Power Generation Plants - Condenser Tube Cleaning

• Posted on 9 February 2023
• By David Bokov
• 0

Steam surface condensers have a crucial role in the operation of power generation plants. Clean condenser tubes lead to increased efficiency of the system and therefore to a higher megawatt production. Goodway Benelux supplies innovative tube cleaning equipment for fast and effective tube cleaning. Read more about it in this blog, which also consists of a 40.000 condenser tube cleaning test case.

Increasing condenser efficiency

Steam surface condensers have thousands of tubes which have a cooling media flowing through them. The cleaner the tubes, the better the heat transfer will be. The condenser has a crucial role in the power generating process. The better the heat transfer, the higher the efficiency of the overal plant will be. Furthermore, it will lead to an increased production of megawatt output which means more revenue.

Online cleaning systems

Some power plants have a taprogge (or similar) online cleaning system installed. Small balls flow through the tubes during operation of the condenser. These oversized, cleaning balls remove fouling that has attached onto the tube walls. Sometimes power plant operators think that this cleaning technology solves all of their fouling problems, which it does - to a certain degree.

These cleaning balls do not choose the tubes that they go in, they are sucked into the tubes that have the highest flow. This means that some tubes will be cleaned more often than others, and some will be cleaned less. Also, these balls can get stuck in the tubes over time. This creates a blocked tube that has no flow. This ''deadzone'' in the tube can lead to corrosion and oxidation.

This cleaning method extends the cleaning interval time, but does not exclude it. In due time, a mechanical cleaning of the condenser tubes is necessary to remove fouling and balls that have gotten stuck in some tubes. This mechanical cleaning should be done once a year, or once every 2 years. Depending on various factors, this interval period can change.

Current cleaning technologies

The cleaning of a surface condenser is not an easy job. Thousands of tubes have to be cleaned thoroughly and carefully, without damaging them. Also, every hour of extra downtime due to cleaning, can cost the plant serious money.

In most cases power plants choose a high pressure lancing system to clean the tubes. While this system removes all the deposits, it is often considered an overkill method. Most of the time, deposits inside the tubes are soft, due to the cooling media being river-, sea-, or lake water. In case of hard scaling, a high pressure cleaning might make more sense.

The big challenge with high pressure cleaning is the downtime. It simply takes quite some time to mechanically feed a lance and nozzle through the long condenser tubes. Multiplied over thousands of tubes, the cleaning can easily take days, if not weeks - depending on the amount of tubes to be cleaned.

Furthermore, the potential operator hazard and risk of tube damages is present. When cleaning with high pressure in enclosed rooms (such as the condenser chambers), things can go wrong when not performed correctly. If a nozzle is stuck in the tube and remains on, it can cause leaking tubes due to extended exposure to high pressure. Furthermore, if operators do not handle the equipment correctly, it can lead to injuries or worse.

Finally, the amount of wastewater created during a high pressure cleaning is tremendous. These systems often use hundreds of liters of water per minute. Multiplied by a continous cleaning for days or weeks will lead to an extremely high amount of water being used.

Projectile tube cleaning

When cleaning a surface condenser, you want to keep the downtime as low as possible, while having the best possible cleaning results. A projectile tube cleaning comes pretty close. In fact, it's the fastest cleaning technology available in the market at this moment.

Goodway Benelux has various specialty projectiles which are used to remove fouling inside the condenser tubes. These projectiles are shot through the tubes at high speed and with low pressure. Projectiles travel through the tubes within seconds, leaving a clean tube behind. Almost always, a single pass is enough to clean the tubes.

The propulsion systems provide the power to actually shoot the projectiles through the tubes. This can be either an air powered system or kinetic hydrostatic pump, which uses 100% waterpower. Depending on factors such as fouling type, tube material, and previous experiences, one of both systems will be the best match.

Propulsion systems

Goodway Benelux offers 2 propulsion devices. These systems are used to shoot the projectiles through the tubes. Depending on various factors, one of both systems will be the best choice. Below you will find a brief explanation of both systems.

The QS-300 Quick-Shot is an easy-to-use device and very compact. This makes it a preferred choice among power plant professionals. Because the system is compact and lightweight, it can be used more easily in tight spaces, such as the condenser chambers. In addition, only air and water is required, which simplifies preparation and use. Depending on the deposits, different types of projectiles can be selected. Below you will find a number of examples of applications for which the QS-300 is often used:

• (Steam) surface condensers of power generation plants
• Large water-cooled chillers

Because the system combines air and water, it is only possible to shoot through 2 types of projectiles. The polyethylene tube scrubbers and nylon coil brushes. The QS-300 is mainly used to remove soft and medium type fouling. These types of deposits are often found in water-cooled installations.

