Working characteristics of high-performance diaphragm coupling

      Diaphragm couplings are one of the main types of non-lubricated couplings used in high-performance turbomachinery to transmit torque and adjust the misalignment between equipment shafts.These couplings rely on the bending of the metal film to accept angular and axial deviations.

      In the diaphragm coupling, the torque is transmitted radially from the outer diameter of the drive flange to the accessories at the inner diameter through one or more metal plates.The thickness of the diaphragm can be constant, it can be tapered, it can be flat, curled, or it can be spoked.The outer diameter of the diaphragm is usually fixed with bolts, and the inner diameter can be electron beam welds, splines or bolts.In a typical flange-flange connection of a diaphragm coupling, the torque mainly causes the bolt to be affected by shear stress.

         The ameriflex diaphragm coupling from zurn industries contains important life and safety factors.The coupled metal film is composed of thin, multiple, crimped and separated diaphragms.Each of these features provides benefits for the overall coupling design.The life of the diaphragm does not depend on the working angle within its design rating.

      The bending area is separated at the inner and outer diameters, and then clamped firmly.This separation prevents fretting corrosion caused by friction in the bending area associated with the multi-membrane coupling.Because there is no fretting, the designer can reasonably use the characteristics of raw materials and adopt the classic infinite-life engineering fatigue analysis method for diaphragm design.The reduction in the durability limit or reliability of the diaphragm material is not caused by fretting corrosion or abrasion in the bending area.In fact, the additional benefits of each individually peened diaphragm were not considered.

       Using appropriate stresses determined by finite element analysis and strain gage tests, Zurn can use any fatigue failure theory (such as goodman, modified goodman, or constant life) to accurately calculate the safety factor. Ameriflex coupling is a truly infinite life design, the service life of the diaphragm assembly is more than 20 years.In operation, this translates into predictable equipment maintenance and inspection intervals, regardless of coupling design ratings, environmental conditions, and angular and axial deviations in usage.

       If the ameriflex diaphragm coupling is excessively misaligned, causing fatigue failure, the crack will gradually expand due to the separation of the diaphragm's bending area.Eventually, when each diaphragm fails, the remaining diaphragm will shear at its inner diameter due to excessive torque.

      Most importantly, regardless of the cause of the failure, due to fatigue or peak overload, the inner diameter of the diaphragm will be sheared from the gasket or spool to prevent the power from being transferred from the driving equipment to the driven equipment.The instantaneous load loss will cause the standard turbomachinery to overspeed trip.After shear failure, the anti-flail protection device of the Ameriflex coupling includes a central part to ensure safety and protect adjacent equipment.