Boiler Compression Tank and how to properly fill with Nitrogen

wshults007 Posted By wshults007, Aug 24, 2018 at 11:23 AM

  1. wshults007

    New Member 2.

    Aug 24, 2018
    richmond, va
    Currently, we are installing a boiler system for our coating line. The process requires a 220 gallon compression tank. The system design calls for nitrogen filled tank. The factory noted that the tank needed to filled in the field; thus, my question is what is the official nitrogen filling method for the compression tank?? I recall that standard practices are as follows

    Purge, Fill with water, pressurize with nitrogen to required pressure; please let me know your thoughts on this and I am very grateful for any advisement on this matter.

  2. BoiledOver

    Minister of Fire 2.

    Apr 14, 2013
    43°58'55 N - 85°20' W
    Pressurized hot water heating systems use an expansion tank due to the fluctuation in water volume as it heats and cools. The use of nitrogen rather than ambient air in the expansion tank is new to me. Larger molecules I presume, maybe other members have something to contribute in that respect.

    Are you doing a self install at a manufacturing facility?
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  3. maple1

    Minister of Fire 2.

    Sep 15, 2011
    Nova Scotia
    Standard practice around here is use a bladder expansion tank(s), and plain air. Which I think is getting to be standard heating system practice.

    A bit more info might help but sounds like you are outside the realm of home heating? What's a coating line?

    Typical expansion tank setup/precharging would involve isolating/valving off from the system, completely draining it (requiring a drain valve at the bottom and an air inlet valve at the top so water will come out the bottom), closing everything up and charging to system low pressure or a pound or two less (usually with air - or your nitrogen), then opening it back up to the system. All done when system is cold and at low system pressure.

    Don't take my word for it though - no idea what you're working with there.

    (On second read, the filling with water might be needed for your nitrogen process, to get all the air out first. But think you would need to be careful how that water gets pushed back out when the nitrogen comes in [a clear path out with no pressure resistance], and then you'd need to be careful you don't go the other way and push nitrogen into your system. Maybe that should all be done with the tank isolated and a hose on the bottom with the end elevated above the tank so you can tell when all the water gets pushed out?).
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