Sea Tel ST88-21 C/Ku-Band TVRO, Installation And Operation Manual

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Site Survey ST88-21 C/Ku-Band TVRO
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.