Tether
Tether connects the ROV to the surface and provides power, communications, video and an APIC (Auxiliary Pair of Independent Conductors) for accessory use. The tether consists of conductors, a Kevlar® strength member, flotation (for Neutral and Performance tethers) and an outer jacket. It is available in three types: Negative, Neutral and Performance (often called PPT). Neutral and Performance are neutrally buoyant in fresh water because they have a specially designed foam jacket.
While larger conductors provide the best power transmission capacity, they lead to thicker tethers, which results in higher drag. Negative tether has the largest conductors (best power transmission capacity), followed by Neutral, and then Performance. Negative and Performance tether have the smallest diameter (least drag), while Neutral tether has the largest diameter.
The tether connectors are wet mateable and can be connected while they are wet. One of the pins in the connector is offset. To connect the tether to the ROV, control panel or another tether, align the offset pin of the connectors and press the two connectors together until the base surface of each connector are touching each other. Then, connect the tether locking sleeves by screwing them together to secure the connection.Multiple tethers can be connected in series like conventional power extension cords. See the Tether Management section of the Operations Guide for recommended tether configurations.
For the ROV and tether to tether connections, there is a strain relief system that consists of a cable and carabineer. The strain relief system should be used to avoid separation and loss of the ROV.
The strain relief carabineer can get hooked on something underwater and cause the ROV to become trapped. To avoid this possibility, tape over the carabineer with electrical or duct tape.
Tether Specifications
Strength - while the Kevlar is rated at 450 kilograms (1000 pounds), the connectors are rated 80 kilograms (175 pounds).
These values are breaking strength. The tether should not be subjected to a working strength greater than one half of the breaking strength. The ROV and tether are equipped with a strain relief cable and connectors, which are rated at 136 kilograms (300 pounds). The strain relief cable should be used to avoid separation of the tether connectors and loss of the ROV.
The maximum tether length is limited by the ability of the tether to transmit power and data signals. The maximum tether length of the Pro 4 is about 600 meters (2,000 feet).
Tether Diameter
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Tether Conductor Pin Configuration
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Always secure the tether connectors using the locking sleeves and strain relief system to avoid separation and loss of the ROV.
The tether connectors should be kept clean to avoid abrasion and corrosion on the electrical contacts and damage to the rubber insulation. Tether connectors should not be lubricated with petroleum products or grease. Petroleum will degrade the rubber and grease will attract dirt and lead to abrasion and corrosion. VideoRay recommends lubricating the tether connectors with pure silicone spray.
Kevlar is a registered trademark of E. I. du Pont de Nemours and Company
