efficiency, and versatile application range. As a result, they are a popular choice in many industrial applications.
Consisting of thin, corrugated metal plates, plate heat exchangers facilitate heat exchange between two fluids without mixing them. They are utilised in numerous settings, from power generation and oil refining to HVAC systems and food production. Their function is crucial for the efficient operation of these processes.
However, like any mechanical system, plate heat exchangers can experience performance issues over time due to scale build-up, fouling, and other forms of contamination. These issues can lead to a drop in heat transfer efficiency and an increase in energy consumption, not to mention the potential for system downtime.
Regular maintenance is imperative to counteract these problems and ensure the continued operation of plate heat exchangers at optimal efficiency. Properly serviced and maintained plate heat exchangers can result in substantial energy and cost savings, extend the lifespan of the equipment, and minimise the risk of unexpected system failures.
This guide explores the various aspects of plate heat exchanger maintenance. From critical definitions to the specifics of cleaning procedures, this comprehensive guide aims to equip you with the knowledge required to keep your plate heat exchangers performing at their best.
Grasping Crucial Terminology and Concepts in Plate Heat Exchanger Operation
To better comprehend the basic maintenance requirements of plate heat exchangers (also known as a frame heat exchanger), it’s beneficial first to understand some critical terminology and concepts integral to these thermal systems.
- Plate Heat Exchanger (PHE): This specific heat exchanger employs metal plates to enable heat exchange between two separate fluids. The design of PHEs prevents the mixing of fluids while facilitating the transfer of heat.
- Heat Transfer refers to the movement of thermal energy from a high-temperature region to a lower temperature. Within PHEs, this phenomenon occurs across the metal plates separating the two fluids.
- Fouling: Fouling denotes the unwanted accumulation of materials on solid surfaces, which can adversely affect the operation of PHEs. Typical fouling substances in the context of heat exchangers can be biological growth, minerals, or sediment, leading to a decrease in heat transfer efficacy.
- Scaling: A subcategory of fouling, scaling is characterised by the formation of hard, crust-like mineral deposits (such as compounds of calcium or magnesium) on the plate surfaces in the heat exchanger. Scaling can significantly hinder heat transfer and fluid flow.
- Cleaning-In-Place (CIP): This technique is used for cleaning the interior surfaces of equipment, pipes, and vessels without disassembly. In the context of PHEs, CIP involves circling a cleaning solution through the system.
- Heat Transfer Efficiency: This metric indicates a heat exchanger’s effectiveness in transferring thermal energy between two fluids. Higher efficiency is desirable, resulting in significant energy savings and enhanced system performance.
- Flow Rate: Flow rate signifies the volume of fluid traversing through the heat exchanger per unit time, typically measured in gallons per minute (GPM) or cubic meters per hour (m³/hr). The flow rate has a direct influence on the efficiency of heat transfer.
A sound understanding of these terms will facilitate a practical approach towards maintaining and servicing plate heat exchangers, helping ensure their optimal operation.
Cleaning and Maintenance: Boosting Your Plate Heat Exchanger’s Performance
To keep your plate heat exchanger working at its best, cleaning and maintaining it regularly is crucial. Let’s walk through how to do this step by step and discuss some essential precautions and best practices.
Two Methods for Cleaning Your Heat Exchanger
You’ve got two main options for cleaning your heat exchanger: cleaning in place (CIP) and manual cleaning.
Cleaning in Place (CIP)
With the CIP method, you circulate cleaning chemicals through the exchanger’s channels. It’s a handy option because it doesn’t require separating the unit. However, ensuring that the cleaning solution won’t harm your exchanger’s materials is essential.
Manual Cleaning
Manual cleaning involves taking the plates off the frame and cleaning each one separately, often using a pressurised water gun. It requires more work but provides a thorough cleaning and lets you inspect each plate closely.
Key Precautions and Practices
Whether you choose CIP or manual cleaning, remember to:
- Follow the manufacturer’s cleaning guidelines and suggested cleaning solutions.
- Dry all parts thoroughly before putting them back together to prevent mould or bacteria.
- Check the plates for any signs of wear or damage during manual cleaning.
- Apply lubrication to the carrying and guide bars when putting everything back together. This will make it easier to take apart next time.
- After reassembling, check that the plate pack is tightened according to the manufacturer’s specifications.
These steps and guidelines help keep your plate heat exchanger clean, efficient, and ready to perform its essential job.
Making the Most of Cleaning-In-Place (CIP) for Plate Heat Exchangers
The Cleaning-In-Place (CIP) method offers a handy way to maintain your plate heat exchanger. Let’s look at what this method involves, its pros and cons, and when it’s best to use.
