Equipment Maintenance Part 3 - Replacing the Internal O Ring on the Ram in a Triaxial Cell

Equipment maintenance
checks are vital to ensure the risk of potential problems is significantly reduced. Part three explains how to replace the internal Ram ‘O’ Ring in a
standard Triaxial Cell, as well as one fitted with an internal load cell.

Standard Triaxial Cell

Remove top section from the valve base using the 3 hand screw knobs (Figure 1) to enable the cell to be worked on a bench.

Remove the three M8 Domed nuts securing the cell top (Figure 2).

Gently prise cell top away from the ‘O’ ring seal and Perspex chamber. The ‘O’ ring and groove should be thoroughly cleaned before re-assembly.

Remove the Ram assembly from the boss by removing the knurled ring at the top of the Ram (using an Allen key to undo the grub screw) (Figure 3).

From the underside of the cell top locate the 15.5mm sealing ‘O’ ring which should be visible inside the ram boss. A very small screwdriver or hooking device may be necessary to tease the ‘O’ ring out of the groove (Figure 4).

Clean the groove as thoroughly as possible.Smear a small amount of Synthetic silicon or PTFE grease around the groove and new ‘O’ ring, before
easing the new ‘O’ Ring into the groove.

Re-assemble the RAM and knurled ring, gently turning the ram as it is pushed through the boss (this helps to bed in the ‘O’ ring).

Re-assemble the cell top, again using a small amount of silicon or PTFE grease around the groove and ‘O’ ring. Take care to ensure it remains in the groove
when the cell top is positioned onto the perspex chamber at each end.

Re-fit to cell base and then fill and pressure test the cell before attempting any soil testing.

Triaxial Cell fitted with Internal Load Cell

Remove the Base by unscrewing the tie rods and lay the Triaxial Cell top on its side so that it is supported (Figure 5).