Measuring and testing – Dynamometers – Responsive to force
Reexamination Certificate
2000-10-13
2002-03-26
Noori, Max (Department: 2855)
Measuring and testing
Dynamometers
Responsive to force
Reexamination Certificate
active
06360616
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
None
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
Not applicable
BACKGROUND OF THE INVENTION
The present invention relates generally to the monitoring of rotating equipment (e.g., pumps, vertical motors, compressors, turbines, and the like) for minimizing operating failures and more particularly to a system that continuously monitors the thrust (i.e. axial, and optionally radial, in direction) force (and, optionally, operating temperature and/or vibration) applied to the thrust bearings of rotating equipment.
Within industrial equipment generally there exist many examples where notification of impending bearing failure in equipment can reduce the possibility of a catastrophic result such as, for example, fire, explosion, the release of poisonous gases or fluids, potential human injury, and/or loss of life. Generally, such catastrophic results can occur because, in centrifugal pump applications, thrust bearing failure, deterioration, or misapplication can cause failure of the mechanical seals allowing loss of fluid.
Within the petrochemical industry in particular, there is a requirement to measure the axial load magnitude and direction (and, optionally, radial load and magnitude) on, and enhance the measurement of operating temperature and vibration characteristics of, the bearings being utilized in pumps, and to allow this information to be used for bearing and pump design, lubrication selection, lubrication change intervals, and system optimization. There also is the requirement to accurately predict bearing replacement prior to complete bearing and/or mechanical seal failure.
The petrochemical industry requires (per API and/or ANSI specifications) that the bearings in use be of a specific type and size for given applications. These required bearings tend to be angular contact ball bearings (typically either single row angular contact bearings mounted back-to-back, face-to-face or in tandem with each other; or double row angular contact ball bearings). These bearings are of relatively large size and are intended to be used on large diameter shafts, because of the need to minimize shaft deflection, which is detrimental to mechanical seal performance and life. Because of the typically high operating speed (e.g., 3,600 rpm) and large diameter bearings, it can be equally catastrophic for the bearings to be under-loaded as well as over-loaded. Thus, the plant operators place a premium on being continuously aware of these loads, temperatures, and vibrations during the bearings' operation. The historical accumulation of this data will assist in future bearing selection, lubrication selection (and for the calculation of how long the lubrication will last until it breaks down and becomes ineffective), system design (e.g., impeller design, piping layouts, etc.), system optimization, shaft alignment verification, and planned maintenance cycles.
Presently, bearing failure in industry can be anticipated to some degree by using temperature and/or vibration sensing of the mechanical environment adjacent to the bearings. Both of these methods of preventing bearing failure have an inherent problem and are of only limited value, i.e., these methods provide no force measurement, no automated feedback, no automated application assistance, and typically are not continuously monitored, etc.). Currently, the bearings sit in an environment in which they are not mechanically isolated from the bearing housing. This allows bearing vibration effects to be absorbed (i.e., changed and/or masked) by the mass of the bearing housing and support structure. For a period of time, the mass of the housing, being significantly larger and with more surface area than the bearings, absorbs, dissipates, and, therefore, masks the heat generated by improperly operating bearings. This bearing housing affect shortens the window of time in which a control system and/or operator can react to the change in the bearing performance and avoid a failure. An uncontrolled bearing failure has ramifications that include high repair cost (because of multiple component interactions), production loss, liability, and human/environmental exposure. In many industrial environments, e.g., a petrochemical plant, equipment and production losses can be high, not to mention worker safety put at risk and the potential for environmental damage.
Heretofore, U.S. Pat. No. 5,503,030 proposes a load sensing bearing comprised of a load measurement in roller bearings that is carried out by sensors arranged to measure forces applied to the bearing, and which communicates with the circuitry for recording, processing, and evaluating the signals from the sensors. U.S. Pat. No. 5,796,349 proposes a system and method for monitoring wear of an axial bearing comprised of a centrifugal pump, wherein if a drive motor is provided with an energy monitoring circuit, then an operator can detect the change in the load. U.S. Pat. No. 5,846,056 proposes a reciprocating pump system and method for operating the same, comprised of a control circuit that continually determines the average cylinder pressure and estimates the pump life. U.S. Pat. No. 4,584,865 proposes a device and method for testing a motor bearing wear, where the displacement of a rotating element causes wear of the coating which reduces its thickness and decreases resistance between the sensing elements through which the coating is measured.
Despite these proposals, there still exists a strong need in industry to be able to continuously monitor applied forces, especially axial thrust, of rotating equipment and to have an enhanced means of measuring temperature and vibration. It is to such need that the present invention is addressed.
BRIEF SUMMARY OF THE INVENTION
The invention is a system for measuring the thrust, and optionally radial, loads placed on a support thrust bearing assembly that supports a rotating shaft in an apparatus. The system includes an apparatus housing and a load isolation member that supports the support thrust bearing. The load isolation member is not directly in contact with the apparatus housing. A force sensor is disposed between the apparatus housing and the load isolation member such that axial (and, optionally, radial) loads are permitted to be transmitted by the load isolation member from the support thrust bearing assembly and are measured by the sensor.
One embodiment of the inventive system includes an apparatus housing and a load isolation member that supports the support thrust bearing. The load isolation member is not in contact with the apparatus housing. A linear bearing assembly is disposed between the load isolation member and the apparatus housing. A force sensor is disposed between the apparatus housing and the load isolation member such that axial loads are permitted to be transmitted by the load isolation member from the support thrust bearing assembly and are measured by the sensor.
The corresponding method for measuring the axial (and, optionally, radial) load placed on a support thrust bearing assembly that supports a rotating shaft in an apparatus includes providing an apparatus housing and a load isolation member supporting the support thrust bearing. The load isolation member is disposed such that it is not in contact with the apparatus housing. A force sensor is disposed between the apparatus housing and the load isolation member. Axial (and, optionally, radial) loads placed on said support thrust bearing assembly are measured with said force sensor.
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patent: 4472107 (1984-09-01), Chang et al.
patent: 4782696 (1988-11-01), Suchoza et al.
patent: 5527194 (1996-06-01), Strong et al.
patent: 5760289 (1998-06-01), Skottegard
patent: 6199425 (2001-03-01), Lee
Halliday Donald R.
Rice Donald W.
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