Replacing the O-rings

Refer to Opening and closing a compact instrument for details on accessing the O-rings.

The O-ring removal tool and silicone compound are available in the support kit.

Care for the O-rings is the single most important item of maintenance on any submersible RBR instrument. A water leak can damage the circuit board beyond repair and cause complete data loss. Every instrument seal depends upon its O-rings; therefore, proper O-ring maintenance is crucial.

The O-rings may lose elasticity over time, even when the instrument is not deployed. RBR strongly recommends replacing the O-rings regularly.

To access the O-rings, open the instrument.

RBR compact instruments use two O-rings. One is the main O-ring, and the other is the backup. Both are required to protect the instrument from flooding.
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Fig. 18.    Location of the O-rings: main O-ring (left), backup O-ring (right)

Inspecting the O-rings and mating surfaces

Visually inspect the O-rings, paying attention to the following areas:

  • The surface of the O-ring itself should be smooth and free of nicks or damage

  • The mating surface on the inside of the case between the threads and the open end

  • The groove in the end-cap where the O-ring sits

When handling the O-rings:

  • Avoid using any object that could scratch the O-ring or any of its mating surfaces.

  • If dirt is present in the O-ring groove, remove the O-ring as described below and thoroughly clean the groove.

  • Do not return this old O-ring to the instrument! If you remove the O-ring from the instrument for any reason, always replace it with a new one.

  • If the surfaces of the O-ring groove are scratched, pitted, or damaged, contact RBR for advice.

Replacing the O-rings

Correct placement and orientation of the two O-rings are critical to maintaining depth rating integrity.

The main O-ring has a round profile. It must be installed first.

The backup O-ring is flat on one side, and concave on the other. When installed, the concave side must face the main O-ring.
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Fig. 19.    Orientation of the O-rings: main O-ring (left), backup O-ring (right)

  1. Use the plastic O-ring tool (included with the support kit) to remove the O-rings from the groove. The O-ring may need to stretch quite a bit as it is pushed out; this requires some effort but can be done by hand.

  2. Clean the groove thoroughly using a soft, lint-free cloth and compressed air if necessary.

  3. Select the proper O-rings and inspect them for damage.

  4. Lubricate with a very light film of silicone grease (included in the support kit).

  5. Install the main O-ring by sliding it over the electronic housings and popping it into its groove.

  6. Install the backup O-ring, ensuring that the concave side is facing toward the main O-ring.

  7. Once in place, inspect the O-rings once more for scratches and debris, and wipe away any silicone compound deposited on the carriage.

  8. Once the inspection is complete, close the instrument.