Wringing capacity and wearability of block gauges

Wringing effect prevention on a piston design in a downhole drilling tool

“…6, the pressure in zones A and B was gradually ramped up from 0 to 18 k psi synchronously. The pressure in zone B was then increased while maintaining pressure in zone A; the separation force F Sep [see (6)] was subsequently slowly increased in a controlled manner to understand the threshold value when the piston began to move. During the process of increasing pressure in zone B, the valve of zone A was turned off, becoming a closed volume.…”

“…9, the pressure in zones A and B were gradually ramped up from 0 to 18 k psi synchronously. Then the pressure in zone B was increased while maintaining the pressure in zone A; as a result, the separation force F Sep [see (6)] was increased slowly in a controlled manner to understand the threshold value until the piston starts moving. Similar to the previous tests, the pressure changes in two zones are used as an indication of the evidence that the piston was moved by the separation force F Sep .…”

“…One design consideration is to eliminate the potential wringing effect on the contact surface between the moving and non-moving parts. Wringing has been widely observed in gauge blocks [6][7][8][9]. The surfaces of gauge blocks are ordinarily joined through light greasing, then adhesion with a pressing, twisting, and sliding motion known as 'wringing'.…”