Guide to Wet Scrubber Maintenance

Guide to Wet Scrubber Maintenance

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Wet scrubbers help to keep workers safe and the environment clean by removing certain substances from exhaust emissions at industrial facilities. To ensure safety, adequate operating performance and regulatory compliance, your facility’s wet scrubbers must function properly. Maintaining proper operation requires regular maintenance, including routine preventative maintenance, planned preventative maintenance and, sometimes, reactive maintenance.

The following guide for wet scrubber maintenance will provide basic information about how to maintain wet scrubbers and why it’s so important.

The Importance of Maintenance

Wet scrubbers have a vital role to play at any industrial facility in which they are used. They remove pollutants from gas streams to minimize the amount of potentially harmful contaminants released into the nearby and larger environment. This capability helps protect workers, the general public and the environment.


After a wet scrubber install, you’ll want to ensure you have a plan in place for maintenance.

To achieve consistent operation at the necessary levels, creating a wet scrubber maintenance plan is necessary. Since wet scrubbers play such an essential role in plant operation, wet scrubber maintenance is also essential, as it enables wet scrubbers to perform their functions correctly and reliably.

Also, without proper process tower maintenance, certain components of a wet scrubber may malfunction. These malfunctions may cause direct threats to workers and anyone nearby. Regular maintenance can help prevent these hazards, which is another reason why regular maintenance is so important for the safety of workers and others.

In addition, regular maintenance of packed bed scrubbers helps keep them functioning efficiently and effectively. Without regular maintenance, wet scrubbers may use more energy, increasing costs. They may also become less effective at removing pollutants, which would put safety, environmental performance and compliance at risk.

Preventative maintenance comes with upfront costs, but these costs can help prevent more significant expenses in the future. Keeping up with daily maintenance tasks helps equipment last longer and helps prevent significant failures that can cause downtime and necessitate expensive repairs. In this way, regular preventative maintenance can help reduce costs and the risk of downtime.

Read on to learn more about what to include in your wet scrubber maintenance checklist.

Routine Wet Scrubber Preventative Maintenance

Routine preventative maintenance is relatively minor maintenance work that is done on a regular basis. To ensure efficient and safe scrubber operation, you need to perform certain industrial scrubber maintenance tasks on a daily, weekly, quarterly and semi-annual basis, as well as keep records of the maintenance work completed. You may want to create a wet scrubber maintenance checklist to assist in performing the necessary maintenance checks. Some important tasks to include are:

Daily Wet Scrubber Maintenance Tasks

Daily wet scrubber inspections can ensure you catch any issues quickly.

You should monitor and alarm the following measures, so you can continuously keep track of them:

  • Fresh water make-up
  • Airflow in the duct system
  • Pressure drop in the scrubber and mist eliminator
  • Blowdown
  • Sump temperature
  • Pump flow rate
  • Pump pressure
  • pH
  • Sump Levels

Check each of these measurements at least once a day and set up a system that will alert if one of them falls out of the normal operating range for your facility.

The daily maintenance of your wet scrubber should include checking the pressure drop across the scrubber. If this measurement is out of the normal operating range for your facility, you will need to perform maintenance to return it to normal. Each facility should define its own normal operating range for pressure drop.

Checking and, if necessary, correcting the pH level in a wet scrubber is another core daily task for packed bed scrubber maintenance. Check the pH level frequently, and if it is moving away from the ideal level, add alkali very slowly as is necessary to adjust it. If the pH levels are incorrect, parts of the equipment will likely become blocked due to crystal formation. If your facility uses automatic dosing systems, check them regularly to ensure they are functioning correctly.

Workers should also check the stack and areas near the stack for droplet re-entrainment due to an improperly functioning mist eliminator. Signs to look for include discoloration in the stack and nearby areas, fallout of droplets that contain solids and a mud lip surrounding the stack. If workers detect droplet re-entrainment, it’s important to correct the issue quickly.

Weekly Wet Scrubber Maintenance Tasks

The weekly maintenance of a wet scrubber should include checking the liquid pressure gauges on the supply headers to the scrubber to check for header pluggage, nozzle pluggage and nozzle erosion. Higher-than-normal pressures indicate a pluggage issue, while lower-than-normal pressures indicate an erosion issue.