A Close Look at the CIP Method
The CIP method is a routine cleaning process that doesn’t involve disassembling your heat exchanger. Instead, its primary goal is to remove the debris that builds up in your unit over time. This debris can vary, depending on what your heat exchanger is used for.
Here’s a basic rundown of the CIP method:
- First, drain both sides of the heat exchanger and isolate it from your system fluid, typically using isolation valves.
- Then, flush water through both sides until it runs clear. Ideally, the water should flow opposite to how the fluids run during operation.
- If the pressure drop is still high after flushing or if you didn’t see much debris, it’s time to use a cleaning agent.
- Pump the cleaning agent through the heat exchanger using a circular pump and a solution tank. Your heat exchanger’s manufacturer can guide what agent to use.
- Ensure the cleaning agent won’t harm your exchanger’s plates and gaskets. For instance, chloride can corrode stainless steel plates, which most heat exchangers have.
- After using the cleaning agent, flush the exchanger with water again until the water on both sides runs clear.
The Pros and Cons of CIP
Benefits of CIP
The most significant advantage of CIP is that it’s less labour-intensive than manual cleaning, as it doesn’t require disassembly. It also lets you keep your heat exchanger in place during cleaning, reducing the risk of damage or misplacement of parts.
Drawbacks of CIP
Conversely, CIP might not be thorough enough for heavily fouled heat exchangers. Determining whether the cleaning was successful without visual inspection can also be challenging.
When to Use CIP
CIP is beneficial for regular, preventative maintenance. It’s also ideal when your heat exchanger is in a difficult-to-access location or has a high plate count, making manual cleaning more challenging.
However, if the heat exchanger’s performance doesn’t improve after CIP or there’s little debris during flushing, you might need manual cleaning.
CIP is a convenient and effective method for regular upkeep of your plate heat exchanger, ensuring its longevity and continued efficiency.
The How-To of Manual Cleaning for Plate Heat Exchangers
When Cleaning-In-Place (CIP) isn’t an option for your heat exchanger, manual cleaning comes into play. Let’s delve into the process, discuss its pros and cons, and highlight some safety measures to consider.
The Steps to Manual Cleaning
Manual cleaning of a heat exchanger involves a series of systematic steps:
1. Dismantling
This initial step requires professional mechanics to shut off all fluids flowing in and out of the heat exchanger. All pressure should be released by opening a valve. Cool the heat exchanger before opening it. To do this:
- Gradually loosen the bolts on the heat exchanger, about 1/4 ft. at a time.
- Slide each removable head back to expose the plate pack.
- To facilitate reinstallation, number all plates in reverse order, displaying the number on the top of each plate.
2. Cleaning the Plates
A thorough cleaning is integral to any heat exchanger’s maintenance plan. Here’s how to go about it:
- Begin by removing the gaskets. Their reusability depends on their current condition. Next, clean them with soap and water and hang them in a clean, dry area if they’re still in good shape.
- Use soap, water, a soft brush or a pressure washer to clean off any loose debris on the plates. Avoid using a grinder or a stiff brush.
- Pay particular attention to the gasket groove. Hot acid and caustic may be needed in severe cases to break down stubborn adhesives and build-up.
3. Inspecting and Testing the Plates
This step involves checking your plates for cracks and pinholes:
- Next, perform a visual inspection, paying close attention to where the plates touch each other. Use lights to aid this process.
- Conduct a dye test to catch any missed pinholes. If more than 10% of the plate set contains defects, replace the plates.
4. Reassembling and Inspection
Before reassembling and preparing the heat exchanger plates, the frame must be cleaned and prepared:
- Inspect the nozzle area, focusing on weld areas where corrosion and defects may occur.
- Check the straightness of the fixed and movable heads.
- Inspect the connection points of the upper and lower rails.
- Once done, reinstall the plates and port ring into the frame.
5. Validation
Finally, hydrostatically test your unit and check it for leaks. First, fill the system with water and let it run for a while to remove excess air. Next, increase the pressure gradually, but do not exceed the design pressure. Then, check the plate pack for water leakage. Common reasons for leaks include debris in the gasket groove, old or defective gaskets, or plate holes.
Manual Cleaning: Advantages, Drawbacks, and Safety Measures
Manual cleaning allows for a deep, thorough cleaning, which is particularly beneficial for heavily fouled heat exchangers. However, it’s more labour-intensive and time-consuming than CIP.
