Prediction method based on strain monitoring for thread root crack in high pressure hydraulic fracturing manifold

• Potential fatigue crack detection method for high pressure manifold joints based on strain analysis. • The strain distribution of non-threaded part under different internal pressures was analyzed. • The regular variation of strain concentration coefficient in non-threaded part was studied. There is a high stress concentration at the connection threads of high-pressure manifolds. Under the action of internal pressure(P int ) and rapid vibration, the root of the thread is prone to fatigue cracking. To study the variation in the damage of a high-pressure manifold with connection threading, this paper first analyzed the strain of the manifold with different P int and with or without defects at different positions on the outer wall shaft. The potential fatigue crack damage of a high-pressure manifold of a hydraulic fracturing truck was monitored and analyzed by strain testing technology. The variation of the strain signals of defected and defect-free high-pressure pipe fittings were compared. The damage stress concentration point of the connection thread of the high-pressure manifold was analyzed. When there is a crack at the root of the thread, results show that there is a large difference in strain in the axial direction of the crack compared to the strain in threading thread without a crack. Meanwhile, the strain concentration coefficients of different stress concentration points change regularly. In this paper, the damage state of the thread is analyzed by strain monitoring. The results can provide a theoretical and practical basis for the prediction of root cracks in connection threads.