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Boiler Basics 101: Deaerators & Feedwater Systems

Deaeration of boiler feed water is primarily known to remove dissolved oxygen from the water, however, there are four additional advantages of utilizing a deaerator: (1) carbon dioxide removal, (2) improved operation, (3) improved heat transfer, and (4) energy savings. In this month’s edition of Boiler Basics 101, we review the importance of including deaerators as part of your boiler plant.

Corrosion in boilers from dissolved gases leads to reduced heat transfer and efficiency losses. Both oxygen and carbon dioxide, if not removed from the water entering a boiler, will cause corrosion. Dissolved oxygen will attach to the metallic components of a steam system and form oxides, or rust, on boiler heat transfer surfaces. If carbon dioxide is present with the oxygen, the two gases together can be up to 40 percent more corrosive than if they were acting individually. Removing non-condensable gases and limiting or avoiding corrosion will greatly improve heat transfer.

Deaerators also serve the purpose of pre-heating the water before it enters the boiler. This process saves energy by recovering flash and exhaust steam from plant returns, energy that would normally be lost to the atmosphere, and utilizing it to pre-heat the feedwater. This recovered steam can account for 20 percent of the fuel typically required to provide heat for that process. Pre-heating the feedwater will also greatly reduce the chance of thermal shock caused by the expansion and contraction of heating surfaces and will ultimately improve the operation of your boiler.

Deaerators and atmospheric feedwater systems both have the same purpose and are made up of several individual devices including feed pumps, a corrosion resistant receiver tank, and a control panel. A deaerator does its job by mixing steam with soft water inside a pressurized tank, removing oxygen molecules which are then vented into the atmosphere. Atmospheric feedwater systems are non-pressurized and perform the same function while operating at a lower (atmospheric) pressure. A notable disadvantage of operating at a lower pressure is that a lesser amount of dissolved gases are removed. Although atmospheric systems are more cost effective, process requirements will dictate which system is ideal for your application.

Overall, if boiler feed water is not properly deaerated, corrosion will occur, and a boiler will operate less efficiently with a higher possibility of facing costly downtime and boiler repairs. Nationwide Boiler provides new deaerators and maintains a rental fleet of deaerating boiler feedwater systems for both low and high pressure applications. Our systems range in size for boilers 24,000 to 225,000 lb/hr, and are configured one of two ways: a skid-mounted deaerator with feed pump stand or complete mobile feedwater system including the deaerator, feed water pumps, water softener, and chemical feed system, all pre-piped and wired and installed inside of a trailer-mounted van.  

Be sure to check out our previous Boiler Basics 101 blogs and stay tuned for the next edition!

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Boiler Basics 101: Burners

The burner is the key equipment component for combustion control systems, providing the heat required for a boiler to convert water into steam. Ideally, a burner should achieve the highest degree of combustion efficiency with the lowest possible excess air. In this month’s edition of Boiler Basics 101, we will discuss the importance of burners and how they fit into the overall picture within the boiler system.

An industrial burner provides a basic function with a simple concept: it mixes fuel and air together to create combustion. Burners can be fired on various types of fuel but the most common utilized are natural gas, oil, propane and coal. In recent years, facilities have moved away from the use of coal to a more efficient and cleaner fuel like natural gas.

Regardless of the type of fuel used, the burner must perform five functions:

  1. Deliver fuel to the combustion chamber
  2. Deliver air to the combustion chamber
  3. Mix the fuel and air
  4. Ignite and burn the mixture
  5. Remove the products of combustion

Complete combustion occurs when all combustible elements and compounds of the fuel are entirely oxidized. However, with complete combustion comes harmful byproducts of combustion, including NOx and CO.

The amount of NOx and CO generated depends greatly on the burner design as well as the fuel fired. Burners with uncontrolled NOx may produce 60 ppm or more. Low NOx burners are the current standard and typically produce NOx of 30 ppm. Ultra-low NOx designs have been developed but are limited to firing on natural gas or propane. These types of burners will reduce NOx emissions to as low as 5 ppm to meet strict environmental requirements that are now common in certain parts of the country. If further NOx reduction is required, Nationwide Boiler’s CataStak™ SCR system can be utilized in conjunction with a low NOx burner.

The right burner design, along with proper combustion controls, will maximize the efficiencies of your boiler system. And as a representative of Webster Combustion, Nationwide Boiler and Pacific Combustion Engineering can help in the proper selection of your new or retrofit burner.