Each week, as part of your wet scrubber inspection, you also need to drain and clean the sump and refill it with clean water. When performing these tasks, check the sump as well.

Quarterly Wet Scrubber Maintenance Tasks

Once a quarter, you should inspect the entire system to check for leaks. If any leaks are found, it’s important to fix them quickly.

Semi-Annual Wet Scrubber Maintenance Tasks

Semi-annually, perform an internal inspection of the wet scrubber and check for signs of corrosion, erosion, plugged or eroded spray nozzles, solids deposits in tray orifices and packed beds and solids accumulation in mist eliminators.

Pre-Startup Maintenance Checklist

before-starting-upBefore starting up a scrubber, conducting a thorough maintenance check is essential. Your pre-startup scrubber maintenance checklist might look like the following:

  • Check ducts for warpage, abrasion, corrosion, solids buildup, gasketing and slip joint.
  • Check gas pretreatment equipment for corrosion, solids buildup, sump sludge, gasketing, proper valve operation and the condition of the nozzles.
  • Check the scrubber for rusting, buildup, clogging, leakage, abrasion, scaling, nozzle condition, riggings condition, corrosion, sump sludge, abrasion, wearing and piping condition.
  • Check the mist eliminator for abrasion, clogging, leakage, proper valve operation, wearing, corrosion, rusting, pitting, piping condition and nozzles condition.
  • Check the mist eliminator media for buildup and determine whether any media need to be cleaned or replaced.
  • Check the liquid treatment system for proper calibration, proper pH level, probe buildup, caustic hold tank condition, proper valve operation, sludge buildup and piping leakage.

Preventative Maintenance Record-Keeping

Keeping accurate, detailed records is also a crucial part of tower maintenance best practices. Create a system for recording information from all inspections and maintenance work and keep those records well-organized and accessible.

Planned Wet Scrubber Preventative Maintenance

If you’re operating a wet scrubber, you will also have some more substantial maintenance work to complete occasionally. These types of maintenance tasks require more significant investments and are planned far in advance. They occur at most every few years. You can refer to these investments as planned preventative maintenance.

Turnarounds are one major form of planned preventative maintenance project. These projects are larger preventative maintenance undertakings, such as upgrades of renovations to the plant. They serve to ensure safe operations, optimal performance, competitiveness or compliance with regulations. Most plants complete these projects every few years after extensive planning and coordination. It’s best to complete these projects during periods of relatively low production.

Many plants also occasionally complete capital projects, which are projects that involve new construction to improve or expand a capability or process. These projects involve significant amounts of capital, are large in scale and typically occur less often than turnarounds. These are not standard investments or maintenance tasks but on-off projects that result in a significant improvement to or expansion of a plant.

Reactive Wet Scrubber Maintenance

While preventative maintenance is work that is planned ahead of time to prevent issues from occurring, reactive maintenance is unplanned work that is completed in response to an issue that has already occurred. Using a preventative maintenance plan to larger to prevent issues that require reactive maintenance is preferred, but occasionally, reactive maintenance is necessary even if a preventative maintenance plan is in place.

Outages are one type of event that requires reactive maintenance. An outage occurs when a piece of equipment or asset fails, causing production to stop immediately. This type of incident requires the quick and thorough repair or replacement of the failed equipment, so operations can begin again as soon as possible. Repairing or replacing the damaged piece of equipment itself may represent a significant cost, but the costs of the missed production time can be even more significant.

A plant may also experience a shutdown in which the operators are forced to stop all or part of its operations due to the occurrence of a critical issue. This issue could be a natural disaster or another large-scale accident. It could also be a situation in which the plant runs out of a required material or resource. These types of disruptions in operations are not planned.

The downtime involved can have notable consequences, financial and otherwise. Shutdowns are also sometimes paired with events, such as natural disasters, that cause damage to equipment. It’s essential to complete any required repairs or wet scrubber maintenance procedures as quickly as possible to minimize downtime. When your machine goes down, we can help determine if you should rent a replacement scrubber to keep operations moving.

