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times line frequency vibration on vertical pump

times line frequency vibration on vertical pump

Vertical Pump Vibration National Pump Company

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The flowing limits are for Vertically Suspended pumps operating at 600 rpm or greater pumping fluids free of solids. Limits vary depending on if the pump is operating within the POR or AOR. https:// 1. Hydraulic Institute ANSI/HI 9.6.4 2016 Rotodynamic Pumps Guideline for Vibration Measurements and Allowable Values Location for testing: Top of the discharge head, reference figure 9.6.4.2.3.1 Allowable field limits: Reference figure 9.6.4.2.5.1b, overall valuesPOR = Preferred Operating RegionAOR = Allowable Operating Region Figure 9.6.4.2.3.1 VS1 VS6 2. American Petroleum Institute API 610 11th edition Centrigugal Pumps for Petroleum, Petrochemical and Natural Gas Industries Location for testing: Reference figure 32 2.1. Top of discharge head for motors which carry the pump thrust 2.2. Thrust bearing location for pumps which have separate thrust bearing assembliesAllowable f...

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A guideline for vibration limits at the top of the motor has been added as to ANSI/HI 9.6.4 2016 under Appendix C. The recommended limit is 1.5 time the limit at the top of the discharge head. Location for testing: The measurement should be taken near the upper motor bearing. Reference figure C.1. Allowable field limits: Reference figure C.1, overall values POR = Preferred Operating Region AOR = Allowable Operating Region Figure C.1 Top of motor locations

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The Hydraulic Institute ANSI/HI 9.6.5 2016 Rotodynamic Pumps Guideline for Condition Monitoring provides a table for recommended alert, alarm and shut down limits. These limits are based on baseline or acceptance level depending on the type. Reference table 9.6.5.8.4. Alert = Limit to identify pump vibration level which the pump may need service and begin the repair planning process . This limit can be much lower than the industry standard equipment acceptance. Continued operation at this level is acceptable provided it is below the Alarm and Shutdown limits. Alarm = Limit at which the maintenance/repair process should begin. Continued operation at this level might be warranted if below Shutdown limits. Shutdown = Limit at which the pump should be shutdown to prevent severe damage which could be unrepairable. Applying an automatic shutdown should be carefully reviewed to ensure other system equipment, processes and safety are not adversely affected by an...

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National Pump Company can provide basic vibration testing in the factory provided that the pump is being tested as a complete unit with the job motor. This test will provide rms velocity vibration measurements in three plane at the top of the discharge head. National Pump Company does not recommend factory vibration testing for the following reasons: 1. The pump installation in the test lab does not represent the installation in the field. This results in the structural natural frequency not matching that of the field, which results in values which may not correlate to the field. 2. A valve is used to throttle the pump in order to vary the system curve during the test. This valve can produce large vibration levels due to cavitation, which would not be representative of the pump in the actual system. National Pump Company guarantees that pumps will meet the applicable vibration limits when installed regardless if factory vibration testing is performed.

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150% of acceptance limit 200% of acceptance limit 130% of baseline

Limiting Vibration Issues in Vertical Turbine Pumps Pumps ...

All machine structures have natural frequencies at which they will easily vibrate. If someone bumps a metal stair railing, for example, it will vibrate at its natural frequency. If a nearby machine happens to rotate at that same frequency, the railing may vibrate violently in response to the slight vibration excitation from the machine. This commonly happens with vertical pumps. When slight vibratory forces from the pump operation excite the natural frequency of the pump structure, the pump is said to have a resonant condition. A natural frequency of any machine structure depends on its stiffness, mass and damping. Generally, stiffness and damping can be adjusted, but machine mass tends to be fixed. Damping is the ability of structural components to absorb vibrationto convert vibratory energy to small amounts of heat energy. Concrete has good damping properties, but metal does not. Increasing stiffness raises a natural frequency, while increasing mass lowers it. Changes in damping...

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When a vertical turbine pump exhibits high vibration characteristics, it is important to analyze and diagnose the problem methodically before jumping to quick fix solutions. This requires instrumentation and the ability to measure vibration amplitude and frequency. Measuring vibration phase angle can be helpful. The basic steps for diagnosing a resonance problem include: 1. Measure the frequency of the vibration.If the frequency does not match the rotating speed, the problem is likely something other than resonance such as cavitation, flow turbulence, a failing bearing or other mechanical issue. 2. Perform a bump test.With the pump not running, bump the machine in the direction of greatest vibration and measure the frequency of the resulting vibration. As with the example of a metal stair railing, the pump will ring at its natural frequency. If that is within 15 percent of the operating speed, a resonant condition exists. Resonance does not cause vibration, although it all...

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When basic analysis indicates a common pump problem such as cavitation, flow turbulence, mechanical looseness or a failing bearing, the corrections will be straightforward as on any other style pump. Cavitation can be corrected by raising the sump level or ensuring that the suction bell is not restricted. Mechanical problems with the machine usually require pump removal and repair. When a resonant condition has been diagnosed, the solution is seldom quick and easy, so attempts at quick fixes often fail. The natural frequency characteristics of vertical turbine pumps are complex, with many natural frequencies present and in varying directions, some of which will likely be within the pumps operating range. While a resonant condition can be diagnosed with a simple bump test, any corrective measures should be undertaken cautiously. Without proper analysis, correcting a resonant condition on one direction or mode may just shift it to another. Besides the bump test, there are two other t...

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