Be sure to check out our next Boiler Basics 101 blog to continue learning about various boiler-related topics.

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Protect Your Rental Equipment This Winter

As we enter the heart of the winter season, it’s important to remember that cold weather conditions have the potential to cause freeze damage to any boiler installed outdoors. In particular, the protection of non-enclosed rental boilers and equipment installed outdoors is imperative to avoid damage. Rental boilers and equipment come in various designs and configurations, and each unique type will require different forms of freeze damage protection. Knowing the type of equipment will help determine the right steps on how to prevent damage.  

 Here are the most common types of rental boilers: 

  - Mobile Boiler Rooms
  - Mobile Steam Plants
  - Trailer-Mounted Boilers
  - Skid-Mounted Boilers
  - Mobile Feedwater Systems
  - Skid-Mounted Deaerators and Other Auxiliary Equipment

Just remember that any lines without a constant flow of water will freeze and must be properly protected from the cold. Always make sound engineering judgment calls to avoid the repercussions of freeze damage. If you have a temporary boiler and want to learn more about the proper ways to avoid freeze damage, read the recent issue of Process HeatingNationwide Boiler was featured and our Marketing Manager, Chelsey Ryker goes over the specifics of boiler protection for each model.

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14 Steps for Winter Boiler Maintenance

Winter is officially here! When cold weather settles in, it is important to make sure that your boiler is well-maintained. Like any other mechanical system, boilers will tend to wear down over time. Boilers can be dangerous if not properly inspected and not working properly. Full boiler efficiency will help avoid boiler downtime and unnecessary expenses. Here are 14 steps to follow to help you get on track with your winter maintenance:

1. Inspect the fuel source.

The fuel used needs to have the proper viscosity for atomization. Test and gauge the fuel viscosity to ensure full efficiency. 

2. Inspect the fireside.

Inspect the fireside and look for any indication of corrosion.  If no corrosion is found, continue to clean the fireside and the furnace area as necessary. 

3. Check the refractory.

Due to the cooler weather, be aware of thermal expansion. Boiler refractors are designed to expand and contract with temperature changes. But all boilers will incur some cracking due to those constant changes. If excessive cracks are found, repair as needed.

4. Inspect the waterside.

Inspect the waterside of the boiler for scale and remove as necessary. Scale prevents heat transfer inside the boiler and can significantly lower efficiency. All water-level controls need to be properly inspected, opened, and cleaned.

5. Inspect the burner.

While the boiler is open, inspect the burner components.  Visually check the boiler’s flames. If there are inconsistencies in the flame patterns or color, there may be an underlying issue. Make sure everything is in order before proceeding. Failure to maintain the fuel system in good working order could result in excessive fuel costs, loss of heat transfer or even a boiler explosion.

6. Inspect the controls.

Any controls used to monitor the water level of the boiler should be checked after reinstalling onto the boiler. Before starting the boiler, inspect all the operating controls and look out for any signs that show of overheating.

7. Close all openings.

Make sure all of the boiler’s openings which include all doors, manholes and handholes are properly closed.

8. Open the boiler’s valves.

This is inclusive of the boiler’s header valves, piping drains and vent valve. Make sure all are operating as required and that the vent is not clogged. All ventilation requirements for the boiler need to be checked and met. 

9. Test the pumps and valves.

You will need to test all of the boiler’s pumps and valves before fully operating to make sure everything is working properly. Once everything has been tested and approved for operation you can start warming up your boiler.

10. Warm up your boiler.

To account for the colder weather it is important to increase the boiler pressure slowly. This allows the joints and metals to heat up evenly and reduce expansion stress. 

11. Switch to automatic operation.

Once your boiler is up to operating pressure, switch to automatic operation.   

12. Analyze combustion.

When you perform a combustion analysis this helps increase performance, verify component operation, decreases maintenance and fuel requirements. This will save some potential expenses made in operation. 

13. Water treatment.

Water treatment is needed before feedwater can be pumped into a boiler. Test the boiler water and treat accordingly. Follow the guidelines provided in the Installation and Operations Manual.

14. Monitor your boiler. 

Within the first few days after start-up, monitor the boiler for any leaks or any additional maintenance items. If you discover water or steam leaks at this point, shut the boiler down and have the leaks repaired.

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