Predictive-Maintenance.org

originally posted by Sanjay B. Chari.

In the pump business alignment means that the centerline of the pump is aligned with the centerline of the driver. Although this alignment was always a consideration with packed pumps, it is critical with sealed pumps especially if you are using rotating seal designs where the springs or bellows rotates with the shaft.

A little misalignment at the power end of the pump is a lot of misalignment at the wet end, and unfortunately that is where the seal is located in most pump applications.

Misalignment will cause many problems:

By John P. Cook, Entergy Nuclear Northeast

Preventive maintenance (PM) is at the heart of maintaining equipment reliability. But one of the dilemmas is how to verify that the right preventive maintenance is being performed at the appropriate times. The solution is to monitor the corrective maintenance (CM) performed during the reporting period.

Preventive maintenance is one part of the overall equipment reliability process, which also includes the corrective maintenance and corrective action (CA) programs. At the James A. FitzPatrick Nuclear Power Plant in Lycoming, NY, PM is defined as reconditioning of a component or component environment before an adverse condition can lead to failure.

Web Based Vibration Analysis Programs
Alan Friedman
Introduction
A number of changes are occurring in the Condition Based Maintenance (CBM) market and in the realm of communications, Internet and database technologies that are resulting in the adoption of Internet based monitoring programs. The following paper will describe the technologies involved as well as the current market climate that is driving this change. This paper will focus on vibration analysis in particular, however, the forces involved are just as applicable to other CBM technologies and Maintenance planning packages.

Any vibration signal may be analyzed into amplitude and phase as a function of frequency. The phase represents fifty percent of the information so it is most important to measure phase for vibration monitoring. Most vibrations on a rotating machine are related to the rotational speed so it is clearly important to have a measure of the speed, either directly or as a once per revolution tacho pulse. A question some time arises as to whether a once per revolution tacho reference signal is needed to measure phase. Is it possible to get phase if we only have a speed signal? This note gives some insight into those questions. Actually the question that should be asked is - “Can we measure a meaningful phase, for use in vibration monitoring, if we only have a speed signal as well as the vibration signals?” Suppose we have a vibration monitoring system that provides shaft speed but does not have a tacho pulse. Knowing the shaft speed means that we know the duration of each revolution. Thus we can ensure we can accurately acquire data over a complete number of revolutions. If we were acquiring hundreds of revolutions any end effects of including only part of a revolution would be very small. But if acquiring only a few revolutions then it is important to acquire an exact number of revolutions for best accuracy. Often the available speed signal is an average speed over a period of time as it is used for instrument readout and perhaps in the main system speed control loop. That is, we do not know the exact speed corresponding to a short segment of data covering, say, eight complete revolutions. In principle, knowing only the average speed is not a problem. What we know is the approximate frequency so we can Fourier analyze the signal and search for the peak of the modulus versus frequency curve closest to the approximate frequency to identify the actual speed. And hence select an exact number of revolutions. In this way knowing only the speed, albeit only approximately, still allows one to avoid end effect problems. If we have a segment from the continuous time signal, then of course it may be Fourier analyzed and this will give both an amplitude curve versus frequency and a phase curve versus frequency. But are these amplitude and phase curves obtained using a speed curve rather than a tacho useful for vibration monitoring? For the amplitudes the answer is “Yes”. For the phase the answer is “No”.

CEC has announced the release in this press submission:

“CEC introduces new low noise remote charge converter for increased measurement certainty of piezoelectric transducers.

CEC Vibration Products Inc., a leader in sensing solutions for harsh environment vibration, temperature and strain applications, today announced the introduction of its new model 1-320 low noise remote charge converter. The 1-320 is the latest product offering by CEC that compliments its expanding measurement and controls instrumentation line like the industry leading 8000 C-CATS system.

Energy and Power Considerations
Energy is required to produce vibration and in the case of machine vibration, this energy comes from the source of power to the machine. This energy source can be the AC power line, an internal combustion engine, or steam driving a turbine, etc. Energy is defined as force multiplied by the distance over which the force acts, and the SI unit of energy is the Joule. One Joule of energy is equivalent to a force of one Newton acting over a distance of one meter. The physical concept of work is similar to that of energy, and the units used to measure work are the same as those for measuring energy.

In its simplest form, vibration can be considered to be the oscillation or repetitive motion of an object around an equilibrium position. The equilibrium position is the position the object will attain when the force acting on it is zero. This type of vibration is called “whole body motion”, meaning that all parts of the body are moving together in the same direction at any point in time.

Nicole J. Kessissoglou and Zhongxiao Peng, School of Engineering, James Cook University, Practicing Oil Analysis Magazine.
Posted 12-01-03

It has long been accepted that condition- based maintenance is the most effective and cost-efficient approach to maximizing the life of industrial machinery. Vibration and wear debris analyses are two key components of any successful condition-monitoring program and can be used as both predictive and proactive tools to identify active machine wear and diagnose faults occurring inside machinery. When these techniques are conducted independently, only a portion of machine faults are typically diagnosed. However, practical experience has shown that integrating these two techniques in a machine condition-monitoring program provides greater and more reliable information, bringing significant cost benefits to industry.