Hydraulic fracturing connection assembly

A hydraulic fracturing connection assembly and a method comprises first 10 and second connector 20 portions having threaded 12, 22 pin and socket and a preload mechanism comprising a plurality of bores 15b and threaded fixings 16 in the form of jackbolts circumferentially spaced around the axis, wherein the preload mechanism is arranged to apply an axial load between shoulders 25 on the first and second connector portions when torque is applied to the threaded fixings. An annular sealing member 18/19 is compressed between the first and second portions, and the axial load applied between first and second shoulders by the preload mechanism exceeds a peak hydrodynamic load urging the first and second connector portions in a direction along the axis. The axial force applied by the preload mechanism reduces the fatigue damage experienced by the connection, for example, by cyclic pressure changes within the connector portions typically caused by pumps operating at high pressures.