Why Craft Breweries Need to Avoid Steam Boiler Carryover



Steam Boilers an Important Factor in Successful Brewing

As the craft brewing industry continues to boom, Brewmasters across America are continually refining their skills to create exceptional beers to please the palates of every beer drinker.  While finding just the right mix of the perfect ingredients is key to a flavorful beer, brewers are also finding that their system and operations plays a huge role in the quality of the beer they produce.

Heating is an integral part of the brewing process, and steam boilers provide the best option for heating kettles and hot liquor tanks.  However, for most people, operating a steam boiler is a foreign venture.  But, with some basic knowledge of proper boiler operation, you can ensure that your equipment is receiving high-quality steam so that you can brew a consistent product.  On the flipside, improper boiler operation and care can lead to problems with your batches and equipment, proving to be very costly.

What is Boiler Carryover?

One of the most common operational issues that boiler novices encounter is known as boiler carryover. Boiler carryover is the term used when boiler water, as opposed to pure steam, gets pulled into the steam lines. Strictly speaking, in terms of personal safety, boiler carryover isn’t usually dangerous unless allowed to persist for weeks or months, corroding your steam lines. In the short term, however, it can affect heat transfer and create inconsistencies that impact your brewing.

The Impact of Carryover on Your Brewing

Boiler carryover can affect heat transfer in your equipment, which is critical since consistency is king when it comes to the kettle boil cycle. It can also cause excessive water hammering in your steam lines and heat exchange equipment.  The violent rattling of the piping can cause secondary issues in the short term.

Because the kettle boil cycle for wort evaporation process is so time-sensitive, it’s important that the kettle is receiving heat at the consistent rate you expect it to. Time and heat-sensitive variables during the wort evaporation include:

  • Reaching a desired wort evaporation percentage
  • Maintaining a vigorous boil
  • Driving off dimethyl sulfides (DMS) that have an undesirable vegetal flavor
  • Protein coagulation and removal
  • Aromatic flavor profile of the hops
  • Sugar profile

Should the heating of the kettle be interrupted by a carryover event, it is extremely difficult to recover that batch when you have this many time-sensitive processes occurring simultaneously. For example, if you lose some heat due to carryover, you have to extend the boil-off time to achieve the same wort evaporation percentage. By doing so, you’re going to also end up driving off more of the desired aromatic flavors from the hops. Brewing is a science, and it’s impossible to do good science when you have multiple related variables being disturbed at the same time.

How to Avoid Boiler Carryover

Now that you know why avoiding carryover is so important, let’s discuss why it happens and how it can be avoided. When analyzing boiler treatment, it’s important to break it down into three aspects of mechanical, operational, and chemical solutions.

  1. Mechanical: First of all, it’s important that the mechanics of your system are plumbed correctly. For example, the steam header coming out of the top of your boiler should extend several feet up (at least 8’ recommended) before leveling off in the rafters. This is simply because the higher the steam header extends, the larger the pressure differential holding the water in the boiler is, thus making it far more difficult for boiler water to make it all the way up to where the piping levels off. The steam lines should never dip below the water level in the boiler, or a carryover event will lead to water being continuously siphoned out of the boiler. As ridiculous as that sounds, we’ve seen it. Also, the further away the equipment that uses steam is away from the boiler, the better.
  1. Operational: Operationally, there are a few ways to fight carryover. For one, the higher pressure you can run your boiler at, the better. Higher pressure in the vapor space of the boiler helps hold the water in the boiler. Because so many craft breweries have small (~25 HP) boilers that operate at a maximum of 15 psi, this is a weak spot they face in fighting carryover. How you operate your steam valves also plays a role. Opening steam valves is similar to opening a carbonated beverage. If you open your soda very aggressively, the quick pressure differential will cause it to bubble over. Opening steam valves slowly is the best practice to avoid carryover, just like opening a soda can.
  1. Chemical: From the chemical aspect, avoiding carryover is simple as long as you’re performing regular blowdowns. The largest cause of boiler carryover is from too high of alkalinity levels in the boiler. Some alkalinity (100ppm+) is necessary to provide a pH buffering capacity, but too much (700ppm+ in small boiler, 900ppm+ in large boiler) will start to form suds on the surface of the boiler water and increase the risk of carryover. To avoid this, you need to perform surface blowdowns, since alkalinity likes to hang out in the top 8” of boiler water. A less common cause of boiler carryover is from suspended solids in the boiler water. Boiler water should be crystal clear, or close to it, but corrosion issues in your steam system can result in rusty colored water. Suspended solids, like iron, in boiler water contribute to carryover by lowering the surface tension of the water.

One of the reasons why our EcoSHIELD boiler treatment is so effective is because, unlike traditional boiler treatment chemicals, EcoSHIELD doesn’t add solids like sulfites or phosphates to your boiler, allowing you to blow down less often. EcoSHIELD consists of volatile organic molecules that travel anywhere steam or water reaches in your system to provide a protective passivation layer without contributing to the number of total solids. Solids are most effectively removed by performing a bottom blow down. Generally speaking, it’s recommended to perform a bottom blowdown once a day to get out solids, and surface blowdowns any other time necessary to get out alkalinity.

How to Check for Carryover

You may be wondering how to know if your boiler is carrying over, and there’s a very easy way to check. Because steam is practically pure H2O, your condensate return water should be extremely low in conductivity, somewhere in between 5-20uS. Boiler water has the highest conductivity of any water in the system, usually around 2500-3500uS. If the conductivity of your condensate return water exceeds 50uS, that is a clear indication that boiler water is being pulled into your steam lines.

If the carryover gets bad enough, you can get caught in a pretty vicious carryover cycle. The way to fight carryover is by blowing down the highly concentrated boiler water and replacing it with fresh feed water. However, if your boiler is carrying over so badly that boiler water is traveling back to your feedwater tank via the condensate return system, then the water you’re blowing down is being replaced by feed water that is equally contaminated. At this point, the best practice is to completely drain your condensate and feed water tanks to rid them of boiler water, and then look to start blowing down your boiler once your feed water is back in shape.

How Clarity Can Help

Boiler carryover can be quite a nuisance, but with the proper blowdown procedure and effective chemical treatment, it can be easily avoided. The steam boiler is the heartbeat of your operation, and issues with carryover can cost you heavily in terms of inconsistent products and lost production time. By taking the time to learn proper steam boiler treatment and operating it with care, carryover can be a thing of the past.

Clarity has extensive experience with boiler operation in brewing applications.  We will do a FREE evaluation of your entire system to ensure your water is properly treated and you are operating at peak efficiency.  To schedule an evaluation, or if you are experiencing any problems or have questions, please contact Clarity Water Technologies today!

About Clarity Water Technologies

Clarity Water Technologies is the leading industrial and commercial water treatment company, providing expert consulting and cutting-edge chemistry for your facility’s heating, cooling, potable and process applications.

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About the Clarity Blog

Clarity’s Water Treatment blog is written to provide tips and helpful information to anyone who is involved in managing a water treatment application at a facility. 

Our water treatment experts are here to help, no matter what your facility’s heating, cooling, potable or process application may be.  Check our blog for articles on topics like boiler and cooling water, cooling tower cleaning, legionella prevention and remediation, and environmentally-friendly water treatment options.

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