When performing manual cleaning, safety is paramount. Always ensure proper lockout procedures are followed. Handle the plates and gaskets carefully to prevent damage and potential injuries.
Remember, regular and meticulous maintenance will ensure the longevity and efficiency of your heat exchanger.
Navigating the Selection of Cleaning Agents for Plate Heat Exchangers
The careful choice of cleaning agents significantly impacts the upkeep and longevity of your plate heat exchanger. Here, we explore the primary considerations when picking these agents, ensuring they are effective and safe for your equipment.
Key Considerations When Choosing Cleaning Agents
Respect for Exchanger Materials
Your cleaning agents must play nicely with your heat exchanger’s plates and gaskets. Some substances, such as acetone, chloroethene, or benzene, can cause harm to these components. As a golden rule, ensure that your chosen cleaning substance is well-suited to the plates’ metal and the gaskets’ composition.
Tailoring to the Task at Hand
Depending on the nature of fouling your exchanger experiences, the choice of the cleaning agent can vary:
- Dealing with Incrustation or Scaling: Removing substances like calcium carbonate, calcium sulphate, or silicates requires an agent compatible with the plate metal. For example, steer clear of hydrochloric acid if your plates are made from stainless steel or titanium. Also, be cautious about using water with high chlorine content while preparing cleaning solutions, as it can decrease the corrosion resistance of certain stainless steels.
- Eradicating Sediment: Sediments often found in exchangers include metal oxides, silt, alumina, and waste from diatomic organisms. Removing these demands a cleaning agent that can handle the job without inducing corrosion or other damaging effects, primarily on stainless steel or titanium plates.
Choosing Effectively and Safely: A Few Tips
- Check for compatibility: Your chosen agent should efficiently clean the exchanger without damaging its components. If you are unsure of what agents to use, check the data plate on the unit and contact the manufacturer directly.
- Steer clear of corrosive chemicals: Some can cause more harm than good. It’s best to consult with your equipment supplier before using an unfamiliar cleaning agent.
- Prioritise safety: The cleaning agent should not pose a hazard to the person using it. Always check for potential risks and ensure the user has appropriate protective equipment.
Carefully selecting the right cleaning agent is pivotal in keeping your plate heat exchanger in tip-top shape.
Keeping a Close Eye on Your Heat Exchanger: Techniques and Factors to Consider
Keeping your heat exchanger at peak performance involves cleaning and maintenance and diligent monitoring. This lets you detect potential problems early and avoid costly, unexpected breakdowns.
Diving into Heat Exchanger Monitoring Techniques
Several techniques can help you monitor the status and performance of your heat exchanger.
Visual Inspections
At a basic level, regular visual inspections can highlight apparent issues such as leaks or physical damage to the exchanger’s components.
Pressure and Temperature Monitoring
By tracking pressure and temperature across the heat exchanger, you can detect deviations from the norm which may indicate blockages, fouling, or other mechanical issues. Modern digital sensors can help you automate this process and provide real-time data.
Vibration Analysis
Unusual vibrations can often be a sign of mechanical problems in the exchanger. Vibration analysis can detect such issues early, allowing for timely intervention.
Advanced Techniques
More sophisticated methods, such as ultrasonic flow meters and thermographic cameras, can give you a more detailed view of your exchanger’s status. However, these techniques require specific equipment and expertise.
Monitoring as a Pillar of Preventative Maintenance
Keeping a keen eye on your heat exchanger helps prevent minor issues from snowballing into significant problems. Regular monitoring can:
- Detect early signs of fouling, allowing for timely cleaning and thus minimising the impact on heat transfer efficiency.
- Identify potential mechanical failures before they result in a breakdown, minimising downtime and repair costs.
- Help you understand your exchanger’s performance over time, guiding maintenance schedules and aiding in planning for eventual replacement.
Diligent monitoring is a crucial aspect of maintaining a heat exchanger. Combining regular visual inspections with more advanced techniques ensures your equipment stays in prime condition for as long as possible.
Useful links
We would always recommend speaking with a reputable service agent to discuss any maintenance to your PHEs. However, we have added links below to some manufacturer’s service manuals that you may find useful. We will add more in the future, so be sure to check back or contact us at 01246 856 396 to discuss a specific brand.
Connect with WCR UK
WCR UK is here to support you in all aspects of heat exchanger maintenance. Our team of experts can guide you through best practices, troubleshoot issues, and provide the services and parts you need. We’re committed to helping you maximise the return on your heat exchanger investment. Contact us today to learn how we can help you maintain your heat exchanger in peak condition.
