COBHAM SEA TEL 9711IMA-70, Руководство по установке

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Site Survey 9711IMA-70
2-2
2.3. Mounting Foundation
2.3.1. Mounting on Deck or Deckhouse
While mounting the ADE on a mast is a common solution to elevate the ADE far enough above the
various obstructions, sometimes the best mounting position is on a deck or deckhouse top. These
installations are inherently stiffer than a mast installation as the design of the deck/deckhouse structure is
prescribed by the ship’s classification society. In the deck/deckhouse design rules, the minimum plating
and stiffener guidelines are chosen to preclude high local vibration amplitudes.
Most installations will have a base frame with multiple attachment points around the perimeter of the
base frame to mount the ADE onto a deck or deckhouse structure of the ship. The base frame may be
mounted using the supplied legs & braces to raise the ADE above the deck for radome hatch access. The
base frame may be directly attached to the deck, in which case the access panel in the floor of the base
frame cannot be utilized. In this case, the installation must allow acces through a door in one of the side
panels or an access opening directly under the hacth. Some care must be taken to ensure the mounting
pedestal is properly aligned with the stiffeners under the deck plating.
Alternately, a specifically designed and stiffened mast may be used to mount the base frame above the
deck; although, this should only be attempted if sufficient deck space high on the ship is not available.
2.3.2. ADE Mounting Considerations
Mounting the radome directly on the deck, or platform prevents access to the hatch in the base of the
radome unless an opening is designed into the mounting surface to allow such entry. If there is no
access to the hatch the only way to service the antenna is to remove the radome top.
Ladder rungs must be provided on all mounting stanchions greater than 3-4 feet tall to allow footing for
personnel safety when entering the hatch of the radome.
The recommended cable passage is through the bottom (near center) of the radome base, down through
the ADE support pedestal (if used), through the deck and into the interior of the ship.
2.3.3. Sizing of the support pedestal
The following should be taken into account when choosing the height of a mounting support stand:
1. The height of the pedestal should be kept as short as possible, taking into account
recommendations given in other Sea Tel Guidelines.
2. The minimum height of the pedestal above a flat deck or platform to allow access into the
radome for maintenance should be 0.6 meters (24 inches).
3. The connection of the ADE mounting plate to the stanchion and the connection of the pedestal
to the ship should be properly braced with triangular gussets (see graphic above). Care should
be taken to align the pedestal gussets to the ship’s stiffeners as much as possible. Doublers or
other reinforcing plates should be considered to distribute the forces when under-deck
stiffeners are inadequate.
4. The diameter of the pedestal stanchion shall not be smaller than 100 millimeters (4 inches).
Where the ADE base diameter exceeds 1.5 meters (60 inches), additional stanchions (quantity
greater than 3) should be placed rather than a single large stanchion.
5. Shear and bending should be taken into account in sizing the ADE mounting plate and
associated gussets.
6. Shear and bending must be taken into account when sizing the pedestal to ship connection.
7. All welding should be full penetration welds –V-groove welds with additional fillet welds – with
throats equivalent to the thickness of the thinnest base material.
8. For an ADE mounted greater than 0.6 meters (24 inches) above the ship’s structure, at least one
(1) foot rung should be added. Additional rungs should be added for every 0.3 meter (12
inches) of pedestal height above the ship’s structure.
9. For an ADE mounted greater than 3 meters (9 feet) above the ship’s structure, a fully enclosing
cage should be included in way of the access ladder, starting 2.3 meters (7 feet) above the ship’s
structure.
2.4. Mounting Height and Fore-Aft Location
Installations with mast or deck vibrations at frequencies between 2 and 15 Hertz have been identified by Sea Tel
as causing problems with the isolation systems of the ADE. Preventing problems prior to installation due to these
vibrations is one of the primary considerations in choosing where to mount the antenna.
In some installations, though, the combination of mounting height, fore-aft location and ship motion can impart
significant accelerations on the entire ADE. Installations where the ADE is situated high on the ship – usually at
the top of a mast – places the ADE is a position where the low frequency ship motion in roll and/or pitch creates
EAR Controlled - ECCN EAR99