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|  MIL-T-21578A
Working surfaces - All working surfaces of the test
3.4.1.1.6
equipment shall be spark-resistant, A suitable surface shall be provided as a
desk top for recording test data. This surface shall be a minimum of 12 inches
wide by 15 inches long; except for the dimensions in 3.4.3.3.1 the distance from the
floor shall be specified in the detail specification. The longitudinal location of
the working area shall be placed so that the operator can readily read the gages
and operate the controls from this location.
Vibration - The cabinet shall be constructed so that
3.4,1.2
vibration from any components shall not be transmitted through the structural
members to the instrumentation to an extent which might impair readability or
accuracy.
Lights - Lights shall be of the type approved by the
3.4.1.3
Underwriters Laboratories for Class 1, Division 1, Group D of the National
Electrical Code, Article 500-Hazardous Locations. Instrumentation other than
direct-reading flow meters, shall not require integral lighting. All direct-reading
flow meters shaLL include integral lighting.
Ventilation - Enclosures shall have air vent louvres near
3.4.1.4
the floor level and at the top or shall be provided with an induction ventilating fan.
Air exhausting - The test equipment shall be provided with
3.4.1.5
an air duct exhaust system near the item on test located well below the face of the
operator. It shall provide a down draft movement of air, with suitable ducting ter-
minating flush at the top-rear of the stand. No exhaust-air blower or fan shall be
required in this system. The capacity and location of the exhaust-air intake shall
be such that the operator will not be subjected to test-fluid vapor during normal
operation of the equipment. A metal plate, bearing the estimated exhaust require-
ments in cubic feet per minute and the static pressure required to overcome the
resistance in the duct work shall be attached on the top of the stand adjacent to the
exhaust, The air quantities shall be sufficient to produce a capture velocity at the
item being tested of not less than 50 feet per minute. Provisions shall be made for
attaching additional duct lengths to the exhaust outlet.
3.4.1.6
Drip pan - A drip pan(s) shall be provided within the en-
closure. The pan(s) shall be installed to catch all leakage which may drip from
any component or flow down to the Inside walls of the enclosure. Drip pan(s) shall
be constructed of not less than 14 gage metal. Pan(s) shall have a minimum of 1 inch
slope towards the center of the unit or section. The center shall be defined as the
center of the instrument panel section(s) normally facing the operator. A gutter
shall be incorporated into the center of each pan which shall have a minimum of 2
inch slope from front to rear of the stand. The gutter(s) shall terminate with 1
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