Hi
I’m experimenting with a small project where I need to push water to a height of around 3 metres. The required flow rate is quite low—between 0.2 to 1 LPM.

I’m using a simple 12V pump (link below). However, after running for a while, the pump fails. On inspection, I noticed that the shaft and impeller have split. This suggests it may be of low quality, but it got me thinking—could the failure be due to the pump being powered at 12V while facing too much resistance at the outlet due to the limited flow?

Appreciate any thoughts or similar experiences.

Dioche 12V 10W DC Brushless High Temperature Solar Water Pump for Circulating Pumping : Amazon.co.uk: Business, Industry & Science

 

Just guessing, but I would go with your diagnosis of poor or inadequate quality. Probably not the right pump for the job.

 

Do low-priced pumps such as this need a minimum flow to prevent damage?

 

Do low-priced pumps such as this need a minimum flow to prevent damage?

We had a fountain that pumps a trickle of water for the cat. I don't know the rate but I'd say there's no way it moves a whole liter in one minute, probably closer to 0.1L. Anyway, because of cat hair and other debris the pump is often pumping next to nothing for days at a time. This pump has lasted for years.
https://www.petmate.com/products/petmate-deluxe-fresh-flow-replacement-pump

Your situation is different, since you're operating with a head of ~5psi on the output instead of blocking the input with cat hair.

I think a pump that can't handle a 5psi head is not much of a pump. I suspect it's a fluke failure - rotten luck.

 

Do low-priced pumps such as this need a minimum flow to prevent damage?

It's likely a centrifugal pump, so the water in the pump may get hot at a slow flow-rate, causing the impellor to weaken if it's make of plastic.
Notice that the maximum rated water temperature is only 55°C.

 

So, do centrifugal pumps create a lot of heat in a short time? What type of pump is best to use?

This is the dataset of the pump:

 

So, do centrifugal pumps create a lot of heat in a short time? What type of pump is best to use?

Centrifugal pumps will just circulate the water inside the impeller housing when the flow rate is low or stopped.
How fast that heats up the water is difficult to estimate.
You can estimate that by feeling the housing temperature after some period of operation.

What type of pump is best to use?

Centrifugal pumps are good for that purpose, but one with a lower flow rate (if available) might be better for your requirements.

 

~3-Meters of Physically-Measured-Head, plus
additional, unknown, Head-Pressure caused by other restrictions in the overall system,
could easily exceed the ratings for this cheap, plastic Aquarium / Fountain-Pump.

If Flow through the Pump gets close to ZERO,
the Water-Temperature in the Pump will gradually go to the Moon,
and then the Pump will start generating STEAM,
and then everything quickly "Goes to Hell in a Handbasket", and melts into a gooey-mess.

There's no wonder that a high-quality Grundfos-brand-Pump,
which is specifically designed for this job,
may exceed the price of ~$300.oo.
They don't fail.
.
.
.
.
.

 

It is entirely possible that the pump is spinning too fast. It is also possible that it is so poorly made that it will fail.

 

The nature of the pump appears to be a impellar radial version, if these types are blocked or have restriction; the current goes down considerably.
so should the heat.

 

You could try a bypass loop so the flow through the pump is higher than you need, then use a smaller tube for your target and restrict the bypass until you get the required flow up the small tube. But a more suitable pump, maybe a diaphragm one would be the way to go.

 

The nature of the pump appears to be a impellar radial version, if these types are blocked or have restriction; the current goes down considerably.
so should the heat.

.
The Motor-Heat goes down, and the Heat imparted to the Water goes UP.

It's a good thing that Water has a huge capacity for absorbing Heat,
but it can't take-away the Heat generated if there is extremely Low, or especially, Zero-Flow.
.
.
.

 

Reading the data sheet,the maximum lift (Zero Flow) is 3.5 meters. So the nine foot lift is close to the pump pressure/delivery limit. At that point the motor is producing 12 watts of heat without enough flow to remove any heat. So the motor gets hot because of no cooling flow, not because pump generated heat, but because of motor running heat. Cheap plastic does not like heat.
Probably the impeller is simply a force-fit on the shaft, meaning a lot of stress on the plastic before even switching on the power. AND, more motor generated heat because of running at about it's maximum capability.

 

AND, BY THE WAY, cheap plastic tends to lose stiffness when it is exposed to a hot motor shaft. AND heavily loaded motors do tend to get hot.