Goulds HSC20 smooth hum

[BobinWA]

Hi - I've got a 25 year old Goulds HSC20 booster pump with a 1000 gallon storage tank supply and 2 pressure tanks. Yearly I check the pressure tanks and they are in good working order. Our pump has worked great for 25 years, and is still working fine - providing 60psi with a flow rate of about 10 or 11 gallons per minute continuous, based on a 5 gallon test I did yesterday.

Over the years it has gotten louder. The noise is a very smooth hum/buzz, while the pump is operating. It doesn't sound like bearings. Everything on the motor, including the capacitor looks as clean and new as the day it was built.

I'm wondering if anyone has any ideas about the sound? I'll obviously keep using it, since it's performing as needed, but if this is something I can fix I'd like to. I can hear the hum/buzz through the poly, at the water entrance in the garage.

Also, does anyone have the resistance measurements for the motor?
Finally, when it's time to replace it, what are your opinions on the HSC20B as a replacement?

Thanks

 

[Reach4]

I'm wondering if anyone has any ideas about the sound?

One possibility that comes to mind is a lamination loosening.

Some stuff I have read says the sound would have a frequency of 120 Hz plus harmonics. I cannot be sure that part is right. I would have thought 60 Hz.

 

[Sponsor]

 

[BobinWA]

Just measured the frequency and both 129 and 64 Hz are the loudest output frequencies (using a free Android app). They both come in at about 55-57 dB. Overall, its very noticeable when its quiet outside, but maybe I don't need to worry about it.