The BFP Big Shot System uses kinetic-hydrostatic technology. In short, this means that the system uses 100% waterpower. In other words, 132 litres/minute at 28 bar pressure. This high and powerful flow ensures that the projectiles are almost instantly pushed through the tubes. The turbulence and flow of the water takes all loosened deposits with it, ultimately leading to a clean tube surface. The projectiles lose all energy when they leave the tubes, they fall out, so to speak. Which benefits general safety.

The BFP Big Shot System can be used for various applications. The system is mainly used to clean larger types of shell and tube heat exchangers in various industries. Depending on the fouling, a different type of projectile can be chosen. Below you will find a number of examples of applications for which the BFP can be used:

• Process shell and tube heat exchangers with 500 tubes or more
• (Steam) surface condensers of power generation plants
• Large water-cooled chillers

It is possible to remove different types of deposits using this technique. Depending on the hardness of the fouling, a different projectile can be chosen. The BFP Big Shot System is powerful enough to shoot through all Goodway projectiles, including carbon steel scrapers.

Advantages of using projectiles for condensers

As mentioned above, a projectile tube cleaning is the fastest cleaning technology to date. Projectiles are the ideal match for deposits that are commonly found in condenser tubes. Some examples of these deposits are:

• Silt, algae, slime (biofilm), sand, mud, sludge, zebra mussels and barnacles.

A projectile tube cleaning also offers a number of advantages. In many cases, this technique is safer, faster and more efficient than traditional cleaning, such as high pressure lancing. Below you will find a brief summary of the main benefits:

• Speed: the time saved when cleaning with projectiles is substantial. First you flush the tube without a projectile. This is done to check whether there is a blockage and to pre-rinse the tube. Afterwards, you load the projectile into the tube and shoot it through. This entire process takes less than 10 seconds, regardless of the length of the tube. Scroll down to see 3 examples of total cleaning time, for a condenser with 40.000 tubes.
  
  
• Water consumption: The QS-300 uses compressed air and water in a 90/10 ratio. This means that only 10% water is used. The QS-300 uses approximately 18-20 liters of water per minute. Divided over a number of tubes, this results in a very low net water consumption per tube. The BFP system uses 132 litres/minute, but you only need about 10 seconds per tube. This amounts to approx. 20-25 liters of water per tube. This is a significant reduction compared to other cleaning techniques.
  
  
• Safety: the system uses a low pressure technology. This makes the cleaning process a lot safer for the operator. In addition, the tubes remain intact and undamaged, because they are not exposed to (extremely) high pressures.
  
  
• Lower costs: Goodway propulsion systems are very affordable and therefore represent a relatively low investment, even if several are purchased at the same time. After that, you only need projectiles that can be purchased on a project basis or for a specific type of heat exchanger. Projectiles can be reused, further reducing variable costs. Below, you can find an example of the material costs for 40.000 condenser tubes.

Projectiles

A complete overview of all available Goodway projectiles can be found on this page. Below you can find a short summary of the different types of projectiles that are usually used for condensers of power plants:

• Polyethylene tube scrubbers:
  
  • For removing light deposits, such as: sludge, algae, mud, slime and sand.
• Nylon coiled brushes (XL):
  
  • For removing light to medium deposits, such as: sludge, algae, sand, barnacles and zebra mussels.
• SSM carbon steel super scrubbers:
  
  • For removing medium to hard deposits, such as: zebra mussels, barnacles, calcium and limescale. (least often used)

(Testcase) Downtime explained

The below examples give a rough calculation of the time required to clean the tubes of a power plant condenser with 40.000 tubes. The condensers are often divided in several units/chambers, containing a couple thousands of tubes. Let's take 10.000 tubes/unit. On average, it takes less than 10 seconds to clean power plant condenser tubes, as long as the deposits are relatively soft (as explained above).

In this example we are using QS-300 propulsion systems with coil brush projectiles to remove soft to medium type fouling, such as sludge, mud, and algae. Please note that this time calculation does not include mechanical activities or whatsoever, this is just purely based on the tube cleaning time with projectiles.

EXAMPLE 1:

• Each unit is cleaned with 2 operators, or in other words, 2 QS-300 devices are used in this example. 
• 10.000 tubes x 10 seconds = 100.000 seconds = 28 hours
• 28 hours divided by 2 operators = 14 hours required to clean 1 unit containing 10.000 tubes.
• 14 hours x 4 units = 56 hours for 40.000 condenser tubes.

