Replacing the O-rings

Refer to Opening and closing the 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’s seal depends upon its O-rings, not the end-cap tightness. Therefore, proper O-ring maintenance is crucial.

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

O-rings on the RBRquartz³ APT

The RBRquartz³ APT instrument has a coupling piece, which connects the two halves of the instrument together. Each of the two joints uses two O-rings. One is the main O-ring, and the other is the backup. Both are required to protect the instrument from flooding.

screen shot 2022 03 24 at 2 01 32 pm
Fig. 8.    Location of the coupling piece on the RBRquartz³ APT
screen shot 2022 03 24 at 1 53 46 pm
Fig. 9.    Locations of the O-rings

Only the O-rings which were exposed during maintenance need to be checked before reassembly.

Inspecting the O-rings

Visually inspect each new O-ring for nicks and scratches before installing it. Pay attention to the following areas:

  • The surface of the O-ring itself

  • 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.

Orientation of 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.

screen shot 2021 10 14 at 9 56 04 am
Fig. 10.    Orientation of the O-rings (main O-ring, backup O-ring)

Replacing the O-rings

Do not use metal screwdrivers or any other metal tool! They may scratch the O-ring groove and render the end-cap useless.

  1. Use the plastic O-ring removal tool (included in the support kit) to remove the old O-ring from its groove. The O-ring may need to stretch quite a bit as it is pushed off. This requires some effort, but can be done by hand.

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

  3. Select a new O-ring and inspect it for damage.

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

  5. Install the main O-ring by pushing it into place and popping it into its groove.

  6. Install the backup O-ring, making sure the concave side is facing 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 end-cap.

  8. Remove electrical tape from the threads.

  9. Close the instrument.