Impellers rotate at very high speeds. When they are out of balance, they can cause tremendous amounts of damage to a pump. The mechanical seal faces will be out of alignment, causing them to break and leak. The bearings will vibrate and cause damage to the balls and outer races.
So, you've just pulled a brand new, shiny impeller out of the packaging. It looks great and ready to install. However, before you do, take the time to have it balanced. You might be thinking, it's brand new! Shouldn't it be balanced already? You would think so, but that is not the case.
The manufacturer assumes that the impeller will be trimmed. According to our Service Pros, about 90% of the impellers they see need trimming before shipping to a customer. For the manufacturer, it does not make sense for them to spend time balancing the impeller if the distributor or end user is going to trim them anyway.
How do you know when an installed impeller is out of balance?
The biggest tell-tale sign of an out-of-balance impeller is vibration.
Can you balance an impeller yourself without a machine?
Balancing an impeller is not a DIY activity. Given the rotation speeds of an impeller, it is best to leave this job to professionals that have the tools and expertise to trim and balance the impeller for a long life.
IndustriTech uses a belt drive dynamic balancing machine. The part is mounted on a horizontal shaft held by a belt-driven spindle. The spindle incorporates a pair of vibration transducers that make it possible to measure dynamic imbalance. When the part is spun, the balancer indicates the amount of correction to be made in each plane in terms of weight to be added or removed and the angular location of the correction.
The process is computerised, and all measurements and calculations are displayed on a large LCD. The part is rotated until the computer angular position display matches the present angle with the angle of imbalance correction for one of the two planes. The operator then knows precisely where to make the correction for that plane.
Can you tell by looking at an impeller if it will be imbalanced?
Short answer, no. There is a better chance of the impeller being balanced if grind marks are present. If there are no grind marks on the vanes and backside of the impeller between the pump out vanes, then the impeller has probably not been balanced.
Our Service Pros highly recommend having a professional balance your new impeller. It costs about $500 to do it, a sound investment when you think about the costs that can pile up after running a pump with an impeller that is out of balance (downtime, new seal, new bearings, etc.)
Next time you receive a new impeller, do not assume it has been balanced! Check with a professional to ensure it is safe to install it in a pump. Double checking up front will save you loads of time and money in the long run.
IndustriTech offers in-house rotor balancing as well as on-site vibration analysis and laser shaft alignment services. We have the equipment, skills, and experience to satisfy your industrial balancing and rotating equipment preventative maintenance requirements.