Benthic elevators

The “general use” benthic elevator

Overview

The “general use” benthic elevator provides a large cargo area for transporting experiments to the seafloor. The floatation can be adjusted for payload, however the large surface area can also be affected by strong currents.

Payload Limits

  • Total in-air weight limit is 2500 pounds. This is set by the largest shackle that fits into the lift point’s ¾-inch pin.

Important: This is the limit established for the lifting bale.  Exceeding this is a safety issue which may endanger the deck personnel.

  • Drop weights in air: 300 pounds.
  • Payload air weight limit: 700 pounds.
  • Payload in-water weight limit: 300 pounds.Note: This is calculated with 60 pounds of net buoyancy for recovery.
  • The elevator carries (2) double-railroad rail drop-weights. Each weighs 150 pounds in air and 130 pounds in water. One drop weight can be loaded on each side of the elevator.
  • Use the general use elevator worksheet to determine elevator weights.

General Use Elevator Dimensions

  • The cargo basket interior dimensions: Width: 5 feet, 9 inches.
  • Side space: 3 feet on each side.
  • Depth: 20 inches.
  • Height: 7 feet.
  • Width: 6 feet, 8 inches.Length: 7 feet, 10 inches.
  • Bare elevator tare weight (without floatation): -300 pounds in air, -170 pounds in water.

Note: This includes the weight of the frame, beacons and hardware. This weight will vary when components such as rigging and additional hardware are added.

Example

With 16 cu ft of syntactic foam, the elevator has an in-air weight of -915.8 pounds without any payload.  The addition of the required anchor (-375# air) brings that total to -1290# in air.  The addition of 1200# of payload brings the in-air total weight very close to the 2500# limit.

In water, the empty elevator has approximately +281.65 pounds of lift. A 375# in-air (steel) / (326.25# in water) anchor will provide -44.6# net weight to keep the elevator on the bottom. The addition of -250# in-water weight of payload will leave + 31.65# of lift to bring the elevator back to the surface once the anchor is released.  This is a minimal amount of lift and may lengthen the time for the elevator to reach the surface.

For additional information, contact the Marine Operations Technician.

Elevator use guidelines

If your cruise requires the use of an elevator, please supply the following information to the Marine Operations Technician (MOT) two weeks prior to the beginning of your cruise:

  • Total payload: Weights will be needed in air and in water for all components you plan to send down or bring up on the elevator.
  • Will the components remain on the elevator or will they be removed at some point? This will determine how much weight will be needed to keep the elevator on the bottom. In most cases special rigging will need to be considered  if the equipment will not remain on the elevator.
  • Which ship will be used to deploy and recover the elevator? Elevator deployment and recovery operations are unique to each ship. Please provide two weeks notice to the MOTs to allow adequate time to work out deployment and recovery issues with the ship’s crew.
  • Are the drop weights going to be recovered? If the elevator is going to be deployed in a Marine Sanctuary we are required to recover the drop weights. If the drop weights are going to be recovered they will be rigged with a yellow poly line for the ROV to pick up. If the weights are not going to be recovered, (I.e.: rust away), then we do not want to leave “plastic” poly line behind. Also, if the drop weights are not going to be recovered, replacements will need to be fabricated.

Custom elevators may be available or built – contact the Marine Operations Technician.

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