TOOL FOR SAFE ASSEMBLY AND DISASSEMBLY OF OVERHUNG IMPELLER LOCKING NUT
Publication Date: 2015-Oct-12
The IP.com Prior Art Database
A tool for safe assembly and disassembly of an overhung impeller locking nut is disclosed The tool includes a cylindrical cage which is made up of a lower metal annulus and an upper metal disk with a hole in the middle The lower metal annulus and the upper metal disk are connected together by means of three metal poles A metal cylindrical socket is welded to upper disk hole facing towards inner of cage Lower annulus includes holes for pins that connect the lower metal annulus to the impeller During assembly after a tie rod is screwed in a head of a shaft and the impeller is inserted on the shaft the locking nut and a socket wrench are inserted on outer head of the tie rod Then the tool is assembled on the impeller by means of centering pins and connected to the tie rod outer head by means of a screw through a socket welded to upper disk hole During disassembly operations the tool is first assembled on the impeller and the tie rod in the same way as done during assembly operations
The present disclosure relates generally to an impeller of a compressor and more particularly to a tool for safe assembly and disassembly of an overhung impeller locking nut.
In many instances, a locking nut in an impeller of a centrifugal compressor scratches an impeller bore during screwing or unscrewing of the locking nut into the impeller bore. This may be due to impeller misalignment owing to weight of the impeller.
Moreover, during disassembly operations, while unscrewing the locking nut, the impeller tends to rotate. Consequently, the impeller disengages from a Hirth coupling and may even allow unscrewing of a tie-rod from a shaft head. In both instances, the impeller may fall and presents a risk of damage to impeller and injury to operators.
Conventionally, in order to prevent impeller rotation during unscrewing of the locking nut, the impeller is fixed by ropes, poles or even by hand for small ones. Further, the impeller bore requires to be centered on the tie-rod to allow easy screwing and unscrewing of the locking nut up to an impeller mating face. In conventional techniques, centering of the impeller bore depends completely on mechanical tolerances.
Impeller nose and bore damaged by the locking nut during screwing is not a rare event. However, such damage is accepted as the damage does not result in problems during regular operation of the impeller. Nevertheless, in recent times overhung impellers have grown in size and weight and therefore disengagement of the impeller has become a more serious challenge, especially safety consideration of operators.
It would be desirable to have a technique that prevents disengagement of impeller during overhung impeller assembly and disassembly.
BRIEF DESCRIPTION OF DRAWINGS
Figure 1 depicts a front view of an overhung impeller.
Figure 2 depicts assembly of the overhung impeller on a shaft by means of a tie rod.
Figure 3 depicts screwing of a locking nut on the tie-rod till impeller mating face, followed by insertion of a socket wrench on the locking nut.
Figure 4 depicts a tool having connection means to the tie-rod.
Figure 5 depicts assembling of the tool on the impeller.
Figure 6 depicts disengagement of the tool from the impeller.
A tool for safe assembly and disassembly of an overhung impeller locking nut is disclosed. The tool creates perfect centering of impeller bore on a tie-rod, thereby allowing easy screwing and unscrewing of the locking nut up to an impeller mating face.
In a centrifugal compressor, overhung impellers are fixed to a shaft by means of the tie-rod with a nut that locks overhung impeller assembly on impeller suction side. Figure 1 depicts a front view of the overhung impeller.
Figure 2 depicts assembly of the overhung impeller on the shaft by means of the tie rod.
During assembly, after the tie-rod is screwed in a head of the shaft and the impell...