have read several posts here in home-barista before of writing this.. but because the circumstances of the thing that have happened to me I think are new on this forum, I have decided to create a new post.
I go directly to the point of the post.

I have a Office dual boiler Rotary-pump Expobar.
I have made a horrible and terrible mistake today. By a very weird way (don't comment why my brain acts like that) I have run the machine trying to refill the boiler (after drain it using the tap) with the input of the water closed from plumb domestic installation... so pump running with no water... 4 minutes
The thing is that I found strange the noise of pump and the time that the pump took trying to refill the boiler.... at last I have realised that of terrible mistake... I have opened again the key of the input to the machine and the machine run/sound correctly refilling the boiler in some seconds properly.
That has been 4 minutes... rotary pump.... I hardly can forgive myself...
The pump was hot (more than normally, but not so hot...)...
I have wait 2 hours and I have checked the pressure of the pump.. and with blind basket is 12 bars... same of usually... thankfully... maybe new record of rotary pump running with no water and no damage???
I have read several post and many forum members have cases like this, but with seconds... no minutes!!

So, if somebody, briefly or widely, can tell me something about if somebody knows if this is normal (that with 4 minutes running with no water can be damaged the rotary pump or not) or I will for sure see the damaged in a short time period, or what else... I would be very grateful for any comment.
Thank in advance for read/answer the post.

burgosma wrote:I have wait 2 hours and I have checked the pressure of the pump.. and with blind basket is 12 bars... same of usually... thankfully... maybe new record of rotary pump running with no water and no damage???

As you've read, while it certainly isn't recommended to run a rotary pump without water, it isn't immediately fatal either. My vague recollection is that Procon rotary pumps, for example, are specified to tolerate 2 minutes without water (corrections with links welcome!). While running the pump dry for 4 minutes is definitely not recommended, the fact that your espresso machine's pump still works is an encouraging sign.

+1 to what Dan said, and the pump was not totally dry either. There was some water in there to begin with, and since it couldn't suck air in through the closed line, it would not be able to push the water completely out (it works by displacement so something has to come is for something else to go out). Even a small amount of water in there would do good.

Additionally, don't panic. Pumps are not terribly expensive, some are rebuildable, and they are relatively easy to replace.

Randy G. wrote: There was some water in there to begin with, and since it couldn't suck air in through the closed line, it would not be able to push the water completely out (it works by displacement so something has to come is for something else to go out). Even a small amount of water in there would do good.

Unfortunately, the input was closed and the boiler drained, so the pump got dry in 0,5 second, because the small amount of water that could have in the circuit went inmediately to the boiler.....

Anyway

Randy G. wrote: Pumps are not terribly expensive, some are rebuildable, and they are relatively easy to replace.

this is right....
I will check it next days if new record have been settled in 4 minutes with no water, or definitely have been damaged....

I think, anyway... like Dan says, the pumps are more heavy than people usually think (people run 1 second and are very alarmed), and I hope mine one is one of them...

Thank you guys for the comment... I think today I am a little more calm
Anyway, more comments are very welcome
bye.

Randy G. wrote:There was some water in there to begin with, and since it couldn't suck air in through the closed line, it would not be able to push the water completely out...

Good catch, thanks.

burgosma wrote:Unfortunately, the input was closed and the boiler drained, so the pump got dry in 0,5 second, because the small amount of water that could have in the circuit went immediately to the boiler.....

No, I don't think so. Randy is right: If the inlet was closed (sealed), not all of the water would be evacuated from the pump once a vacuum formed on the inlet side. Like he said, even a small amount of water in there would do good.

HB wrote:No, I don't think so. Randy is right: If the inlet was closed (sealed), not all of the water would be evacuated from the pump once a vacuum formed on the inlet side. Like he said, even a small amount of water in there would do good.

I don't know how much water can be in the hose of inlet side. Even could be 20cl, the pump took few seconds to suck all the water it can (not so much...), leaving just little bubbles, as I can image :/ .
Now we could think that not whole water was drain from the hose because like Randy says "displacement so something has to come is for something else to go out" and because no all of water can suck from the hose, never all the water would be taken from it......but the amount of water were bubbles at most, and I don't think that the little bubbles that could be there have been what have saved the machine... I suspect have been just that the durability of the pump running without water....
Anyway, the pump seems/sounds work properly.... I hope...

burgosma wrote:I suspect have been just that the durability of the pump running without water...

The only way to be certain is run the pump without the inlet hose connected for 4 minutes. If the pump doesn't seize, you've proven that you're right. Let us know how it works out.

HB wrote:The only way to be certain is run the pump without the inlet hose connected for 4 minutes. If the pump doesn't seize, you've proven that you're right. Let us know how it works out.

mmmmm... I will think about it....
mmmmm....maybe not... !!!

I would be more worried about an empty boiler and energised heater for 4 minutes. That has a bad tendency to blow out heating elements. If you hook everything back up and it works without issue, count yourself lucky and make some coffee. The good thing about these parts (or bad thing) is that there is very little to go wrong. It will work, or it will not.

(attempting spanish) Lo siento, pienso tu vas a estar bien.