Mode bolt operating instructions for the Pressure Vessel Laboratory.

The pressure vessel has $2$ testing modes.

Mode $1-$ Both Circumferential $($Hoop$)$ and Longitudinal cylinder stresses.

Unwind the mode bolt so it is not contacting the piston. In this position, the piston bottoms out on the cylinder end cap and the longitudinal forces are reacted by the cylinder.

Tighten the hydraulic pump release valve and pressurise the cylinder to $15$ MPa max.

Mode $2-$ Only Circumferential cylinder stresses.

With the hydraulic pump release valve open, wind in the mode bolt so that it contacts the piston, then wind a further $1$ to $2$ full turns so that the piston no longer contacts the end stop.

The longitudinal forces are now reacted by the mode bolt, the end plates and tie bars leaving only circumferential forces in the cylinder.

Piston force induces

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