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Air Management in Hydronic Piping Loops - This is a secondary chilled water pump in a large pump room designated for pumps and piping in a data center. After a few minor tweaks and corrections, these pumps all operated flawlessly. There were very few issues with the secondary pump start-ups.
Unlike the primary pumps where cavitation was encountered on the primary chilled water pumps and the condenser water pumps for the chiller. The diagnosis for the cavitation of the primary pumps and the condenser water pumps was that the loops were not properly purged. This caused those pumps to cavitate.
The secondary pumps, pictured here, did not have that problem. Kudos to the team that purged the loops on this side of the chilled water system.
That was an initial installation issue. It was also a lesson in priming the system to ensure all the air purged from the loop. After all, cavitation in the pumps can cause damage to the pumps. Even after the initial installation purge, it is important to ensure air does not build up in the water piping loop. To do this we need a few devices to help purge the air before it becomes a problem. This will prevent nuisance problems such as hydronic air block in branch circuits of the loop. It will also prevent any damage that may be caused by pump cavitation as a result of too much air in the system.
Air Bubbles | Air Management in Hydronic Piping Loops
Proper air management is important in any type of loop. Whether it is a chilled water loop or a hot water loop. As the water moves around in a closed-loop over time it becomes de-oxygenated. It loses little air bubbles that are in all water. This air becomes a problem when it builds up in the pipe risers.
It will impede the water flow in the pipe loop system. In some cases, this build-up of air can cause a decreased flow of water. In other cases, it restricts the flow of water altogether. It does not really matter what type of water loop is used air can become a problem if it is not properly dealt with from the beginning.
Risers and Loop | Air Management in Hydronic Piping Loops
This air (tiny air bubbles) can build up in risers and other places that make it difficult to purge. When enough air builds up in the loop it can cause a hydronic air block. New water is introduced to the loop system through the make-up water. This normally comes from the municipal water supply or a well in rural areas. It is not a bad installation practice to design the loop in such a way as to catch many of the air bubbles before they make their way into the loop.
In this case, the use of a Spirovent is the best solution I have found. This device catches much of the air in any type of water loop system. It does not require high velocity to achieve results. In the risers, on the smaller piping, I use automatic air vents to catch other residuals in the system.
Air Management in Hydronic Piping Loops | Conclusion
This water has these tiny air bubbles in it. These air bubbles need to be purged before they end up in the loop and trapped in one of the branch loop circuits or a riser. Typically there is an air management system in all chilled water or hot water loops where the air is purged. Sometimes you will find these systems at the expansion tank or where the make-up water enters the hot water or chilled water loop.
You may also find these through the system on risers. Take care of your system and your system will take care of you. Finally, without good air management, your boiler loop may not function properly. Additionally, you will experience boiler pressure problems.
Air Management in Hydronic Piping Loops