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Boiler Basics 101: Blowdown

Routine maintenance on your boiler is a critical component for proper and efficient boiler operation. One of the main factors to improper maintenance that can also lead to boiler failure is not understanding the concept of blowdown. In this month’s Boiler Basics 101, we will be going over what blowdown is and how it will help improve your boiler’s health.

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When boiler water turns to steam, solids from the water are left behind. The blowdown process involves partially draining the boiler to remove the sludge those solids create. If these are not removed, boiler performance will be reduced and ultimately, it can lead to boiler failure.

Industrial boilers have three types of blowdown procedures:

  • Low Water Cutoff
    This blowdown procedure should take place after every shift. The water column must be kept clean to ensure the water level in the gauge glass accurately represents the water level in the boiler. Regular checks on the boiler verifies that the low water cutoff is operating correctly and cleans it out.
  • Bottom Blowdown
    Bottom blowdown is done by manually opening a set of two valves that drains water out of the bottom of the boiler. The purpose of the bottom blowdown activity is to clean out solids that accumulate at the bottom of a firetube boiler or in the mud drum of a watertube boiler. Solids are pushed through a blowdown separator designed to take water from the boiler during blowdown and reduce it to atmospheric pressure for disposal. During this process, steam is rapidly separated from blowdown water and vented out the top of the blowdown separator. From there, the cooled blowdown solids can be safely removed from the boiler.
  • Continuous Blowdown
    The purpose of the continuous blowdown is to help control the water quality in the boiler; the more impurities and the more chemical treatment required, the greater the amount of blowdown required. It is a procedure facilitated by a pipe entering the upper section of the boiler, typically located in the steam drum of a watertube boiler or the upper steaming portion of a firetube boiler.

The continuous blowdown process is generally automated and does not require much manual interaction, like with bottom blowdown. When operating continuous blowdown, adjust the valve to maintain the recommended boiler water dissolved solids level. This helps control the dissolved solids in boilers that are operated at a steady load.

It is important to consider proper blowdown procedures to keep the water piping clean and the boiler in working condition. If you would like to learn more about the different blowdown procedures, check out ABMA’s article outlining the steps for each type.

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

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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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Free Webinar Alert: Keep Your Boiler Operating Safely at Peak Efficiency

Cleaver-Brooks hosts a number of informative and educational webinars throughout the year.

Be sure to check out the next webinar, scheduled for September 26, 2018 at 2:00pm EST. The material will be focused on educating boiler operators and owners why preventative maintenance is so important. What routine boiler maintenance tasks are required? What is the recommended frequency of each task? All of these questions, and more, will be covered.

Cleaver-Brooks' Warranty & Service Manager John Pemerton will host the webinar - and you won't want to miss it!

Register today!

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A Practical Approach to Easily Decrease NOx, Save Energy, & Improve Your Operations

Our latest case study, highlighting a major food processor is another example of how Nationwide Boiler can help achieve the best performance standards (BPS) for your boilers. We presented a E2Stak solution with a CataStak SCR system and an EconoStak economizer to a food processor in CA to achieve 5 ppm NOx and decease the plant's energy use, which resulted in the customer receiving a rebate check of almost $150,000. Not only did the we help the boilers achieve optimum performance, we also improved the operation and maintenance of the boiler. The plant manager's quote says it all: "This was the first year we could operate the boiler in automatic!"

If you are interested in decreasing your operating costs by saving energy and if you need to comply with tough emission standards, give Nationwide Boiler a call today at 800-227-1966. Our experience and expertise will provide you with additional options you may never have thought possible.

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Recent comment in this post
Guest — wayne feragen
We have two 50k lbs per hour and one 75k lbs per hour boiler. Permit is 30 ppm and we bearly pass on two of the boilers but and j... Read More
Thursday, 04 October 2012 15:28
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