Tagged With "V.FFT"

Topic

Belt Tensioning Charts / Formulas

Dustin Faust ·
My predecessor at this company applied labels to all belt covers for equipment around the plant. Listing the belt model number, our internal part number, the span, and tension to be applied. This is a very good practice and the maintenance guys like having the information easily accessible. However they have been complaining about the very high tensions being specified. We use the deflection tensioning method. I am unsure of the source for the tension specifications my predecessor used,...
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Re: Belt Tensioning Charts / Formulas

John from PA ·
See https://www.google.com/search?...biw=1440&bih=781 and you can see there are many different methods/guidelines. One issue I often saw overlooked in establishing belt tension is the overhung load created on the shaft. I am aware of some gearboxes where the shaft broke off within hours of startup due to excessive belt tension. One should know how to calculate the overhung load due to belt tension. If you don't know how to do the calculation, see...
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Re: Belt Tensioning Charts / Formulas

Dustin Faust ·
Thanks, but a google search was my first step. There are many good charts out there, but none of them take into account what type of bearing is being used. Also very few account for banded belts (which are becoming very popular lately). Just looking for some input on what others around the world use.
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Re: Belt Tensioning Charts / Formulas

John from PA ·
Belt tension is in the realm of the belt OEM/supplier and most have a CYA statement that tension should follow the machine OEM recommendatios. Why should a belt vendor have to worry about the type or size of bearing? In my experience very few end users known enough about the machines under their responsibility to even answer the question accurately.
Topic

Vibration at 5X NDE AND DE V for Centrifugal Pump

wss ·
Vibration was observed in a recently overhauled centrifugal pump in 5X at pump NDE and DE V.FFT is attached There is no chance of vane pass effect since the pump was overhauled recently and no damages where observed.
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Re: Vibration at 5X NDE AND DE V for Centrifugal Pump

wss ·
The pump was overhauled as a part of routine maintenance ,there was no indication of vibration prior to overhauling. LPT was carried out on impeller during overhauling and no damages where observed also when we calibrated the rotor for balancing we found that it was already under tolerance. This are the main reasons I ruled out vane pass. This horizontally mounted centrifugal pump acts as a overhung rotor,having a bellow in the suction side and connected to motor using a flexible...
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Re: Vibration at 5X NDE AND DE V for Centrifugal Pump

Rotating Guy ·
WSS spectrum wasn't sufficient enough for analysing, if you could provide enveloping and TWF will help to know what is fault. try to run motor alone and gathered the data and check if this frequency arise. regards,
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Re: Vibration at 5X NDE AND DE V for Centrifugal Pump

Dave Reynolds ·
WSS Many styles of centrifugal pumps, can you add more detail Most of the time, pumps have 2-3 bearings/shaft/impeller/coupling. So if you truly have a 5x peak synchronous to machine running speed and you have 5 vanes on the impeller, then it is vane pass. Bearings will be non-synchronous data I also see what appears to be harmonics of vane pass, did you change impeller size recently, is there a check valve or valve in general that is stuck or not working properly? Just by "overhauling" a...
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Re: Vibration at 5X NDE AND DE V for Centrifugal Pump

Dave Reynolds ·
The pump was overhauled as a part of routine maintenance ,there was no indication of vibration prior to overhauling. ok, then it should not be vibrating now right....then something changed...is the pump running backwards, just because the valve handle moved does not mean the internals moved, did something fall/collapse and block pump inlet, are flows and pressure normal, did you change impeller size I assume "calibrated" means balanced the impeller This are the main reasons I ruled out vane...
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Re: Vibration at 5X NDE AND DE V for Centrifugal Pump

wss ·
Thank you guys for your reply.The pump is at site and we are service contractors.So is it safe to conclude that occurrence of vibration is not due to any wrong procedure in overhauling (ie. balancing,Replaced bearings and gasket,mech seal test)? Please note we had changed the bearings too.
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Re: Vibration at 5X NDE AND DE V for Centrifugal Pump

wss ·
Dear Mr.Chary, Its 4.8mm/s now.We are planing to take it down once it peaks over 5.5mm/s and give a check of the valves and other flow condition.The check valve on discharge line is normally on full open or full closed condition.
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Re: Vibration at 5X NDE AND DE V for Centrifugal Pump

chary tatta ·
Greetings team Very Interesting case. only 5X dominating. No problems noticed in spectrum. All unique components are in good condition. 3.84 mm/s at 5X is still in normal condition. However, the cause of 5X dominant can appear due to flow conditions like impeller stall. Check the pump suction and delivery valves, system flow conditions (full flow or throttled flow) Load on motor etc., Pleased to see such isolated case. regards Chary
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Re: Vibration at 5X NDE AND DE V for Centrifugal Pump

chary tatta ·
GREETINGS WELL NOTED. THANKS FOR YOUR FEEDBACK. PLEASE FOLLOW THIS METHOD AND TRY HOW YOUR VIBRATIONS ARE INDICATING. 1. CLOSE DISCHARGE VALVE AND START THE PUMP AFTER FEW SECONDS AT FULL SPEED AT MAXIMUM PRESSURE MEASURE THE VIBRATION SLOWLY OPEN DISCHARGE VALVE AND MEASURE THE VIBRATION. IF FLOW INCREASING TIME VIBRATION RISING IT IS RELATED TO FLOW SURGES CAUSING THE VIBRATION. IF STEADY AT EVERY DISCHARGE VALVE POSITION THEN THE VIBRATION IS NOT FLOW RELATED. ALSO TAKE RUN UP AND COAST...
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