Equipment Maintenance Part 3–Replacing the Internal 'O' Ring on the Ram in a Triaxial Cell
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.
To perform this equipment maintenance procedure the following tools will be required:
Allen Key set
Small Screwdriver or hooking device
silicon or PTFE grease NOT mineral based
- Circlip Pliers (for Triaxial Cell 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).
Undo the 4 bolts holding the internal load cell ball seat to ram coupling (Figure 6).
Remove top half of the ball seat to ram coupling (Figure 7).
Remove the external circlip using circlip pliers (Figure 8).
Slide the collar back over the cable (Figure 9).
Remove the Transducer bracket (Figure 10).
Pull out the Internal Submersible Load Cell with its cable (Figure 11).
Remove the four screws holding the Ram boss cover (Figure 12).
Slide off the Ram boss cover (Figure 13).
Push back through and remove the Ram boss from the cell (Figure 14).
The Internal ‘O’ Ring is located inside the Ram boss (Figure 15).
Remove the internal ‘O’ Ring and replace with a new one (Figure 16).
Put a smear of synthetic grease on the internal ‘O’ ring and also the external one. Push the Ram boss back through, ensuring it is
tight against the top of the cell (Figure 17).
Reassemble the cell in the reverse order from that described above to complete the job.
Fill and pressure test the cell before attempting any soil testing.
Contact VJ Tech For Further Information
If you experience any problems when following these equipment maintenance instructions then please contact a member of the team and we
will be happy to help.
Contact us if you require any more information with any of our equipment maintenance blogs, please call: +44 (0) 118 945 3737