O-rings

The single most important item of maintenance on any RBR submersible instrument is the care of the O-rings. Any water leak can damage the circuitry beyond repair and cause complete data loss. Every instrument seal depends upon its O-rings, not the end-cap tightness. Proper O-ring maintenance is crucial.

O-rings may crack when they are in very cold conditions or due to abrasive chemicals. If silt, which is a fine powder of clay or sand, is covering the instrument and O-rings, a slow leak can occur. O-rings may lose elasticity over time due to pressure, even when the instrument is not deployed.

The cost of an O-ring is negligible compared with the cost of the instrument and its deployment. Routine replacement of O-rings, therefore, is cheap insurance.

RBR recommends replacing the O-rings before every deployment. Use a small amount of silicone compound for lubrication, and the O-Rings should appear to be wet without having excess lubricant as this could entrap particles and cause leaks.

See the applicable RBR instrument guides for instructions on inspecting and replacing the O-rings on your instrument. 

O-ring types

Standard instruments in plastic housing: #2-225 N70 O-ring; standard instruments in titanium housing: #2-225 N70 O-ring, #8-225 N90 backup ring

Compact instruments (any housing): #2-115 N70 O-ring, 8-115 N90 backup ring