Custom Fume Scrubber Maintenance

Custom Fume Scrubber MaintenanceYour maintenance needs may differ slightly depending on the type of wet scrubber you have at your facility, so you should tailor your maintenance plan to reflect the specific technologies you use. For instance, some types of scrubbers are more sensitive to changes in pressure and temperature than others, and, because of this, require more frequent monitoring and adjusting. However, all scrubber types require replacement of tower packing and internals at around the same intervals. Some of the most common types of wet scrubbers are:

Hydrogen Sulfide Scrubbers

Hydrogen sulfide (H2S) scavengers or H2S scrubbers are in hydrocarbon processing facilities and various other types of industrial facilities. These scrubbers remove H2S, a toxic, foul-smelling gas, from gas streams to protect workers. Filtering out H2S also helps protect pipework and equipment, as H2S can interact with steel and create iron sulfide corrosion.

H2S scavengers are some of the most difficult types of scrubbers to maintain because they are highly sensitive to temperature and pressure changes. This property means they require closer monitoring and more frequent pH and temperature adjustments.

Carbon Dioxide Degassifiers

Aqueous carbon dioxide (CO2) is the most common reason for acidity in water in municipal and industrial settings, so carbon dioxide degassifiers are common in these kinds of facilities. CO2 degassifiers remove CO2 from water to help prevent corrosion in piping and machinery and keep fish healthy in aquaculture operations.

Like with H2S scrubbers, CO2 degassifiers are more challenging to maintain than other systems because they are sensitive to changes in pressure and temperature. You may also need to make frequent adjustments to ensure proper pH, especially in aquaculture applications.

Nitrogen Oxide Scrubbers

Nitrogen oxide (NOx) scrubbers protect workers, the public and the environment and enable regulatory compliance by removing nitrogen oxides, such as nitrogen oxide (NO) and nitrogen dioxide (NO2), from gas streams. NOx scrubbers are useful in a wide range of industries, from the petrochemical industry to food processing to wastewater management. In regards to sensitivity to pressure and temperature change, NOx scrubbers require a moderate amount of monitoring and adjustment.

Sulfur Dioxide Scrubbers

Sulfur dioxide (SO2) scrubbers are important for a wide range of industrial facilities. SO2 emissions can be a threat to the environment, plant workers and people living near a given facility, and facilities need to control their SO2 emissions to maintain compliance with regulations. SO2 scrubbers provide that control by removing the foul-smelling potentially harmful gas. SO2 scrubbers are also moderately sensitive when it comes to sensitivity to changes in pressure and temperature.

Hydrochloric Acid Scrubbers

Hydrochloric acid (HCl) is the most common non-sulfurous gas that manufacturing facilities emit. Landfills and wastewater treatment facilities also emit HCl. Filtering HCl with HCl scrubbers is crucial because the gas can have toxic and corrosive properties around liquids and can produce irritating fumes.

Facilities can use either a horizontal or vertical scrubber configurations to filter out the gas. Hydrochloric acid scrubber maintenance is fairly easy compared to maintenance for other types of scrubbers because HCl scrubbers are only notably sensitive to changes in pH and not temperature and pressure changes like other kinds of systems.

Water-Only Scrubbers

Water-only scrubbers are rarer than many other types of scrubbers, but they are useful in certain applications, such as when other chemicals can’t be added to the tower to improve its efficiency. They’re useful for removing organic compounds, such as ethanol and formaldehyde, from gas streams, as well as dust and other particulate matter. Facilities also often use water-only scrubbers in situations in which gases are highly pressurized or at high temperatures and to reduce fire risk.

One design consideration for water-only scrubbers is properly containing the contaminated water exiting the scrubber, so the contaminants do not leak into the environment. Compared to other types of scrubbers, water-only scrubbers are fairly easy to maintain, making them useful in the right situations.

Wet Scrubber Solutions From MACH Engineering

Wet Scrubber Solutions From MACH EngineeringThorough preventative and reactive maintenance and inspections are crucial to keeping wet scrubbers operating properly, so they can help protect workers, the public and the environment and help your facility maintain regulatory compliance. It’s also crucial that you get the design of your system right from the start and use high-quality products in your towers.

As a full-service company with more than 25 years of experience in the mass transfer industry, MACH engineering can help ensure your wet scrubbers and other pollution control systems work optimally for your applications. We offer quality products, engineering services and installation guidance to companies in a wide range of industries, from pharmaceutical manufacturing to wastewater treatment.

We’ll work with you to design the ideal system for your needs, help you install the wet scrubber and supply the products best suited to your needs. To learn more about working with us, contact us today.

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