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Paired Generator House Sub-base Fuel Tank Separation

Question asked by druschc on Oct 9, 2020
Latest reply on Oct 10, 2020 by milt.werner

Situation:  A common configuration for multiple site generators ~3250KW size is to pair the generators together with a common enclosure and put subbase fuel tanks beneath, one per generator, approximately 5220g each. The tanks are typically UL142 listed with each having a containment shell.  The generators would sit atop the tanks and each draw directly from their tank.  I am aware of multiple installations with this type of configurations as are the generator and enclosure vendors I've spoken with.  These pairs of generators then have a greater separation to adjacent pairs (10+ feet).

 

Problem:

This creates an issue as the two tanks may be considered separately for the purposes of NFPA 30 (2018 ed) chapter 22.4.2.1.  This separation is more than would be possible given the configuration of the paired generators.

(NFPA 30 applying through the via NFPA 37)

 

Question:

1. Has anyone found a firm code-interpretation curing this conflict?

2. Does UL 2200 listing of the enclosure with the provision for the second (or more) generator and tank create a single assembly that should be evaluated as one unit?  

3.  Is there a way to join the tanks to create a single tank?

4.  Is there a way to consider the tanks as a single tank with a separator?

 

Separate question:

On another note, generator tanks are rectangular, is there an accepted way to convert to a radius as required by 22.4.2.1?  The tanks are approximately 12'x35'x3' tall.  

 

If a variance is required:  I'd believe this would be an overall improvement on a small site as the alternative is a single very large tank with distribution piping that would present a greater hazard.

 

This post may be more applicable to Industrial due to fuel, posted here due to the generator audience.

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