Shaft to impeller integrity determination in assembled pumps by remote sensing

• US 4,805,457 A
• Filed: 05/28/1987
• Issued: 02/21/1989
• Est. Priority Date: 05/28/1987
• Status: Expired due to Fees

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Sundaram, Swaminathan H., Oates, James H., Liu, Lun K., Tafarrodi, Hassanali
• Primary Examiner(s): Levy, Stewart J.
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US07/054,930
• Time in Patent Office: 635 Days
• Field of Search: 73/579, 73/583, 73/572, 73/659, 73/660, 415/118, 416/61, 376/245
• US Class Current: 73/572
• CPC Class Codes: G01M 7/08 Shock-testing

Abstract

In the test of a casing enclosed shaft and impeller for structural integrity against defects such as loose bolts or cracks, an apparatus and process is disclosed which enables in-situ testing to occur within a casing. A model of the shaft and impeller, such as a spare part, is suspended so as to simulate the in casing boundary conditions and is then vibrated. Vibration or "ringing" occurs through a normally exposed end of the shaft far removed from suspected defects. A cap can be used to suspend the shaft and impeller or rotor. Vibration is imparted to the remote end of the shaft, sometimes on the cap, with an instrumented hammer blow of specific duration and known energy. Measurement and resolution of the resultant vibrations and energy dissipating damping occurs by mounting accelerometers to the remote normally exposed shaft end and recording and playing back the vibrations from the mounted accelerometers through a spectrum analyzer. Defects are created on the suspended model and the vibration signatures recorded. Thereafter, the same test is conducted on the casing enclosed suspect shaft and impeller or rotor and the vibrational signature obtained in the rotor matched to the model generated vibrational signature. Prediction of either intact structural integrity or defect is made on the basis of the comparison of measured vibrations. A simultaneous technique of computer modeling the vibrations is disclosed which enables expansion of actual test results to defects outside those specific signatures obtained from the model testing.

Claims

1. A process of testing a casing-enclosed shaft and impeller without removal of said shaft and impeller comprising the steps of:

placing said casing-enclosed shaft and impeller in a static condition;

suspending the casing-enclosed shaft and impeller in the casing;

observing said suspended casing-enclosed shaft and impeller as suspended relative to said casing and noting the boundary conditions of said suspension;

suspending a model of said shaft and impeller exterior of a casing and duplicating said observed boundary conditions of suspension;

vibrating said model as suspended with said duplicated boundary conditions of suspension;

simultaneous with said vibrating of said model reproducing suspected defects of said suspended casing-enclosed shaft and impeller on said model of said shaft and impeller;

analyzing the vibrational signature of said model of said shaft and impeller and correlating said signature to said reproduced defects;

vibrating said suspended casing-enclosed shaft and impeller without disassembly,

analyzing the vibrational signature of said casing-enclosed shaft and impeller; and

,

correlating the vibrational signature of said model of said shaft and impeller to the vibrational signature of said suspended casing-enclosed shaft and impeller to determine the structural integrity of said suspended shaft and impeller.

2. The process of claim 1 and wherein said suspending a model step includes suspending a spare part of said casing-enclosed shaft and impeller.

3. The process of claim 1 and wherein said vibrating steps includes impacting with an instrumented hammer.

4. The process of claim 1 and wherein said vibrating steps include the steps of vibrating at natural frequencies.

5. The process of claim 1 and wherein said vibrating steps include vibrating said shaft remote from said impeller or rotor to detect defects in the vicinity of said impeller or rotor.

6. The process of claim 1 and wherein said process includes the step of constructing a model of said shaft and impeller or rotor.

7. The process of testing a casing-enclosed shaft and impeller without casing disassembly, said shaft and impeller of the type having an overlying motor for rotating a shaft and a shaft attached impeller enclosed within a casing, said shaft connected to said motor by a coupling, said process comprising the steps of:

placing said casing-enclosed shaft and impeller, in a static condition;

removing said coupling;

suspending said shaft and impeller from said motor relative to said casing and observing said casing-enclosed shaft and impeller boundary conditions of suspension;

suspending a model of said shaft and impeller exterior of said casing and duplicating said observed casing-enclosed shaft and impeller boundary conditions of suspension;

vibrating said model as suspended with said duplicated casing-enclosed shaft and impeller boundary conditions of suspension;

simultaneous with said vibrating of said model reproducing suspected defects of said casing-enclosed shaft and impeller on said model of said casing-enclosed shaft and impeller;

analyzing the vibrational signature of said model of said casing-enclosed shaft and impeller and correlating said signature to said reproduced suspected defects;

vibrating said suspended shaft and impeller of said casing-enclosed shaft and impeller without removal from said casing; and

,

analyzing the vibrational signature of said suspended casing-enclosed shaft and impeller; and

,

correlating the vibrational signature of said model to the vibrational signature of said suspended casing-enclosed shaft and impeller to determine the structural integrity of said casing-enclosed shaft and impeller.

8. The process of claim 7 and wherein said suspended model is a spare part of said casing-enclosed shaft and impeller.

9. The process of claim 7 and wherein said step of suspending said shaft and impeller from said motor relative to said casing occurs after vibration of said model.

10. The process of testing a casing-enclosed turbine without turbine disassembly, said turbine of the type having a turbine shaft and shaft attached rotor without a casing, said shaft connected to said rotor by a coupling, said process comprising the steps of:

placing said turbine, including said casing-enclosed shaft and rotor, in a static condition;

removing said coupling;

suspending said casing-enclosed shaft and rotor of said turbine from said generator relative to said casing and observing said turbine boundary conditions of suspension;

suspending a model of said shaft and rotor exterior of said casing and duplicating said observed turbine boundary conditions of suspension;

vibrating said model as suspended with said duplicated turbine boundary conditions of suspension;

simultaneous with said vibrating of said model reproducing suspected defects of said turbine shaft and rotor on said model of said turbine shaft and rotor;

analyzing the vibrational signature of said model of said turbine shaft and rotor and correlating said signature to said reproduced suspected defects;

vibrating said suspended casing-enclosed shaft and rotor of said turbine without removal of said casing; and

,

analyzing the vibrational signature of said shaft and rotor of said turbine; and

,

correlating the vibrational signature of said model of said shaft and rotor to the vibrational signature of said suspended casing-enclosed shaft and rotor of said turbine to determine the structural integrity of said casing-enclosed shaft and rotor of said turbine.