Andrews Air Force Base Hangar Walk-Through

Fire Protection Site Visit to Andrews Air Force Base
by
Atif M. Qureshi

Introduction

On April 26, 1996, a site visit was made to Andrews Air Force Base located in Camp Springs, MD. Assistant Chief Tackish and Mechanical Engineer Dominick Freeley conducted the tour of the facilities. The purpose of this visit was to examine the fire detection/suppression systems in the aircraft hangars.

Hangar 1915 is the first hangar located along the flight line. The hangar is part of the 89th Airlift Wing, Air Mobility Command of Andrews Air Force Base. The 89th Airlift Wing provides worldwide airlift and logistical support for the President of the United States, the vice president, cabinet members and other high ranking U.S. and foreign government officials. In addition, the 89th is the host wing of Andrews Air Force Base.

The primary purpose for this hangar is for the repair of fuel tanks on planes. The hangar was primarily designed to accommodate the largest plane the Air Force uses: the C-141B transport plane. The hangar is a Class 1 hanger as per NFPA409. The overhead sprinkler system is a closed head preaction deluge system.

Hangar Description

To accommodate any fuel spill and fire protection fluids that might be discharged into the hangar, there is a concrete drainage ditch. The ditch has removable slotted steel covers and is monitored by a vapor detection system. Gaseous vapors given off by the jet fuel activate fans that are intended to help draw away the vapors to the exterior of the hangar. The ditch runs along the length of the hangar parallel to the hangar doors. The pit drains into an oil-water separator. The hangar has slightly sloped floors in order to aid the fluids towards the ditch.

The overhead suppression system consists of rate compensated detectors that have an actuation temperature at 195^oF. The system is a closed pre-action system that flows 3% AFFF foam solution.

The hangar is also protected by 4 stationary underwing foam monitors. Three of the monitors provide coverage for the underwing of the plane and the last one provides coverage for the nose of the aircraft. The monitors are simultaneously actuated only when the overhead system actuates and flows AFFF. No valve will be operated by the building fire evacuation alarm system. However all of the monitors can be actuated by manual trip valves located near each monitor. Doing this also prefills the pipes at the ceiling with solution but does not actually discharge them. The methodology used in installing stationary monitors instead of WOMs was that they are generally more tamper-proof than the WOMs. WOMs have adjustable settings that can easily be tampered with and they also have moving parts which tend to break down much more quickly than stationary WOMs because of the physical and mechanical abuse that they are put through by untrained people. The monitors are protected by bollards (concrete barriers) to help prevent collisions from other equipment and vehicles. A draft "fire" curtain runs perpendicular to the hangar doors and it’ intended purpose is to separate the hangar into two fire protection zones for the detection and suppression systems. The fire curtain works as a barrier to keep heat generated from the fire in that particular zone so that the heat actuated sprinklers can activate and smother the fire with the solution.

2 CO2 Hose Lines are currently still a part of the fire suppression system of the hangar. There are future plans to have them replaced.

The hangar uses a unique approach in its fire detection/suppression system setup. The hangar has 3-4 combination UV/IR detectors. Although the detectors originally would have actuated the suppression system, they are now solely used for fire alarm notification purposes. The reasoning behind this was there have been previous incidents of AFFF actuation by backfires and other non-threatening scenarios.

Power supply problems and any open or ground in any supervised circuit activates system trouble.

The second hangar that we were able to visit also used an AFFF overhead and monitors. This hangar is being used for storage and repairs of learjets and helicopters. The monitors in this hangar are WOMs.

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