CommScope ConQuest Conduit Construction - Manual (Page 37)

Underground Installation Methods 4.19
Submarine Installation
So How Much Weight is Needed?
To calculate the weight needed to overcome buoyancy the appropriate displacement volume is first multiplied with the
appropriate weight per cubic foot of water to obtain the gross buoyancy of the conduit.
The next step is to factor in the weight of the conduit and the cable, which will offset some of the buoyancy. Conduit
weights can be found in the specifications section. Cable weights for CommScope cables can be found in the cable
catalog. Subtract the per foot weight of the conduit and the cable from the gross buoyancy to obtain the net buoyancy.
The Answer…
In slow moving or non-tidal waters where there is no prop-wash or dragging anchors, multiply the net buoyancy per foot
by 4 times to obtain the anchor weight.
In fast moving and tidal waters, multiply the net buoyancy per foot by 10 times to obtain the anchor weight.
What to Use…
Buoyancy compensation can be accomplished using:
• Class C type galvanized strand(s) lashed to the conduit with dielectric lashing to retard corrosion
Or by anchoring with:
• Cinder blocks
• Concrete bags
• Sand bags
Placement of the weight must be equally distributed and meet minimum interval requirements to prevent the buoyant
sections of conduit from bowing between anchor locations. Spacing is dependent on the expected turbulence of the
water. In fast moving and tidal waters, anchor weights should be spaced in the shorter recommended interval.
The appropriate interval of anchor weights for conduit sizes 1.25” and smaller is 2 - 3 feet. At 2 foot intervals the anchor
weight is multiplied by 2 for each anchor. At 3 foot intervals the anchor weight is multiplied by 3 for each anchor.
The appropriate interval of anchor weights for conduit sizes 1.50” and larger is 3 - 4 feet. At 3 foot intervals the anchor
weight is multiplied by 3 for each anchor. At 4 foot intervals the anchor weight is multiplied by 4 for each anchor.