EXAMPLE 2:

• The cleaning downtime can be further shortened by increasing the amount of operators that are cleaning at the same time. Instead of 2 QS-300's, you could for instance decide to use 4 QS-300's at the same time.
• 10.000 tubes x 10 seconds = 100.000 seconds = 28 hours
• 28 hours divided by 4 operators = 7 hours required to clean 1 unit containing 10.000 tubes.
• 7 hours x 4 units = 28 hours for 40.000 condenser tubes.

EXAMPLE 3:

• A last example, instead of 4 QS-300's, you could go for 8 QS-300's, 2 operators per unit.
• 10.000 tubes x 10 seconds = 100.000 seconds = 28 hours
• 28 hours divided by 2 operators = 14 hours required to clean 1 unit containing 10.000 tubes.
• Because you have 4 groups of 2 people cleaning a unit around the same time, it takes 14 hours to clean all 40.000 tubes.

In other words, in 1 full day (24 hours), or 2 days in case you use 8-12 hour shifts, all 40.000 condenser tubes can be cleaned with projectiles. The speed of cleaning partly depends on the experience of the operators performing the cleaning, but in general, a projectile tube cleaning process for large condensers takes days, rather than weeks.

(Testcase) Costs explained

In the above described cases, respectively 2, 4 and 8 operators are using QS-300 devices to clean the condenser tubes of all 4 units with projectiles. To clean 40.000 condenser tubes with the soft deposits described above, you would need about 10.000 coil brush projectiles. These projectiles can be reused 3-5 times depending on the tube length, fouling type, and method of catching them during their exit of the tube. We went with a reuse rate of 4 in our test case. The costs are explained below, for each example:

EXAMPLE 1:

• 2x QS-300 (one-time investment) = € 3.390,00 (€ 1.695,00 /piece)
• 10.000 x coil brush projectile = € 25.000,00 (€ 2,50 /piece)
• Total costs equipment/projectiles = € 28.390,00

EXAMPLE 2:

• 4x QS-300 (one-time investment) = € 6.780,00
• 10.000 x coil brush projectile = € 25.000,00
• Total costs equipment/projectiles = € 31.780,00

EXAMPLE 3:

• 8x QS-300 (one-time investment) = € 13.560,00 
• 10.000 x coil brush projectile = € 25.000,00
• Total costs equipment/projectiles = € 38.560,00

In general, the QS-300's need to be purchased once. After that, you can use those for several condenser cleanings. Say 2023 is the year you start using Goodway's projectile tube cleaning equipment, for future cleanings the material costs for your 40.000 condenser tubes would be € 25.000,00, since you only need 10.000 nylon coiled brushes.

Of course, these are just the costs for the equipment and projectiles required, for this specific test case. They act as an indication for the average power plant condenser in Europe. Labour costs and mechanical activities are not included. Nevertheless, the costs for the equipment and projectiles will be far lower than any other method. Combined with the savings in cleaning downtime, the ROI will almost always be seen straight after the cleaning. Cleaning the condenser tubes regularly with projectiles makes sense for the power plant. Even a very small increase in megawatt production will lead to a short payback time.

Preventive cleaning and maintenance

Goodway Benelux's experts recommend power generation plants to opt for a preventive cleaning and maintenance strategy. A projectile tube cleaning combined with the online (taprogge) ball cleaning system is a powerful duo that can lead to a constant, highly efficient surface condenser. Furthermore, a regular mechanical cleaning with projectiles will keep fouling at check and easy to remove. (Most of our power plant clients clean their condenser tubes once per year, or once per two years)

When tubes are cleaned at a higher interval rate of for example 4 years or more, the deposits will multiply further and grow into a harder substance. At that point, it could be inevitable to use harder types of  projectiles (such as carbon steel scrapers) or even other cleaning technologies such as high pressure. All this could lead to much higher cleaning costs, more risk, and a much longer downtime.

When the mechanical cleaning occurs on a regular basis, deposits will remain soft and easy to remove. That way, tubes do not get plugged with hard deposits and softer projectiles can be used to shoot through the tubes. This leads to a much easier cleaning process, less risk and lower costs due to more affordable projectiles like tube scrubbers/coil brushes being used. Regular cleaning of the condensers also means that its efficiency will remain higher over time.

In short, a preventive cleaning and maintenance strategy for power plant condenser tubes pays itself back pretty easily. The condenser tubes remain clean, which increases heat transfer and thus the efficiency of the whole plant. Which down the line creates a higher megawatt production and thus more revenue for the company.

Get in touch with the experts!

Are you interested to learn more about Goodway's projectile tube cleaning technology and equipment? Or would you like to discuss if a projectile tube cleaning solution could be interesting for your (power) plant? Easily reach out to our product experts and they will be happy to assist you with more information and pricing. They are also able to provide a customized strategy and plan for your specific application.

Click on this link to go to our customer service page and get in touch with us!