Questions_from_Site_Visit.pdf

Questions from Site Visit

The following clarifications result from the Site Visit for the Bead Blast Booth Fire Suppression at the

115th Fighter Wing on 24 January 2019:

1. Bonding and Grounding – The issue of the plastic tubing used on the reclaim stream from the floor of the unit is currently made of non‐conductive plastic piping. This can lead to a build up of static electricity within the system. Per the NFPA 77, Static Electricity, it is acceptable to use conductive materials to dissipate static by bonding to a conductive object elsewhere in the system (See para 7.4.1.4 – 7.4.1.6). In the case of our system, the rest of the system tubing is metal, grounded and bonded to other sections. The addition of a grounding wire assembly within the plastic tubing which is then bonded to the rest of the grounded system is acceptable. (See Annex G of NFPA 77, Figure G.1(d) included within this correspondence) Currently the metal portion of the system maintains a resistance of below

10 Ohms, as prescribed in the NFPA 77, para 7.4.1.3.1.

2. Exhaust Extension – Currently the exhaust air from the system is generated upwards through the system and vents vertically facing the ceiling. This reduces the overall exhaust pressure and limits the required exhaust pressure in order to install chemical isolation devices. The sought remedy for this is to angle the exhaust 90 degrees and extend 6‐10 feet further to not only provide adequate back pressure, but to improve the air flow of the system as well. This adjustment then leads into the chemical suppression device request.

3. Exhaust Extension – Currently the exhaust air from the system is generated upwards through the system and vents vertically facing the ceiling. This reduces the overall exhaust pressure and limits the required exhaust pressure in order to install chemical isolation devices. The sought remedy for this is to angle the exhaust 90 degrees and extend 6‐10 feet further to not only provide adequate back pressure, but to improve the air flow of the system as well. This adjustment then leads into the chemical suppression device request.

References:

NFPA 77:

Questions from Site Visit

NFPA 77 Annex G: