Vibration issues with your slurry pump might be obvious: your slurry pump shakes like a wet dog, or subtle: you keep losing bearings or seals prematurely and don’t understand why. In either case vibration can cause a number of problems with your pump that can lead to costly repairs, downtime and shorter mean times between failure.
How to Confirm a Slurry Pump Vibration Problem
The Hydraulic Institute publishes acceptable vibration limits for all vertical, horizontal and submersible slurry pumps. But how do you verify whether or not you are within these limits? A trained vibration engineer/technician can take readings using a vibration analyzer to determine exactly where the problem lies.
If everything seems to check out, then you can start looking at how the slurry pump is running. Sometimes the pump performs differently on site than when it was purchased from the factory. For example, a slurry pump may have been sized to deliver a much higher design head. This can cause problems with vibration as well as premature failure of the wet end. To check the actual function of the piece of equipment in question, you can install a pressure gauge, or if one is already installed, take a pressure reading.
Using the following formula, the TDH can be easily calculated:
TDH = Hs + (Psig x 2.31/Slurry SG) + 0.00259*GPM²/D4
A flow reading is also needed. If no flow meter is installed, a portable one can be used to obtain a fairly accurate reading. Once the TDH is calculated and a flow reading is available, check the curve shown in the manual to determine the performance of your slurry pump. The best efficiency point will already be marked on your curve.
Here is an example of a curve:
6 Steps to Take When You Have a Vibration Issue
SO, WHAT DO YOU DO WHEN YOU EITHER SUSPECT OR CONFIRM A VIBRATION ISSUE?
- Check the framework for loose bolts and/or cracked welds. A loose bolt or cracked weld can cause looseness and allow the pump to vibrate. Depending on the severity, this can lead to bearing failure.
- Use some sort of listening device to detect irregular noise in the bearings. Most of the time if you are losing a bearing, you will hear a popping noise. If you are unsure of the noise you are hearing, go listen to a good bearing on another piece of rotating equipment so you can judge whether the noise you are hearing in the suspect bearing is abnormal.
- Check for coupling or sheave misalignment. Always check that keys are 180 degrees apart as this can be a source of imbalance.
- Open the wet end and check for blockage in the impeller vanes. Check for looseness of the impeller.
- Check and make sure the sheaves are correct for the speed at which you are supposed to be operating. If direct drive and running on a VFD, check your setting to ensure you are not running in the critical speed range.
- Check for airlocks. An airlock in the pump can cause a shut-off scenario, high vibration and ultimately pump failure.
Vibration as a Problem Indicator
Vibration checks should be a regular part of your preventative maintenance program. If checked for properly, vibration can be a leading indicator of a number of common pump ailments, including:
- Bad bearings
- Coupling or sheave misalignment
- Impeller balance
- Running the pump off the curve
- Critical speeds
- Improper frame support or improperly designed baseplate
- Bent shaft
If you feel uncomfortable or have any issues with your slurry pumps, don’t hesitate to contact us. As always, we will be happy to help in any way possible.