Research On Failure Mechanism Of Cold Cylinder In Mud Pump On Offshore Drilling Platform

Drilling mud pump is compared to―heart‖of the drilling system. When in the operate ofusing rotary drilling method to drill oil and gas wells, drilling mud pump is used for pumpingdrilling mud to wash the wells. Mud pump cold cylinder as one of the main components ofmud pump, its failure lead to the mud pump disabled directly, it not only makes drillingoperation been forced to shut down, and cause huge trouble and loss to engineering, but alsogenerate huge safe hidden trouble to the drilling personnel. The research on drilling mudpump cold cylinder cracking failure mechanism has the important value of engineeringapplication and safety prevention.This research on failure mechanism of cold cylinder in mud pump on offshore drillingplatform is based on material conditions, environmental conditions and stress conditions, andstudied by the technological means of physical and chemical testing and finite elementnumerical simulation.First, through the physical and chemical testing of the mud pump cold cylinder material,it can conclude that the material of cold cylinder’s base metal and welding fusion zonematerial has high hardness and strength, and its toughness and plasticity are not meet therequirements, it reduces the metal’s ability to resist deformation, brittle fracture andintergranular corrosion. The poor welding quality and improper heat treatment cause a lot ofwelding porosity and slag in welding area material, it lead to the bad material mechanicalproperties.Second, by the chemical analysis of drilling mud medium, it can conclude that thedrilling mud’s alkaline conditions and it rich in carbonates and halogen ions may lead to lowalloy steel and high Cr-Ni alloy steel takes place stress corrosion cracking. The rich halogenions also easy cause corrosion on cold cylinder runner surface and intergranular corrosion ofmaterials.Thirdly, through the finite element numerical simulation analysis of the cold cylinder, itcan conclude that under the condition of normal working load, the cold cylinder’s wordinginternal stress is well below the cold cylinder’s material yield strength. In welding parts ofcold cylinder, the residual stress of the smaller flow diameter and variable diameter runnersurface is up to494.38MPa, which constitutes the stress condition to the cold cylindercracking.Comprehensive analysis shows that under the combined action of the material factors,environmental factors and stress factors, The cold cylinder occurs stress corrosion cracking. The cracks originate in the stress concentration areas of the weld defects part, and extendalong the runner path.Finally, on the basis of the three factors which lead to the mud pump cold cylinder stresscorrosion cradking, from material heat treatment, medium purification and cold cylinderstructure optimization to put forward proposal to avoid or reduce the mud pump cold cylinderstress corrosion cracking.