Vibration Isolated Television Frame (VIT)
Description
The Vibration Isolated Television (VIT) frame is primarily used to provide visual observation of the sea floor during reentry of an existing borehole. Sonar capability, primarily used to locate objects such as reentry cones which are initially out of camera range, is and integral part of the system. The sonar, in conjunction with a compass attached to the VIT frame, provides primary range and bearing from the VIT frame to the reentry cone. An acoustic beacon can be attached to the VIT frame which allows the ships dynamic positioning system computers to fix the position of the VIT frame relative to the ship.The VIT frame is deployed by latching its guide sleeve around the drill string. The drill string is used as a guide as the VIT is lowered to the sea floor by means of an armored coaxial cable attached to a special winch located in the ships moonpool area. Power is transmitted down the coaxial cable to operate the underwater lights, camera and sonar. The TV and sonar signals are then transmitted up the coaxial cable for display and recording on board the ship.
The VIT can also be used to precisely locate spudding sites. Once located, the sites
can be marked by dropping an identifying marker from the VIT frame itself, via an
acoustic release.
Specifications
- Design Features
- Underwater Lights
- Remote Video Camera
- Telemetry System
- Sonar Head
- Remote Video Camera
Specifications
Depth Rating: 22,500 ft (10,000 psi)
Operating Temperatures: -20 degrees C to +60 degrees C (-68 degrees F to + 140 degrees F)
Shock Rating: 100 G's @ 11 milliseconds, 3 axis
Umbilical Cable: double armored coaxial
Design Features
Underwater Lights:
Lamps: 100 & 250 watt quartz halogen, w/reflectors 2000 hrs. avg. rated life, 5000 lumens output
Beam pattern: 60-70 degree field of view in water, 20-40 foot range
Power: 120 volt AC
Type: Videospection SIT (high sensitivity)
Power: -15 VDC
Video Output: 1VPP negative sync composite video, 75 ohm
Weight: 28 lbs.
Light Sensitivity: .001 candlepower, low level (star light)
Type: TVTM-3015 (CSE) Colmek Systems Engineering
Control: zoom control signals are telemetered to the unit.
Cable Power: Surface: voltage is stepped up to 480VAC, Subsea: voltage is stepped down to 120VAC
Weight: Multiplexer, 212 lbs
Line voltage: 120 VAC +/- 10%, 60 Hz (at the surface)
Subsea Power: subsea TVTM 8.4 watts, 590 watts available to operate camera & lights.
Video resolution: ~300 TV lines horizontal
Type: Simrad Mesotech, model 971
Frequency: 675 kHz
Beam Width: 1.7 degrees horizontal, 60 degrees vertical
Mechanical Resolution: 0.225 degree (step angle)
Scanning: 360 degrees continuous, or locked
Connector: DG O'Brien 9 pin
Cable: DG O'Brien oil filled assembly
Dimensions: 3.5 in (89 mm) dia, ~ 60 in long
Weight: ~75 lbs (in air), ~50 lbs (in water)