Sludge piping from digester - piped through building - is building a "classified" area? 1

[USAeng]

We have anaerobic digesters at work. We pull the digested sludge out of the tanks and pump it into wells. The piping goes through a building that is about 400' away from the digesters. That building was classified by the engineering firm and approved by the county as unclassified. A worker asked me today why it isnt a classfied area. If a pipe broke in the bulding there would be digested sludge on the floor and some methane would most likely be present until valves were closed and the floor cleaned. There are drains and there is ventilation of 12 air changes per hour in the building. Any one have a good answer?

 

[QualityTime]

The analogy would be if I had a natural gas line running 400 ft inside a building and the line broke i would be spilling out natural gas in the atmophere and it would ignite. Therefore thd entire building would have to be explosion rated....not likely.

if you carry this argument to your home gas heating system...your entire home would need to be explosion rated

 

[USAeng]

funny after I posted this I thought of the exact same analogy for the NG piping in my basement! Definately makes sense

 

[bimr]

From NFPA 497 (API RP 500 has a similar statement

5.4 Unclassified Locations.
5.4.1 Experience has shown that the release of ignitible mixtures from some operations and apparatus is so infrequent that area classification is not necessary. For example, it is not usually necessary to classify the following locations where combustible materials are processed, stored, or handled:
(1) Locations that have adequate ventilation, where combustible materials are contained within suitable, well maintained, closed piping systems
(2) Locations that lack adequate ventilation, but where piping systems are without valves, fittings, flanges, and similar accessories that may be prone to leaks
(3) Locations where combustible materials are stored in suitable containers Essentially, a "closed piping system" [5.4.1(1)] is one that has no designed paths to atmosphere, such as relief valves.

You can look up the code:

http://submittals.nfpa.org/TerraViewWeb/ViewerPage.jsp?id=820-2012.ditamap&toc=false&draft=true

Areas adjacent to natural gas flanges and valves are classified.